Communication device, communication method, and program

Abstract

To appropriately communicate frames between an access point (AP) and a designated station (STA) in communication sharing a transmission opportunity (TXOP) acquired by the AP with the STA.SOLUTION: A communication device operates as a role of building a wireless network, transmits a trigger frame conforming to IEEE802.11, participates in the wireless network built by the communication device, checks whether another first communication device that is not permitted to share a first period in the trigger frame is communicable in the first period by transmitting a checking frame, and when the communication device is not communicable, does not transmit frames to the another first communication device in the first period. The trigger frame permits communication with at least one of the other communication devices participating in the wireless network by sharing the first period of at least part of a TXOP acquired by the communication device.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to wireless communication technology.

Background Art

[0002] The wireless LAN (Local Area Network) technology has been standardized by IEEE802.11, which is a standardization organization for wireless LAN technology. The standards for wireless LAN technology include IEEE802.11 / a / b / g / n / ac / ax, etc. Here, IEEE is an abbreviation for Institute of Electrical and Electronics Engineers.

[0003] In IEEE802.11ax described in Patent Document 1, in addition to a high peak throughput of up to 9.6 gigabits per second (Gbps) by OFDMA, an improvement in communication speed under congested conditions is realized. Note that OFDMA is an abbreviation for Orthogonal Frequency-Division Multiple Access.

[0004] In order to further improve throughput, a Task Group for formulating the IEEE802.11be standard has been established as a successor standard to IEEE802.11ax.

[0005] As a successor standard aiming at further throughput improvement, improvement in frequency utilization efficiency, and improvement in communication latency, a task group called IEEE802.11be has been established. In the IEEE802.11be standard, for example, Multi-Link communication is being considered in which one AP (Access Point) establishes multiple links with one STA (Station) via different multiple frequency channels and communicates in parallel.

[0006] Furthermore, IEEE 802.11be proposes Triggered TXOP sharing, which uses a trigger frame to share a portion of the TXOPs acquired by an AP with STAs participating in the network. Here, TXOP stands for Transmission Opportunity. By sharing the TXOPs acquired by the AP with STAs designated by the AP, and prohibiting the transmission of frames to undesignated STAs between the shared TXOPs, unnecessary transmission frame collisions can be avoided, enabling efficient communication. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-50133 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, a method has been considered to improve communication efficiency by sharing the TXOP acquired by the AP with a designated STA. However, there are no regulations regarding the behavior of an STA that does not share a TXOP, and there is a risk that it may not be able to properly exchange frames with APs and STAs that share a TXOP.

[0009] Therefore, the objective of the present invention is to enable the communication of frames between the AP and the STA in communication in which the AP shares a TXOP acquired with a designated STA. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides a communication device that operates in the role of constructing a wireless network, and includes a transmission means that transmits a trigger frame compliant with the IEEE 802.11 series standard which permits the communication device to share a first period, which is at least a part of the TXOP (Transmission Opportunity) acquired by the communication device, with at least one other communication device participating in the wireless network, and to communicate in that manner, and a confirmation means that confirms whether a first other communication device participating in the wireless network, which is not permitted to share the first period in the trigger frame transmitted by the transmission means, is in a state where it can communicate during the first period, by transmitting a confirmation frame, wherein if the confirmation means confirms that the first other communication device is not able to communicate during the first period, the communication device does not transmit a frame to the first other communication device during the first period.

