Communication device, communication method, and program

Abstract

To appropriately share information on a period during which a plurality of access points operate in cooperation with each other.SOLUTION: A communication device functioning as an access point conforming to the IEEE802.11 standard generates a predetermined frame including information representing a period during which the communication device should operate in cooperation with another communication device functioning as an access point, with reference to the timing when a Beacon frame is transmitted by the communication device, and transmits the frame including the information to another access point to perform communication in cooperation with the another access point in the period.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cooperative communication technology using a plurality of access points.

Background Art

[0002] As a communication standard for wireless LAN (Local Area Network), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards is known. The IEEE 802.11 series of standards includes standards such as IEEE 802.11a / b / g / n / ac / ax / be / bn. For the IEEE 802.11be standard and its successor standards, the introduction of a technology for improving communication efficiency and throughput by causing a plurality of access points (hereinafter, may be referred to as "AP") to operate cooperatively has been considered (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a plurality of APs perform cooperative operation for communication, it is necessary to share information on the period of cooperative operation among the plurality of APs.

Means for Solving the Problems

[0005] The present invention provides a technology for appropriately sharing information on a period of cooperative operation among 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 of the IEEE 802.11 standard. Based on the timing when a Beacon frame is transmitted by the communication device, generation means for generating a predetermined frame including information representing a period during which the communication device should cooperate with other communication devices functioning as access points, and communication means for communicating in cooperation with the other access points during the period by transmitting the predetermined frame including the information to the other access points.

Effect of the Invention

[0007] According to the present invention, information on a period of cooperative operation can be appropriately shared among a plurality of access points.

Brief Description of the Drawings

[0008]

Figure 1

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Figure 11

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted 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 IEEE802.11bn standard. Note that IEEE is an abbreviation for Institute of Electrical and Electronics Engineers. In the following, a WLAN compliant with the IEEE802.11bn standard is assumed for explanation, but it is not limited thereto, and the methods described below may be applied to communications compliant with other wireless communication standards. For example, the methods described below may be applicable to communications compliant with any of the successor standards of the IEEE802.11be standard. Also, the following methods may be applied to communication standards other than WLAN. In the example of FIG. 1, two access points (AP101 and AP102) and two stations (STA111 and STA112) are shown as communication devices for performing wireless communication. In the following, the access point is referred to as AP, and the station is referred to as STA. Also, the example of FIG. 1 is merely 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 three or more. Also, the number of STAs may be one or three or more. Note that AP101, AP102, STA111, and STA112 are configured to be able to perform communication compliant with the IEEE802.11 series standards other than the IEEE802.11bn standard. In the following, the roles of AP101 and AP102 are described separately, but the roles of AP101 and AP102 may be interchanged. AP101 and AP102 can operate in both the roles of AP101 and AP102 described below.

[0011] AP101 and AP102 each form and manage a network called a Basic Service Set (BSS). By participating in the BSS managed by either AP, STA111 and STA112 can communicate with the AP that forms the BSS. In one example, STA111 may participate in the BSS managed by AP101, and STA112 may participate in the BSS managed by AP102. Also, STA111 and STA112 may participate in both the BSS managed by AP101 and the BSS managed by AP102.

[0012] Also, AP101 - AP102 and STA111 - STA112 can be configured to support wireless communication based on other communication standards such as Bluetooth (R), NFC, Bluetooth (R) LE (Low Energy). Here, NFC is the abbreviation of Near Field Communication. Also, AP101 - AP102 may be configured to support wired communication using an Ethernet (R) cable or wired communication using an optical fiber. AP101 - AP102 can be, for example, a wireless LAN router or a personal computer (PC), etc., but is not limited thereto. Also, STA111 - STA112 can be, for example, a wearable device such as a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, smart glasses, etc., but is not limited thereto. AP101 - AP102 and STA111 - STA112 may be information processing devices such as a wireless chip that supports at least either transmission or reception of a wireless frame conforming to the IEEE802.11 series standard.

[0013] In the wireless communication system according to this embodiment, it is assumed that communication involving cooperative operation between APs is performed for improving the utilization efficiency of the wireless medium, reducing the transmission delay, extending the communication distance, etc. That is, AP101 and AP102 cooperate to communicate with STA111 or STA112. Hereinafter, this communication is called AP cooperative communication.

[0014] AP coordinated communication includes, for example, coordinated spatial reuse (CSR). In CSR, multiple APs cooperate to perform communication using the spatial reuse function in the IEEE 802.11 series of standards since the IEEE 802.11ax standard. Note that in CSR, multiple APs can cooperate to perform communication using the spatial reuse function, for example, only for a predetermined period. In addition, AP coordinated communication includes coordinated orthogonal frequency multiple access (OFDMA) / time division multiple access (TDMA). In coordinated OFDMA / TDMA, for example, multiple APs divide and share a plurality of Resource Units (RUs) and transmission opportunities (TXOPs) included in one OFDM symbol. In addition, AP coordinated communication includes coordinated beamforming (CBF). In CBF, by cooperation of multiple APs, for example, communication between a certain AP and an STA and communication between another AP and the STA are spatially multiplexed. In addition, AP coordinated communication includes joint transmission / reception (JT / JR) OFDMA / TDMA. In JT / JR OFDMA / TDMA, multiple APs cooperate to transmit and receive the same signal with one STA while performing multiple access by OFDMA / TDMA, for example. These cooperative operations are executed during a predetermined period determined by any one of the APs.

