Communication device, control method, and program

Abstract

A communication device corresponding to standards for the IEEE 802.11 series includes a communication means for communicating with a first other communication device in a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device, and determines whether or not the first other communication device permits transmission in the TXOP period by a second other communication device different from the first other communication device on the basis of a signal received from the first other communication device, and when it is determined that transmission in the TXOP period by the second other communication device is permitted by the first other communication device, sets a standby time before the communication device transmits any of the frames addressed to the first other communication device in the TXOP period to be longer than a standby time for the case when it is determined that transmission in the TXOP period by the second other communication device is not permitted by the first other communication device.

Description

Communication device, control method, and program

[0001] The present invention relates to a communication device, a control method, and a program that comply with the IEEE 802.11 series of standards.

[0002] The IEEE 802.11 series of standards is known as a communication standard for wireless local area networks (WLANs). The latest IEEE 802.11be standard uses multi-link technology to achieve high peak throughput and low latency communications (Patent Document 1).

[0003] US Patent Application Publication No. 2021 / 0211375

[0004] Currently, the IEEE has launched the IEEE 802.11bn Task Group (TG) to establish a successor standard to 802.11be, aiming to further improve reliability. One of the targets of the IEEE 802.11bn TG is low latency communication (LL communication). In this LL communication, even when a first communication device (TXOP holder) that has acquired a transmission opportunity (TXOP) and a second communication device (TXOP responder) are communicating, a third communication device may need to interrupt and transmit. Such interrupt communication by a third communication device is called a preemption operation. Even if the third communication device waits until the TXOP period has elapsed before transmitting and is unable to satisfy the delay requirement for LL communication, the delay requirement for LL communication of the third communication device can be satisfied by transmission related to the Preemption operation (Preemption transmission).On the other hand, since communication between the first communication device and the second communication device that have acquired a transmission opportunity is delayed by the Preemption transmission, there has been a problem in that there are cases where the Preemption transmission should not be permitted.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a technique for improving the convenience of preemption operations.

[0006] In order to solve the above-mentioned problems, the communication device of the present invention is a communication device compatible with the IEEE 802.11 series of standards, and comprises: communication means for communicating with a first other communication device during a transmission opportunity (TXOP) period reserved by the communication device for transmitting one or more data frames to the first other communication device; receiving means for receiving from the first other communication device information for specifying whether the first other communication device will accept a second other communication device different from the first other communication device transmitting one or more data frames to the communication device during the TXOP period; and control means for, when it is determined based on the received information that the first other communication device will accept the second other communication device transmitting the one or more data frames during the TXOP period, setting a waiting time before the communication device transmits at least one data frame addressed to the first other communication device during the TXOP period to be longer than the waiting time when it is determined that the first other communication device will not accept the second other communication device transmitting the one or more data frames during the TXOP period.

[0007] According to the present invention, it is possible to provide a technique for improving the convenience of preemption operations.

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

[0009] The accompanying drawings are included in and constitute a part of the specification, illustrate embodiments of the present invention, and together with the description, are used to explain the principles of the present invention. A configuration diagram of a wireless communication system according to this embodiment A hardware configuration diagram of a communication device according to this embodiment A software configuration diagram of a communication device according to this embodiment A diagram showing the structure of a MAC frame A diagram showing the structure of a Frame Control field A diagram showing the Action frame structure of a Preemption request / response A diagram showing the structure of an Action field A diagram showing a list of category values ​​A diagram showing a frame structure in which a Category for "UHR" is set A diagram showing the structure of an Action field A diagram showing the frame structure of a Preemption request A diagram showing the frame structure of a Preemption response A diagram showing the structure of Common Info included in a Multi-Link Element A diagram showing the structure of a profile subelement for each STA A diagram showing the structure of STA Control A diagram showing the structure of an EDCA parameter set element Parameter Diagram showing the structure of Record Diagram showing the structure of ACI / AIFSN Diagram showing the correspondence between ACI and Access Category Diagram showing the correspondence between MAC frame Type and Subtype Diagram showing the correspondence between Type, Subtype and Control Frame Extension Diagram showing the structure of pRTS Diagram showing the structure of pCTS Diagram showing the structure of the MAC frame of BlockACK (BA) BA 1. Diagram showing the structure of Control. 2. Flowchart showing the processing executed by AP. 3. Flowchart showing the downlink processing executed by AP. 4. Processing flow executed by TXOP responder (STA). 5. Flowchart showing the processing executed by preemption requesting STA. 6. Flowchart showing the processing executed by preemption requesting STA when receiving pRTS. 7. Flowchart showing preemption transmission processing executed by preemption requesting STA. 8. Sequence diagram showing an example of processing according to Examples 1 to 4. 9. Sequence diagram showing an example of processing according to Example 5.

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] The configuration of a system according to this embodiment will be described with reference to Fig. 1. The wireless communication system 1 includes an access point (AP) 101 and a distributed system (DS) 105.

[0012] AP 101 is a wireless communication device that communicates with terminals (STAs) that may be located within the area indicated by a circle in Fig. 1. In the example of Fig. 1, three STAs 102 to 104 are assumed to exist within the range (service area) that can be connected to AP 101, but the number of STAs is not limited. AP 101 manages a basic service set (BSS), which is a network configured by AP 101 and STAs 102 to 104.

[0013] The STAs 102 to 104 are wireless communication devices that connect to the AP 101 and communicate as clients. The STAs are also called non-AP STAs. In this embodiment, the AP 101 and the STAs 102 to 104 communicate in accordance with the IEEE 802.11 series standards.

[0014] The DS 105 is a network device that provides the AP 101 with a distributed system access function (DSAF) and can connect to the BSS formed by the AP 101 and the STAs 102-104 as well as other BSSs and external networks. This access function (connection means) is provided via wired communications such as Ethernet (registered trademark) or telephone lines, or via wireless communications such as LTE (Long-Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). Furthermore, the access function may be provided via wireless local area network (WLAN) communications conforming to the IEEE 802.11 series standards. In this case, the wireless channel used for WLAN communications between the AP 101 and the DS 105 may be the same as or different from the wireless channel used for communications between the AP 101 and the STAs 102-104.

[0015] 2 shows a hardware configuration diagram of a wireless communication device according to this embodiment, including the AP 101 and the STAs 102 to 104. As an example of the hardware configuration, the wireless communication device has 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.

[0016] The storage unit 201 is configured with memories such as ROM (read only memory) and RAM (random access memory), and stores programs for performing various operations described below, and various information such as communication parameters for wireless communication described below. Note that, in addition to ROM, RAM, etc., storage media such as a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, non-volatile memory card, DVD, etc. may be used as the storage unit 201. Furthermore, the storage unit 201 may be equipped with multiple memories.

[0017] The control unit 202 includes one or more processors and controls the overall operation of the wireless communication device by executing programs stored in the storage unit 201. The processor includes at least one or more of a central processing unit (CPU), a microprocessing unit (MPU), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), and a field-programmable gate array (FPGA). The control unit 202 may control the wireless communication device through cooperation between the programs stored in the storage unit 201 and an operating system (OS). The control unit 202 may also include multiple processors, such as multi-core processors, and the processors may cooperate to control the wireless communication device. The control unit 202 also controls the function unit 203 to perform predetermined processing to realize the functions of the wireless communication device. For example, the wireless communication device may perform different processing depending on the role of the wireless communication device, such as performing an AP function when the wireless communication device is the AP 101 and performing an STA function when the wireless communication device is one of the STAs 102 to 104. Furthermore, the control unit 202 can execute processes for realizing different functions, such as an imaging function, a printing function, and a projection function, depending on the hardware included in the functional unit 203 .

[0018] The functional unit 203 is hardware that enables the wireless communication device to execute predetermined processes. In one example, the functional unit 203 includes at least one of an imaging unit, a printer unit, a projector unit, and a scanner unit. The functional unit 203 can realize different functions, such as an imaging function, a printing function, and a projection function, under the control of the control unit 202.

[0019] The input unit 204 includes input interfaces such as buttons, a microphone, and a pointing device for receiving various operations from the user. The output unit 205 includes output interfaces such as a display and a speaker for providing various outputs to the user. Here, output by the output unit 205 includes at least one of a display on a screen, an audio output by a speaker, a vibration output, and the like. Note that both the input unit 204 and the output unit 205 may be implemented by a single module, such as a touch panel. For example, the input unit 204 and the output unit 205 may be implemented by a touch panel.

[0020] The communication unit 206 controls wireless communication compliant with the IEEE 802.11 series standards, wireless communication compliant with Wi-Fi (registered trademark), and IP (Internet Protocol) communication. Furthermore, the communication unit 206 controls the antenna 207 to transmit and receive wireless signals for wireless communication. Specifically, the communication unit 206 is configured to be able to communicate wireless frames compliant with the IEEE 802.11bn standard, which is the successor to the IEEE 802.11be standard and targets a maximum transmission speed of 46.08 Gbps. IEEE stands for Institute of Electrical and Electronics Engineers. IEEE 802.11bn, the successor standard to IEEE 802.11be, lists high-reliability communication, low-latency communication, and improved throughput during congestion as its main features. One of the goals of 802.11bn is also to reduce power consumption in APs. Wireless frames communicated using this successor standard are also referred to as UHR (Ultra High Reliability) PPDUs. PPDU stands for Physical Layer Protocol Data Unit. In other words, the AP 101 and STAs 102-104, each having a communication unit 206, communicate by exchanging UHR PPDUs with each other. The name UHR was established for convenience, reflecting the goals to be achieved by the successor standard and the key features of the standard; it may be called something different once the standard is fully established. Similarly, the name IEEE 802.11bn may be changed to a different name once the standard is fully established. However, please note that this specification and the accompanying claims are essentially applicable to all successor standards to the 802.11be standard. Furthermore, while the AP 101 and STAs 102-104 having the communication unit 206 are described as supporting UHR PPDU communication (transmission and reception), they may also be configured to support PPDU communication of legacy standards that predate the UHR standard. Specifically, they may be configured to support PPDU transmission and reception of IEEE 802.11a / b / g / n / ac / ax / be standards, etc.