[0011] Furthermore, the communication device according to the present invention is characterized by having: a receiving means for receiving a trigger frame compliant with the IEEE 802.11 series standard which permits a first period, which is at least a part of a TXOP (Transmission Opportunity) acquired by another communication device playing a role in constructing a wireless network, to communicate by sharing that first period with at least one of the communication devices participating in the wireless network; and a transmitting means for transmitting a response frame to an acknowledgment frame transmitted from the other communication device to the other communication device by the communication device that is not permitted to share the first period in the trigger frame received by the receiving means. [Effects of the Invention]

[0012] According to the present invention, in communication in which an AP shares a TXOP acquired by an AP with a designated STA, frames can be properly communicated between the AP and the STA. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the network configuration established by the communication device 101. [Figure 2] This diagram shows the hardware configuration of communication devices 101 to 105. [Figure 3] This figure shows an example of the functional configuration of communication devices 101 to 105. [Figure 4] This diagram shows a sequence diagram for checking whether the AP in Embodiment 1 is in a state where it can communicate with an STA that has not been assigned a TXOP it has acquired. [Figure 5] This is a flowchart illustrating the operation of AP in Embodiment 1. [Figure 6] This diagram shows a sequence diagram for checking whether the AP in Embodiment 2 is in a state where it can communicate with an STA that has not been assigned a TXOP it has acquired. [Figure 7] This is a flowchart illustrating the operation of AP in Embodiment 2. [Figure 8] This is a flowchart of the TXOP processing in Embodiment 2. [Modes for carrying out the invention]

[0014] Figure 1 shows an example of the network configuration in which the communication device 101 according to this embodiment participates. The communication device 101 can communicate with communication devices 102 to 105. The communication device 101 is an access point (AP) that plays a role in constructing the wireless network 106, and the communication devices 102 to 105 are stations (STAs) that play a role in participating in the wireless network 106.

[0015] Each of communication devices 101 to 105 can perform wireless communication compliant with the IEEE802.11be standard. Note that IEEE is the abbreviation of Institute of Electrical and Electronics Engineers. Communication devices 101 to 105 can communicate in frequency bands of 2.4 GHz band, 5 GHz band, and 6 GHz band. Also, communication devices 101 to 105 can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz.

[0016] By performing OFDMA communication compliant with the IEEE802.11be standard, communication devices 101 to 105 can realize multi-user (MU) communication that multiplexes signals of multiple users. OFDMA is the abbreviation of Orthogonal Frequency Division Multiple Access. In OFDMA communication, a part (RU, Resource Unit) of the divided frequency band is assigned so as not to overlap each STA, and the carriers of each STA are orthogonal. Therefore, the AP can communicate with multiple STAs in parallel.

[0017] Note that communication devices 101 to 105 are assumed to be compliant with the IEEE802.11be standard, but in addition to this, they may also be compliant with a legacy standard that is a standard prior to the IEEE802.11be standard. Specifically, communication devices 101 to 105 may be compliant with at least any one of the IEEE802.11a / b / g / n / ac / ax standards. Or, they may be compliant with a standard that is a successor to IEEE802.11be.

[0018] In addition to the IEEE 802.11 series standards, it may also be compatible with other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA. Note that UWB is the abbreviation of Ultra Wide Band, and MBOA is the abbreviation of Multi Band OFDM Alliance. Also, NFC is the abbreviation of Near Field Communication. UWB includes wireless USB, wireless 1394, WiNET, etc. Also, it may be compatible with the communication standards of wired communication such as wired LAN.

[0019] Specific examples of the communication devices 101 to 105 include, but are not limited to, wireless LAN routers and personal computers (PCs). Also, the communication devices 101 to 105 may be information processing devices such as wireless chips that can perform wireless communication compliant with the IEEE 802.11be standard. Specific examples of the communication devices 102 to 105 include, but are not limited to, cameras, tablets, smartphones, PCs, mobile phones, video cameras, etc. Also, although the wireless network in FIG. 1 is composed of one AP and three STAs, the number of APs and STAs is not limited to this. The technology of allocating and sharing a part of the TXOP acquired by the AP to the STA using the Trigger Frame is called Triggered TXOP sharing. TXOP (Transmission Opportunity) refers to the period during which the AP or STA is exclusively permitted to use the channel after obtaining the access right to the channel through contention control by EDCA. Here, EDCA is the abbreviation of Enhanced Distributed Channel Access. The AP permits the STA to share a part of the acquired TXOP through Triggered TXOP sharing, allowing the sharing of the TXOP acquired by the AP. Hereinafter, the TXOP that can be shared and used by the STA with the TXOP acquired by the AP is referred to as the TXOP sharing period.