[0015] In AP cooperative communication, an AP operates in either the role of a sharing AP that leads the cooperative communication or a shared AP that is controlled by the sharing AP. The period during which the above-described cooperative operation is executed can be determined, for example, by the sharing AP. Here, the sharing AP needs to notify the shared AP of the information on that period in order to perform AP cooperative communication. On the other hand, each AP has its own individual timer, and those timers operate independently. For this reason, there is no common time between the sharing AP and the shared AP. Therefore, it is not possible to use time information or the like to notify the shared AP of the period during which the sharing AP performs cooperative operation. For this reason, in the present embodiment, based on the transmission timing of the Beacon frame periodically transmitted by the AP, information such as the time difference (offset) from that timing to the timing at which cooperative communication starts and information on the period during which the cooperative communication is performed is shared. For example, the sharing AP notifies the shared AP of information indicating at what timing cooperative communication is to be performed from the timing at which the own device transmits the Beacon frame and the length of the period during which the cooperative communication is to be performed. Then, the shared AP can specify the period during which cooperative communication is to be executed based on that information and the reception timing of the Beacon frame from the sharing AP.

[0016] Hereinafter, an example of the configuration of the AP that performs such processing and the flow of the processing executed by the AP will be described.

[0017] (Device Configuration) Using FIG. 2, a configuration example of communication devices (AP101 to AP102) that function as APs according to the present embodiment will be described. FIG. 2 shows an example of the hardware configuration 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 an antenna 207.

[0018] 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, as well as 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. In addition to or instead of memories such as ROM and RAM, 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, and a DVD. Further, the storage unit 201 may include a Solid State Drive (SSD). Also, the storage unit 201 may include a plurality of memories and the like.

[0019] The control unit 202 is configured by one or more processors such as a CPU or an MPU, and controls the entire AP by executing, for example, a computer program stored in the storage unit 201. 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 (other APs and STAs). 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). Also, the control unit 202 may include a plurality of processors such as a multi-core, and execute processes such as controlling the entire AP by the plurality of processors. Further, the control unit 202 may be configured by an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

[0020] 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 APs such as AP101 to AP102 using protocols such as SMB, FTP, and WebDAV. Then, another communication device such as an STA can upload a file to the storage service or download a file in the storage. Data communication for uploading and downloading at this time can be performed using a wireless communication function conforming to, for example, the IEEE802.11 series standards.

[0021] 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, and the like. 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 incorporated in the AP respectively, or may be configured as an external device connected to the AP.

[0022] The communication unit 206 controls wireless communication compliant with the IEEE802.11 series standards and controls Internet Protocol (IP) communication. The communication unit 206 executes transmission and reception of wireless frames of the IEEE802.11 standard in cooperation with the antenna 207, for example. The antenna 207 is an antenna capable of transmitting and receiving signals in at least one 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 this embodiment, one antenna 207 is shown, but a plurality of 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, the AP may have a plurality of communication units 206 respectively corresponding to the plurality of antennas. Note that when the AP supports communication standards such as the NFC standard and the Bluetooth (registered trademark) standard, a communication unit 206 configured to control wireless communication compliant with these communication standards may be prepared.

[0023] Fig. 3 shows an example of the functional configuration of the AP. As its functional configuration, the AP has a communication control unit 301, a Sharing AP function unit 302, and a Shared AP function 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 function unit in the communication unit 206. Note that Fig. 3 is a diagram for explaining the main functions of the present embodiment, and other functions are omitted. For this reason, the AP can naturally have functions for establishing a connection with a STA as a normal AP and for control of communication, as well as functions generally possessed by communication devices. 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.

[0024] The communication control unit 301 performs communication control for wireless communication compliant with IEEE 802.11 series standards such as the IEEE 802.11bn standard. For example, the communication control unit 301 executes control for generating and transmitting wireless frames such as control frames like Beacon frames and data frames to be transmitted to the communication partner device, and receiving and decoding wireless frames transmitted from other APs. Note that the communication control unit 301 performs control such as inter-AP communication between other APs in addition to connection and communication with the STA. The Sharing AP function unit 302 executes communication control as a sharing AP. The Sharing AP function unit 302 determines, for example, the period during which AP cooperative communication is performed. Then, the Sharing AP function unit 302 generates information representing the specified period based on the transmission timing of the Beacon frame, and transmits it to other APs operating as shared APs in AP cooperative communication via the communication control unit 301. Also, the Sharing AP function unit 302 executes various controls related to AP cooperative communication such as transmitting a trigger frame for data transmission by cooperative communication to other APs operating as shared APs. The Shared AP function unit 303 executes communication control as a shared AP. The Shared AP function unit 303 acquires, for example, information indicating the period for performing cooperative communication based on the transmission timing of the Beacon frame from other APs functioning as sharing APs in AP cooperative communication, and specifies that period. Then, the Shared AP function unit 303 communicates in cooperation with other APs functioning as sharing APs during that period. For example, the Shared AP function unit 303 can receive a trigger frame transmitted from a sharing AP and use the information in the trigger frame to transmit a data frame to the STA.

[0025] Note that the STA has the hardware configuration and functional configuration of a normal STA. The details thereof are omitted here.

[0026] (Communication flow) The process of AP cooperative communication according to this embodiment will be described. FIG. 4 shows an example of the communication process flow when AP101 and AP102 in FIG. 1 cooperate to transmit data frames to STA111 and STA112. When three or more APs cooperate to communicate, one AP functions as a sharing AP, and the other (two or more) APs function as shared APs. Then, similar to the processes described later, the shared AP identifies the period during which it performs cooperative communication based on the information from the sharing AP, and performs AP cooperative communication within that period.

