Communication device, communication method, and program

Abstract

To improve the certainty of communication between a plurality of access points.SOLUTION: A communication device functioning as an access point conforming to the IEEE802.11 series standard receives a radio frame including capability information indicating preparation time required for preparation of transmission of signals to the communication device, from one or more other communication devices functioning as access points, on the basis of the capability information, determines the length of padding in a trigger frame for causing the one or more other communication devices to transmit signals to the communication device, and when data from the one or more other communication devices are to be received, transmits the trigger frame including the padding with the determined length to the one or more other communication devices.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

[0002] As communication standards related to wireless local area networks (LANs), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards are known. The IEEE 802.11 series of standards include 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 a technique for improving communication efficiency and throughput by causing a plurality of access point devices (hereinafter sometimes referred to as "APs") to cooperate has been studied. A communication technique in which a plurality of 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The Coordinator AP is assumed to perform control to allocate a Transmission Opportunity (TXOP) to the Coordinated AP for a predetermined period, for example. Here, the Coordinated AP may require a certain amount of time until the preparation for the communication to be executed at that AP is completed, depending on the content of the communication to be executed at that AP and the like. For this reason, it is important for the Coordinator AP to set the TXOP for the Coordinated AP in consideration of the period of communication preparation.

Means for Solving the Problems

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

[0006] A communication device according to an aspect of the present invention is a communication device that functions as an access point compliant with the IEEE802.11 series standard, and includes a receiving means for receiving a wireless frame including capability information indicating a preparation time required for preparing for transmission of a signal to the communication device from one or more other communication devices that function as access points, and based on the capability information, a 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, and a transmitting means for transmitting the trigger frame including the determined length of Padding to the one or more other communication devices when data from the one or more other communication devices is to be received.

Effects of the Invention

[0007] According to the present invention, the reliability of communication between a plurality of access points can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] (Configuration of Wireless Communication System) Fig. 1 shows a configuration example 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 (WLAN) compliant with the IEEE802.11 series standards. Note that IEEE is an abbreviation for Institute of Electrical and Electronics Engineers. In the following, the description will be based on a WLAN compliant with the IEEE802.11 series standards, but it is not limited to this, and the methods described below may also be applied to communication compliant with other wireless communication standards. In the example of Fig. 1, three access points (AP101 to AP103) and four stations (STA122 to STA124) are shown as communication devices for performing wireless communication. Note that in the following, the access point may sometimes be referred to as AP or AP STA, and the station may sometimes be referred to as STA or Non-AP STA. Also, the example of Fig. 1 is just an example, and this wireless communication system is configured such that at least two APs share a transmission opportunity (TXOP) to perform communication (cooperative communication). That is, the number of APs may be two, or may be four or more. Similarly, the number of STAs may be 1 to 3, or may be 5 or more.

[0011] AP101 to AP103 are successor standards to the IEEE802.11be standard targeting a maximum transmission speed of 46.08 Gbps (gigabits per second), and are configured to be operable in accordance with a standard targeting a maximum transmission speed exceeding 90 to 100 Gbps. Similarly, STA121 to 124 can also be configured to be operable in accordance with this successor standard. Hereinafter, this successor standard is referred to as the IEEE802.11bn standard or the UHR standard. Also, the wireless frame transmitted and received in this successor standard is called a UHR PPDU. Note that UHR is an abbreviation of Ultra High Reliability. Also, PPDU is an abbreviation of PLCP Protocol Data Unit, and PLCP is an abbreviation of Physical Layer Convergence Protocol. The UHR standard features support for high-reliability communication, low-latency communication, and AP cooperation. Note that the names such as the IEEE802.11bn standard and the UHR standard are names set for convenience for successor standards having such features, and may become different names when the standard formulation is completed. That is, hereinafter, the explanation will be given using the names of the IEEE802.11bn standard or the UHR standard, but the following discussion can also be applied to standards with other names such as further successor standards of the UHR standard. Note that AP101 to AP103 and STA121 to 124 can be configured to also perform communication compliant with any of the legacy standards other than the UHR standard, such as the IEEE802.11a / b / g / n / ac / ax / be standards.

