Communication device, control method, and program

Abstract

This communication device acquires a transmission opportunity (TXOP) for transmitting a radio frame. The communication device uses a first radio frame to ensure a first TXOP period. The communication device uses a Trigger frame to allocate a second TXOP period within the first TXOP period to another communication device. During the second TXOP period, the communication device receives a prescribed control frame indicating that the second TXOP period will end. When the communication device receives the prescribed control frame during the second TXOP period, the communication device performs control so as to transmit a second radio frame after the passage of a prescribed Inter Frame Space (IFS) time from the reception. The communication device performs control so as to transmit the second radio frame on the basis of a prescribed condition.

Description

Communication device, control method, and program

[0001] The present invention relates to a communication device that performs wireless communication, a control method for the communication device, and a program.

[0002] In recent years, with the increase in the amount of data being communicated, the development of communication technologies such as wireless LANs (Local Area Networks) has been progressing. The IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard series is known as a major communication standard for wireless LANs. The IEEE 802.11 standard series includes standards such as IEEE 802.11a / b / g / n / ac / ax. Currently, the IEEE 802.11be standard, which is the successor standard to IEEE 802.11ax, is being developed.

[0003] Also, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) is known as a channel access method of the IEEE 802.11 standard. In the CSMA / CA method, a communication device attempting to start communication always checks whether other surrounding communication devices are emitting radio waves before starting communication, and starts communication only after confirming that other surrounding communication devices are not emitting radio waves (the channel is idle). For example, if other surrounding communication devices are emitting radio waves (the channel is busy), the communication device waits for a predetermined period (IFS: Inter Frame Space), and after the predetermined period, the communication device again checks whether other surrounding communication devices are emitting radio waves. If the confirmation result shows that the channel is idle, the communication device waits for a certain random waiting time. If the channel is still idle after waiting for the random waiting time, the communication device assumes that it has acquired a transmission opportunity (TXOP: Transmission Opportunity) and starts communication. Furthermore, the communication device that has acquired the transmission opportunity declares the time of the transmission opportunity (TXOP period) in the first frame to be transmitted, thereby causing other surrounding communication devices to set a Network Allocation Vector (NAV) for the TXOP period. The other surrounding communication devices are controlled not to perform the above-described channel access process during the period for which this NAV is set, regardless of whether the channel is idle or not.

[0004] A Contension Free-End (CF-End) frame is also known as a radio frame for canceling a set NAV. This is a radio frame used when a communication device that has secured a TXOP notifies other surrounding communication devices of the end of the TXOP period. Therefore, a communication device that receives a CF-End frame cancels the NAV set in the device itself and resumes the above-mentioned channel access process.

[0005] Japanese Patent Application Laid-Open No. 2021-103805

[0006] Furthermore, a mechanism called TXOP sharing is being considered for the above-mentioned IEEE 802.11be. This is a mechanism in which an AP (Access Point) allocates a portion of its acquired TXOP to a station (STA), thereby sharing the TXOP it has secured with the STA. Triggered TXOP sharing is a mechanism in which an AP sends a trigger frame to a STA, thereby allocating a portion of the TXOP it has acquired to the STA. By sharing the TXOP acquired by the AP with a STA designated by the AP in this way, only the AP and the designated STA can communicate during the period of this shared TXOP. In other words, prohibiting communication by non-designated STAs during this shared TXOP period can avoid communication collisions and channel usage due to unnecessary transmission frames, thereby improving communication efficiency.

[0007] In TXOP sharing, when a STA that shares a TXOP terminates communication before the end of the shared TXOP period, the STA is considered to notify the end of the TXOP period by transmitting a CF-End frame. This allows the STA to return the remaining TXOP period to the AP, and the AP can start communication during the remaining TXOP period as needed.

[0008] However, it is assumed that other surrounding communication devices that receive the CF-End frame will cancel the NAV set for their own devices and start communication, even though the AP has reserved the remaining TXOP period. Therefore, if a communication device that has canceled the NAV starts communication after waiting for the same waiting time as the AP that has reserved the TXOP period, there is a risk of communication collision between the communication device and the AP that has reserved the TXOP period.

[0009] In view of the above-mentioned problems, one of the objects of the present invention is to reduce communication collisions between a communication device that has acquired a TXOP and shared it with other communication devices and other surrounding communication devices.

[0010] In order to achieve the above object, a communication device according to one aspect of the present invention comprises: an acquisition means for acquiring a Transmission Opportunity (TXOP) for transmitting a radio frame; an acquisition means for reserving a first TXOP period using a first radio frame; a sharing means for allocating a second TXOP period of the first TXOP period to another communication device using a trigger frame; a receiving means for receiving a predetermined control frame during the second TXOP period indicating the end of the second TXOP period; and a control means for, when the predetermined control frame is received during the second TXOP period, controlling the communication device to transmit a second radio frame after a predetermined Inter Frame Space (IFS) time has elapsed since the reception of the control frame, wherein the control means controls the communication device to transmit the second radio frame based on a predetermined condition.

[0011] According to one aspect of the present invention, it is possible to reduce collisions in communication between a communication device that has acquired a TXOP and shared it with other communication devices and other surrounding communication devices.

[0012] Fig. 1 is a diagram showing an example of a network configuration. Fig. 2 is a diagram showing an example of a hardware configuration of an AP / STA. Fig. 3 is a diagram showing an example of a block diagram of the functional configuration of an AP / STA. Fig. 4 is a diagram showing an example of a sequence diagram of a mechanism for acquiring a TXOP. Fig. 5 is a diagram showing an example of a sequence diagram of a mechanism for TXOP sharing. Fig. 6 is a diagram showing an example of a sequence diagram when TXOP sharing is performed in this embodiment. Fig. 7 is a diagram showing an example of a flowchart of the processing of a Coordinator AP that has acquired a transmission opportunity.