[0021] The antenna 207 includes one or more antennas. For simplicity, only one antenna is shown in Fig. 2. In general, the number of antennas included in the antenna 207 corresponds to the number of spatial streams.

[0022] The communication unit 206 and the antenna 207 may include a plurality of communication units 206 and antennas 207, the number of which corresponds to the corresponding frequency bands (2.4 GHz band, 5 GHz band, 6 GHz band) and the corresponding number of streams.

[0023] 3 shows an example of the functional (software) configuration of a wireless communication device. The wireless communication device has, as its software configuration, a wireless LAN control unit 301, an Enhanced Distributed Channel Access (EDCA) control unit 302, and a priority EDCA control unit 303. The wireless communication device also has, as its software configuration, a preemption control unit 304, a low latency (LL) communication function unit 305, a storage unit 306, a user interface (UI) control unit 307, and an antenna control unit 308.

[0024] The wireless LAN control unit 301 includes circuits for transmitting and receiving wireless signals to and from other wireless LAN devices (e.g., other APs or STAs) and programs for controlling these circuits. The wireless LAN control unit 301 performs wireless LAN communication control, such as frame generation and frame transmission, and reception of wireless frames from other wireless LAN devices, in accordance with the IEEE 802.11 standard series.

[0025] After recognizing that the wireless medium is idle, the EDCA control unit 302 performs transmission processing after a predetermined frame interval and a backoff counter time have elapsed. EDCA is a priority control method defined by the IEEE 802.11 standard. Packets are classified into four access categories (ACs), stored in a transmission queue, and transmitted according to their respective priorities.

[0026] When the preemption operation is possible, the priority EDCA control unit 303 performs transmission (preemption transmission) related to the EDCA operation during a preemption declaration period, which will be described later.

[0027] The preemption control unit 304 requests permission for preemption transmission from the AP 101 and determines whether preemption transmission is permitted in the BSS. Here, preemption transmission refers to an interruption by another STA (preemption STA) during a period (TXOP period) allocated for communication between the AP 101, which is the TXOP holder, and one STA, which is the TXOP responder. Preemption transmission by the preemption STA during the TXOP period is realized by accessing the wireless medium using priority EDCA parameters instead of normal EDCA parameters.

[0028] The LL communication control unit 305 controls communications that are sensitive (have constraints) to delay and jitter (fluctuation), such as video communications and audio communications. The LL communication control unit 305 performs transmission related to EDCA operation when an application requiring communications that are sensitive to delay and jitter is executed. In other words, the LL communication control unit 305 controls the EDCA control unit 302 to access the wireless medium using normal EDCA parameters for transmissions other than preemption transmissions. On the other hand, when preemption transmission is permitted by the preemption control unit 304, the LL communication control unit 305 controls the priority EDCA control unit 303 to access the wireless medium using priority EDCA parameters.

[0029] The storage unit 306 includes storage devices such as a ROM (read only memory) and a RAM (random access memory) that store programs executed by the wireless communication device and various data.

[0030] The UI control unit 307 is configured to include hardware related to a user interface (UI), such as a touch panel or buttons, for accepting operations by a user (not shown) on the AP 101 and the STAs 102 to 104, and a program for controlling these. The UI control unit 307 also has a function for presenting information to the user, such as displaying images or outputting audio. The antenna control unit 308 controls the antenna function.

[0031] <MAC Frame Structure> The structure of a medium access control (MAC) frame related to the preemption operation will be described.

[0032] 4A shows the structure of a MAC frame used in the IEEE 802.11 series of standards. MAC frame 400 includes Frame Control 401, Duration 402, Addresses 1 to 3 403 to 405, Sequence Control 406, and Address 4 407. MAC frame 400 also includes Quality of Service (QoS) Control 408, High Throughput (HT) Control 409, Frame Body 410, and Frame Check Sequence (FCS) 411.

[0033] Frame Control 401 is a two-octet (16-bit) field including subfields 412 to 422, which will be described later with reference to FIG. 4B, and contains control information for the frame.

[0034] Duration 402 is a two-octet (16-bit) field, and can indicate the time such as the frame length or the length of the TXOP period by setting the MSB (most significant bit: B15) to "1." In this case, the 15 bits other than the MSB indicate the frame length or the length of the TXOP period with a value from 0 to 32767 microseconds.

[0035] Addresses 1 to 4 403, 404, 405, and 407 are 6-octet (42-bit) fields that store information indicating the address of the wireless communication device. The BSSID, source address, destination address, and so on are set depending on the type (Type 413) and subtype (Subtype 414) of the MAC frame 400. Note that the address fields used differ depending on the type, and Addresses 2 to 4 404, 405, and 407 may be omitted.

[0036] Sequence Control 406 is a 0- or 2-octet field that indicates the sequence number of the data to be transmitted, or the fragment number if the data is fragmented.

[0037] QoS Control 408 is a 0 or 2-octet field for controlling the QoS of a data frame. A BSR (Buffer Status Report) in standards prior to IEEE 802.11ax is stored in QoS Control 408.

[0038] HT Control (HTC) 409 is a 0 or 4 octet field that contains control information related to high throughput HT or very high throughput (VHT).

[0039] The Frame Body 410 is a variable-length field that stores various information elements (IEs) when the Type 422 of the Frame Control 401 indicates a management frame, that is, a beacon or a probe request / response.

[0040] FCS 411 is a 4-octet field that stores a value for checking whether there are any errors in the MAC header or data portion. The MAC header consists of Frame Control 401 to QoS Control 408, and HT Control 409 and Frame Body 410 are called a MAC Service Data Unit (MSDU).

[0041] 4B, the Frame Control 401 will be described in detail. The Frame Control 401 includes a Protocol Version 412, a Type 413, a Subtype 414, a To DS 415, a From DS 416, and a More Fragment 417. The Frame Control 401 also includes a Retry 418, a Power Management 419, More Data 420, a Protected Frame 421, and a +HTC 422.

[0042] Protocol Version 412 is a 2-bit field that indicates the version of the protocol under which the MAC frame is transmitted, and is set to "0" for IEEE 802.11 frames.

[0043] Type 413 is a 2-bit field that indicates whether the MAC frame is of management, control, or data type.

[0044] Subtype 414 is a 4-bit field that indicates a subtype that further classifies the type of management, control, or data indicated by Type 413.

[0045] The To DS 415 is a 1-bit field indicating whether the destination of the MAC frame is the DS 105. The From DS 416 is a 1-bit field indicating whether the source of the MAC frame is the DS 105.

[0046] More Fragment 417 is a 1-bit field indicating whether the MAC frame has been fragmented. Retry 418 is a 1-bit field indicating whether the MAC frame has been retransmitted. Power Management 419 is a 1-bit field indicating whether the STA is in power save mode. More Data 420 is a 1-bit field indicating whether there is data addressed to an STA in power save mode. Protected Frame 421 is a 1-bit field indicating whether the MSDU is encrypted. +HTC 422 is a 1-bit field indicating whether the MAC frame 400 includes HT Control 409. +Frames in which the HTC 422 can set bit "1", that is, frames that can include the HT Control 409, are QoS data, Management, or RTS (Request to Send) frames. There are further detailed conditions, but the explanation is omitted here.

[0047] 5A to 5N, a description will be given of an example of the configuration of an action frame transmitted and received when requesting or responding to a preemption operation according to this embodiment.

[0048] The action frame 500 shown in Fig. 5A is similar to the MAC frame 400 described with reference to Fig. 4A, and therefore will not be described further. A MAC frame in which Type 413 (bits B3 to B2) in Frame Control 401 is set to "00" and Subtype 414 (bits B7 to B4) is set to "1101" is an action frame, which is a type of management frame.

[0049] 5B shows an example of the structure of the frame body 410 of the action frame 500. The frame body 410 of the action frame 500 includes a category 501 and an action 502. The category 501 indicates that the MAC frame is an action frame. The category 501 is a one-octet field, and the action 502 is of variable length.

[0050] 5C shows the correspondence between codes set in Category 501 and their meanings. In FIG. 5C, codes "0" to "37" are defined in IEEE 802.11be Draft 4.0. For example, code "0" indicates "Spectrum Management," code "3" indicates "Block ACK (BA)," code "36" indicates "Very High Throughput (EHT)," and code "37" indicates "Protected EHT." For each category, a format for Action 502 is defined.

[0051] In this embodiment, a new code "38" is defined as the value of Category 507 for "UHR," enabling transmission and reception of control signals related to preemption operations. However, Action Details for control signals related to preemption operations may be defined in the Action Details of an existing Category 507 value, for example, code "37." This means that reserved values ​​for the EHT category are used for UHR. A more specific explanation follows. Action 502 for EHT consists of a one-octet Action Value field that stores a type value indicating the type of action, and a variable-length field that stores detailed information about the action corresponding to the value of the Action Value field. In this case, the type value, which is a reserved value in EHT, is assigned to the control signal related to preemption operations. Then, the field configuration of the detailed information for the action corresponding to the type value is defined. This mechanism allows the reserved values ​​of the EHT category to be used for transmitting control signals related to UHR preemption operations. Note that the specific action types and corresponding detailed information may be configured in the same manner as the action types and detailed information of the UHR category, which will be described later.

[0052] 5D shows the configuration of a Frame Body in which the value of Category 501 is set to the code "38," which indicates UHR. In the action field for UHR, Action 502 includes Action Value 508, which stores a one-octet type value indicating the type of action, and variable-length Action Details 509, which stores detailed information for the action corresponding to the type value. Because Action Value 508 is an Action value for UHR, it is also called the UHR Action Value.