[0012] In the example of FIG. 1, it shows a state where STA121 and STA122 participate in network 112 formed by AP102, and STA123 and STA124 participate in network 113 formed by AP103. AP101 to AP103 can perform MU (Multi User) communication to communicate with a plurality of STAs in parallel using OFDMA (Orthogonal Frequency Division Multiple Access) technology. In MU communication using OFDMA technology, one frequency channel is divided into a plurality of sub-channels each called an RU (Resource Unit). And each of the divided RUs is assigned as a resource to be used for communication with different STAs (or a group of STAs composed of a plurality of STAs). Thereby, it becomes possible for an AP and a plurality of STAs to communicate in parallel via one frequency channel. At this time, when data is transmitted from an AP to one or more STAs, the AP transmits a MU (Multi User) PPDU in which the data is modulated by OFDMA. When all communication devices involved in MU communication comply with the UHR standard, a UHR MU PPDU, which is a MU PPDU compliant with the UHR standard, can be transmitted to one or more STAs.

[0013] In addition, AP101 to AP103 and STA121 to STA124 can be configured to support wireless communication based on other communication standards such as Bluetooth (registered trademark), NFC, and Bluetooth (registered trademark) LE (Low Energy). Here, NFC is the abbreviation of Near Field Communication. In addition, AP101 to AP103 may be configured to support wired communication using an Ethernet (registered trademark) cable or wired communication using an optical fiber. AP101 to AP103 can be, for example, a wireless LAN router, a personal computer (PC), etc., but are not limited thereto. In addition, STA121 to STA124 can be, for example, wearable devices such as a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, and smart glasses, but are not limited thereto. 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.

[0014] In this embodiment, when AP101 to AP103 provide a network, the BSSIDs of each network are all different. Note that BSSID is the abbreviation of Basic Service Set Identifier and is an identifier for identifying an access point. In addition, 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.

[0015] In this embodiment, it is assumed that APs AP101 to AP103 have an AP cooperation function that operates with emphasis compared to other APs. Here, AP101 is an AP that performs overall control for AP cooperation, and in the following, such an AP may be referred to as a Coordinator AP. Also, APs AP102 to AP103 are APs that function as controlled devices controlled by the Coordinator AP, and in the following, 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 AP101 functions as a Coordinator AP, AP102 or AP103 may function as a Coordinator AP and control AP101 that functions as a Coordinated AP. Note that AP101 provides network 111, AP102 provides network 112, and AP103 provides network 113. STAs STA121 to STA124 are STAs that participate in the network provided by any of the APs.

[0016] AP101 transmits a trigger frame to APs AP102 and AP103. The trigger frame is a mechanism introduced in standards after IEEE802.11ax, and is used to enable a plurality of STAs to receive the trigger frame transmitted from the AP and transmit frames in parallel. More specifically, when a STA receives a trigger frame targeted at itself, after the elapse of the SIFS period, it performs uplink (UL) communication using the assigned resource unit (RU). Here, SIFS is the Short IFS defined in the IEEE802.11 series of standards, and IFS is the Inter-Frame Space. This mechanism enables efficient use of the wireless medium.

[0017] By using such a trigger frame mechanism, AP102 and AP103 can perform uplink (UL) communication in parallel at the timing based on the trigger frame from AP101. Note that in this embodiment, "UL" in the communication between APs refers to the link in the direction of transmitting data from the Coordinated APs (AP102, AP103) to the Coordinator AP (AP101). Here, AP102 and AP103 may need to make preparations for transmission using the assigned RUs. For example, AP102 and AP103 may need a certain amount of time until the preparation for UL communication is completed by performing communication control such as scheduling in the network formed by the device itself, or processing for handling a relatively large amount of data. Therefore, it can be assumed that AP102 and AP103 may not be ready for UL communication at the time after the elapse of the SIFS period since receiving the trigger frame transmitted from AP101. Here, if AP102 and AP103 are not ready for UL communication at the time when the SIFS has elapsed since receiving the trigger frame from AP101, they can wait until the preparation is completed and then transmit the frame for UL communication. However, in this case, a period longer than the SIFS may occur between the end of the trigger frame transmitted from AP101 and the start of the frame for UL communication transmitted from AP102 or AP103. As a result, during that period, other communication devices may determine that the frequency channel is not being used and start transmitting frames. In this case, although AP101 has assigned a transmission opportunity (TXOP) to AP102 and AP103 by the trigger frame, it is assumed that AP102 or AP103 may not be able to perform communication during that TXOP.

[0018] In this embodiment, in view of such circumstances, the length of the trigger frame is increased so that AP101 can start UL communication at the timing when the preparation for UL communication is completed in AP102 or AP103. That is, AP101 adds Padding to the trigger frame to adjust the length of the trigger frame, and after a SIFS period has elapsed from the end of the trigger frame, UL communication can be surely performed. Here, if this Padding is excessively long, the communication efficiency will decrease, while if the Padding is short, the communication of AP102 or AP103 may not start after SIFS from the end of the trigger frame. In this embodiment, in view of such circumstances, each AP is configured to perform control processing for setting Padding of an appropriate length. Hereinafter, the configuration of the AP that performs such processing, the flow of the processing executed by the AP, and an example of the control information used for such control will be described.