[0013] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0014] (Network Configuration) Fig. 1 shows an example of a network configuration according to this embodiment. The network of this embodiment includes networks (100, 110, and 111) constructed by three access point (hereinafter, AP) devices (AP 101, AP 102, and AP 103). A station (hereinafter, STA) device (STA 105) participates in network 100, and STA 104 participates in network 110. Hereinafter, APs 101 to 103 and STAs 104 to 105 will be collectively referred to as communication devices.

[0015] Each communication device is configured to be able to communicate wireless frames compliant with the IEEE 802.11bn standard, a successor to the IEEE 802.11be standard that targets a maximum transmission speed of 90 Gbps to 100 Gbps. STA 104 and STA 105 are also configured to be able to communicate wireless frames compliant with IEEE 802.11bn. IEEE stands for Institute of Electrical and Electronics Engineers. The main features of IEEE 802.11bn are support for highly reliable communication, low latency communication, and AP cooperation. Wireless frames communicated according to this successor standard are also called UHR (Ultra High Reliability) PPDUs. PPDU is an abbreviation for physical layer (PHY) protocol data unit.

[0016] The name UHR was chosen for convenience, taking into account the goals and key features of the successor standard, and may be renamed once the standard is fully developed. Similarly, the name IEEE 802.11bn may be renamed once the standard is fully developed. However, please note that this specification and the accompanying claims are essentially applicable to all successor standards to the 802.11be standard. Each communication device can communicate at frequencies in the 2.4 GHz, 3.6 GHz, 5 GHz, and 6 GHz bands, as well as the 45 GHz and 60 GHz bands known as millimeter waves. The frequency bands used by each communication device are not limited to these, and a different frequency band, such as the Sub-1 GHz band, may also be used. Each communication device can communicate using a bandwidth of 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 540 MHz, 640 MHz, 1080 MHz, and 2160 MHz. The bandwidth used by each communication device is not limited to these, and each communication device may use a different bandwidth, such as 240 MHz or 4 MHz.

[0017] Note that Figure 1 shows an example of a wireless network consisting of three APs and two STAs, but the number of these may be more or less than shown, as long as the network configuration consists of at least two APs.

[0018] APs 101 to 103 are APs that perform cooperative operations, and AP 101 is an AP that performs overall control for the cooperation. In this embodiment, an AP such as AP 101 that performs overall control is also called a Coordinator AP. Also, APs 102 to 103 are APs that function as controlled devices controlled by the Coordinator AP. In this embodiment, APs such as AP 102 to AP 103 that are controlled by the Coordinator AP are also called Coordinated APs.

[0019] Furthermore, APs 101 to 103 can perform cooperative operation. Specifically, AP 101 can allocate part or all of the period (TXOP period) of the transmission opportunity (TXOP) of a wireless frame in the communication channel secured by the AP itself to AP 102. AP 102 that has been allocated the TXOP period can transmit wireless frames to STAs participating in its wireless network or to surrounding APs during that period. Note that in this embodiment, the backhaul line for transmitting and receiving data and control signals between each AP for the cooperative operation of each AP described above is a communication path using a wireless medium.

[0020] APs 101 to 103 can perform MU (Multi-User) communication, which uses OFDMA technology to simultaneously communicate with multiple STAs. In MU communication using OFDMA technology, one channel is divided into multiple subchannels called RUs (Resource Units). Each RU is then treated as a resource for communication with a different STA (which may be a group of STAs consisting of multiple STAs), allowing the AP and multiple STAs to communicate simultaneously on one channel. In this case, the AP transmits an MU (Multi-User) PPDU, in which data is modulated using OFDMA, to one or more STAs. If all devices are compatible with the IEEE 802.11bn standard, a UHR MU PPDU, which is an MU PPDU compliant with the IEEE 802.11bn standard, is transmitted to one or more STAs.

[0021] Furthermore, each communication device may be a multi-link device (MLD) that can establish multiple parallel links with other communication devices via multiple different frequency channels. Each communication device that is an MLD can perform multi-link communication with other communication devices by establishing the multiple links in parallel with the other communication devices.

[0022] Although each communication device is described as being compatible with the IEEE 802.11bn standard, it may also be compatible with a legacy standard that predates the IEEE 802.11bn standard. Specifically, the AP 101 and the STA 102 may be compatible with at least one of the IEEE 802.11a / b / g / n / ac / ax / be standards. Furthermore, in addition to the IEEE 802.11 series standards, they may also be compatible with other communication standards such as Bluetooth (registered trademark), NFC, BLE (registered trademark), UWB, ZigBee, and MBOA. UWB stands for Ultra Wide Band, and MBOA stands for Multi Band OFDM Alliance. NFC stands for Near Field Communication, and BLE stands for Bluetooth Low Energy. UWB includes wireless USB, wireless 1394, WiNET, etc. The APs 101 to 103 may also be compatible with wired communication standards such as wired LAN. Specific examples of the APs 101 to 103 include, but are not limited to, wireless LAN routers and personal computers (PCs). The APs 101 to 103 may also be information processing devices such as wireless chips capable of performing wireless communication compliant with the IEEE 802.11bn standard. Specific examples of the STAs 104 and 105 include, but are not limited to, cameras, tablets, smartphones, PCs, mobile phones, video cameras, and headsets. The STAs 104 and 105 may also be information processing devices such as wireless chips capable of performing wireless communication compliant with the IEEE 802.11bn standard.

[0023] In this embodiment, it is assumed that the BSSIDs corresponding to the wireless networks provided by AP101 to AP104 are all different. BSSID stands for Basic Service Set Identifier and is an identifier for identifying an access point. On the other hand, it is assumed that the SSIDs indicated by AP101 to AP103 in the wireless networks are all the same. SSID stands for Service Set Identifier and is an identifier for identifying a wireless network.

[0024] 2 shows an example of the hardware configuration of each communication device (AP and STA). The communication device includes, as an example of its hardware configuration, a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0025] The storage unit 201 is configured with ROM and / or RAM, and stores various information such as programs for performing various operations described below and communication parameters for wireless communication. RAM stands for Random Access Memory, and ROM stands for Read Only Memory. Note that the storage unit 201 may be a storage medium such as a non-volatile storage device, such as a hard disk or SSD (Solid State Drive), in addition to memories such as ROM and RAM.