[0053] 5E is a diagram showing the definition of the correspondence between the value set in Action Value 508 and its meaning. When "0" is set as Action Value, a permission request (preemption request) 510 requesting permission for the preemption operation is indicated. When "1" is set as Action Value, a response (preemption response) 511 to the permission request for the preemption operation is indicated.

[0054] 5F shows the configuration of an action frame for a request for permission to perform a preemption operation when the Action Value 508 is set to "0." The permission request is transmitted from the STA to the AP 101.

[0055] In the action field for a Preemption request, Action 502 includes Action Value 508 with a code set to "0", Dialog Token 512, and Multi-Link Element 513.

[0056] The Dialog Token 512 is a one-octet field that is used to distinguish between multiple requests when multiple requests exist.

[0057] The Multi-Link Element 513 is a field that is also used in the Action frame described below with reference to FIG. 5G. The preemption operation can also be performed in the IEEE 802.11be Multi-Link configuration. For this reason, it is defined as a Multi-Link Element. The Multi-Link Element 513 includes common information (Common Info) and a profile subelement for each STA, as described below with reference to FIG. 5H.

[0058] 5G shows the configuration of an action frame when the Action Value is set to "1," i.e., for a response to a permission request for a preemption operation. The permission request is transmitted from the AP 101 to the STA.

[0059] 5G, Action 502 includes Action Value 508 with a code set to "1." Action 502 also includes Dialog Token 514, Status Code 515, and Multi-Link Element 516.

[0060] The Dialog Token 514 is a one-octet field that is used to distinguish between multiple requests when multiple requests exist.

[0061] Status Code 515 is a two-octet field and is defined in IEEE 802.11. If the AP 101 accepts the request for permission of preemption operation, it sets "0 (SUCCESS)." If the request is not accepted, it indicates non-permission (rejection) using a value reserved in the previous standard. For example, the AP 101 can determine whether to permit or reject preemption operation based on predetermined conditions, such as a fixed number of STAs that can perform preemption operation within a BSS. Note that in this embodiment, preemption operation can also be permitted or rejected by a STA operating as a TXOP responder, as described below. The structure of the MAC frame transmitted by a STA to permit or reject preemption operation will be described later with reference to FIGS. 6A, 6B, and 7.

[0062] The multi-link element 516 is similar to the multi-link element 513 in FIG. 5F, and therefore a description thereof will be omitted.

[0063] 5H shows an example of the configuration of common information (Common Info) included in Multi-Link Elements 513 and 516. The common information includes Common Info Length 517 and AP MLD MAC Address 518. Common Info Length 517 is a 1-octet field, and AP MLD MAC Address 518 is a 6-octet field.

[0064] 5I shows the configuration of the profile subelement for each STA included in the Multi-Link Element 513, 516. The profile subelement for each STA includes a Subelement ID 519, Length 520, STA Control 521, and STA Profile 522. The Subelement ID 519 is a one-octet field, the Length 520 is a two-octet field, and the STA Control 521 is a two-octet field. The STA Profile 522 is a variable-length field. The STA Profile 522 includes at least an EDCA parameter set element. As described above, the EDCA parameter set included in the STA Profile 522 of the MAC frame transmitted in response to the preemption permission request is the priority EDCA parameters for performing preemption transmission during the TXOP period.

[0065] 5J shows an example of the configuration of STA Control 521. STA Control 521 includes a 4-bit Link ID 523, and the remaining 12 bits are reserved. Link ID 523 is an identifier of the link requesting the preemption operation.

[0066] Fig. 5K shows an example of the configuration of an EDCA parameter set element included in STA Profile 522 in Fig. 5I. Since the EDCA parameter set element conforms to the IEEE 802.11-2020 standard, items with the same meaning and usage as those in the previous standard are simply shown as field names.

[0067] The EDCA parameter set element includes Element ID 524, Length 525, QoS Info 526, and Update EDCA Info 527, each of which is a one-octet field. The EDCA parameter set element also includes parameter records 528 to 531 for four access categories (BE: Best Effort, BK: Background, VI: Video, VO: Audio), each of which is a four-octet field. Parameter record 528 is an AC_BE Parameter Record, and parameter record 529 is an AC_BK Parameter Record. Parameter record 530 is an AC_VI Parameter Record, and parameter record 531 is an AC_VO Parameter Record.

[0068] As shown in FIG. 5L, each parameter record 528 to 531 includes an Arbitration Inter Frame Space Number (ACI / AIFSN) 532, an ECWmin / ECWmax 533, and a TXOP Limit 534.

[0069] The ACI / AIFSN 532 is a one-octet field that includes four subfields, as described below with reference to FIG. 5M.

[0070] ECWmin / ECWmax 533 is a one-octet field used to calculate a contention window for collision avoidance during EDCA access, and is defined by the following formula:

[0071] CWmin=2 ＥＣＷｍｉｎ -1 CWmax=2 ＥＣＷｍａｘ -1 Here, CWmin indicates the lower limit of the contention window, and CWmax indicates the upper limit of the contention window. In the conventional standard, the range of the above CWmin and CWmax is 0 for the minimum value and 32767 for the maximum value. In this case, priority control is realized by providing differences for each access category in the range indicated by the default value or the value notified by the beacon.

[0072] In one example, both CWmin and CWmax are set to 0. This setting sets the backoff counter to 0 (zero), and the access right is acquired after the time corresponding to AIFSN after SIFS (Short IFS) has elapsed, enabling access control suitable for LL communication.

[0073] TXOP Limit 534 is a two-octet field that indicates the time limit for one access right, measured in 32 microseconds. In the previous standard, AC_VI is specified as 4.096 milliseconds and AC_VO is specified as 2.080 milliseconds. TXOP Limit = 0 has a special meaning, indicating that only one MSDU (MAC Service Data Unit) or MMPDU (MAC Management Protocol Data Unit) can be transmitted.

[0074] 5M shows an example of the structure of ACI / AIFSN 532. ACI / AIFSN 532 includes a 4-bit AIFSN 535, a 1-bit ACM (Admission Control Mandatory) 536, a 2-bit ACI (Access Category Index) 537, and a 1-bit reserved field.

[0075] AIFSN 535 indicates the number of slots (time) after SIFS before backoff control is initiated during EDCA access. In the previous standard, the minimum value was 2, but in this embodiment, 0 or 1 can be specified. The slot time is also called aSlotTime, and the IEEE 802.11 standard defines values ​​for each physical layer. For example, in OFDM used in 802.11n and later, the aSlotTime is 9 microseconds in the 5 or 6 GHz band, and 9 or 20 microseconds in the 2.4 GHz band.

[0076] 5N, ACI 537 is associated with four access categories. For example, when ACI 537 is set to "0", it indicates that the access category is "AC_BE", that is, best-effort communication is performed.

[0077] Note that the STA Profile 522 of the Preempt response may include information indicating that the request is not permitted, rather than the EDCA parameters themselves. For example, a new ID indicating that the request is not permitted can be added to the Element ID 524.

[0078] 6A is a table of combinations of Type 413 and Subtype 414 in the header of the MAC frame shown in FIG. 4B. The table includes a Type-Subtype combination 601 that indicates a control frame extension when Type 413 is set to "01" and Subtype 414 is set to "0110." When Type 413 and Subtype 414 in the header of the MAC frame are set to combination 601, the following four bits are interpreted as a Control Frame Extension field.

[0079] 6B is a diagram showing details of the control frame extension value in the control frame extension field. In the control frame extension 601 according to this embodiment, pRTS (Preempt Request To Send) 602 and pCTS (Preempt Clear To Send) 603 are newly defined as control frame extension values. Here, a control frame extension value of 1100 indicates pRTS, and a control frame extension value of 1101 indicates pCTS. A frame (pRTS frame) in which the control frame extension value is set to pRTS is treated as an exclusive request frame transmitted to secure the TXOP period. A frame (pCTS frame) in which the control frame extension value is set to pCTS is treated as an exclusive response frame, which is a response to the exclusive request frame. 6B, in accordance with the conventions of the IEEE 802.11 standard, bit numbers are shown in descending order from left to right. That is, a MAC frame in which the Type field is set to "01", the Subtype field is set to "0110", and the Control Frame Extension field is set to "1100" is called a pRTS frame. Similarly, a MAC frame in which the Type field is set to "01", the Subtype field is set to "0110", and the Control Frame Extension field is set to "1101" is called a pCTS frame.

[0080] 6C shows the frame structure of a pRTS frame. The pRTS frame is an occupancy request frame that requests a STA in a BSS to reserve a transmission opportunity, and is also a control frame that indicates the period during which preemption operation is possible. Furthermore, the pRTS frame is interpreted by the destination of the pRTS as a permission request signal that requests permission for preemption operation.

[0081] The pRTS frame includes a Frame Control 604 , a Duration 605 , a receiving address (RA) 606 , a transmitting address (TA) 607 , and an FCS 608 .

[0082] Frame Control 604 is the same as Frame Control 401 in the MAC frame structure of Fig. 4A. Duration 605 is the period during which preemption operation is possible, and is also referred to as the preemption declaration period. RA 606 indicates the MAC address of the destination of the pRTS frame, and in this embodiment, the MAC address of the TXOP responder is set. TA 607 indicates the MAC address of the sender of the pRTS frame, and in this embodiment, the MAC address of the TXOP holder is set. FCS 608 is the same as FCS 411 in the MAC frame structure of Fig. 4A.

[0083] In this embodiment, after the preemption declaration period is notified by the pRTS frame, the preemption operation may be rejected by the pCTS frame. In this case, Duration 605 is interpreted as the TXOP period.

[0084] 6D shows the structure of a pCTS frame. As described above, the pCTS frame is a control frame that indicates that the TXOP responder allows the STAs in the BSS to perform preemption. The pCTS frame includes a Frame Control 609, a Duration 605, an RA 611, and an FCS 612.