[0019] Note that hereinafter, the case where AP101 is the Coordinator AP and AP102 and AP103 are the Coordinated APs will be described, but it is not limited thereto. That is, AP102 or AP103 may function as the Coordinator AP. Also, for example, the roles of the Coordinator AP and the Coordinated AP may be dynamically changed. Further, in the following description, an example in which two APs (AP102 and AP103) perform UL communication in parallel will be described, but the same procedure can be used when one AP performs UL communication. When only one AP performs UL communication, by performing Padding in consideration of the preparation time for the UL communication, it is possible to prevent interruptions by other communication devices during the UL communication of that one AP. Also, when a plurality of APs perform UL communication, by performing Padding in consideration of the preparation time in each AP, it is possible for the plurality of APs to communicate in parallel at a common timing while preventing interruptions by other communication devices.

[0020] (Configuration of the device) Using FIG. 2, a configuration example of a communication device (AP101 to AP103) that functions as an AP according to this embodiment will be described. FIG. 2 shows a hardware configuration example of the AP. As shown in FIG. 2, as its hardware configuration, the AP includes, for example, a storage unit 201, a control unit 202, a functional unit 203, an input unit 204, an output unit 205, a communication unit 206, and antennas 207 to 209.

[0021] The storage unit 201 is configured to include one or more memories such as a ROM and a RAM, and stores various computer programs for performing various operations described later, and various information such as communication parameters for wireless communication. Note that ROM is an abbreviation for Read Only Memory, and RAM is an abbreviation for Random Access Memory. Note that the storage unit 201 may include, in addition to or instead of memories such as a ROM and a RAM, 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, and a DVD. Further, the storage unit 201 may include a Solid State Drive (SSD). Further, the storage unit 201 may include a plurality of memories and the like.

[0022] The control unit 202 is composed of one or more processors such as a CPU or an MPU, for example, and controls the entire AP by executing a computer program stored in the storage unit 201, for example. Note that CPU is an abbreviation for Central Processing Unit, and MPU is an abbreviation for Micro Processing Unit. In addition to controlling the entire AP, the control unit 202 may be configured to execute a process of generating data and signals to be transmitted in communication with other communication devices. Note that the control unit 202 may be configured to execute processes such as controlling the entire AP in cooperation with a computer program stored in the storage unit 201 and an OS (Operating System), for example. Further, the control unit 202 may include a plurality of processors such as a multi-core, and processes such as controlling the entire AP may be executed by the plurality of processors. Further, the control unit 202 may be composed of an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

[0023] In addition, the control unit 202 controls the functional unit 203 to execute predetermined processes such as imaging, printing, and projection. The functional unit 203 is hardware for the AP to execute predetermined processes. For example, when the AP is a camera such as a digital still camera or a smartphone having a camera, the functional unit 203 is an imaging unit that performs imaging processing of surrounding images. Also, for example, when 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 the outside via wireless communication or the like. Also, for example, when 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 the outside via wireless communication or the like. In the case of smart glasses, the projection surface is the retina of the end user or the like. The data processed by the functional unit 203 may be data stored in the storage unit 201 or data communicated with other APs or STAs via the communication unit 206 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 the network storage service provided by the APs 101 to 103 or the like using a protocol such as SMB, FTP, or WebDAV. Then, another communication device such as an STA can upload a file to the storage service or download a file in the storage. The data communication for upload and download at this time can be performed using a wireless communication function conforming to, for example, the UHR standard.

[0024] The input unit 204 receives various operations from the user. The output unit 205 performs various outputs to the user. Here, the output by the output unit 205 includes at least one of, for example, display on the screen, audio output by the speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be realized by one module such as a touch panel. Also, the input unit 204 and the output unit 205 may be built into the AP respectively, or may be configured as external devices connected to the AP.