[0026] The control unit 202 is configured with, for example, a processor such as a CPU or MPU, an ASIC (application-specific integrated circuit), a DSP (digital signal processor), an FPGA (field programmable gate array), etc. Here, CPU stands for Central Processing Unit, and MPU stands for Micro Processing Unit. The control unit 202 executes programs stored in the storage unit 201 and controls the entire device by operating hardware circuits such as the ASIC. Note that the control unit 202 may control the entire device in cooperation with the programs stored in the storage unit 201 and an OS (operating system).

[0027] The control unit 202 also controls the functional unit 203 to perform predetermined processes such as capturing images, printing, and projection. The functional unit 203 is hardware that enables the device to perform predetermined processes. For example, if the communication device is a camera such as a digital still camera or a smartphone equipped with a camera, the functional unit 203 is an imaging unit that captures images of the surroundings via a camera unit (not shown) included in the communication device. For example, if the communication device is a printer, the functional unit 203 is a printing unit that performs printing on a sheet such as paper based on print data obtained from the outside via wireless communication. For example, if the communication device is a projector or smart glasses, the functional unit 203 is a projection unit that performs projection of image data or video data obtained from the outside via wireless communication. In the case of smart glasses, the projection surface is the end user's retina, for example. The data processed by the functional unit 203 may be data stored in the storage unit 201 or data communicated with another AP or STA via the communication unit 206 (described later). Furthermore, communication devices such as AP 101 can also provide network storage functions 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, a communication device such as an STA connects to a network storage service provided by APs 101 to 103 using a protocol such as SMB, FTP, or WebDAV. The communication device such as an STA then uploads files to the storage service and downloads files from the storage. This upload and download data communication is also realized by communicating UHR PPDU between devices.

[0028] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user. Here, the output by the output unit 205 includes, for example, at least one of display on a screen, audio output by a speaker, and vibration output. Note that both the input unit 204 and the output unit 205 may be implemented by a single module, such as a touch panel.

[0029] The communication unit 206 controls wireless communications compliant with the IEEE 802.11 series of standards and IP communications. In this embodiment, the communication unit 206 cooperates with the antenna 207 to execute communication control for transmitting and receiving UHR PPDUs, which are wireless frames of the UHR standard, and PPDUs conforming to earlier standards. The antenna 207 is, for example, an antenna capable of transmitting and receiving signals in at least one frequency band, including the sub-GHz band, the 2.4 GHz band, the 5 GHz band, the 6 GHz band, and the millimeter wave band. While the present embodiment describes the use of three antennas, the communication unit 206 may be a single antenna or multiple antennas, each corresponding to a different frequency band. Furthermore, if multiple antennas are used, the communication unit 206 may be provided corresponding to each antenna.

[0030] If the communication device is compatible with the aforementioned NFC standard, Bluetooth standard, wired communication standard, or the like, the communication unit 206 may be configured to control wireless communication or wired communication in accordance with these communication standards.

[0031] (Functional Configuration of Communication Device) Next, FIG. 3 shows an example of a block diagram of the functional configuration of the communication device (AP and STA). In this embodiment, each functional block is stored as a program in the storage unit 201, and the function is implemented by executing the program by the control unit 202. By executing the program, the control unit 202 realizes each function by controlling each piece of hardware and calculating and processing information. Note that some or all of the functional blocks may be implemented as hardware. In this case, some or all of the functional blocks may be configured by, for example, an ACIC (Application Specific Integrated Circuit).

[0032] In this embodiment, the communication device includes a frame generation unit 301 , a frame analysis unit 302 , a wireless communication control unit 303 , a TXOP sharing control unit 304 , a multi-AP control unit 305 , a UI control unit 306 , and a storage unit 307 .

[0033] The frame generation unit 301 is a functional unit that performs processing to generate a wireless frame to be transmitted by the wireless communication control unit 303 .

[0034] The frame analysis unit 302 is a functional unit that performs analysis processing of the wireless frame received by the wireless communication control unit 303 .

[0035] The wireless communication control unit 303 notifies the surrounding terminals of the frames generated by the frame generation unit 301, transmits them to the other communication device by unicast, or sends wireless frames received from the surrounding terminals or the other communication device to the frame analysis unit 302.

[0036] The TXOP sharing control unit 304 controls allocation of the period during which it obtains a transmission opportunity (TXOP) to other APs. Alternatively, it instructs the frame generation unit 301 to generate the next wireless frame to be transmitted during the period it has obtained. Furthermore, it grasps the implementation status of TXOP sharing based on the results of interpretation by the frame analysis unit 302.

[0037] The multi-AP control unit 305 controls the operation of the multi-AP in cooperation with other APs. It identifies the APs currently participating in the multi-AP group from the content interpreted by the frame analysis unit 302, and instructs the frame generation unit 301 to generate a wireless frame to be transmitted in cooperation with other APs.

[0038] The UI control unit 306 includes hardware related to a user interface (UI), such as a touch panel or buttons (not shown), for accepting user operations on the communication device, and a program for controlling these. The UI control unit 306 also has a function for presenting information to the user, such as displaying images or outputting audio. For example, the UI control unit 306 can display a setting screen related to the multi-AP of the communication device 101 and accept user operations on the display. In this case, the UI control unit 306 of the communication device 101 displays a setting screen for selecting several other APs that can cooperate with the communication device 101 to form a multi-AP. The user may then select, via the setting screen, which other APs the communication device 101 will cooperate with to form the multi-AP.

[0039] The storage unit 307 is a storage device that can be configured with a ROM, a RAM, etc., that stores programs and data that the communication device 101 operates on.

[0040] (Acquisition of TXOP) Next, an example of a sequence diagram of a mechanism by which each communication device in this embodiment acquires a TXOP will be described. FIG. 4 is a diagram showing an example of a mechanism by which the communication device 101 acquires a TXOP using Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA). In this embodiment, the communication device 101 and the communication device 105 perform channel access based on Enhanced Distributed Channel Access (EDCA). EDCA is a mechanism for performing CSMA / CA that takes data priority into consideration by varying parameters for setting an IFS (Inter Frame Space) and a waiting time (to be described later) depending on the type of data (Access Category: AC). IFS stands for Inter Frame Space. It is also assumed that the parameters relating to EDCA (EDCA parameters) are broadcast by the AP periodically (for example, at intervals of 100 time units) using a beacon frame.