[0085] Frame Control 609 is the same as Frame Control 401 in the MAC frame structure of Fig. 4A. Duration 610 stores a value indicating the end point of a period that coincides with the end point of the period indicated by Duration 605 of pRTS. RA 611 is the destination of the pCTS frame and indicates the MAC address of the TXOP holder that transmitted the pRTS frame. In this embodiment, the MAC address of the TXOP holder is set. FCS 612 is the same as FCS 411 in the MAC frame structure of Fig. 4A.

[0086] In this embodiment, if the TXOP responder does not permit preemption operation, the receiving station of the pRTS returns a conventional CTS frame. In this way, by switching between transmitting a pCTS frame or a conventional CTS frame in response to a pRTS frame, the TXOP responder can notify a group of terminals including the TXOP holder whether to permit preemption operation.

[0087] However, the TXOP responder may notify whether or not to permit the preemption operation by including information indicating whether or not to permit the preemption operation in the CTS frame. For example, if the RA 611 is a broadcast address, it may indicate that the preemption operation is permitted, and if the RA 611 is the address of the TXOP holder, it may indicate that the preemption operation is denied. In other words, information that can specify whether or not to permit the preemption operation may be included in any of the Frame Control 609, Duration 610, and RA 611 of the CTS frame.

[0088] Furthermore, the pCTS frame, which is an exclusive response, may include information indicating whether or not the preemption operation is permitted. As in the case of notification using a CTS frame, information that can specify whether or not the preemption operation is permitted may be included in any of the Frame Control 609, Duration 610, and RA 611 of the pCTS frame. Alternatively, unlike in FIG. 6B , two types of pCTS frames may be defined as the pCTS frame, which is an exclusive response. For example, this can be achieved by defining a value that permits the preemption operation and a value that rejects the preemption operation in the control frame extension value.

[0089] Furthermore, the TXOP responder according to this embodiment may include information indicating whether or not to permit preemption operation in a Block ACK (BA) that notifies that a data frame has been received.

[0090] 7A shows the structure of the BA frame. In the explanation of the BA frame, only the names of items that have the same meaning and usage as the conventional standard are listed.

[0091] Frame Control 701 is similar to Frame Control 401 in the MAC frame structure of Fig. 4A. By setting the value of Frame Control 401 as shown in Fig. 5C, it is possible to indicate that the MAC frame is a BA frame.

[0092] Duration 702, RA 703, and TA 704 are the same as Duration 605 to TA 607 described in Fig. 6C, and therefore will not be described here. Details of BA Control 705, a two-octet field, will be described later with reference to Fig. 7B. In this embodiment, BA Information 706, a variable-length field, may include, in addition to information about BA, a one-bit field indicating whether the TXOP responder permits preemption operation. FCS 707 is the same as the FCS in the MAC frame structure of Fig. 4A.

[0093] 7B shows the structure of the BA Control 705 in FIG. 7A. The BA Control 705 includes a Preemption 708, a multi-traffic identifier (TID) 709, a Compressed Bitmap 710, a GCR Mode 711, a Reserved 712, and a TID_INFO 713.

[0094] Preemption 708 is a field indicating whether or not preemption operation is permitted, and is set to 1 if permitted and 0 if denied. Note that this field is reserved in the conventional standard. Multi-TID 709, Compressed Bitmap 710, GCR Mode 711, Reserved 712, and TID_INFO 713 are the same as in the conventional IEEE 802.11 standard, so their explanation will be omitted.

[0095] Alternatively, as shown in FIG. 7A, whether or not Preempt is permitted may be indicated by the value of BA Information 706 .

[0096] In this way, in this embodiment, the TXOP responder can indicate permission or denial of the preemption operation not only by transmitting a pCTS frame but also by transmitting a BA frame. Therefore, a STA that is permitted to perform the preemption operation may monitor BAs from other terminals without entering a Power Save mode during the preemption declaration period, and determine whether to permit or deny the preemption operation.

[0097] 8 is a flowchart showing an example of processing executed by the control unit 202 of the AP 101. Unless otherwise specified, the following description will be given assuming that the AP 101 is the subject of the operation.

[0098] In S800, the control unit 202 starts processing. For example, the processing may be started during control processing other than data frame processing, and may be executed at any timing other than the preemption operation period. For example, the processing may be started at the start of processing to generate beacons transmitted at predetermined intervals, or when a MAC frame is received from a STA.

[0099] In S801, the control unit 202 determines EDCA parameters in a normal state (normal EDCA parameters). The normal state means a state in which a preemption operation is not in progress. Note that if default values ​​for the EDCA parameters are set in the wireless communication system or if default values ​​are specified by the standard, the process of S801 may be omitted.

[0100] In S802, the control unit 202 determines a policy for preemption operation. Here, the first parameter of the policy is the number of wireless communication devices capable of preemption operation. This value ranges from 0 to the number of connectable devices. The second parameter of the policy is a setting of access conditions when the number of wireless communication devices capable of preemption operation is two or more. Specifically, the setting of conditions includes rejecting a request from a STA when the limit on the number of connectable devices for preemption operation has been reached, or canceling the preemption operation of the wireless communication device with the lowest priority. Here, the priority can be arbitrarily determined based on, for example, the type of wireless communication device (XR / AR / VR / MR related to virtual reality, game console, etc.). The preemption operation policy may be selected from policy candidates predefined by the operator of the AP 101, or may be determined based on the communication environment, such as the packet loss rate and the number of packet collisions. Furthermore, the preemption operation policy may be determined according to the state of the AP 101, such as the buffer state or load state of the AP 101.

[0101] In S803, the control unit 202 detects the timing of transmitting a beacon signal. In S804, the control unit 202 controls the communication unit 206 to transmit a beacon signal including the normal EDCA parameters determined in S801. Note that if the processing of S801 is omitted, the control unit 202 may transmit a beacon signal not including the normal EDCA parameters in S803.

[0102] In S805, the control unit 202 determines whether the frame transmitted from any STA indicates a preemption operation request. If it is determined that the frame transmitted from the STA indicates a preemption operation request (Yes in S805), the control unit 202 proceeds to S806. If it is determined that a conventional standard frame, i.e., a frame that is not a preemption operation request, has been received (No in S805), the control unit 202 proceeds to S810.

[0103] In S806, it is confirmed whether there is another STA that has been permitted to perform preemption operation in S805. If there is another STA that has been permitted to perform preemption operation (Yes in S806), the control unit 202 proceeds to S807; otherwise, the control unit 202 proceeds to S809.

[0104] In S807, the control unit 202 determines whether a hidden terminal state has occurred in the wireless communication system. If not, the process proceeds to S809. If a hidden terminal state has occurred (Yes in S807), the control unit 202 proceeds to S808. The determination of whether a hidden terminal state has occurred in S807 is based on a report of the number of recognized terminals from each STA. The report of the number of recognized terminals is sent from each STA to the AP 101 at regular intervals and includes information indicating that each STA has detected a signal transmitted from another STA. This allows the AP 101 to determine whether each STA connected to the AP 101 can detect each other. The AP 101 stores the number of recognized terminals for each STA from the received report of the number of recognized terminals. Based on the report of the number of recognized terminals, the AP 101 may detect that a STA has not detected any other STA connected to the AP, i.e., that the STA cannot detect signals transmitted from other STAs in the wireless communication system. In such a case, the AP 101 determines that a hidden terminal state has occurred. On the other hand, it can be determined that a hidden terminal state has not occurred if all STAs have mutually detected the STAs connected to AP 101. In reporting the number of recognized terminals, a STA reports the other STAs that it has recognized as the number of recognized terminals, but in one example, the report to AP 101 may include the identifiers of the recognized STAs.

[0105] In S808, the control unit 202 determines the STAs to which preemption operation is permitted in accordance with the policy determined in S802. As described above, this policy can be arbitrarily determined for each wireless communication system, such as "preferentially permitting preemption operation to STAs whose device type is a game console." In another example, the policy may permit preemption operation in the order in which preemption operation requests are transmitted. For example, if a setting is made to not permit preemption operation when a hidden terminal state occurs, it may be determined that preemption operation is not permitted for any STA. This prevents collisions caused by a STA that fails to detect a transmission from a STA operating as a TXOP responder through carrier sensing transmitting a preemption. In this example, the description will be given assuming that preemption operation is permitted for the STA that transmitted the preemption request.

[0106] In S809, the control unit 202 determines priority EDCA parameters to be used when accessing the medium according to the policy. Note that if the STA that transmitted the preemption request in S808 is not permitted to perform the preemption operation, the process of S809 may be omitted. In one example, S809 may include determining an Arbitrate Inter Frame Spacing Number (AIFSN). In this embodiment, the priority EDCA parameters include an AIFSN with a value greater than 0.

[0107] In one example, in S809, the control unit 202 may determine priority EDCA parameters based on other STAs that have permitted preemption operation. For example, the control unit 202 may determine priority based on the traffic type of the STA. If it is determined that the priority of the STA is lower than that of other STAs that have already permitted preemption operation, the control unit 202 may notify the other STAs of parameters that are lower than the priority EDCA parameters notified to the other STAs. The lower parameter may be, for example, a parameter including a large AIFSN. In this way, by allowing STAs that permit preemption operation to access the medium using different EDCA parameters, it is possible to prevent collisions between transmissions from multiple STAs and improve the convenience of preemption operation.

[0108] In S810, the control unit 202 responds to the preemption permission request. If the preemption operation is permitted, the response to the preemption permission request (preemption response) includes information indicating permission and priority EDCA parameters. If the preemption operation is not permitted, the response includes only information indicating that permission, or includes normal EDCA parameters that are the same as the EDCA parameters in the normal state. Here, permission / denial is indicated by Status Code 515 shown in FIG. 5G.