[0025] The communication unit 206 controls wireless communication compliant with the IEEE802.11 series standards and controls Internet Protocol (IP) communication. The communication unit 206, for example, in cooperation with the antennas 207 to 209, executes transmission and reception of a UHR PPDU which is a wireless frame of the UHR standard and a PPDU corresponding to the previous standards. The antennas 207 to 209 are antennas capable of transmitting and receiving signals in at least any one of the frequency bands of, for example, the sub-GHz band, 2.4 GHz band, 5 GHz band, 6 GHz band, 7 GHz band, and 60 GHz band. In the present embodiment, three antennas 207 to 209 are shown, but the number of antennas may be one or two, or four or more antennas may be prepared. In one example, different antennas may be prepared for each frequency band. Also, when the AP has a plurality of antennas, it may have a plurality of communication units 206 respectively corresponding to the plurality of antennas. Note that when the AP supports the above-mentioned NFC standard, Bluetooth (registered trademark) standard, etc., a communication unit 206 configured to control wireless communication compliant with these communication standards may be prepared.

[0026] Fig. 3 shows an example of the functional configuration of the AP. As its functional configuration, the AP has a frame processing unit 301, a Padding processing unit 302, and a frame transmission / reception unit 303. 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 functional unit in the communication unit 206. Note that Fig. 3 is a diagram for explaining the main functions of this embodiment, and other functions are omitted. Therefore, the AP can naturally have functions for establishing a connection with an STA as a normal AP and for control in communication, and functions that a communication device generally has. Also, a plurality of functional blocks in Fig. 3 may be integrated into one functional block, or one functional block may be divided into a plurality of functional blocks.

[0027] The frame processing unit 301 interprets various wireless frames received from the outside, and performs control processing of wireless communication based on notifications to upper layer functions (not shown) and information obtained by the interpretation. Also, when transmitting data to the communication partner device, the frame processing unit 301 of the AP101 generates a data frame including the data. The frame processing unit 301 of the AP101 can acquire capability information for determining Padding from the frames received from the AP102 to AP103. Also, the frame processing unit 301 of the AP101 generates a trigger frame including the Padding determined based on the acquired capability information. Also, the frame processing unit 301 of the AP101 can generate a request frame for requesting the above-described capability information to be transmitted to the AP102 to AP103. Also, the frame processing unit 301 of the AP102 to AP103 generates a notification frame including the capability information for the AP101 to determine Padding. Also, the frame processing unit 301 of the AP102 to AP103 processes the trigger frame and request frame including the Padding received from the AP101. Note that the notification frames and request frames transmitted and received between the APs can be management frames compliant with the IEEE802.11 series standards, such as Probe Reuqest, Probe Response, Beacon, and Action frames. When an Action frame is used, the value of its Category code can be set to a value indicating that it is used for transmission and reception of information for determining the length of Padding. However, this is just an example, and any frame that can be used for notification of information for determining Padding or request for such information may be used as the above-described notification frame or request frame, even if it is not a management frame.

[0028] The Padding processing unit 302 of AP101 determines the Padding to be added to the trigger frame based on the capability information included in the notification frames (e.g., management frames) from AP102 to AP103. Also, the Padding processing units 302 of AP102 to AP103 notify the frame processing unit 301 of the capability information used to determine the Padding corresponding to the preparation time required to start UL communication, and cause the notification frame to be generated. The frame transceiver unit 303 receives wireless frames such as UHR PPDUs transmitted from other external communication devices by cooperating with antennas 207 to 209. Also, the frame transceiver unit 303 transmits wireless frames such as UHR PPDUs generated in the frame processing unit 301 to the communication partner device (other APs or STAs).

[0029] (Frame Configuration) Subsequently, the configuration of the frames transmitted and received for the cooperative communication between APs in this embodiment will be described with reference to FIGS. 4 and 5.

[0030] FIG. 4 shows an example of an information element used when Coordinated APs (AP102 to AP103) transmit capability information that can be used to determine Padding to the Coordinator AP (AP101). This information element is stored and transmitted in a management frame such as a Beacon, Probe Response, or Action frame, or other wireless frames. In this information element, the Element ID field 401 is a field in which information for identifying the type of the information element is stored. Here, for example, information specifying that it is an information element for storing the Capability group of the UHR standard is stored in the Element ID field 401. The Length field 402 stores a value indicating the length of this information element. The UHR MAC Capabilities field 403 stores, for example, capability information related to the MAC (Media Access Control) layer among the Capability groups of the UHR standard. In one example, the Multi-AP TF MAC Padding Duration subfield 404 is included in the UHR MAC Capabilities field 403. The Multi-AP TF MAC Padding Duration subfield 404 stores capability information indicating (or at least capable of specifying) the preparation time required for the Coordinated AP to start UL communication. 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 another name storing the same information may be used. For example, information as shown in Table 1 is stored in the Multi-AP TF MAC Padding Duration subfield 404. TIFF2025107933000002.tif65161