[0041] 401 indicates that the communication channel of the network 100 is busy (a state in which other terminals in the vicinity are emitting radio waves). For example, it is assumed that the communication device 103 is communicating during the period indicated by 401. Furthermore, checking whether the channel is busy or idle in this way is called carrier sense.

[0042] Next, when the channel changes from a busy state to an idle state, the communication device 101 checks whether the channel is idle for an AIFS period (402). AIFS is a type of IFS and is an abbreviation for Arbitration IFS. The AIFS is determined based on the AIFSN of the EDCA parameters. If the channel changes to a busy state during the AIFS period in 402, the communication device 101 checks again for an AIFS period after the channel changes to the idle state whether the channel is idle.

[0043] After confirming that the channel is idle during the AIFS period in 402, the communication device 101 waits for the backoff period (403). The backoff period is managed by a backoff timer held by each communication device. The backoff period for each data item is also determined based on EDCA parameters, and a random value is set within the range from 0 to the value of the Contension Window (CW) parameter. When the AIFS waiting time in 402 expires, the backoff timer starts decrementing. For example, if another communication device starts communication during the backoff period, causing the channel to become busy, the decrement of the backoff timer is suspended. Then, when the channel returns to the idle state, the decrement of the backoff timer resumes after the AIFS waiting time has elapsed. In other words, even if the channel becomes busy during the backoff period, the backoff timer is not reset, but decrement resumes from the intermediate value.

[0044] When the backoff timer reaches 0, the communication device 101 acquires a TXOP (transmission opportunity) and starts transmitting a wireless frame (404). In this embodiment, the communication device 101 transmits a CTS-to-self frame as the wireless frame to be transmitted after backoff, but this is not limited to this. The wireless frame here may be a wireless frame that includes at least a MAC header. Note that CTS stands for Clear to Send, and MAC stands for Medium Access Control. The CTS-to-self frame is a CTS frame that the communication device 101 transmits to the communication device 101 as the destination. Furthermore, the CTS frame is a frame that notifies other communication devices to refrain from communication during the TXOP period. Therefore, other communication devices that receive a CTS frame set a NAV for themselves, thereby controlling themselves not to transmit during the NAV period.

[0045] The communication device 101 notifies surrounding communication devices of the TXOP period secured by the device itself in a wireless frame communicated at 403. Specifically, the communication device 101 transmits a CTS-to-self frame at 404, and stores the TXOP in a Duration field included in the frame, thereby notifying other surrounding communication devices of the TXOP period acquired by the communication device 101.

[0046] The communication device 105, which has received a wireless frame containing a value other than 0 in the Duration field, sets the NAV based on the value contained in the Duration field (405). The communication device 105 considers the channel to be busy during the NAV period, and does not perform channel access processing for transmitting the wireless frame.

[0047] After transmitting the CTS-to-self frame, the communication device 101 transmits data to other communication devices within the TXOP that it has acquired (406).

[0048] In this manner, in this embodiment, a communication device that has a wireless frame to transmit waits for a predetermined IFS period after the channel becomes idle, and then waits for a backoff period before transmitting. In this manner, the communication device that has the shortest waiting time, including the predetermined IFS period and the backoff period, acquires a transmission opportunity (TXOP) and transmits the wireless frame.

[0049] (TXOP sharing) Next, an example of a TXOP sharing mechanism in this embodiment will be described. In Fig. 5, a TXOP acquired by the communication device 101 is assigned to the communication device 105 through TXOP sharing, thereby sharing the TXOP acquired by the communication device 101 with the communication device 105. This enables the communication device 105 to transmit radio frames during the period of the assigned TXOP.

[0050] First, the communication device 101 acquires a TXOP based on the above-mentioned channel access and transmits a CTS-to-self frame (501). Information about the TXOP period (502) secured by the communication device 101 is stored in the Duration field of the frame. Therefore, the communication device 105 that receives the frame sets a NAV corresponding to the TXOP period in its own device.

[0051] Next, the communication device 101 decides to allocate part or all of the TXOP it has acquired to another communication device, and transmits a Trigger frame (TF) (503). In this embodiment, the communication device 101 decides to allocate part of the TXOP it has acquired to the communication device 105, and transmits a TF including information regarding the allocation. For example, the communication device 101 transmits an MU-RTS TXS Trigger frame as the Trigger frame. The communication device 101 stores information indicating the duration of the TXOP to be allocated to the communication device 105 in the MU-RTS TXS Trigger frame. This allows the communication device 105 to grasp the TXOP duration (504) allocated by the communication device 101. At this time, the communication device 101 may store information indicating the TXOP duration in the Allocation Duration subfield of the MU-RTS TXS Trigger frame. Furthermore, the communication device 101 stores "1" or "2" in the Triggered TXOP Sharing Mode subfield. Storing "1" in this subfield means that the destination of data transmission in the TXOP is limited to the communication device 101. Storing "2" in the subfield means that the destination of data transmission in the TXOP is not limited. The MU-RTS TXS Trigger frame is an abbreviation for Multi User-Request To Send TXOP Sharing Trigger frame.

[0052] Next, the communication device 105 transmits a CTS frame (505) in response to the TF 503. The communication device 105 stores information indicating the TXOP period 504 allocated by the communication device 101 in the Duration field included in the CTS frame, thereby causing communication devices around the communication device 105 to set NAVs.

[0053] Thereafter, the communication device 105 starts communicating data with other communication devices (506-509). First, the communication device 105 transmits a CTS frame 505, and then transmits data after an SIFS period (506). After the communication device 101 receives the data 506, it transmits a Block Ack frame as an acknowledgment of the receipt of the data 506 after an SIFS period (507). After receiving the Block Ack frame 507, the communication device 105 transmits data after an SIFS period because it has an allocated TXOP 504 remaining and has data to transmit (508). The communication device 104 transmits a Block Ack frame 509 in the same manner as the communication device 101 transmitted the Block Ack frame 507. Note that SIFS stands for Short Inter Frame Space.