[0020] Triggered TXOP sharing is initiated when the AP sends a MU-RTS TXS Trigger frame to the STA. Here, MU-RTS TXS Trigger frame is an abbreviation for Multi User-Request to Send TXOP sharing Trigger Frame. At this time, the AP includes the AID of the STA that is authorized to share a portion of the allocated TXOP and perform communication in the User Info field of the MU-RTS TXS Trigger frame. In Triggered TXOP sharing, a MU-RTS TXS Trigger frame is used, in which the Trigger Type of the Trigger frame is specified as MU-RTS.

[0021] An STA to which a portion of the TXOP acquired by an AP via a MU-RTS TXS Trigger frame is allocated can transmit data to the AP or other STAs during the TXOP sharing period. Whether communication occurs between STAs and APs, or between STAs and STAs during the TXOP sharing period can be specified in the TXOP sharing mode subfield included in the Common Info field of the Trigger frame.

[0022] (AP and STA configuration) Figure 2 shows an example of the hardware configuration of the communication device 101, which is an AP in this embodiment. Note that the communication devices 102 to 105, which are STAs, can have a similar configuration. The communication device 101 includes a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0023] The storage unit 201 is composed of memory such as ROM and RAM, and stores various information such as computer programs for performing various operations described later, and communication parameters for wireless communication. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. In addition to memory such as ROM and RAM, the storage unit 201 may also use storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs. Furthermore, the storage unit 201 may have multiple memories.

[0024] The control unit 202 is composed of one or more processors, such as a CPU or MPU, and controls the entire communication device 104 by executing computer programs stored in the memory unit 201. CPU stands for Central Processing Unit, and MPU stands for Micro Processing Unit. The control unit 202 may also control the entire communication device 101 in cooperation with the computer programs stored in the memory unit 201 and the OS (Operating System). The control unit 202 also generates data and signals to be transmitted in communication with other communication devices. The control unit 202 may also be equipped with multiple processors, such as a multi-core processor, and the entire communication device 101 may be controlled by multiple processors. The control unit 202 also controls the function unit 203 to perform predetermined processes such as wireless communication, imaging, printing, and projection. The function unit 203 is hardware for the communication device 101 to perform predetermined processes.

[0025] The input unit 204 receives various operations from the user.

[0026] The output unit 205 provides various outputs to the user via a monitor screen or speaker. These outputs may include displays on the monitor screen, audio output via the speaker, or vibration output. Furthermore, both the input unit 204 and the output unit 205 may be implemented in a single module, similar to a touch panel. The input unit 204 and the output unit 205 may also be integrated with the communication device 101 or they may be separate components.

[0027] The communication unit 206 controls wireless communication in accordance with the IEEE 802.11be standard. In addition to the IEEE 802.11be standard, the communication unit 206 may also control wireless communication in accordance with other IEEE 802.11 series standards, or control wired communication such as wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive wireless signals for wireless communication generated by the control unit 202.

[0028] Furthermore, if the communication device 101 supports NFC, Bluetooth, or other standards in addition to the IEEE 802.11be standard, it may control wireless communication compliant with these communication standards. Also, if the communication device 101 can perform wireless communication compliant with multiple communication standards, it may be configured to have separate communication units 206 and antennas 207 corresponding to each communication standard. The communication device 101 communicates data such as image data, document data, and video data with communication devices 102 to 105 via the communication unit 206.

[0029] Figure 3 shows a block diagram of the functional configuration of the communication device 101, which is an AP, in this embodiment. Note that the communication devices 102-105, which are STAs, can have a similar configuration. Here, the number of wireless LAN control units in AP101 is not limited to one; there may be two or more. AP101 further includes a frame generation unit 302, a frame analysis unit 303, a channel allocation unit 304, and a UI control unit 305.