[0031] As a subfield in which the ability information regarding the above-mentioned preparation time is stored, a subfield defined by a conventional standard may be used. For example, as such a subfield, a Trigger Frame MAC Padding Duration subfield defined by a standard after the IEEE802.11ax standard as shown in Table 2 may be used. TIFF2025107933000003.tif65161

[0032] Here, the information shown in Table 2 can be used for both the AP and the STA (Non-AP STA). That is, in both the notification of the ability information from the conventional STA and the notification of the ability information from the Coordinated AP according to the present embodiment, information like that in Table 2 can be used. In one example, when the frame including this information element includes information indicating that it is used for transmitting the ability information between APs, this information element can be interpreted as being for the AP. Also, when the frame including this information element is used for communication between the AP and the STA, this information element can be interpreted as being for the STA. Also, as shown in Table 3, by expanding the number of bits of this subfield from 2 to 3 (enabling the use of values 0 to 7), it may be possible to distinguish whether the information indicating either the STA information or the AP information is stored depending on the content of the information. The information element in Table 3 indicates whether it is STA information or AP information by the first 1 bit out of 3 bits. That is, when the first 1 bit is 0 (in the case of values 0 to 3), the STA information is indicated, and when the first 1 bit is 1 (in the case of values 4 to 7), the AP information is indicated. However, this is just an example, and for example, the information may be notified in any format such as indicating whether it is STA information or AP information by the last bit. TIFF2025107933000004.tif103161

[0033] Also, in one example, the preparation time of the AP can vary significantly depending on, for example, the load due to communication with the STA. Therefore, the number of bits of this information may be increased to expand the range of the preparation time values for the AP (in Tables 1 to 3, 0 to 16 μs (microseconds)). For example, the preparation time values may be indicated in 8 levels using 3 bits, or may be indicated in 16 levels or more using 4 bits or more.

[0034] Figure 5 shows an example of the format of a trigger frame that the Coordinator AP (AP101) transmits to the Coordinated APs (AP102, AP103) when performing inter-AP coordinated communication. In the Frame Control field 501, for example, a value indicating that this frame is a trigger frame used in a standard after the IEEE802.11ax standard is stored. In the Common Info field 502, information that is commonly applied to a plurality of Coordinated APs that are the destinations of this trigger frame is stored. This Common Info field 502 includes a Trigger Type field 503 and a Trigger Dependent Common Info field 504. In the Trigger Type field 503, information for identifying the type of the trigger frame is stored. In the Trigger Dependent Common Info field 504, information that depends on this trigger frame is stored. Padding 505 is added to give a time margin for UL transmission preparation to the group of APs that received this trigger frame. The length of Padding 505 is specified, for example, based on 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 corresponding to the longest value of the time length indicated by the received capability information is determined as the length of Padding 505. For example, if the capability information of AP102 indicates 8 μs (microseconds) and the capability information of AP103 indicates 16 μs, Padding 505 with a length corresponding to the longer of these values, 16 μs, can 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.

[0035] (Processing flow) Next, an example of the communication processing flow will be described. FIG. 6 shows an example of the communication processing flow when the Coordinated AP spontaneously provides the capability information. In the example of FIG. 6, two APs (AP102 and AP103) are shown as the Coordinated AP, but the Coordinated AP may naturally be one or three or more.

[0036] The Coordinated AP (AP102, AP103) includes the capability information indicating the preparation time required to start the UL communication in the Beacon frame and broadcasts (transmits by broadcast) the respective Beacon frames 601 to 602. In the example of FIG. 6, an example in which the capability information is notified using the Beacon frames 601 to 602 is shown, but it is not limited thereto. For example, the Coordinated AP may include the capability information indicating the preparation time in the Action frame and spontaneously transmit it. At this time, the Coordinated AP can unicast the Action frame to the Coordinator AP. That is, the Coordinated AP can notify the Coordinator AP of the preparation time information in any form such as broadcast, multicast, or unicast using any frame that can include the information indicating the preparation time.