[0109] In S811, if control processing other than responding to the preemption request is necessary, the control unit 202 executes that processing. That is, the processing of S811 may be omitted. After the processing of S811, the control unit 202 ends the processing shown in FIG. 8 (S812).

[0110] 9A and 9B are flowcharts illustrating an example of processing performed by the AP 101 in downlink communication from the AP 101 to a STA. The processing in FIGS. 9A and 9B will be described assuming that it is performed by the control unit 202 of the AP 101.

[0111] 9A and 9B is initiated when a data frame addressed to a connected STA is recognized. This data is generated by a communication device on the DS 105, another STA in the BSS, or an application on the AP 101. In this example, the description will be given assuming that the AP 101 receives downlink data addressed to the STA 102 from the DS 105.

[0112] In S902, the control unit 202 checks whether any STAs have permitted preemption operation. If no permitted STAs exist (No in S902), the control unit 202 executes the same processing as conventional (S903). That is, the control unit 202 executes the RTS / CTS procedure as necessary during the TXOP period, includes the data in a physical layer protocol data unit (PPDU), and transmits multiple PPDUs aggregated together. Since no STAs have permitted preemption operation, no transmission by preemption operation is executed during the TXOP period in S903. The maximum length of the PPDU transmitted from the AP 101 to the STA 102 in S903 is referred to as the "normal PPDU length."

[0113] If a permitted STA exists (Yes in S902), the control unit 202 proceeds to S904 and transmits a pRTS frame to the STA 102 that is the destination of the data frame, i.e., the TXOP responder. By receiving the pRTS frame, the STA 102 recognizes that permission for preemption operation has been requested. Therefore, the STA 102 determines whether or not to permit preemption operation in accordance with the policy, and transmits a response that can specify whether or not the operation is permitted.

[0114] Next, the control unit 202 proceeds to S905 to determine whether or not a pCTS frame has been received. If the AP 101 has received a pCTS frame (Yes in S905), the control unit 202 proceeds to S906. If the AP 101 has not received a pCTS frame (No in S905), the control unit 202 proceeds to S918. As described above, the pCTS is a response signal that is transmitted when the TXOP responder permits preemption operation. Therefore, the AP 101 executes the processes from S906 onward as processes when it determines that the preemption operation has been permitted by the TXOP responder.

[0115] In S906, the control unit 202 determines the maximum length (first length) of the PPDU to be transmitted during the period in which the preemption operation is permitted. The first length is determined to be shorter than the maximum length (second length) of the PPDU to be transmitted when the preemption operation is not permitted, in order to provide an opportunity for transmission from STAs other than the TXOP responder earlier through the preemption operation.

[0116] In this embodiment, the first length and the second length are determined as predetermined values ​​within the wireless communication system. In one example, the first length is set to be shorter than the second length by a predetermined ratio, such as half of the second length. In another example, the first length may be determined based on the length of the remaining time of the TXOP period, such as half or less of the remaining time of the TXOP period.

[0117] In S906, any change can be made to the PPDU as long as the preemption operation is performed to give an opportunity for transmission to STAs other than the TXOP responder earlier.

[0118] For example, it is possible to simply shorten the length of any of the PPDUs transmitted from the AP 101 to the STA 102 during the TXOP period. For example, the maximum length of the PPDU transmitted from the AP 101 to the STA 102 during the first half of the TXOP period may be shortened, and the maximum length of the PPDU transmitted during the second half of the TXOP period may be the normal PPDU length. In this case, although the maximum length of the PPDU transmitted during the TXOP period appears unchanged, the number of inter-data frame intervals increases because a short PPDU is transmitted during the first half. This increases the opportunities for transmissions due to preemption operation.

[0119] In S907, the control unit 202 determines an IFS within the period during which the preemption operation is permitted. The value of IFS can be determined arbitrarily by the AP 101 according to a policy. For example, if the policy is that the first PPDU must be transmitted, the IFS value is set to SIFS. In this case, the AIFSN of the STA that requested the preemption operation is not set to 0. This allows the SIFS to end in a time shorter than the backoff time of the STA that requested the preemption operation, thereby providing the AP 101 with an opportunity to transmit a PPDU. On the other hand, if the policy is that the first PPDU does not necessarily have to be transmitted, the IFS value may be set to a different value, such as a Distributed Coordination Function (IFS) (DIFS).

[0120] When the AP 101 according to this embodiment determines that the TXOP responder permits transmission by preemption operation, the AP 101 sets a waiting time to lengthen the waiting time before transmitting any of the frames communicated between the AP 101 and the STA 102 during the TXOP period. That is, when preemption operation is permitted, the AP 101 lengthens the waiting time before transmitting any of the frames compared to when preemption operation is not permitted. For example, when the STA 102 does not permit transmission by preemption operation, the AP 101 sets all interframe intervals to SIFS, whereas when the STA 102 permits transmission by preemption operation, the AP 101 sets at least one interframe interval to DIFS. This allows the STA 103 or 104 that requested preemption operation to detect the idle state of the medium and execute transmission by preemption operation. It should be noted that the inter-frame interval when transmission by preemption operation is permitted is not limited to DIFS, but may be any interval greater than SIFS.

[0121] In this embodiment, the AP 101 sets the waiting time before transmitting a frame addressed to a TXOP responder by adjusting the IFS. However, the method for adjusting the waiting time before transmitting a frame is not limited to this, and the waiting time before transmitting a frame may be adjusted by adjusting the number of slots in the contention window.

[0122] Furthermore, setting the waiting time so as to lengthen the waiting time before transmitting any data frame addressed to STA 102 during the TXOP period includes AP 101 not transmitting any data frame addressed to STA 102 during the TXOP period. For example, if preemption operation is not permitted, a second data frame is transmitted following the first data frame with a waiting time of SIFS. Here, if preemption operation is permitted, the first data frame is not transmitted, and the waiting time before transmitting the second data frame may be set to the length of two SIFS and the first data frame. This also allows transmission via preemption operation to occur.

[0123] S908 is processing during the IFS period. In S908, the control unit 202 monitors whether the medium remains idle for the time determined in S907. If the IFS period has elapsed while the medium remains idle, the control unit 202 proceeds to S909. On the other hand, if the medium remains idle and the IFS time has not elapsed, such as when a PPDU is received from STA 103 that has requested a preemption operation before the IFS has elapsed, the control unit 202 executes predetermined processing, such as transmitting a BA after STA 103 has finished transmitting.

[0124] In S909, the control unit 202 transmits the downlink data frame received in S901 to the destination STA, which is the TXOP responder in this example. In S910, the control unit 202 receives a BA for the data frame transmitted in S909 from the TXOP responder.

[0125] In S911, the control unit 202 checks the remaining time of the TXOP, i.e., the remaining time of the period during which the preemption operation is permitted, based on the time specified in the pRTS frame transmitted in S904 and the time specified in the pCTS frame received in S905.

[0126] If the TXOP period remains (Yes in S911), the control unit 202 proceeds to S912. If it is determined that the TXOP period does not remain (No in S911), the control unit 202 ends the downlink processing shown in Figs. 9A and 9B.

[0127] In S912, the control unit 202 checks whether the TXOP responder is in a state where preemption operation is permitted. This is performed by the AP 101 determining whether the TXOP responder permits preemption operation based on the received pCTS frame or CTS frame. If the control unit 202 determines that preemption operation is permitted (Yes in S912), the control unit 202 proceeds to S913. If the control unit 202 determines that preemption operation is denied (No in S912), the control unit 202 proceeds to S915.

[0128] In S913, the control unit 202 checks whether the BA frame received in S910 indicates that the preemption operation is permitted. If the control unit 202 determines that the BA frame indicates that the preemption operation is permitted (Yes in S913), the control unit 202 returns the process to S907. On the other hand, if the control unit 202 determines that the received BA frame indicates that the preemption operation is rejected (No in S913), the control unit 202 proceeds to S914.

[0129] In S914, the control unit 202 sets the length of the PPDU to the normal PPDU length, and proceeds to S919. That is, if the BA frame indicates that preemption operation is not permitted, S914 and S919 set the waiting time before transmitting a frame addressed to the TXOP responder to be longer than the waiting time when preemption operation is permitted.

[0130] In S915, the control unit 202 checks whether the BA frame received in S910 indicates that the preemption operation is permitted. If the control unit 202 determines that the BA indicates that the preemption operation is permitted (Yes in S915), the control unit 202 proceeds to S916. On the other hand, if the control unit 202 determines that the BA indicates that the preemption operation is rejected (No in S915), the control unit 202 proceeds to S919.

[0131] In S916, the control unit 202 sets the length of the PPDU to a length shorter than the normal PPDU length, and the process proceeds to S907. The process of S916 is the same as the process of S906.

[0132] In S918, the control unit 202 determines whether or not a CTS frame has been received. If a CTS frame has been received, the control unit 202 proceeds to S919. In S919, the control unit 202 sets the IFS to SIFS, and proceeds to S908.

[0133] In this embodiment, the preemption operation is permitted when a pCTS frame is received, and the preemption operation is denied when a CTS frame is received. However, if the information in the pCTS frame indicates whether the preemption operation is permitted or denied, different processes may be executed in steps S905 and S918. For example, after step S904, if the information in the pCTS frame indicates that the preemption operation is permitted, the process may proceed to step S906, and if the information in the pCTS frame indicates that the preemption operation is not permitted, the process may proceed to step S919.

[0134] In other words, S906 is a process performed when the received pCTS permits the preemption operation, and S919 is a process performed when the received pCTS rejects the preemption operation. Similarly, as described above, the processes of Figures 9A and 9B can be replaced and performed when the information in the CTS frame indicates whether the preemption operation is permitted or not, or when the information in another frame indicates whether the preemption operation is permitted or not.