[0030] The wireless LAN control unit 301 comprises an antenna and circuit for sending and receiving wireless signals with other wireless LAN devices, and a program for controlling them. The wireless LAN control unit 301 performs wireless LAN communication control based on frames generated by the frame generation unit 302 in accordance with the IEEE 802.11 standard series.

[0031] The frame generation unit 302 generates a wireless control frame to be transmitted by the wireless LAN control unit 301. The content of the wireless control generated by the frame generation unit 302 may be constrained by settings stored in the storage unit 305. It may also be changed by user settings from the UI control unit 304.

[0032] The frame analysis unit 303 interprets the frame received by the wireless LAN control unit 301 and reflects its contents back to the wireless LAN control unit 301. Regardless of which control unit received the frame, by passing it through the frame control unit 303, it becomes possible to control wireless LAN control units that did not receive the frame.

[0033] The channel allocation unit 304 determines the appropriate channel for communication between the AP and STA when instructing communication with a communication partner or with an STA. According to the allocation determined here, for example, AP101 and STA102 communicate on the channel or a subchannel defined within it.

[0034] The UI control unit 305 includes hardware related to a user interface, such as a touch panel or buttons, for receiving operations on the AP by a user (not shown) of the AP, and a program to control them. The UI control unit 305 also has functions for presenting information to the user, such as displaying images or outputting audio.

[0035] <Embodiment 1> Figure 4 is a sequence diagram showing an example of checking whether communication is possible with STAs that are not permitted to share the TXOP during the TXOP sharing period. In this embodiment, the TXOP acquired by the AP is shared with STA1 and STA2, and communication takes place between STA1 and STA2 during the TXOP sharing period. Since STA3 and STA4 are not permitted to share the TXOP acquired by the AP, a Network Allocation Vector (NAV) is set for them during the TXOP sharing period.

[0036] The AP acquires a TXOP by sending a CTS-to-self frame 401. Subsequently, the AP sends a MU-RTS TXS Trigger frame 402 from STA1 to STA4. This MU-RTS TXS Trigger frame includes a TXOP sharing Mode subfield. If this subfield is 1, it indicates that the STA is in a mode to send a PPDU to the AP. Here, PPDU stands for PLCP Protocol Data Unit, and PLCP stands for Physical Layer Convergence Protocol. If this subfield is 2, it indicates that the STA is in a mode to send a PPDU to the AP or another STA that shares the TXOP. In this embodiment, the TXOP Sharing Mode subfield is 2, indicating that communication will occur between STAs. In this embodiment, STA1 and STA2 are permitted to share the TXOP sharing period, which is part of the TXOP acquired by the AP, and to perform communication during that period. However, STA3 and STA4 are not permitted to share the TXOP sharing period and perform communication.

[0037] Upon receiving frame 402, STA1 confirms that frame 402 has allocated a TXOP sharing period to its device, and then sends a CTS frame 403, which is a response frame to frame 402, to the AP. Here, to determine if a TXOP sharing period has been allocated to its device, STA1 checks whether the User Info field of frame 402 contains the AID of an STA that has been allocated a TXOP sharing period.

[0038] After STA1 transmits CTS frame 403, STA1 transmits data 404 to STA2. STA3 and STA4, which were not allocated a TXOP sharing period, configure NAV based on the duration information of the received MU-RTS TXS Trigger frame 402 or CTS frame 403. In this case, STA3 and STA4 are configured with NAVs of the same length.

[0039] If the AP detects that no communication has occurred between STA1 and STA2 for a certain period of time during the TXOP sharing period, it sends a Null QoS Data frame 408 to STA3, which is configured with NAV. This Null QoS Data frame 408 is a confirmation frame used to verify whether STA3, which is configured with NAV, is in a state where communication is possible during the TXS sharing period.