[0027] In response to the wireless communication function by the wireless LAN being effectively set in AP101 and AP102 respectively, they start transmitting Beacon frames. AP101 and AP102 periodically transmit Beacon frames at a timing called Target Beacon Transmission Time (TBTT). Note that the transmission period (Beacon Interval (BI)) of the Beacon frame in each AP can be set individually. After transmitting Beacon frame 401, AP101 transmits the next Beacon frame 402 after the elapse of BI. Similarly, Beacon frame 403 is transmitted after the elapse of BI from the transmission of Beacon frame 402, and Beacon frame 404 is transmitted after the elapse of BI from the transmission of Beacon frame 403. Also, in one example, AP102 transmits Beacon frames at a different timing (TBTT) and BI from AP101. AP102 transmits Beacon frame 406 after the elapse of BI from the transmission of Beacon frame 405, and transmits Beacon frame 407 after the elapse of BI from the transmission of Beacon frame 406.

[0028] Here, when AP101 decides to perform cooperative communication with AP102, it starts the cooperative operation request phase 411. Here, with reference to FIG. 5, an example of the processing flow of the cooperative operation request phase 411 will be described. In the cooperative operation request phase 411, AP101 transmits a cooperative operation request frame 501 to AP102. The cooperative operation request frame 501 includes a request for AP102 to perform cooperative operation with AP101, the type of cooperative operation, and information indicating the period during which the cooperative operation should be performed. FIG. 6 shows a configuration example of the information element indicating the period during which the cooperative operation should be performed. As shown in FIG. 6, this information element can be described in the form of an Information Element (IE) defined in the IEEE802.11 standard. Note that this is just an example, and information elements for specifying the period during which the cooperative operation should be performed may be described in other formats. In the example of FIG. 6, this information element includes Element ID601 and Length602. Further, this information element includes Multi-AP Count603, Multi-AP Period604, Multi-AP Duration605, and Multi-AP Offset606.

[0029] Element ID601 is a field indicating the identifier of this IE. Length602 is a field indicating the length of this IE. Multi-AP Count603 is a field indicating the number of TBTTs of AP101 that exist from when the cooperative operation request frame 501 is transmitted until the period during which the cooperative operation should be performed starts. That is, Multi-AP Count603 is information indicating the number of times the Beacon frame is transmitted after the transmission of the cooperative operation request frame 501 until the period during which the first cooperative operation is performed starts. In the example of Figure 4, between the cooperative operation request phase 411 when the cooperative operation request frame 501 is transmitted and the first cooperative operation phase 441 when the cooperative operation is actually performed, the Beacon frame 402 and the Beacon frame 403 are transmitted. That is, the number of times the Beacon frame is transmitted between when the cooperative operation request frame 501 is transmitted and the period during which the cooperative operation is performed (cooperative operation phase 441) is 2 times (2 TBTTs exist). Therefore, in this case, the value "2" is stored in Multi-AP Count603. Note that this is just an example. For example, it may be indicated that the number of times the Beacon frame is transmitted between when the cooperative operation request frame is transmitted and the period during which the cooperative operation is performed is "n times" by the value "n - 1". If the Beacon frame is not transmitted after the transmission of the cooperative operation request frame, it is not necessary to express "0 times" because the period of the cooperative operation based on the timing of the Beacon frame cannot be specified. Multi-AP Period604 is a field indicating whether the period during which the cooperative operation should be performed is periodically repeated and the number of set periods. For example, when the value "0" is stored in this field, it is indicated that the period during which the cooperative operation should be performed is set only once after the cooperative operation request frame 501 is transmitted. For example, in the example of Figure 4, if only the cooperative operation phase 441 is set and the cooperative operation phase 442 is not set, the value "0" is stored in Multi-AP Period604. When a non-zero value is stored in this field, the value specifies the number of times the period during which the cooperative operation should be performed is set.Note that the period during which the cooperative operation should be performed is set in the time interval (BI) sandwiched between two Beacon frames. Therefore, the number of times the period during which this cooperative operation should be performed is set can be specified by the number of BIs from the transmission of the cooperative operation request frame 501 until the completion of the cooperative operation. In the example of FIG. 4, since two periods, i.e., the cooperative operation phase 441 and the cooperative operation phase 442, are set in two BIs, "1" is stored in the Multi-AP Period 604. Also, when a non-zero value is stored in this field, it indicates that the period during which the cooperative operation is performed comes periodically, and the period may be indicated by that non-zero value. Here, the period may be expressed in units of the length of the BI. For example, when there is a period during which the cooperative operation is performed in all BIs, the period is one BI length, so the value "1" may be stored. Also, when there is a period during which the cooperative operation is performed every other BI, the period is two BI lengths, so the value "2" may be stored. Also, when a non-zero value is stored in this field, the value may indicate both the number of times the period during which the cooperative operation should be performed is set and the period. In this case, this field may be composed of two or more sub-fields including a sub-field indicating the number of times the period during which the cooperative operation should be performed and a sub-field indicating the period. The Multi-AP Duration 605 is a field indicating the length of the period during which the cooperative operation should be performed. The Multi-AP Offset 606 is a field indicating the time difference (offset) between the timing at which the period during which the cooperative operation should be performed starts and the TBTT of the AP 101 immediately before that period. That is, in the example of FIG. 4, the time difference from the transmission timing (TBTT) of the Beacon frame 403 immediately before the cooperative operation phase 441 is stored in the Multi-AP Offset 606. Similarly, the cooperative operation phase 442 starts at the timing after the elapse of the offset stored in the Multi-AP Offset 606 from the Beacon frame 404. That is, when a non-zero value is stored in the Multi-AP Period 604, the period during which the cooperative operation is performed can be set at the same period as the transmission period of the Beacon frame or an integer multiple thereof.Note that this is just an example, and the period in which a plurality of periods are set may be set separately from the period of the Beacon frame.