[0135] If a CTS is not received in S918 (No in S918), the control unit 202 proceeds to S920. The process of S920 is executed when the TXOP responder fails to receive a pRTS frame, or when the TXOP holder fails to receive a pCTS frame or a CTS frame. Therefore, in S920, the control unit 202 determines whether or not a pRTS frame needs to be retransmitted. If the pRTS frame needs to be retransmitted (Yes in S920), the process returns to S904; otherwise, the process shown in FIGS. 9A and 9B ends (S921) as a downlink processing failure. One example of a case in which a pRTS frame should not be retransmitted is when the limit on the number of pRTS frame retransmissions has been reached.

[0136] 10 is a flowchart showing an example of processing by a wireless communication device (TXOP responder) that receives a pRTS frame. The processing shown in FIG. 10 is realized by the control unit 202 of the STA 102 operating as the TXOP responder executing a program at the start of the TXOP period (S1000).

[0137] In S1001, the control unit 202 receives a pRTS frame addressed to STA 102. Based on the received pRTS signal in S1001, it can be recognized that a request has been made to permit transmission by a preemption operation by a STA other than STA 102 and AP 101 during the TXOP period allocated to STA 102. In S1002, the control unit 202 determines whether to permit or reject transmission by a preemption operation by a STA other than STA 102 and AP 101.

[0138] If transmission by a STA other than STA 102 and AP 101 is permitted during the TXOP period (Yes in S1002), the control unit 202 proceeds to S1003 and transmits a pCTS signal indicating that transmission by preemption operation is permitted. The destination of the pCTS frame is AP 101, but other terminals that detect the pCTS signal can recognize that transmission by preemption operation is permitted, and preemption operation becomes possible.

[0139] On the other hand, if transmission by preemption operation is not permitted (No in S1002), the control unit 202 proceeds to S1004 and transmits a CTS frame indicating that transmission by preemption operation is not permitted, i.e., is rejected. The destination of the CTS frame is the AP 101, but other STAs that detect the CTS frame can recognize that transmission by preemption operation has been rejected. In one example, the STA 102 may transmit a CTS frame when it recognizes that data should be received uninterrupted before receiving a PPDU, i.e., that there is a time limit (timeout) for data reception. For example, the STA 102 may recognize that there is a time limit for data reception based on the application executed by the STA 102.

[0140] In S1005, the control unit 202 of the STA 102 receives a PPDU (data frame) from the AP 101. In S1006, the control unit 202 determines whether a subsequent PPDU exists. If the control unit 202 determines that reception of the data frame has ended, i.e., that data frame reception will not continue (No in S1006), the process proceeds to S1010; otherwise, the process proceeds to S1007. In S1010, the STA 102 transmits a BA compliant with the conventional standard, i.e., a BA that does not indicate whether transmission by preemption operation is permitted, to the AP 101, and ends the downlink reception of FIG. 10 .

[0141] In S1007, the control unit 202 determines whether to change the state of permission or denial of transmission by preemption operation. That is, in S1007, after the determination in S1002, it determines whether there is a change in permission or denial of preemption operation. If it is determined that the state of permission or denial of transmission by preemption operation is to be changed (Yes in S1007), the control unit 202 proceeds to S1008, and if not, the control unit 202 proceeds to S1009.

[0142] In S1008, the STA 102 transmits a BA indicating whether transmission through the preemption operation is permitted or denied. In one example, if an application performing low-latency communication is executed after the decision to permit transmission through the preemption operation in S1002, transmission through the preemption operation may be denied. In another example, after deciding to deny transmission through the preemption operation in S1002, the STA 102 may receive at least one PPDU and analyze the data, and then transmit a BA frame indicating that transmission through the preemption operation is permitted in S1008. Furthermore, even if the STA 102 transmits a pCTS frame in S1003, the STA 102 may analyze the data after receiving one or more PPDUs and determine that downlink data should be received without interruption. In such a case, the STA 102 may transmit a BA frame denying transmission through the preemption operation. This means that permission for transmission by the preemption operation by the pCTS frame transmitted in S1003 is cancelled. Also, after transmitting the BA frame in S1008, the process of S1007 is executed again, and as a result of determining to change the state of permission or denial of preemption, a BA specifying a state different from the previous state can be transmitted. Note that, within the TXOP period, BA frames indicating permission or denial of transmission by this preemption operation can be transmitted without any restrictions.

[0143] In S1009, the control unit 202 transmits a BA frame (a conventional BA frame) that does not include information on whether the preemption operation is permitted or denied. After the process of S1008 or S1009, the control unit 202 returns the process to S1005.

[0144] 11 is a flowchart illustrating an example of processing executed by a STA requesting transmission through preemption operation. In this processing example, the STAs 103 and 104 are described as requesting transmission through preemption operation. The processing illustrated in FIG. 11 is implemented by the control units 202 of the STAs 103 and 104 executing a program. In one example, the processing illustrated in FIG. 11 is executed when traffic with a delay requirement occurs, such as when the STAs 103 and 104 execute an application that performs low-latency communication in a normal state after connecting with the AP 101.

[0145] In S1101, the control unit 202 transmits a preemption request to the AP 101 and receives a preemption response. Subsequently, in S1102, the control unit 202 determines whether the preemption response received from the AP 101 indicates that transmission by the preemption operation is permitted. If the control unit 202 determines that the preemption response received from the AP 101 indicates that transmission by the preemption operation is permitted (Yes in S1102), the control unit 202 proceeds to S1103; otherwise, the control unit 202 proceeds to S1104.

[0146] In S1103, the EDCA parameters (priority EDCA parameters) included in the preemption response are stored separately from the normal EDCA parameters, and the process proceeds to S1200. The priority EDCA parameters may include the AIFSN for determining the contention window, as described above. In S1104, it is determined that transmission by preemption operation is not permitted, and channel access parameters are set so that the STAs 103 and 104 do not transmit during TXOP periods in which they are not TXOP responders, and the process ends. In one example, after the process of S1104, the control unit 202 may wait for a predetermined time and then execute the process shown in FIG. 11 again.

[0147] Fig. 12 is a flowchart showing details of the process of S1200. S1200 is realized by the control unit 202 of the STA 103 or 104 executing a program following the process of S1103 in Fig. 11. In the following explanation, it is assumed that the control unit 202 of the STA 103 executes the process of Fig. 12. Note that the process of Fig. 12 is executed before the preemption declaration period.

[0148] In S1201, the control unit 202 receives a pRTS frame from the AP 101. In S1202, the control unit 202 sets a timer for the period during which the preemption operation is performed based on the received pRTS frame. The time of this timer is the Duration included in the pRTS frame.

[0149] Here, during the period specified by Duration, there is a possibility that the TXOP responder will permit preemption operation. Therefore, when the control unit 202 functions as a state control unit that controls the state of the STA 103, the STA 103 requesting preemption operation maintains the normal state (first state) during the TXOP period and does not transition to the power saving mode (second state). In one example, the first state is a state in which a MAC frame such as a BA frame transmitted from another STA is decoded and the frame is analyzed. The second state is a state in which a MAC frame such as a BA frame transmitted from another STA is not decoded, or information on the decoded MAC frame such as a BA frame is not analyzed.

[0150] In S1203, the control unit 202 waits until the SIFS time has elapsed since the reception of the pRTS frame. Next, in S1204, the control unit 202 determines whether or not a pCTS frame has been detected. If a pCTS frame has been detected (Yes in S1204), the control unit 202 proceeds to S1205; otherwise, the control unit 202 proceeds to S1207.

[0151] In S1205, the control unit 202 updates the timer for the period during which the preemption operation is performed based on the value of Duration in the pCTS frame.

[0152] In S1206, the control unit 202 determines that the state of the STA 103 is a state in which preemption operation is permitted. In this state, access is performed using the priority EDCA parameters included in the preemption response, rather than the normal EDCA parameters or default EDCA parameters included in the beacon signal transmitted from the AP 101. Here, the default EDCA parameters are parameters used when accessing the medium outside the preemption declaration period.

[0153] The process of S1207 is performed when the STA 103 detects a CTS frame after an SIFS, which is the interframe interval after a pRTS frame, or when the STA 103 does not detect anything, and the control unit 202 determines that the preemption operation is not permitted. In this case, the control unit 202 operates as usual, that is, does not perform medium access using the priority EDCA parameters included in the preemption response during the preemption declaration period.

[0154] After the process of S1206 or S1207, the control unit 202 of the STA 103 advances the process to the process during the preemption declaration period of S1208.

[0155] 13 is a flowchart showing an example of processing executed by the control unit 202 of the STAs 103 and 104 that have requested transmission by preemption operation during the preemption declaration period. In this example, the processing in FIG. 13 will be described as being executed by the STA 103. The processing shown in FIG. 13 is executed by starting the preemption declaration period timer following S1206 or S1207 in FIG. 12.

[0156] In S1301, the control unit 202 determines whether uplink data of LL communication is accumulated in the buffer. If it is determined that uplink data of LL communication is accumulated (Yes in S1301), the control unit 202 proceeds to S1302 and determines whether preemption operation is permitted. If it is determined that uplink data of LL communication is not accumulated (No in S1301), the control unit 202 does not transmit data and proceeds to S1308.

[0157] If it is determined that the preemption operation is permitted (Yes in S1302), the control unit 202 proceeds to S1303 and determines whether or not the access right for transmitting the preemption has been acquired. If it is determined that the preemption operation is not permitted (No in S1302), the control unit 202 proceeds to S1306.

[0158] In S1303, the control unit 202 performs carrier sensing during the contention window identified from the priority EDCA parameters included in the preemption response, and if it determines that the medium is in an idle state, it determines that the access right has been acquired. If the access right has been acquired (Yes in S1303), the control unit 202 proceeds to S1304 and transmits LL data to the AP 101. A UHR PPDU can be used for the wireless frame of this transmission. If it has been determined that the access right has not been acquired (No in S1303), the control unit 202 proceeds to S1306.