[0040] If the AP cannot receive a response frame from STA3, it will retransmit a Null QoS Data frame 409. In Figure 4, STA3 determines that communication is not possible if it sends Null QoS Data frames three times and does not receive a response frame even once. The number of Null QoS Data frames sent is not limited to three; the system may be configured to determine that communication is not possible if a response frame is not received even after sending a predetermined number of Null QoS Data frames.

[0041] If the AP determines that STA3 is not in a state where it can communicate, it does not send data to STA3 and instead sends a Null QoS Data frame 411 to STA4 in order to send data to STA4, which is not permitted to share TXOP. In this embodiment, STA3 has NAV set and is in a power save state, so it cannot respond to the acknowledgment frame, but STA4 is in an Awake state during the period when NAV is set, so it can respond. Therefore, STA4 cancels the set NAV and sends a response frame 412 to the AP in response to the Null QoS Data frame 411. Upon receiving the response frame 412 from STA4, the AP determines that STA4 is in a state where it can communicate and sends a data frame to STA4.

[0042] In this embodiment, Null QoS Data frames were sent in the order of STA3 and STA4, but this is not limited to this. For example, the order in which Null QoS Data frames are sent may be determined by the amount of data to be sent, or it may be determined randomly.

[0043] Using Figure 5, we will explain the process when TXOP sharing is executed by the control unit 202 executing a program stored in the memory unit 201 of the AP (Access Point) communication device 101. This flowchart is initiated when the AP discloses DL MU or Triggered TXOP sharing communication.

[0044] By sending a MU-RTS TXS Trigger Frame, STA1 and STA2, who are permitted to share the TXOP acquired by the AP, set up Triggered TXOP sharing (S501). In this embodiment, STA1 and STA2 are permitted to send frames during the TXOP sharing period, but STA3 and STA4 are not permitted to send frames during the TXOP sharing period.

[0045] In S501, when a MU-RTS TXS Trigger frame is sent, it is determined whether the TXOP sharing period has ended (S502). If it is determined in S502 that the TXOP sharing period has ended, this flowchart is terminated.

[0046] If it is determined in S502 that the TXOP sharing period has not ended, it is determined whether a period of time has passed during the TXOP sharing period in which no communication has been performed (S503).

[0047] If it is determined in S503 that no communication has been taking place for a certain period of time, a Null QoS Data frame is sent to STA3 that has not been assigned a TXOP to determine whether STA3 is in a state where it can communicate or not (S504). In this embodiment, a Null QoS Data frame is sent in S504, but this is not limited to this. For example, an RTS frame may be sent instead of a Null QoS Data frame to determine whether STA3 is in a state where it can communicate or not.

[0048] If it is determined that an ACK frame, which is the response frame to the Null QoS Data frame sent in S504, has been received from STA3 (S505), the data frame is sent to STA3 (S506). After sending the data frame, it is determined whether the TXOP sharing period has ended (S507). If it is determined that the TXOP sharing period has ended, this flowchart is terminated.

[0049] If it is determined in S505 that an ACK frame was not received from STA3, it is determined whether or not a Null QoS Data frame was sent a predetermined number of times (S508).

[0050] If it is determined in S508 that the predetermined number of transmissions have not been made, a Null QoS Data frame is sent to STA3 again. If it is determined in S508 that the predetermined number of transmissions have been made, a Null QoS Data frame is sent to STA4, which is not assigned a TXOP (S509).

[0051] If it is determined that an ACK frame, which is the response frame to the Null QoS Data frame sent in S509, has been received from STA4 (S510), the data frame is sent to STA4 (S511). After sending the data frame, it is determined whether the TXOP sharing period has ended (S507). If it is determined that the period has not ended, or if it is determined that the TXOP sharing period has ended, this flowchart is terminated.

[0052] If it is determined in S510 that an ACK frame from STA4 has not been received, it is determined whether or not a Null QoS Data frame has been sent a predetermined number of times (S512).