[0054] After the TXOP period allocated to the communication device 105 has elapsed, the communication device 101 performs carrier sensing for a PIFS period longer than the SIFS period (510). If the communication device 101 determines that the channel is in an idle state through the carrier sensing, it transmits data (511).

[0055] As described above, in conventional TXOP sharing, it is assumed that during the allocated TXOP period, communication may occur between communication devices other than the communication device that allocated the TXOP. In such a case, the communication device 101 performs carrier sensing for a PIFS period after the allocated TXOP period has elapsed, and then resumes data transmission. For example, it is assumed that the communication device 105 runs out of data to transmit, and a certain remaining period occurs between the Block Ack frame 509 and the allocated TXOP period 504 has elapsed. In such a case, communication devices surrounding the communication device 105 cannot communicate during the remaining period, even though the channel is idle.

[0056] Therefore, when the remaining period occurs, the communication device 105 may transmit a CF-End frame to notify surrounding communication devices that the allocated TXOP period 504 is ending. However, at this time, the communication device 101 still has the TXOP period acquired by the CTS frame 501 remaining. In addition, communication devices surrounding the communication device 105 cancel their NAVs using a CF-End frame. Therefore, depending on the waiting time after receiving a CF-End frame from a surrounding communication device that has canceled its NAV, there is a risk of collision between the transmission of wireless frames between the communication device 101 and surrounding communication devices. Therefore, the present invention proposes a control method after receiving a CF-End frame by the communication device 101 that allocates a TXOP.

[0057] (TXOP Sharing in the Present Embodiment) Next, FIG. 6 shows an example of an operation sequence for TXOP sharing in the present embodiment. In this sequence, AP 101 acquires a transmission opportunity (TXOP) and performs TXOP sharing, allocating part or all of the acquired TXOP to AP 102. Next, AP 102 terminates and returns the remaining TXOP to AP 101 during the allocated TXOP period. After receiving a wireless frame indicating the end of the TXOP, AP 101 adjusts the transmission wait time and transmits the wireless frame so that it can communicate before other communication devices. In the present embodiment, AP 101 sets the SIFS time as the wait time. The SIFS is the IFS with the shortest time set among the IFSs. Therefore, AP 101 can transmit a wireless frame before other communication devices start transmitting wireless frames. This allows other communication devices to determine that the channel is busy based on AP101's wireless frame and not transmit wireless frames, thereby reducing collisions between wireless frames transmitted by AP101 and other communication devices.

[0058] First, AP 101 secures TXOP period 602 by transmitting a CTS-to-self frame 601. AP 101 decides to allocate TXOP period 603 of TXOP period 602 to AP 102. AP 101 allocates TXOP period 603 of TXOP period 602 to AP 102 using an MU-RTS TXS Trigger frame 604. That is, AP 101 transmits to AP 102 an MU-RTS TXS Trigger frame 604 that stores information indicating the TXOP period 603 in the Allocation Duration subfield. AP 102 receives the MU-RTS TXS Trigger frame 604 and recognizes that TXOP 603 has been allocated to its own device. The AP 101 may reserve the TXOP period 602 and allocate the TXOP period 603 using only the MU-RTS TXS Trigger frame 604 without transmitting the CTS-to-self frame 601 .

[0059] Next, AP 102 transmits a CTS frame 605 in response to the MU-RTS TXS Trigger frame 604. Note that AP 102 stores information indicating the TXOP period 603 in the Duration field, causing other surrounding communication devices to set a NAV of a period equivalent to the TXOP period 603. For example, by receiving the CTS frame 605 transmitted by AP 102, STA 104 recognizes that AP 102 has secured the TXOP period 603 and sets NAV 606. In this way, through the exchanges up to the CTS frame 605 in this sequence, surrounding communication devices recognize the TXOP period secured by AP 101 and AP 102 as a NAV period, and perform control so as not to generate unnecessary radio waves during that NAV period.

[0060] Next, the AP 102 transmits data 607 to the STA 104 during the TXOP period 603. The AP 102 can prompt other STAs to transmit data by transmitting a Trigger frame instead of transmitting the data. The data may also be transmitted to multiple communication devices. The AP 102 may transmit the data 607 with directionality toward the STA 104 (directional). For example, the AP 102 controls the directivity of the data 607 by beamforming. Controlling the directivity in this way can improve communication speed and communication error rate, and stabilize communication.

[0061] Next, the STA 104 transmits a Block Ack (BA) frame 608 to the AP 102 indicating that it has received the data from the AP 102 .

[0062] Upon receiving the BA frame, the AP 102 confirms that communication with the STA 104 has ended during the TXOP period allocated to the AP 101, and transmits a CF-End frame 609 to the AP 101, indicating the end and return of the remaining period of the TXOP period 603. By receiving the CF-End frame 609 during the TXOP period 603, the AP 101 recognizes that the AP 102 has truncated the remaining period of the TXOP period 603. Furthermore, the STA 104 that has set a NAV for the TXOP period 603 cancels the NAV 606 in response to receiving the CF-End frame 609. Then, upon confirming that the channel is idle, the STA 104 resumes channel access processing. By canceling the NAVs of the surrounding communication devices (STA 104) in this way in conjunction with the return of the TXOP, it is possible to prevent communication devices (STA 104) that are outside the communication range of the communication device (AP 101) that has secured the TXOP from retaining unintended NAVs.