[0037] When the Coordinator AP (AP101) receives the Beacon frames 601 - 602, it analyzes the frames and checks the capability information indicating the preparation time required for each AP to start UL communication. Thereby, AP101 can determine the length of the Padding to be added to the trigger frame. Based on the received information, when AP101 determines the length of the Padding to be added to the trigger frame, it transmits the trigger frame 603 with the Padding 604 of that length to AP102 - AP103. AP102 - AP103 perform the reception process of the trigger frame 603 with this Padding 604 added. Then, after the period of SIFS605 has elapsed from the end of the trigger frame 603, AP102 - AP103 transmit the UL PPDUs 606 - 607 to AP101. In this way, in the process of FIG. 6, the Coordinator AP can adjust the length of the Padding in the trigger frame based on the information on the preparation time spontaneously transmitted from the Coordinated AP. And by adjusting the length of the Padding in this way, the Coordinated AP can complete the preparation for UL communication when the SIFS period has elapsed from the end of the trigger frame.

[0038] FIG. 7 shows an example of the communication process flow when the Coordinated AP notifies the capability information in its response frame when it receives a request frame from the Coordinator AP. In the example of FIG. 7, only one AP (AP102) is shown as the Coordinated AP, but the Coordinated AP can of course be two or more. That is, whether the Coordinated AP spontaneously transmits the capability information or transmits the capability information in response to the reception of a request, the number of Coordinated APs is arbitrary.

[0039] In FIG. 7, the Coordinator AP (AP101) transmits a predetermined request frame to request the capability information used to determine the length of the Padding to be added to the trigger frame. In the example of FIG. 7, AP101 transmits Probe Request frame 701 as this request frame. When AP102 receives this request frame, it transmits a response frame including the capability information indicating the preparation time required to start UL communication. In FIG. 7, AP102 transmits Probe Response frame 702 as the response frame to Probe Request frame 701. Note that AP101 may transmit the Probe Request frame including the request information indicating that it requests the capability information indicating the preparation time. AP102 may return the response frame including the capability information only when it receives the Probe Request frame including this request information. However, this is just an example, and even when AP102 receives a Probe Request frame not including the request information, it may return the response frame including the capability information. Also, the Probe Request frame and the Probe Response frame are examples of the request frame for requesting the capability information and the response frame corresponding thereto, and frames other than these may be used. For example, AP101 may transmit an Action frame including the information indicating that it requests the information on the preparation time to AP102, and AP102 may notify the information on the preparation time in the response frame to the Action frame.

[0040] When AP101 receives the Probe Response frame 702, it analyzes the frame to check the capability information indicating the preparation time required for AP102 to start UL communication. Thereby, AP101 can determine the length of the Padding to be added to the trigger frame. Based on the received information, when AP101 determines the length of the Padding to be added to the trigger frame, it transmits the trigger frame 703 with the Padding 704 of that length to AP102. AP102 performs the reception process of the trigger frame 703 with this Padding 704 added. Then, after the period of SIFS 705 has elapsed from the end of the trigger frame 703, AP102 transmits the UL PPDU 706 to AP101. In this way, in the process of FIG. 7, the Coordinator AP requests the preparation time information from the Coordinated AP and obtains the preparation time information through the response to the request. Then, the Coordinator AP can adjust the length of the Padding in the trigger frame based on the preparation time information. And by adjusting the length of the Padding in this way, the Coordinated AP can complete the preparation for UL communication when the period of SIFS has elapsed from the end of the trigger frame.

[0041] In the above example, FIGS. 6 and 7 are used to distinguish and explain the case where the Coordinated AP spontaneously notifies the preparation time information and the case where it notifies when receiving a request. However, the Coordinated AP may perform both. That is, the Coordinated AP may notify the information (for example, temporarily) when receiving a request frame from the Coordinator AP while spontaneously (for example, periodically) notifying the preparation time information.

[0042] Next, an example of the processing flow executed by the Coordinator AP (AP101) 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. Further, this processing may be realized by a processor included in the communication unit 206, for example. AP101 starts this processing, for example, in response to determining to transmit a trigger frame for communication between APs.

[0043] AP101 receives a frame including capability information indicating the preparation time required to start UL communication (S803). AP101 can receive the frame, for example, by waiting for a frame spontaneously transmitted from another AP that performs cooperative communication using a trigger frame. Also, AP101 can generate and transmit a request frame for requesting information indicating the preparation time as needed (S801, S802), and may receive a response frame to the request frame including the information on the preparation time. AP101 can use, for example, a Probe Request frame as the request frame. In one example, information elements as shown in FIG. 4 can be set in the request frame. AP101 acquires the capability information included in the frame received in S803 (S804), and based on the capability information, determines the length of the Padding to be added to the trigger frame (S805). AP101 can determine, for example, the length corresponding to the longest time among the preparation times in each of one or more Coordinated APs targeted by the trigger frame as the length of the Padding. Also, AP101 may specify the length of the Padding according to information such as the number of connected STAs to the Coordinated AP targeted by the trigger frame. In one example, there may be a tendency that the higher the load of the Coordinated AP, the longer the preparation time. In such a case, according to the tendency, the length of the Padding can be calculated based on the number of STAs connected to each AP. For example, the preparation time indicated by the capability information is set to the minimum time required to start UL communication, and AP101 may specify the time length corresponding to the length of the Padding by adding a certain time to the minimum time according to the load. Also, AP101 may specify the length of the Padding according to, for example, the traffic volume in the Coordinated AP.