[0159] After transmitting a signal using the preemption operation in S1304, the control unit 202 advances the process to S1305, receives a BA frame from the AP 101, and advances the process to S1308. In S1308, the control unit 202 compares the Duration value included in the received pRTS frame with the elapsed time on the timer, and determines whether the preemption declaration period timer has expired. If the preemption declaration period timer has expired (Yes in S1308), the control unit 202 returns the process to S1100 and transitions to the normal state; if the timer has not expired (No in S1308), the control unit 202 returns the process to S1301.

[0160] In S1306, the control unit 202 determines whether downlink communication is occurring from the AP 101 to the STA 102 (TXOP responder). If it is determined that downlink communication is occurring (Yes in S1306), the control unit 202 proceeds to S1307.

[0161] In S1307, the control unit 202 updates the permission status of the preemption operation according to the contents of the BA frame from STA102 (TXOP responder). That is, even if the preemption operation is rejected in the CTS frame, if the BA frame received in S1307 indicates that the preemption operation is permitted, STA103 determines that the preemption operation is permitted when executing the process of S1302 again. This allows the STA performing the preemption operation to detect that the permission or denial status of the preemption operation by STA102, the TXOP responder, has changed during the preemption declaration period. Here, the BA frame transmitted from the TXOP responder can be detected because the pCTS frame has been detected in S1204. If the access right has not been acquired through the preemption operation while no downlink communication is occurring, the control unit 202 advances the process to S1308.

[0162] Hereinafter, several examples will be described with reference to the operation sequences of the DS 105, AP 101, and STAs 102 to 104.

[0163] 14A and 14B show an operation sequence of a first example according to this embodiment. In the following description, the reference numerals in Figures 8 to 13 are shown in parentheses to correspond to the reference numerals in Figures 14A and 14B.

[0164] In step F1400 (S801), the AP 101 determines EDCA parameters for the normal state. In step F1401 (S804), the AP 101 transmits a beacon signal. In the examples of Figures 14A and 14B, it is assumed that the STAs 102 to 104 receive the beacon signal.

[0165] In F1402 (S1101), the STA 103 transmits a preemption request to the AP 101. This enables the AP 101 to detect that the STA 103 is requesting permission to transmit using the preemption operation.

[0166] In step F1403 (S805), the AP 101 analyzes the preemption response and determines EDCA parameters (priority EDCA parameters) for preemption operation according to the policy. In this case, if the policy is to accept preemption operation, the EDCA parameters are more favorable than the EDCA parameters notified in the beacon. Here, the "superior parameters" refer to parameters that are expected to enable medium access in a shorter time when determining a contention window compared to when the contention window is determined according to inferior parameters. Parameters that enable medium access in a shorter time refer to at least one of having a smaller CWmin, a smaller CWmax, and a smaller (CWmax-CWmin) / 2.

[0167] In F1404 (S809), the AP 101 returns a preemption response to the STA 103. This allows the STA 103 to obtain EDCA parameters for accessing the medium when performing a preemption operation.

[0168] In F1405 (S1101), the STA 104 transmits a preemption request to the AP 101. In F1406 (S806 to S808), the AP 101 analyzes the preemption response and determines priority EDCA parameters in accordance with the policy. In this case, if the policy is to perform priority control on a first-come, first-served basis when the number of STAs requesting preemption operation is two or more, the AP 101 may notify the STA 104 of parameters that are more prioritized than the EDCA parameters notified in the beacon but less prioritized than the EDCA parameters notified to the STA 103. This reduces the possibility of collisions when multiple STAs transmit using preemption operation during the preemption declaration period. In F1407 (S809), the AP 101 returns a preemption response to the STA 104. In this embodiment, it is assumed that STA103 and STA104 are not hidden terminals.

[0169] At F1408, the DS 105 transmits data for the STA 102 to the AP 101.

[0170] In F1409 (S901), the AP 101 detects that downlink data addressed to the STA 102 has been generated.

[0171] In F1410 (S904), AP 101 transmits a pRTS frame to STA 102. In F1411 (S1003), STA 102 transmits a pCTS frame to AP 101 as a response to the pRTS frame received in F1410. Here, STA 103 and STA 104 may or may not be able to recognize this pCTS frame.

[0172] In F1412 (S906, S907), AP 101 executes a process not to induce STA 103 or STA 104 to transmit using preemption operation. Here, as a process not to induce preemption, AP 101 sets the value of IFS to SIFS. The process of F1412 is executed, for example, when transmitting the first PPDU to STA 102. At this time, STA 102 recognizes the attribute (sender) and content of the data in the subsequent PPDU from the content of the PPDU, and can therefore determine whether to continue the permitted state of preemption operation based on the PPDU.

[0173] At F1413 (S1301), LL communication data is generated at STA 103, and at F1414 (S1301), LL communication data is generated at STA 104. That is, STAs 103 and 104 determine that transmission by preemption operation is necessary at F1413 and F1414. The timing of the generation of this LL communication data is assumed to be unpredictable (unschedulable). In this sequence, it is assumed that the LL communication data is generated before the start of IFS, which is the inter-frame interval after transmission from AP 101 to STA 102.

[0174] In step F1415 (S909), AP 101 transmits a PPDU after the SIFS has elapsed following the pCTS frame. At this time, STA 103 and STA 104 cannot obtain access rights because the IFS of STA 103 and STA 104 is greater than the SIFS, i.e., the AIFSN is not 0.

[0175] In F1416 (S910), the STA 102 transmits a BA frame to the AP 101. This BA frame is a conventional BA frame, that is, it does not include information that can identify whether or not preemption operation is permitted. The AP 101 determines that the STA 102 that received the BA frame transmitted in F1416 is in a state in which preemption operation is permitted.

[0176] In F1417 (S907 and S908), the AP 101 performs processing to induce transmission by preemption operation. The processing to induce transmission by preemption operation means not transmitting a PPDU even if SIFS has elapsed since the reception of the BA frame. This control not to transmit is performed until a time equivalent to the AIFSN for preemption notified to the STA 103 has elapsed. This allows the AP 101 to provide an opportunity for transmission by a STA requesting preemption operation during the preemption declaration period.

[0177] In F1418 (S1303), the STA 103 acquires the access right. Here, in the preemption operation, the STA 103 sets CWmin and CWmax to 0 (zero) and does not perform decrement of the back-off counter.

[0178] In step F1419 (S1304), the STA 103 transmits a PPDU including data for LL communication to the AP 101. In step F1420 (S1305), the AP 101 transmits to the STA 103 a BA frame for the PPDU transmitted in step F1419.

[0179] In this sequence, the AIFNS of STA 104 is larger than the AIFS of STA 103 by N, and STA 104 and STA 103 are not in a hidden terminal relationship. This prevents collisions caused by STA 104 transmitting while STA 103 is transmitting.

[0180] The processing from F1421 to F1424 is the same as that from F1412 and F1415 to F1417. However, it is assumed that no LL data is retained in STA 103, and that the LL data of F1414 is retained in STA 104. Also, it is assumed that in F1424, the medium is in an idle state until a time equivalent to the AIFSN for preemption notified to STA 104 by AP 101 has elapsed.

[0181] At F1425 (S1303), the STA 104 acquires access rights. At F1426 (S1304), the STA 104 transmits a PPDU including LL data. At F1427 (S1305), the AP 101 transmits a BA frame to the STA 104. Steps F1428 to F1430 are the same as steps F1412 and F1415 to F1416, and therefore description thereof will be omitted.

[0182] In F1431, the preemption declaration period specified by the Duration of the pRTS ends, and the processing of FIGS. 14A and 14B ends.

[0183] As described above, in this embodiment, collisions due to preemption operations can be avoided by differentiating (ranking) the AIFSNs of the EDCA parameters notified when permitting preemption operations to multiple terminals. This allows flexible priority control and improves the convenience of preemption operations.

[0184] 14A and 14B, a description will be given of a second embodiment of the present invention. Note that the process up to F1422 is the same as that in the first processing example, and therefore the description will be omitted.

[0185] In the second embodiment, in F1423, the STA 102 transmits a BA frame including information indicating that the preemption operation is not permitted to the AP 101. In this case, the processing from F1425 to F1427 does not occur, and the processing proceeds to F1431.

[0186] In this way, after a TXOP responder has authorized preemption operation by a pCTS frame, it can revoke authorization for preemption operation during the preemption declaration period specified by the Duration included in the pCTS frame. This allows the TXOP responder to flexibly respond to changes in its situation and improves the convenience of preemption operation.

[0187] 14A and 14B, a description will be given of a third embodiment of the present invention. Note that the process up to F1410 is the same as that in the first processing example, and therefore the description will be omitted.

[0188] In F1411, the STA 102 transmits a CTS frame instead of a pCTS frame to the AP 101. In this case, the processing from F1418 to F1420 or from F1425 to F1427 does not occur, and the processing proceeds to F1431.

[0189] In this way, the TXOP responder can reject the preemption operation by using the CTS frame, and the preemption operation can be performed in accordance with the intention of the TXOP responder, thereby improving the convenience of the preemption operation.

[0190] Fourth Embodiment In the first embodiment, the AP 101 notifies the end of the preemption declaration period at any timing after F1412. This can be done in the following two ways.

[0191] In the first method, the AP 101 transmits a preemption response to the STA in F1404 or F1407, indicating that the preemption operation is not permitted. This is indicated by a Status Code or an EDCA parameter. This is not a direct response to the preemption request, but a response using an unsolicited response action frame.

[0192] In the second method, the AP 101 transmits a CF-End (RA is a broadcast address) during the TXOP period as a notification of the end of the preemption declaration period. This notification of the end of the preemption declaration period can be performed at the AP 101's discretion or upon request from the TXOP holder. Here, this request can be realized by the reserved field (7 bits) of the BA frame.

[0193] By using such an end frame, it is possible to flexibly respond to changes in the status of the TXOP holder during the preemption period specified by the Duration included in the pRTS frame, thereby improving the convenience of the preemption operation.