[0053] If it is determined in S512 that the predetermined number of transmissions have not been made, a Null QoS Data frame is sent to STA4 again. If it is determined that the predetermined number of transmissions have been made, the system waits until the TXOP sharing period ends (S513). Once the TXOP sharing period ends, this flowchart is terminated.

[0054] According to this embodiment, when sending data to an STA that has not been assigned a TXOP during the TXOP sharing period, it becomes possible to check whether the STA is in a state where it can communicate by sending a Null QoS Data frame. By checking whether an STA that has not been assigned a TXOP is in a state where it can communicate, for example, the STA can suppress packet loss of data frames from the AP.

[0055] <Embodiment 2> Embodiment 1 showed an example of checking whether an STA that has not been assigned a TXOP during the TXOP sharing period is in a state where it can communicate by sending a Null QoS Data frame. This embodiment shows an example of checking whether an STA that has not been assigned a TXOP is in a state where it can communicate during the TXOP sharing period by sending a data frame.

[0056] Figure 6 is a sequence diagram showing an example of checking whether communication is possible with an STA that has not been assigned a TXOP during TXOP sharing communication. In this embodiment, the AP assigns the acquired TXOP to STA1, and communication takes place between STA1 and AP during the TXOP sharing period. The AP has not assigned the acquired TXOP to STA2.

[0057] The AP obtains a TXOP by sending a CTS-to-self frame 401. The AP then sends a MU-RTS TXS Trigger frame 602 to STA1 and STA2.

[0058] Upon receiving the MU-RTS TXS Trigger frame 602, STA1 checks whether the frame 602 has assigned it a TXOP acquired by the AP. If it has been assigned a TXOP acquired by the AP, it sends a CTS frame 603, which is a response frame to frame 602, to the AP. To determine if it has been assigned a TXOP sharing period, it checks whether the User Info field of frame 402 contains the AID of an STA that has been assigned a TXOP sharing period.

[0059] After STA1 transmits CTS frame 603, it sends data 604 to AP. STA2, which was not assigned a TXOP acquired by AP, configures NAV based on the received MU-RTS TXS Trigger frame 602 or CTS frame 603's Duration information.

[0060] When STA1 sends PPDU604 to AP, the receiving AP sends Block Ack605 to STA1. If there are any further PPDUs to send, STA1 sends PPDU606 to AP, and AP sends Block Ack607 to STA1.

[0061] If the AP detects that no communication has occurred between the AP and STA1 for a certain period of time using the TXOP assigned by the AP, it sends Data frame 608 to STA2, which was not assigned a TXOP and has NAV configured. This Data frame 608 is a confirmation frame to check whether STA2, which has NAV configured, is in a state where communication is possible.

[0062] In this context, the reason why communication between the AP and STA1 does not occur for a certain period of time in the TXOP assigned by the AP could be, for example, that the STA finishes sending the data it was supposed to send to the AP before the TXOP sharing period ends, or that the data transmission fails midway.

[0063] In this embodiment, STA2 is not in a communication state during the TXOP sharing period and is unable to receive data frames transmitted from AP.

[0064] If AP does not receive an Ack frame for Data frame 608 sent from STA2 to AP, AP resends the same Data frame 609 to STA2. In existing technology, there is a mechanism that resends the Data frame up to a specified number of times if an Ack frame for the Data frame is not received. In this embodiment, the upper limit on the number of Data frame transmissions is set lower than in existing technology, so the number of Data frame transmission failures can be kept lower. If AP sends the Data frame up to a predetermined upper limit and still does not receive an Ack frame, AP determines that STA2 is not in a state where communication is possible. If it is determined that communication is not possible, AP waits without sending data to STA2 until the TXOP sharing period ends. Once the TXOP sharing period ends, AP may preferentially send Data frames to STA2.

[0065] Using Figure 7, we will explain the process when TXOP sharing is executed by the control unit 202 executing a program stored in the memory unit 201 of the AP (Access Point) communication device 101. This flowchart is initiated when the AP discloses DL MU or Triggered TXOP sharing communication.