[0063] The CF-End frame is an abbreviation for Contention Free-End frame. The CF-End frame is a type of control frame, and is a frame in which the Type field of a MAC frame indicates 01 and the Subtype field indicates 1110. The CF-End frame is a frame that can be transmitted by a communication device holding a TXOP. By transmitting the CF-End frame, a communication device can notify other communication devices of the end of the TXOP it holds. Furthermore, a communication device that receives a CF-End frame can resume channel access processing by canceling its own NAV setting. Note that, in this embodiment, the AP 102 notifies the end of the remaining period of the TXOP period 603 by using the CF-End frame, but the frame used is not limited to this. For example, the frame that notifies the end of the remaining period of the TXOP period 603 may be a predetermined control frame. The predetermined control frame in this embodiment is a MAC frame, and is a frame in which the Type field indicates 01 and the Subtype field indicates 1110. The predetermined control frame can also notify the end of the remaining period of the TXOP period. The predetermined control frame can also cancel the NAV of other surrounding communication devices. The control frame transmitted here does not have to be a CF-End frame. For example, the Type field may indicate 01 and the Subtype field may indicate 1111. This frame may be defined as a frame for the Shared AP to return the shared TXOP to the Sharing AP.

[0064] When the AP 101 receives the CF-End frame 609 transmitted by the AP 102 , it waits until a SIFS time 610 has elapsed since the completion of reception of the CF-End frame, and transmits a data frame 611 to the STA 105 after the SIFS time 610 has elapsed.

[0065] In this way, AP 101 starts transmitting wireless frames after the SIFS period, which is shorter than the waiting time of other communication devices, has elapsed, allowing it to transmit data before other communication devices acquire new TXOPs. As a result, other communication devices determine that the channel is busy based on the data frame 606, and therefore determine that they do not yet have a chance to transmit. This makes it possible to avoid collisions between the transmission of wireless frames by AP 101 and those of other communication devices.

[0066] 7 shows an example of a flowchart showing the operation of AP 101 when performing TXOP sharing. This operation flow is processed by AP 101 receiving a connection instruction or a communication instruction from a communication partner, and the control unit 202 reading and executing a computer program stored in the storage unit 201. The following description will be of the operation of AP 101, but AP 102 and AP 103 can also operate in the same way. At the start of this flowchart, AP 101 to AP 103 have already formed a multi-AP group for cooperative operation.

[0067] First, the control unit 202 of the AP 101 attempts to acquire a TXOP (transmission opportunity) by checking whether the channel is idle during the randomly determined collision avoidance waiting time (S701). If it is confirmed that the channel is idle during the collision avoidance waiting time, it determines that the AP 101 has acquired a transmission opportunity. If the control unit 202 determines that the AP 101 has acquired a transmission opportunity, it proceeds to S702. On the other hand, if the operating channel is busy or if another communication device acquires a transmission opportunity and starts data transmission during the AP 101's waiting time, making the operating channel busy, it determines that the transmission opportunity has not been acquired. If the control unit 202 determines that the transmission opportunity has not been acquired, it waits until the channel becomes idle again and then attempts to acquire a transmission opportunity again. If the AP 101 acquires a transmission opportunity, it transmits a CTS-to-self frame 601 to secure the acquired TXOP period 602. Furthermore, other communication devices that receive the CTS-to-self frame are assumed to set NAVs corresponding to the TXOP period.

[0068] The control unit 202 then determines whether to allocate a portion of the TXOP period acquired by the AP 101 to another AP (S703). In this step, the AP 101 makes this determination based on, for example, information acquired in advance. For example, the previously acquired information may indicate that the other AP has a large amount of data to communicate with the connected STA. In this case, the AP 101 determines in S703 to allocate a portion of the TXOP to the other AP. Alternatively, the previously acquired information may indicate that low-latency information is periodically communicated between the other AP and the connected STA. In this case, the AP 101 determines in S703 to allocate a portion of the TXOP to the other AP. If the control unit 202 determines to allocate a portion of the period in which the AP has a transmission opportunity based on the acquired transmission opportunity to the other AP, the process proceeds to S704. If the control unit 202 determines not to allocate a portion of the period in which the AP has a transmission opportunity to the other AP, the process proceeds to S711.

[0069] In S704, the control unit 202 transmits an MU-RTS TXS Trigger frame to perform TXOP sharing, which allocates a portion of the period during which the control unit has secured a transmission opportunity to another AP. In this embodiment, the AP 101 transmits an MU-RTS TXS Trigger to the AP 102, and TXOP sharing with the AP 102 is performed. When transmitting the MU-RTS TXS Trigger frame, the communication unit 206 controls the antenna 207 to transmit the signal omnidirectionally to the outside. Note that if the control unit 206 wants to maintain a longer period of time secured by itself than the period allocated by the MU-RTS TXS Trigger frame, the communication unit 206 controls the antenna 207 to transmit a CTS-to-self frame. The AP 101 presents a period indicating that it has a transmission opportunity in a CTS-to-self frame, and transmits an MU-RTS TXS Trigger frame to allocate part of that period to the AP 102. The frame transmission operation is performed by the functional units 301 to 304 operating in cooperation with each other. In this embodiment, the AP 101, which has secured a TXOP period 602, allocates a TXOP period 603 to the AP 102 using the MU-RTS TXS Trigger frame.

[0070] Next, the wireless communication control unit 303 waits for reception of a CTS frame, which is a response to the transmitted MU-RTS TXS Trigger frame (S705). The frame received (detected) by the wireless communication control unit 303 is analyzed by the frame analysis unit 302, and reception is confirmed by determining whether the frame is a CTS frame. If the AP 102 receives the MU-RTS TXS Trigger frame, the AP 102 will transmit a CTS frame after the SIFS time has elapsed since transmitting the MU-RTS TXS Trigger frame. If the CTS frame is not received within a certain period of time, the process returns to S702. If the CTS frame is received, the process proceeds to S706. Note that the TXOP period indicated in the CTS frame is equal to the period assigned to the AP 102 in the MU-RTS TXS Trigger frame transmitted by the AP 101.