[0030] Returning to FIG. 5, when the AP 102 receives the cooperative operation request frame 501, as a response to that frame, the AP 102 transmits a cooperative operation response frame 502 to the AP 101. This cooperative operation response frame 502 includes information indicating whether to accept the cooperative operation indicated by the cooperative operation request frame 501. Further, the cooperative operation response frame 502 may include information proposing the type and period of the cooperative operation, similar to the cooperative operation request frame 501. In this case, the cooperative operation response frame 502 may include information explicitly indicating that it proposes the type and period of the cooperative operation. Further, the cooperative operation response frame 502 may include information rejecting the request by the cooperative operation request frame 501. That is, acceptance or proposal of the type and period of the cooperative operation may not be performed. Note that the cooperative operation response frame 502 indicating acceptance of the cooperative operation may be a frame indicating the same type and period as the type and period of the cooperative operation indicated by the cooperative operation request frame 501. In this case, a cooperative operation response frame 502 including information different from the information indicated by the cooperative operation request frame 501 may be treated as a frame proposing the type and period of the cooperative operation based on that information. That is, the cooperative operation response frame 502 may not include explicit information indicating that it proposes the type and period of the cooperative operation. Also, in this case, the cooperative operation response frame 502 may indicate rejection of the cooperative operation request by including a predetermined value as the type and period of the cooperative operation.

[0031] When AP101 receives a cooperative operation response frame 502 for which it has not been shown that the cooperative operation is rejected, it transmits a cooperative operation confirmation frame 503 to AP102. The cooperative operation confirmation frame 503 may include information indicating that the cooperative operation response frame 502 has been received normally and that the cooperative operation is to be performed, for example. Further, the cooperative operation confirmation frame 503 may include information indicating whether or not to accept the proposal if the cooperative operation response frame 502 includes a proposal regarding the cooperative operation. Here, the cooperative operation confirmation frame 503 including information not accepting the proposal may implicitly indicate not to perform the cooperative operation. Also, the cooperative operation confirmation frame 503 may include information explicitly indicating acceptance of the proposal when the proposal is accepted, or instead of or in addition to that, may include the same information as the type and period of the cooperative operation proposed in the cooperative operation response frame 502. Note that when a cooperative operation response frame 502 indicating acceptance of the cooperative operation has been received, information indicating acceptance of the cooperative operation may be included in the cooperative operation confirmation frame 503 in order to indicate that cooperative communication is to be performed with the content of the cooperative operation request frame 501.

[0032] When AP102 receives the cooperative operation confirmation frame 503 indicating acceptance of the cooperative operation, AP101 and AP102 are considered to have agreed to perform the cooperative operation. Note that AP101 may recognize that the cooperative operation confirmation frame 503 has been received by AP102 by receiving an Acknowlegement (ACK) frame (not shown) transmitted by AP102 or the like.

[0033] As shown in FIG. 5, in the cooperative operation request phase 411, AP101 requests a cooperative operation from AP102 and negotiates with AP102. When AP101 and AP102 reach an agreement on the cooperative operation by transmitting and receiving each of the above frames, or when either AP rejects the cooperative operation without reaching an agreement on the cooperative operation, this cooperative operation request phase 411 ends. In this embodiment, the AP (AP101) that starts the cooperative operation request phase 411 is called a sharing AP, and the AP (AP102) that responds to the request from the sharing AP is called a shared AP.

[0034] Returning to FIG. 4, when AP101 and AP102 reach an agreement on the cooperative operation, they transition to the sounding phase 421. In the sounding phase 421, according to the type of cooperative operation, the necessary sounding procedures between communication devices are executed. As a result, the transfer function regarding radio wave propagation between communication devices necessary for the cooperative operation is specified. For example, AP101 and AP102 can specify the transfer function regarding radio wave propagation between them and STA111 and STA112. Note that the sounding phase 421 can be executed only when it is necessary to execute the sounding procedure according to the type of cooperative operation.

[0035] When the sounding phase 421 ends, it transitions to the inter-AP data sharing phase 431. In the inter-AP data sharing phase 431, when a cooperative operation that requires sharing data between AP101 and AP102 is performed, data sharing between those APs is performed. For example, AP101 and AP102 execute data sharing when performing joint transmission / reception (JT / JR) OFDMA / TDMA. Note that the inter-AP data sharing phase 431 can be executed only when data sharing is necessary according to the type of cooperative operation.

[0036] When the AP - to - AP data sharing phase 431 ends, the cooperative operation phase 441 is started during the period agreed upon in the cooperative operation request phase 411. The cooperative operation phase may be repeated periodically. FIG. 4 shows an example in which, following the cooperative operation phase 441, the cooperative operation phase 442 is repeatedly set as the second cooperative operation phase. In the cooperative operation phase, the cooperative operation is executed according to the content agreed upon in the cooperative operation request phase 411.

[0037] Here, with reference to FIG. 7, an example of the flow of processing executed in the cooperative operation phase 441 and the cooperative operation phase 442 will be described. When the cooperative operation phase is started, AP101 transmits a trigger frame 701 to AP102. Thereafter, AP101 transmits a data frame 702 to at least one of STA111 and STA112. When AP102 receives the trigger frame 701 from AP101, it transmits a data frame 703 to at least one of STA111 and STA112. The transmission of the data frame 702 and the data frame 703 is executed using the type of cooperative operation agreed upon in the cooperative operation request phase 411. When STA111 receives the data frame 702, it transmits an ACK frame 704 (Block ACK frame in FIG. 5) to AP101. Also, when STA111 receives the data frame 703, it transmits an ACK frame 705 to AP102. Similarly, when STA112 receives at least one of the data frame 702 and the data frame 703, it transmits an ACK frame 705 (Block ACK frame in FIG. 5) to the AP that is the source of the data frame.