[0066] The AP sends a MU-RTS TXS Trigger Frame to set up Triggered TXOP sharing with STA1, which is authorized to share the TXOP (S701).

[0067] If it is determined that the TXOP sharing period has not ended (S702), it is determined whether or not a certain period of time has passed without communication during the TXOP sharing period (S703). If it is determined in S703 that a certain period of time has passed without communication during the TXOP sharing period, it is determined whether or not there is data to send to STA2 that has not been assigned a TXOP (S704).

[0068] If it is determined in S704 that there is a data frame to send to STA2, the data frame is sent to STA2 (S705).

[0069] If it is determined in S704 that there are no data frames to send to STA2, the system waits until the TXOP sharing period ends (S710) and then terminates this flowchart.

[0070] In S705, it is determined whether or not an ACK, which is a response frame to the data frame transmitted, has been received (S706). If it is determined in S706 that an ACK has not been received, it is determined whether or not the frame has been transmitted a predetermined number of times (S707). Here, the upper limit for the number of frame retransmissions in this embodiment is set to be smaller than that of existing frame retransmission technologies. If it is determined in S707 that the frame has not been transmitted a predetermined number of times, the Data frame is sent to STA2 again. If it is determined that the frame has been transmitted a predetermined number of times, the system waits until the TXOP sharing period ends (S710), and once it has ended, this flowchart is terminated.

[0071] If S706 determines that an ACK has been received, and there is any data to be transmitted before the TXOP sharing period ends, the data frame is sent to STA2 (S708).

[0072] The AP determines whether the TXOP sharing period has ended (S709). If it determines that the TXOP sharing period has ended, it proceeds to the TXOP processing in S711.

[0073] In this embodiment, if there is still data that AP should send to STA2 when the TXOP sharing period ends, the TXOP process (S711) continues to send the data.

[0074] A detailed flowchart of S711 is shown in Figure 8. This flowchart is initiated when the communication device 101, which is an AP, processes S711.

[0075] Determine whether there is any data to send to STA after the TXOP sharing period has ended (S801).

[0076] In S801, if it is determined that there is data to send to the STA, it is determined whether the TXOP period acquired by the AP has ended. (S802) If it is determined that the TXOP period acquired by the AP has ended, this flowchart is terminated.

[0077] If it is determined in S802 that the TXOP period acquired by AP has not yet ended, the data frame is sent to STA (S803).

[0078] S803 determines whether an ACK, which is a response frame to the data frame sent in S803, has been received from STA (S804). S805 determines whether an ACK has been received, and if so, whether the frame has been sent a predetermined number of times (S805). If it is determined that the data frame has not been sent a predetermined number of times, the process returns to S802; if it is determined that the data frame has been sent a predetermined number of times, the process returns to S801. The number of times the data frame is sent in S805 may be set to be the same as the number of times it is sent in S707, or it may be set to be less than the number specified in S708.

[0079] If S801 determines that there is no data to send to STA, this flowchart will terminate.

[0080] According to this embodiment, during the TXOP sharing period, the AP can send a data frame to an STA that has not been assigned a TXOP acquired by the AP, thereby confirming whether the STA is in a state where it can communicate data. By confirming whether an STA that has not been assigned a TXOP is in a state where it can communicate data, for example, the STA can suppress packet loss of data frames from the AP.

[0081] <Other Embodiments> Alternatively, a recording medium containing program code for software that implements the above-described functions may be supplied to a system or device, and the computer (CPU, MPU) of the system or device may read and execute the program code stored on the recording medium. In this case, the program code read from the storage medium itself will implement the functions of the above-described embodiment, and the storage medium containing that program code will constitute the above-described device.

[0082] For storing program code, storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs can be used.

[0083] Furthermore, the above-mentioned functions may be realized not only by the computer executing the program code it reads, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of that program code. OS stands for Operating System.