[0071] When the AP 101 receives a CTS frame, it means that the AP 102 recognizes TXOP sharing and will start communication during the allocated TXOP period. Here, the control unit 202 checks whether the frame analysis unit 302 has received a CF-End frame from the AP 102 indicating that the allocated period will be returned midway (S706). If a CF-End frame has not been received, the process proceeds to S707. If a CF-End frame has been received, the process proceeds to S708. If a CF-End frame has not been received, the control unit 202 checks whether the allocated period has elapsed (S707). S706 and S707 are repeated until the allocated period has elapsed. If the allocated period has elapsed, the process proceeds to S709. In S708, the AP 101 also waits for a predetermined period after receiving the CF-End frame (S708). In this embodiment, the predetermined period is set to be the SIFS time. The waiting time may be shorter than the time from when the CF-End frame is received until all other communication devices determine that they have received a transmission opportunity, and may be, for example, a PIFS (PCF (Point Coordination Function) Inter Frame Space) time.

[0072] In S708, the control unit 202 checks whether or not the TXOP period secured by transmitting the CTS-To-self frame in S702 remains, using the TXOP sharing control unit 304. If there is a remaining period, the process proceeds to S710. If there is no remaining period, the process ends, assuming that the TXOP period secured by the device itself has expired.

[0073] In addition, in S704, a portion of the TXOP period may be allocated to a STA connected to AP 101. In this case, in S706, the AP 101 also waits to receive a frame containing a CAS Control subfield in the HT Control field, with the RDG / More PPDU subfield of said field set to a value of 0. This allows the STA to return the TXOP by using a frame with the RDG / More PPDU subfield set to a value of 0 or a CF-End frame. For example, if the STA to which the TXOP is allocated wishes to return the TXOP in conjunction with transmitting data, it can use a frame with the RDG / More PPDU subfield set to a value of 0. On the other hand, if the STA to which the TXOP is allocated wishes to return the TXOP in conjunction with canceling the NAV of another nearby communication device, it can use a CF-End frame. In this way, the STA to which the TXOP is allocated can perform a more efficient TXOP return process by selectively using the two frames described above.

[0074] If there is any remaining time in the TXOP period acquired by the AP itself, the control unit 202 determines whether to re-allocate part of the period to another AP or STA (S710). If re-allocation is to be performed, the process returns to S704. If no allocation is to be performed, the process proceeds to S711.

[0075] In S711 and S712, the AP 101 determines whether to transmit a trigger frame or a data frame based on predetermined conditions. The determination based on each condition is a determination for determining the operation to be performed by the AP 101 after the SIFS time has elapsed after receiving the CF-End frame in this embodiment. The content of the determination based on each condition after the SIFS time has elapsed in this embodiment is not limited to these. Furthermore, the order in which the determination based on each condition is made is not limited to these. Furthermore, the timing of the determination based on each condition for determining the operation after the SIFS time has elapsed is not limited to these. For example, the determination based on each condition for determining the operation may be made in parallel with the SIFS period wait (S708) as the predetermined period described above. Furthermore, the determination based on each condition for determining the operation may be made in advance by making a determination at the timing of receiving each data or at regular intervals. In this way, the AP 101 makes a determination based on each condition for determining the operation and determines what wireless frame to transmit.

[0076] In S711, the control unit 202 cooperates with the communication unit 206 and the communication control unit 303 to determine whether to prompt another communication device to transmit data and to communicate data as the data receiving side (S711). If it is determined that the other communication device should be prompted to transmit data, the AP 101 transmits a Trigger frame (S712). In this case, for example, the AP 101 transmits a Trigger frame to the STA 105 to prompt the STA 105 to transmit uplink data. When transmitting the Trigger frame, the communication unit 206 controls the antenna 207 to transmit the signal omnidirectionally to the outside. If the STA 105 is prompted to transmit data, after receiving a data frame from the STA 105, the communication unit 206 transmits a Block Ack (BA) frame to the STA 105 to confirm receipt. When the data reception procedure is completed, the process proceeds to S716.

[0077] In S712, the control unit 202 cooperates with the communication unit 206 and communication control unit 303 to determine whether to transmit data to another communication device (S712). When transmitting a data frame, the communication unit 206 controls the antenna 207 so that the signal is transmitted omnidirectionally to the outside. Thereafter, a BA frame is received to confirm reception. When the data transmission procedure is completed, the process proceeds to S716.

[0078] In S715, the control unit 202 ends and releases the TXOP period secured in S702. S715 is an operation executed in response to the AP 101 determining to release the remaining TXOP period. In this embodiment, the AP 101 executes this process in response to a No determination in S711 or S712, but this is not limited to this. For example, the determination of whether to release the TXOP period may be made before the determinations in S711 and S712.

[0079] In this embodiment, in S715, the AP 101 controls to transmit a CF-End frame or not transmit any wireless frames. In S715, the AP 101 controls to transmit a CF-End frame in response to determining that it is necessary to cancel the surrounding NAV. By transmitting a CF-End frame, the AP 101 can cancel the unintended NAV of the surrounding communication devices. Furthermore, in S715, the AP 101 controls not to transmit any wireless frames in response to determining that it is not necessary to cancel the surrounding NAV. Since there are no communication devices that have set an unintended NAV among the surrounding communication devices, it is possible to release the TXOP period for other surrounding communication devices without transmitting unnecessary wireless frames. Note that, in this embodiment, an example has been described in which the AP 101 transmits a CF-End frame in S715, but this is not limited to this. For example, a frame in which the value of the RDG / More PPDU subfield in the CAS Control subfield of the HT Control field is 0 may be transmitted.

[0080] In S716, the control unit 202 checks whether or not the TXOP period secured by transmitting the CTS-to-self frame in S702 remains, using the TXOP sharing control unit 304. If there is a remaining period, the process returns to S703. If there is no remaining period, the process ends.

[0081] (Other Embodiments) A recording medium on which program code for software that realizes the above-described functions is recorded may be supplied to a system or device, and a 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 itself read from the recording medium realizes the functions of the above-described embodiments, and the recording medium on which the program code is stored constitutes the above-described device.

[0082] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

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

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

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

[0086] The disclosure of the above-described embodiment also includes the following configurations.