[0038] Note that in FIGS. 5 and 7, except for the ACK frames 704 and 705, ACK frames indicating that a frame has been received are not illustrated. However, when any communication device receives any frame, subsequently, it may transmit an ACK frame to the communication device that is the source of the frame.

[0039] (Operation of AP) FIG. 8 is a diagram showing an example of a processing flow executed by communication devices (AP101, AP102) that function as APs. The processing in FIG. 8 starts, for example, when the wireless LAN function of the communication device is started (activated) in response to the power-on of the communication device or the input of information to the communication device via the input unit 204 by the user. Note that the order of each processing step described below may be changed, or a plurality of processing steps may be executed in parallel. Also, some processing steps may be omitted, or may be replaced with processing steps having the same general idea but different details.

[0040] The AP starts transmitting a Beacon frame (S801). Here, the transmission period of the Beacon frame is determined based on information input by the user to the input unit 204, information stored in advance in the storage unit 201, and the like. Then, the AP determines whether it has received any wireless frame (S802). If the AP has received any wireless frame (YES in S802), the process proceeds to S803, and if it has not received any wireless frame (NO in S802), the process proceeds to S806.

[0041] In S803, the AP determines whether the received wireless frame is a cooperative operation request frame. If the AP has received a cooperative operation request frame (YES in S803), it executes a shared AP process, which will be described later with reference to FIG. 10 (S804). On the other hand, if the AP has received a wireless frame that is not a cooperative operation request frame (NO in S803), it executes processing corresponding to the received wireless frame (S805). After executing the processing in S804 or S805, the AP proceeds to S806.

[0042] In S806, the AP determines whether there is a wireless frame to be transmitted. For example, the AP checks whether there is a wireless frame to be transmitted in any of the storage unit 201, the control unit 202, the functional unit 203, the input unit 204, and the communication unit 206. If the AP determines that there is a wireless frame to be transmitted (YES in S806), the process proceeds to S807. If it determines that there is no such wireless frame (NO in S806), the process proceeds to S810. In S807, the AP determines whether cooperative operation with other APs should be used for transmitting the wireless frame to be transmitted. If the AP determines that the wireless frame should be transmitted using cooperative operation (YES in S807), it executes the sharing AP process described later with reference to FIG. 9 (S808). On the other hand, if the AP determines that the wireless frame should be transmitted without using cooperative operation (NO in S807), it transmits the wireless frame alone without cooperating with other APs (S809). After executing the process of S808 or S809, the AP proceeds to S810. Note that in S807, the AP can determine whether to use AP cooperative communication for transmitting the wireless frame based on, for example, the congestion status of the wireless medium, the attribute of the data to be transmitted, the distance to the STA which is the transmission destination of the frame, etc. For example, the AP can determine to transmit the wireless frame using AP cooperative communication when the use efficiency of the wireless medium, the transmission delay, the communication distance, etc. become advantageous by performing AP cooperative communication.

[0043] In S810, the AP determines whether the wireless LAN function has been stopped (disabled), for example, by information input to the input unit 204 by the user. If the AP determines that the wireless LAN function has been disabled (YES in S810), it stops transmitting the Beacon frame (S811) and ends the process. On the other hand, if the AP determines that the wireless LAN function has not been disabled (NO in S810), the process returns to S802.

[0044] Subsequently, with reference to FIG. 9, an example of the flow of the sharing AP process executed in S808 will be described.

[0045] When the AP starts operating as a sharing AP, it transmits a cooperative operation request frame to other APs that should function as the shared AP (S901). This cooperative operation request frame contains information such as the type of cooperative operation and the period during which the cooperative operation should be performed. The AP determines whether it has received a cooperative operation response frame from the shared AP that contains information indicating acceptance of the content such as the type and period of the cooperative operation indicated in the cooperative operation request frame, or that contains a proposal for the type and period of the cooperative operation (S902). If the AP does not receive a cooperative operation response frame or receives a cooperative operation response frame that does not contain acceptance or a proposal for the type and period of the cooperative operation (NO in S902), it ends the process without performing the cooperative operation. Note that when the AP ends the process without performing the cooperative operation, it moves the process to S809 in FIG. 8 and can transmit wireless frames alone. Also, if the AP has not received a cooperative operation response frame that contains acceptance or a proposal for the type and period of the cooperative operation, it may return the process to S901 and repeatedly transmit the cooperative operation request frame.

[0046] When the AP receives a cooperative operation response frame including an acceptance or a proposal such as the type and duration of the cooperative operation (YES in S902), it determines whether to accept the cooperative operation indicated by the content of the cooperative operation response frame (S903). For example, when the AP receives a cooperative operation response frame indicating that the type and duration of the cooperative operation proposed in the cooperative operation request frame are accepted, the AP determines to accept the cooperative operation with that content. Also, for example, when the AP receives a cooperative operation response frame including a proposal for the type and duration of the cooperative operation, the AP determines whether to accept the proposal. The AP can determine whether to accept the proposal based on, for example, the congestion status of the wireless medium, the attributes of the data to be transmitted, the distance to the STA which is the destination of the frame, etc. For example, when the AP determines that advantageous effects such as improvement of the utilization efficiency of the wireless medium, shortening of the transmission delay, and shortening of the communication distance can be obtained when the proposal is accepted, the AP can determine to accept the proposal. Note that, for example, depending on the content of the proposal, even if communication can be performed under more advantageous conditions than the proposal when the requirements (e.g., required wireless quality, required delay, etc.) required when transmitting data can be satisfied, the AP may determine to accept the proposal.