[0044] In the above manner, the Coordinator AP can acquire the capability information indicating the preparation time required for each Coordinated AP to start UL communication. Then, based on the acquired capability information, the Coordinator AP can determine the length of the Padding of the trigger frame to be transmitted to that Coordinated AP.

[0045] FIG. 9 shows an example of the flow of processing executed by the Coordinated APs (AP102, AP103). This processing can be realized by the control unit 202 executing the program stored in the storage unit 201. Also, this processing may be realized by a processor included in the communication unit 206, for example. AP102 to AP103 start this processing in response to determining to transmit the capability information indicating the preparation time required for UL communication. Note that hereinafter, the description will be made assuming that AP102 is the execution entity of the processing, but AP103 also performs the same processing.

[0046] The AP 102 specifies (for example, calculates) a preparation time required for UL communication in the own device, and generates capability information indicating the preparation time (S901). The preparation time indicated here may be the minimum value of the time required for UL communication. Then, the AP 102 generates a frame including the capability information, and transmits it to the Coordinator AP (S902). For example, information as described with reference to any one 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 specify the length of padding, such as the number of connected STAs and information capable of specifying the communication load of the connected STAs. The Coordinator AP (AP 101) may obtain information used to specify the length of padding, such as information indicating the load, from the Coordinator AP by a frame separate from the frame in which the capability information is transmitted. In one example, the Coordinator AP may notify information on the connection form with the Coordinator AP. For example, when the connection form is a wired connection, it is assumed that the processing load is lower than that of a wireless connection. For this reason, information on the connection type, such as "wired connection" or "wireless connection", may be notified from the Coordinator AP to the Coordinator AP.

[0047] In this manner, the Coordinated AP can transmit capability information required to determine the length of padding to be added to the trigger frame to the Coordinated AP. The Coordinated 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 Coordinated AP. Even if the Coordinated AP does not receive a request frame, the Coordinated AP may decide to start transmitting capability information based on, for example, a user operation. The Coordinated AP may start transmitting capability information using, for example, a Beacon frame when it starts functioning as an AP.

[0048] The present invention can also be implemented by supplying a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be implemented by a circuit (for example, an ASIC) that realizes one or more functions.