[0087] (Configuration 1) A communication device comprising: an acquisition means for acquiring a Transmission Opportunity (TXOP) for transmitting a radio frame; an acquisition means for reserving a first TXOP period using a first radio frame; a sharing means for allocating a second TXOP period of the first TXOP period to another communication device using a trigger frame; a receiving means for receiving a predetermined control frame during the second TXOP period indicating the end of the second TXOP period; and a control means for, when the predetermined control frame is received during the second TXOP period, controlling the communication device to transmit a second radio frame after a predetermined Inter Frame Space (IFS) time has elapsed since the reception of the control frame, wherein the control means controls the communication device to transmit the second radio frame based on a predetermined condition.

[0088] (Configuration 2) The communication device according to configuration 1, wherein the predetermined control frame is a Contention Free-End (CF-End) frame.

[0089] (Configuration 3) The communication device according to configuration 1 or 2, wherein the predetermined IFS is a Short IFS.

[0090] (Configuration 4) The communication device according to configuration 1 or 2, wherein the predetermined IFS is a Point Coordination Function IFS.

[0091] (Configuration 5) The communication device according to any one of configurations 1 to 4, wherein the Trigger frame is a Multi User-Request To Send TXOP Sharing Trigger (MU-RTS TXS Trigger) frame.

[0092] (Configuration 6) The communication device according to any one of Configurations 1 to 5, wherein the communication device and the other communication device are APs, and the communication device further comprises construction means for constructing a wireless network.

[0093] (Configuration 7) The communication device according to any one of Configurations 1 to 6, wherein the second radio frame is the Trigger frame, and the control means controls to transmit the Trigger frame based on a determination that a third TXOP period of the first TXOP period is to be allocated to another communication device different from the other communication device.

[0094] (Configuration 8) The communication device according to any one of configurations 1 to 6, wherein the second wireless frame is a data frame, and the control means controls the communication device to transmit the data frame based on a determination that data is to be transmitted to a communication device participating in the wireless network.

[0095] (Configuration 9) The communication device according to any one of configurations 1 to 6, wherein the second wireless frame is the Trigger frame, and the control means controls the communication device to transmit the Trigger frame based on a determination that the communication device participating in the wireless network should be prompted to transmit a data frame.

[0096] (Configuration 10) The communication device according to any one of configurations 1 to 6, wherein the second radio frame is the predetermined control frame, and the control means controls to transmit the predetermined control frame based on determining that the first TXOP period has ended.

[0097] (Configuration 11) The communication device according to any one of Configurations 1 to 10, wherein when the control means determines that the first TXOP period should end after receiving the predetermined control frame, the control means controls so as not to transmit the second radio frame in the second TXOP period after a predetermined IFS time has elapsed since receiving the predetermined control frame.

[0098] (Configuration 12) The communication device according to any one of configurations 1 to 11, wherein the first wireless frame used by the securing means and the trigger frame used by the sharing means are the same frame.

[0099] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0100] This application claims priority based on Japanese Patent Application No. 2023-201135, filed November 28, 2023, the entire contents of which are incorporated herein by reference.

[0101] 201 Storage unit 202 Control unit 203 Functional unit 204 Input unit 205 Output unit 206 Communication unit

Claims

1. A communications device comprising: an acquisition means for acquiring a Transmission Opportunity (TXOP) for transmitting a wireless frame; an acquisition means for acquiring a first TXOP period using a first wireless frame; a sharing means for allocating a second TXOP period of the first TXOP period to another communications device using a trigger frame; a receiving means for receiving a predetermined control frame indicating the end of the second TXOP period during the second TXOP period; and a control means for controlling the transmission of a second wireless frame after a predetermined Inter Frame Space (IFS) time has elapsed since the reception of the predetermined control frame during the second TXOP period, wherein the control means controls the transmission of the second wireless frame based on predetermined conditions.

2. The communication device according to claim 1, wherein the predetermined control frame is a Contention Free-End (CF-End) frame.

3. The communication device according to claim 1, wherein the predetermined IFS is a Short IFS.

4. The communication device according to claim 1, wherein the predetermined IFS is a Point Coordination Function IFS.

5. The communication device according to claim 1, wherein the Trigger frame is a Multi User-Request To Send TXOP Sharing Trigger (MU-RTS TXS Trigger) frame.

6. A communication device according to any one of claims 1 to 4, characterized in that the communication device and the other communication device are APs, and the communication device further comprises construction means for constructing a wireless network.

7. The communication device according to claim 6, characterized in that the second radio frame is the Trigger frame, and the control means controls to transmit the Trigger frame based on a determination that a third TXOP period of the first TXOP period is to be allocated to another communication device different from the other communication device.

8. The communication device according to claim 6, characterized in that the second wireless frame is a data frame, and the control means controls the transmission of the data frame based on a determination that data is to be transmitted to a communication device participating in the wireless network.

9. The communication device according to claim 6, characterized in that the second wireless frame is the Trigger frame, and the control means controls the communication device to transmit the Trigger frame based on a determination that the communication device participating in the wireless network should be prompted to transmit a data frame.

10. The communication device according to claim 6, characterized in that the second radio frame is the specified control frame, and the control means controls to transmit the specified control frame based on a determination that the first TXOP period has ended.

11. The communication device according to claim 6, characterized in that, when the control means determines that the first TXOP period is to end after receiving the specified control frame, the control means controls so as not to transmit the second radio frame in the second TXOP period after a specified IFS time has elapsed since receiving the specified control frame.

12. The communication device according to claim 1, wherein the first wireless frame used by said securing means and the Trigger frame used by said sharing means are the same frame.

13. A control method for a communication device, comprising: an acquisition step of acquiring a Transmission Opportunity (TXOP) for transmitting a radio frame; a securing step of securing a first TXOP period using a first radio frame; a sharing step of allocating a second TXOP period of the first TXOP period to another communication device using a trigger frame; a receiving step of receiving a predetermined control frame indicating the end of the second TXOP period during the second TXOP period; and a control step of, when the predetermined control frame is received during the second TXOP period, controlling to transmit a second radio frame after a predetermined Inter Frame Space (IFS) time has elapsed since the reception, wherein the control step controls to transmit the second radio frame based on a predetermined condition.

14. A program for causing a computer to function as the control method for a communication device according to claim 13.

Images