[0047] When the AP determines not to accept the content of the cooperative operation response frame (NO in S903), the AP transmits a cooperative operation confirmation frame indicating that it does not accept the content indicated by the cooperative operation response frame to the shared AP (S910), and ends the process without performing the cooperative operation. Note that when the AP ends the process without performing the cooperative operation, the process proceeds to S809 in FIG. 8, and the AP can transmit a wireless frame alone. Also, when the AP has not received a cooperative operation response frame including an acceptance or a proposal such as the type and duration of the cooperative operation, the AP may return the process to S901 and repeatedly transmit the cooperative operation request frame.

[0048] When the AP determines to accept the content of the cooperative operation response frame (YES in S903), it sends a cooperative operation confirmation frame indicating acceptance of the content shown in the cooperative operation response frame to the shared AP (S904). Then, the AP executes the processing of the sounding phase and the processing of the inter-AP data sharing phase when it is determined necessary according to, for example, the type of cooperative communication (S905). Then, the AP waits for the start of the cooperative operation period (YES in S906), and after the period starts, it sends a trigger frame to the shared AP to cause the shared AP to send a data frame (S907). Then, the AP cooperates with the shared AP to send a data frame (S908). While the cooperative operation period continues (NO in S909), the AP repeatedly executes the processing of S907 and S908 to send the data to be transmitted in cooperation with the shared AP. When the cooperative operation period ends (YES in S909), the AP ends the processing of FIG. 9.

[0049] Subsequently, with reference to FIG. 10, an example of the flow of the shared AP processing executed in S804 will be described.

[0050] First, the AP operating as a shared AP checks the information such as the type and duration of the cooperative operation included in the cooperative operation request frame determined to be received in S802 and S803 of FIG. 8. Then, the AP determines whether to accept the type and duration of the cooperative operation or propose different content regarding the type and duration of the cooperative operation (S1001). If the AP does not accept the type and duration of the cooperative operation and does not make another proposal (NO in S1001), the AP transmits a cooperative operation response frame rejecting the cooperative operation (S1009) and ends the process. On the other hand, if the AP accepts or proposes the type and duration of the cooperative operation (YES in S1001), the process proceeds to S1002. In S1002, the AP transmits a cooperative operation response frame including information indicating acceptance of the content such as the type and duration of the cooperative operation shown in the cooperative operation request frame, or a proposal of content different from that shown in the cooperative operation request frame. Based on, for example, the congestion status of the wireless medium, the attributes of the data to be transmitted, the distance to the STA which is the destination of the frame, etc., the AP can determine whether to accept the content such as the type and duration of the cooperative operation shown in the cooperative operation request frame or propose different content. For example, if the AP can perform sufficiently good communication with the content shown in the cooperative operation request frame, the AP may determine to accept the cooperative communication with that content. Also, if the AP can present another type and duration of cooperative operation etc. that enables communication under better conditions than communicating with the content shown in the cooperative operation request frame, the AP may determine to propose that content to the sharing AP. Also, if the AP cannot perform communication with sufficient quality with the content shown in the cooperative operation request frame and furthermore cannot present another type and duration of cooperative operation etc., the AP may determine to reject the request for the cooperative operation.

[0051] After the AP sends a cooperative operation response frame including information indicating acceptance of the content such as the type and period of the cooperative operation included in the cooperative operation request frame or a proposal of another content, the AP waits for a cooperative operation confirmation frame from the sharing AP (S1003). Then, if the AP does not receive a cooperative operation confirmation frame indicating acceptance of the cooperative operation according to the content of the cooperative operation response frame from the sharing AP (NO in S1003), the AP simply ends the process. On the other hand, if the AP receives a cooperative operation confirmation frame indicating acceptance of the cooperative operation according to the content of the cooperative operation response frame from the sharing AP (YES in S1003), the process proceeds to S1004. In S1004, the AP executes, for example, the processing of the sounding phase and the processing of the inter-AP data sharing phase when it is determined to be necessary according to the type of cooperative communication. Then, the AP waits for the start of the cooperative operation period (YES in S1005), and after the period starts, waits for the reception of a trigger frame from the sharing AP (S1006). Then, when the AP receives the trigger frame (YES in S1006), the AP transmits a data frame in cooperation with the sharing AP (S1007). While the cooperative operation period continues (NO in S1008), the AP transmits the data to be transmitted in cooperation with the sharing AP in response to the trigger frame from the sharing AP. When the cooperative operation period ends (YES in S1008), the AP ends the process of FIG. 10.

[0052] (Operation of STA) FIG. 11 is a diagram showing an example of a processing flow executed by communication devices (STA111, STA112) functioning as STAs. The processing in FIG. 11 starts (is activated) when the wireless LAN function of the communication device is started and connected to the AP in response to, for example, turning on the power of the communication device functioning as an STA or input of information to the communication device by the user via the input unit 204. Note that the order of each processing step described below may be changed, or a plurality of processing steps may be executed in parallel. Also, some processing steps may be omitted or replaced with processing steps having the same meaning but different details.

[0053] When the STA receives a certain frame (YES in S1101), it executes processing corresponding to that frame (S1102). Also, the STA determines whether there is a frame to be transmitted (S1003). The STA determines, for example, whether there is a frame to be transmitted to any of the storage unit 201, the control unit 202, the functional unit 203, the input unit 204, and the communication unit 206. When there is a frame to be transmitted, the STA transmits that frame (S1104). Then, the STA determines, for example, whether the wireless LAN function has been stopped (disabled) due to information input to the input unit 204 by the user or the like (S1105). When the STA determines that the wireless LAN function has been disabled (YES in S1105), it ends the processing. On the other hand, while the wireless LAN function has not been disabled (NO in S1105), the STA returns the processing to S1101.