[0049] (Summary of Embodiments) Summarizing at least a part of the above-described embodiments, it is as follows. (Item 1) A communication device that functions as an access point compliant with the IEEE802.11 series standards, a receiving means for receiving a wireless frame including capability information indicating a preparation time required for preparation for transmission of a signal to the communication device from one or more other communication devices functioning as an access point; a 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; a transmitting means for transmitting the trigger frame including the Padding having 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; A communication device characterized by comprising: (Item 2) 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. The communication device according to Item 1, characterized by this. (Item 3) The management frame is a Beacon frame or an Action frame spontaneously transmitted from each of the one or more other communication devices. The communication device according to Item 2, characterized by this. (Item 4) The management frame is a Probe Response frame or an Action frame, The receiving means receives, from each of the one or more other communication devices, the Probe Response frame including the capability information by transmitting a Probe Request frame including information indicating a request for the capability information, and receives, from each of the one or more other communication devices, a second Action frame including the capability information by transmitting a first Action frame including information indicating a request for the capability information. The communication device according to item 2 or 3, characterized in that. (Item 5) The management frame is a Probe Response frame, When the receiving means transmits a Probe Request frame not including information indicating a request for the capability information, the receiving means receives, from each of the one or more other communication devices, the Probe Response frame in which each of the one or more other communication devices spontaneously includes the capability information. The communication device according to item 2 or 3, characterized in that. (Item 6) 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 items 1 to 5, characterized in that. (Item 7) The Trigger Frame MAC Padding Duration subfield includes a bit indicating whether to indicate the preparation time for communication between an access point and another access point or the preparation time for communication between an access point and a station. The communication device according to item 6, characterized in that. (Item 8) 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 included in a field indicating the capability information in the wireless frame. The communication device according to any one of items 1 to 5, characterized in that. (Item 9) A communication device that functions as an access point compliant with the IEEE802.11 series of standards, transmission means for transmitting a wireless frame including capability information indicating the preparation time required for preparing to transmit a signal to another communication device that functions as an access point; receiving 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; having Based on receiving the trigger frame, the transmission means transmits data to the other communication device. A communication device characterized by the above. (Item 10) The communication device according to item 9, wherein the transmission means transmits a management frame including the capability information to the other communication device. (Item 11) The management frame is a Beacon frame or an Action frame, The communication device according to item 10, wherein the transmission means spontaneously transmits the management frame to the other communication device. (Item 12) The management frame is a Probe Response frame or an Action frame, When a Probe Request frame including information indicating a request for the capability information is received from the other communication device, the transmission means transmits the Probe Response frame including the capability information to the other communication device, and when a first Action frame including information indicating a request for the capability information is received from the other communication device, the transmission means transmits a second Action frame including the capability information to the other communication device. The communication device according to item 10 or 11, characterized by the above. (Item 13) The management frame is a Probe Response frame, The transmitting means transmits the Probe Response frame that spontaneously includes the capability information to the other communication device when a Probe Request frame that does not include information indicating a request for the capability information is received from the other communication device. The communication device according to item 10 or 11, characterized by this. (Item 14) The information indicating the preparation time is stored in the Trigger Frame MAC Padding Duration subfield included in the field indicating the capability information in the wireless frame. The communication device according to any one of items 9 to 13, characterized by this. (Item 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 item 14, characterized by this. (Item 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 the field indicating the capability information in the wireless frame. The communication device according to any one of items 9 to 13, characterized by this. (Item 17) A communication method executed by a communication device functioning as an access point compliant with the IEEE802.11 series standard, Receiving a wireless frame including capability information indicating the preparation time required for preparation for transmission of a signal from one or more other communication devices functioning as access points to the communication device; 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; When it is necessary to receive data from the one or more other communication devices, transmitting the trigger frame including the Padding of the determined length to the one or more other communication devices; A communication method characterized by including the above. (Item 18) A communication method executed by a communication device functioning as an access point compliant with the IEEE802.11 series standards, 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; 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 of a length determined based on the capability information; Transmitting data to the other communication device based on receiving the trigger frame; A communication method characterized by including the above. (Item 19) A program for causing a computer to function as each means included in the communication device according to any one of Items 1 to 16.

[0050] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Explanation of Signs

[0051] 301: Frame processing unit, 302: Padding processing unit, 303: Frame transmission / reception unit

Claims

1. A communication device that functions as an access point compliant with the IEEE 802.11 series standards, receiving means for receiving a wireless frame including capability information indicating a preparation time required for preparation 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 determined length of Padding to the one or more other communication devices when data from the one or more other communication devices is to be received; A communication device characterized by comprising the above.

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, The receiving means receives the Probe Response frame including the capability information from each of the one or more other communication devices by transmitting a Probe Request frame including information indicating a request for the capability information, 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, characterized by the above.

5. The management frame is a Probe Response frame, The communication device according to claim 2, wherein 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.

6. 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 claim 1, characterized in that.

7. The Trigger Frame MAC Padding Duration subfield includes a bit indicating whether to indicate 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 6, characterized in that.

8. 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 claim 1, characterized in that.

9. A communication device that functions as an access point compliant with the IEEE 802.11 series standards, 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; Receiving 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; Having Based on receiving the trigger frame, the transmission means transmits data to the other communication device. The communication device, characterized in that.

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

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

12. The management frame is a Probe Response frame or an Action frame, 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 the 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, characterized in that.

13. The management frame is a Probe Response frame, 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, characterized in that.

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 claim 9, characterized in that.

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, characterized in that.

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 claim 9, characterized in that.

17. A communication method executed by a communication device functioning as an access point compliant with the IEEE 802.11 series standard, Receiving a wireless frame including capability information indicating a preparation time required for preparation for transmission of a signal from one or more other communication devices functioning as an access points to the communication device, Determining the length of Padding in a trigger frame for causing one or more other communication devices to transmit a signal to the communication device based on the capability information; When data is to be received from the one or more other communication devices, transmitting the trigger frame including the Padding of the determined length to the one or more other communication devices; A communication method characterized by including the above.

18. A communication method executed by a communication device functioning as an access point compliant with the IEEE 802.11 series standards, the method including: 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; 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 of a length determined based on the capability information; Transmitting data to the other communication device based on receiving the trigger frame; A communication method characterized by including the above.

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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