[0084] Furthermore, the program code read from the storage medium is written to the memory of a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of that program code, the CPU of the function expansion board or function expansion unit may perform some or all of the actual processing to realize the above-mentioned functions.

[0085] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of symbols]

[0086] 201 Storage section 202 Control Unit 203 Functional Section 204 Input section 205 Output section 206 Communications Department 207 Wireless Antenna

Claims

1. A communication device that operates in the role of building a wireless network, A transmission means that transmits a Trigger frame compliant with the IEEE 802.11 series standard, which allows the communication device to share a first period of at least a portion of the TXOP (Transmission Opportunity) acquired by the communication device with at least one other communication device participating in the wireless network for communication, A confirmation means that confirms whether a first other communication device participating in the wireless network, which is not permitted to share the first period in the Trigger frame transmitted by the transmitting means, is in a state where it can communicate during the first period, by transmitting a confirmation frame. It has, If the verification means confirms that the other first communication device is not able to communicate during the first period, then no frame is transmitted to the other first communication device during the first period. A communication device characterized by the following features.

2. The device further includes receiving means for receiving a response frame to the aforementioned confirmation frame from the first other communication device, The communication device according to claim 1, characterized in that the confirmation means resends the confirmation frame if it does not receive the response frame transmitted from the other communication device, and if it fails to receive the response frame a predetermined number of times, it confirms that the first other communication device is not in a state where it can communicate.

3. The communication device according to claim 1 or 2, characterized in that, if the confirmation means confirms that the first other communication device is not in a state where it can communicate, it transmits the confirmation frame to a second other communication device, which is different from the first other communication device and is not permitted to share the first period in the Trigger frame transmitted by the transmission means.

4. The communication device according to claim 2 or 3, characterized in that the confirmation frame is a data frame containing data that the communication device transmits to the first other communication device.

5. The communication device according to claim 2 or 3, characterized in that the confirmation frame is a Null QoS Data frame.

6. The communication device according to claim 2 or 3, characterized in that the confirmation frame is an RTS frame.

7. A communication device, A receiving means for receiving a Trigger frame compliant with the IEEE 802.11 series standard, which allows other communication devices responsible for constructing a wireless network to share and communicate with at least one of the communication devices participating in the wireless network for a first period of at least a portion of the TXOP (Transmission Opportunity) acquired by the other communication devices, A communication device that is not permitted to share the first period in the Trigger frame received by the receiving means transmits a response frame to the other communication device for an acknowledgment frame transmitted from the other communication device, A communication device characterized by having the following features.

8. A communication method for a communication device that operates in the role of building a wireless network, A transmission step of transmitting a Trigger frame compliant with the IEEE 802.11 series standard, which allows the communication device to share a first period of at least a portion of the TXOP (Transmission Opportunity) acquired by the communication device with at least one other communication device participating in the wireless network for communication, A confirmation step that confirms whether a first other communication device participating in the wireless network, which is not permitted to share the first period in the Trigger frame transmitted by the transmission step, is in a state where it can communicate during the first period, by transmitting a confirmation frame; It has, If the verification process confirms that the first other communication device is not able to communicate during the first period, then no frame is transmitted to the first other communication device during the first period. A communication method for a communication device characterized by the following features.

9. A communication method for communication devices, A receiving step of receiving a Trigger frame compliant with the IEEE 802.11 series standard, which allows a first period, which is at least a portion of a TXOP (Transmission Opportunity) acquired by other communication devices playing a role in constructing a wireless network, to share and communicate with at least one of the communication devices participating in the wireless network, A transmission step in which a communication device that is not permitted to share the first period in the Trigger frame received by the receiving step transmits a response frame to the other communication device for an acknowledgment frame transmitted from the other communication device, A communication method for a communication device characterized by having the following features.

10. A program for causing a computer to operate as one of the means of a communication device described in any one of claims 1 to 6.

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