[0054] Thus, according to this embodiment, in an environment where multiple APs cooperate, one of the multiple APs generates information on the period for performing the cooperative operation based on the timing of transmitting the Beacon frame and transmits it to other APs. According to this, even if multiple APs performing the cooperative operation do not hold common time information, they can mutually receive the Beacon frames, so that the period during which the cooperative operation should be performed can be specified based on the frames. Here, the information transmitted from an AP to other APs may include, for example, the number of TBTTs existing until the start of the period, the time difference (offset) from the transmission timing (TBTT) of the Beacon frame, and information indicating the length of the period. Further, this information may include information such as whether this period is periodically repeated, and the number and period of the Beacon Intervals (BIs) including this period. According to these, the period during which the cooperative operation should be performed can be flexibly expressed, and the period during which the cooperative operation should be performed can be flexibly set. In the above example, the case where only one period for performing the cooperative operation is set for one BI has been described, but it is not limited to this. For example, multiple periods for performing the cooperative operation may be set for one BI. In this case, for each of the multiple periods, the offset from the previous TBTT and the time length may be specified. In this case, for example, in the cooperative operation request frame, a plurality of IEs shown in FIG. 6 may be included, or information regarding a plurality of periods may be included in one IE. Further, in the above example, the case where the periods for performing the cooperative operation are respectively set in a plurality of consecutive BIs has been described, but for example, the periods for performing the cooperative operation may be set every predetermined number of BIs. In this case, for example, the number of TBTTs arriving between two periods for performing the cooperative operation may be notified. For example, in every other BI, when the cooperative operation should be performed, since two TBTTs arrive between two periods for performing the cooperative operation, information indicating "two times" may be notified.Note that these are just examples, and in other formats, information specifying the period during which cooperative operation should be performed may be expressed based on the timing of the Beacon frame.

[0055] Note that in the above example, the process of determining the type and period of cooperative communication among multiple APs that execute AP cooperative communication through negotiation using a cooperative operation request frame and a cooperative operation response frame has been described, but it is not limited to this. For example, the sharing AP may notify the shared AP of the determined period information, and the shared AP may always follow that determination. Also, in the above example, it has been described that the AP that transmits the cooperative operation request frame becomes the sharing AP, but the role determination between the sharing AP and the shared AP may be determined in advance through negotiation. Also, during that role determination, information on the period during which cooperative operation should be performed as described above may be shared.

[0056] Note that in the above example, an example in which the period during which cooperative operation is performed is expressed based on the transmission timing of the Beacon frame has been described, but it is not limited to this. For example, the start timing of the period may be specified by the time difference (offset) from the end of the cooperative operation request frame or the cooperative operation confirmation frame. Similarly in this case, information indicating the length of the period can be notified in the same way as the method based on the Beacon frame. Note that when cooperative operation is repeatedly executed periodically, information indicating the period is expressed using the Beacon frame, and when only one cooperative operation is executed, information indicating the period may be expressed based on the transmission timing of a cooperative operation request frame or the like. In this case, for example, the cooperative operation request frame may include information indicating which frame's transmission timing is used as a reference.

[0057] 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, ASIC) that realizes one or more functions.

[0058] (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 of the IEEE802.11 standard, generation means for generating a predetermined frame including information representing a period during which it should cooperate with other communication devices functioning as access points, based on the timing at which a Beacon frame is transmitted by the communication device; communication means for communicating in cooperation with the other communication device during the period by transmitting the predetermined frame including the information to the other communication device; A communication device, characterized by comprising: (Item 2) The communication device according to item 1, wherein the predetermined frame is a first frame that requests the other communication device to cooperate with the communication device. (Item 3) The communication means receives, from the other communication device, a second frame that responds to the first frame and includes information representing a period proposed by the other communication device as a period during which the communication device and the other communication device should perform cooperative communication, based on the timing at which a Beacon frame is transmitted by the communication device; communicates in cooperation with the other communication device during the period when accepting the period indicated by the information included in the second frame; The communication device according to item 2, characterized by: (Item 4) The communication means, when receiving from the other communication device a second frame that responds to the first frame and indicates acceptance of cooperative communication with the communication device during the period indicated in the first frame, communicates in cooperation with the other communication device during that period. The communication device according to item 2, characterized in that. (Item 5) A communication device that functions as an access point of the IEEE802.11 standard, Receiving means for receiving from the other communication device a predetermined frame including information expressing a period during which the communication device should cooperate, based on the timing at which a Beacon frame is transmitted by the other communication device functioning as an access point; Specifying means for specifying the period based on the information; Communication means for communicating in cooperation with the other communication device during the period when accepting cooperative operation with the other communication device during the period; A communication device, characterized by comprising. (Item 6) The predetermined frame is a first frame that requests a cooperative operation between the other communication device and the communication device from the other communication device. The communication device according to item 5, characterized in that. (Item 7) The communication means, Transmits to the other communication device a second frame that responds to the first frame and includes information expressing a period proposed as the period during which the communication device and the other communication device should perform cooperative communication, based on the timing at which the other communication device transmits a Beacon frame, When the period indicated by the information included in the second frame is accepted by the other communication device, communicates in cooperation with the other communication device during that period. The communication device according to item 6, characterized by that. (Item 8) The communication means is a second frame that responds to the first frame, and when the second frame indicating acceptance of cooperative communication with the other communication device during the period indicated in the first frame is transmitted to the other communication device, communication is performed in cooperation with the other communication device during that period. The communication device according to item 6, characterized in that. (Item 9) The information includes information indicating the number of times the Beacon frame is transmitted from when the predetermined frame is transmitted until the first period starts. The communication device according to any one of items 1 to 8, characterized in that. (Item 10) The information includes information on the time difference from the Target Beacon Transmission Time (TBTT) of the Beacon frame immediately before the period starts to the timing when the period starts. The communication device according to any one of items 1 to 9, characterized in that. (Item 11) The information includes information indicating the length of the period. The communication device according to any one of items 1 to 10, characterized in that. (Item 12) The information includes information indicating whether the period is periodically and repeatedly set. The communication device according to any one of items 1 to 11, characterized in that. (Item 13) When the period is repeatedly set, the communication device according to item 12, further including information indicating the number of times the period is set. (Item 14) When the period is repeatedly set, the communication device according to item 12 or 13, further including information indicating the period in which the period is set. (Item 15) A communication method executed by a communication device functioning as an access point of the IEEE802.11 standard, Based on the timing when the Beacon frame is transmitted by the communication device, generate a predetermined frame including information representing a period during which cooperation should be performed with other communication devices functioning as access points; By transmitting the predetermined frame including the information to the other communication device, communicate in cooperation with the other communication device during the period; A communication method characterized by including the above. (Item 16) A communication method executed by a communication device functioning as an access point in the IEEE 802.11 standard, Based on the timing when the Beacon frame is transmitted by another communication device functioning as an access point, receive from the other communication device a predetermined frame including information representing a period during which cooperation should be performed with the communication device; Specify the period based on the information; When accepting cooperation with the other communication device during the period, communicate in cooperation with the other communication device during the period; A communication method characterized by including the above. (Item 17) A program for causing a computer provided in a communication device functioning as an access point in the IEEE 802.11 standard to execute the communication method according to Item 15 or 16.

[0059] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Explanation of Signs

[0060] 301: Communication control unit, 302: Sharing AP function unit, 303: Shared AP function unit

Claims

1. A communication device that functions as an access point according to the IEEE 802.11 standard, generating means for generating a predetermined frame including information representing a period during which it should cooperate with other communication devices functioning as access points, based on the timing at which the communication device transmits a Beacon frame; communication means for transmitting the predetermined frame including the information to the other communication devices, and communicating in cooperation with the other communication devices during the period; A communication device characterized by comprising the above.

2. The communication device according to claim 1, wherein the predetermined frame is a first frame that requests the other communication devices to cooperate with the communication device.

3. The communication means: receives from the other communication device a second frame that responds to the first frame and includes information representing a period proposed by the other communication device as a period during which the communication device and the other communication device should perform cooperative communication, based on the timing at which the communication device transmits a Beacon frame; communicates in cooperation with the other communication devices during the period when it accepts the period indicated by the information included in the second frame; The communication device according to claim 2, characterized by the above.

4. The communication device according to claim 2, wherein the communication means communicates in cooperation with the other communication devices during the period when it receives from the other communication device a second frame that responds to the first frame and indicates acceptance of cooperative communication with the communication device during the period indicated in the first frame.

5. A communication device that functions as an access point according to the IEEE 802.11 standard, receiving means for receiving from the other communication devices a predetermined frame including information representing a period during which the communication device should cooperate, based on the timing at which the other communication devices functioning as access points transmit a Beacon frame; specifying means for specifying the period based on the information; communication means for communicating in cooperation with the other communication devices during the period when it accepts cooperative operation with the other communication devices during the period; A communication device characterized by comprising the above.

6. The communication device according to claim 5, wherein the predetermined frame is a first frame that requests a cooperative operation between the other communication device and the communication device from the other communication device.

7. The communication means transmits to the other communication device a second frame that responds to the first frame and includes information representing a period during which the communication device and the other communication device should perform cooperative communication based on the timing at which the Beacon frame is transmitted by the other communication device, and communicates in cooperation with the other communication device during the period when the period indicated by the information included in the second frame is accepted by the other communication device. The communication device according to claim 6, characterized in that.

8. The communication means is a second frame that responds to the first frame, and when the second frame indicating acceptance of cooperative communication with the other communication device during the period indicated in the first frame is transmitted to the other communication device, communicates in cooperation with the other communication device during the period. The communication device according to claim 6, characterized in that.

9. The communication device according to any one of claims 1 to 8, wherein the information includes information indicating the number of times the Beacon frame is transmitted from when the predetermined frame is transmitted until the first period starts.

10. The communication device according to any one of claims 1 to 8, wherein the information includes information on the time difference from the Target Beacon Transmission Time (TBTT) of the Beacon frame immediately before the period starts to the timing when the period starts.

11. The communication device according to any one of claims 1 to 8, wherein the information includes information indicating the length of the period.

12. The communication device according to any one of claims 1 to 8, wherein the information includes information indicating whether the period is periodically repeated.

13. The communication device according to claim 12, further including information indicating the number of times the period is set when the period is repeatedly set.

14. The communication device according to claim 12, further comprising information indicating a period in which the period is set when the period is repeatedly set.

15. A communication method executed by a communication device functioning as an access point of the IEEE 802.11 standard, generating a predetermined frame including information representing a period during which cooperation with another communication device functioning as an access point should be performed, based on a timing at which a Beacon frame is transmitted by the communication device; transmitting the predetermined frame including the information to the other communication device, and performing communication in cooperation with the other communication device during the period; A communication method characterized by including the above.

16. A communication method executed by a communication device functioning as an access point of the IEEE 802.11 standard, receiving, from the other communication device, a predetermined frame including information representing a period during which cooperation with the communication device should be performed, based on a timing at which a Beacon frame is transmitted by the other communication device functioning as an access point; identifying the period based on the information; when accepting cooperation with the other communication device during the period, performing communication in cooperation with the other communication device during the period; A communication method characterized by including the above.

17. A program for causing a computer provided in a communication device functioning as an access point of the IEEE 802.11 standard to execute the communication method according to claim 15 or 16.

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