[0194] Fifth Embodiment With reference to FIG. 15, a process will be described in which the timing at which the AP 101 induces a preemption operation and the timing at which LL data is generated in the STA are close to each other.

[0195] In F1500, STA103 is set to operate with AIFSN=1, and in F1501, STA104 is set to operate with AIFSN=2. In other words, STA103 has more advantageous access parameters than STA104.

[0196] At F1502, LL communication data is generated at STA 104. At F1503, a PPDU is transmitted from AP 101 to STA 102. At this time, AP 101 performs access control to prevent STA 103 and STA 104 from performing preemption operations. At F1504, a BA frame is transmitted from STA 102 to AP 101.

[0197] In F1505, the AP 101 starts a process of inducing transmission related to the preemeration operation. In this case, the AP 101 refrains from transmitting for two slots (two aSlotTimes) after the SIFS in order to target the STA 104.

[0198] At F1506, SIFS elapses, and at F1507, one slot after SIFS elapses.

[0199] Here, assume that LL data occurs in STA 103 in F1508. In this embodiment, STA 103 does not perform transmission by preemption operation even if there is no LL communication data when AIFSN elapses and LL communication data occurs before the next slot time elapses. Therefore, in F1509, STA 103 refrains from medium access.

[0200] At F1510, two slots after the SIFS have elapsed. As a result, at F1511, the STA 104 acquires the access right, and at F1512, the STA 104 transmits a PPDU (LL data). At F1513, the AP 101 transmits a BA frame to the STA 104.

[0201] In this way, STA 103 refrains from accessing the medium at F1509, thereby preventing collision with F1512 transmitted by another STA. Here, the transmission timing of each STA, including AP 101, is determined on a slot-by-slot basis, and transmission is not started in the middle of a slot.

[0202] 15 shows a modification of this embodiment in which steps F1511 to F1513 are not performed. In step F1514, the STA 103 acquires access rights (F1515) after the slot time of the normal AIFSN, which is not a preemption operation, has elapsed. This allows the STA 103 to transmit LL data to the AP 101.

[0203] In this way, by limiting the medium access timing of the preemption operation to AIFSN slot units, the possibility of collision is reduced, the utilization efficiency of the wireless medium is improved, and the convenience of the preemption operation is improved.

[0204] The present invention can also be realized by a process in which a program that realizes one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a 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.

[0205] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention.

[0206] This application claims priority based on Japanese Patent Application No. 2023-215051, filed December 20, 2023, the entire contents of which are incorporated herein by reference.

[0207] 101: AP, 102-104: STA, 105: DS, 510: Preemption request, 511: Preemption response, 532: ACI / AIFSN, 533: ECWmin / ECWmax, 534: TXOP Limit, 602: pRTS, 603: pCTS, 708: Preemption

Claims

1. A communications device conforming to the IEEE 802.11 series of standards, comprising: a communications means for communicating with a first other communications device during a transmission opportunity (TXOP) period reserved by the communications device for transmitting one or more data frames to the first other communications device; a receiving means for receiving from the first other communications device information for specifying whether the first other communications device will accept a second other communications device different from the first other communications device to transmit one or more data frames to the communications device during the TXOP period; and a control means for, when it is determined based on the received information that the first other communications device will accept the second other communications device to transmit the one or more data frames during the TXOP period, setting a waiting time before the communications device transmits at least one data frame addressed to the first other communications device during the TXOP period to be longer than the waiting time when it is determined that the first other communications device will not accept the second other communications device to transmit the one or more data frames during the TXOP period.

2. The communication device of claim 1, wherein the communication means transmits a permission request to the first other communication device requesting that the second other communication device accept transmitting the one or more data frames during the TXOP period, the receiving means receives a response to the permission request from the first other communication device, and the control means determines whether the first other communication device accepts the second other communication device transmitting the one or more data frames during the TXOP period based on the response received by the receiving means.

3. The communication device according to claim 2, wherein the communication means transmits an occupancy request frame requesting the reservation of the TXOP period as the permission request, and the control means determines that the first other communication device will not accept the second other communication device from transmitting the one or more data frames during the TXOP period when the receiving means receives a Clear To Send (CTS) frame in response to the occupancy request frame, and determines that the first other communication device will accept the second other communication device from transmitting the one or more data frames during the TXOP period when the receiving means receives an occupancy response frame different from the CTS frame in response to the occupancy request frame.

4. The communication device of claim 2 or 3, wherein the communication means transmits an occupancy request frame requesting the reservation of the TXOP period as the permission request, the receiving means receives an occupancy response frame as a response to the occupancy request frame, and when the control means determines that the received occupancy response frame contains specified information, it determines that the first other communication device accepts the second other communication device from transmitting the one or more data frames during the TXOP period.

5. The communication device according to claim 3 or 4, wherein the occupation request frame and the occupation response frame are different from a Request To Send (RTS) frame or a Clear To Send (CTS) frame in at least one of a Type field, a Subtype field, and a Control Frame Extension field of a Medium Access Control (MAC) frame.

6. The communication device according to any one of claims 2 to 5, wherein the communication means transmits a Request To Send (RTS) frame as the permission request, the receiving means receives a Clear To Send (CTS) frame as the response, and the control means, when determining that the received CTS frame contains predetermined information, specifies that the first other communication device accepts the second other communication device from transmitting the one or more data frames during the TXOP period.

7. The communication device according to any one of claims 1 to 6, wherein when the control means receives a Block ACK (BA) frame by the receiving means as a response to a data frame transmitted by the communication means to the first other communication device within the TXOP period, the control means determines whether or not the first other communication device accepts the second other communication device transmitting the one or more data frames during the TXOP period based on the received BA frame.

8. The communication device according to any one of claims 1 to 7, wherein the receiving means receives a transmission request from the second other communication device requesting that the second other communication device be accepted to transmit the one or more data frames during the TXOP period, and in response to the transmission request, transmits to the second other communication device Enhanced Distributed Channel Access (EDCA) parameters to be used for accessing a medium when the second other communication device is accepted to transmit the one or more data frames during the TXOP period.

9. The communications device of claim 8, wherein the EDCA parameters include an Arbitration Inter Frame Space Number (AIFSN) having a value greater than zero.

10. A communication device as described in any one of claims 1 to 9, characterized in that when the control means determines that the first other communication device will accept the second other communication device to transmit the one or more data frames during the TXOP period, it sets the maximum length of the data frame transmitted from the communication device to the first other communication device during the TXOP period to be shorter than when the control means determines that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period.

11. A communication device as described in any one of claims 1 to 10, characterized in that when the control means determines that the first other communication device will accept the second other communication device to transmit the one or more data frames during the TXOP period, it controls the frame length of the data frames so that the number of inter-frame intervals between data frames transmitted from the communication device to the first other communication device during the TXOP period is greater than when the control means determines that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period.

12. The communication device according to any one of claims 1 to 11, wherein the control means, when it is determined that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period, sets all inter-frame intervals before frames transmitted from the communication device to the first other communication device to Short Inter Frame Space (SIFS), and when it is determined that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period, sets the inter-frame interval before transmitting any of the frames addressed to the first other communication device from the communication device to be larger than SIFS.

13. A communication device as claimed in any one of claims 1 to 12, wherein, when the control means determines that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period, it sets the waiting time before the communication device transmits any of the frames addressed to the first other communication device during the TXOP period to a longer inter-frame interval than the waiting time before the first other communication device accesses the medium during the TXOP period.

14. A communication device as described in any one of claims 1 to 13, wherein the receiving means receives information capable of identifying whether or not each of the other communication devices connected to the communication device can be detected by each other, and the control means, when it has determined that the first other communication device will accept the second other communication device to transmit the one or more data frames during the TXOP period and a predetermined condition regarding whether or not each of the other communication devices connected to the communication device can be detected by each other, sets a waiting time before any of the frames transmitted from the communication device to the first other communication device during the TXOP period to be longer than the waiting time when it has determined that the first other communication device will accept the second other communication device to transmit the one or more data frames.

15. A communication device as described in any one of claims 1 to 14, wherein the control means further determines whether or not to accept the second other communication device from transmitting the one or more data frames during the TXOP period, and when the communication means determines that the second other communication device does not accept the second other communication device from transmitting the one or more data frames during the TXOP period, it notifies the communication device that it does not accept the second other communication device from transmitting the one or more data frames during the TXOP period.

16. A communications device conforming to the IEEE 802.11 series of standards, comprising: a communications means for receiving a signal transmitted from a first other communications device during a transmission opportunity (TXOP) period reserved for transmitting a data frame from the second other communications device to the second other communications device; and a communications control means for controlling the communications means to transmit a signal to the first other communications device during a period in which no frames are transmitted to the second other communications device during the TXOP period, when the signal received by the communications means indicates that the second other communications device permits transmission by the communications device during the TXOP period.

17. The communication device according to claim 16, further comprising a determination means for determining whether or not the second other communication device permits transmission by the communication device during the TXOP period based on a signal received by the communication means, wherein the communication means receives a response transmitted from the second other communication device in response to an occupancy request frame transmitted from the first other communication device requesting permission to transmit during the TXOP period, and wherein the communication control means, when the communication means receives an occupancy response frame other than a Clear To Send (CTS) frame in response to the occupancy request frame, determines that the occupancy response frame indicates that the second other communication device permits transmission by the communication device during the TXOP period.

18. A communication device as described in claim 16 or 17, further comprising a judgment means for judging whether or not the second other communication device permits the communication device to transmit during the TXOP period based on a signal received by the communication means, wherein the communication means receives an occupancy response frame transmitted from the second other communication device in response to an occupancy request frame transmitted from the first other communication device requesting permission to transmit during the TXOP period, and when the communication control means judges that the occupancy response frame received by the communication means includes specified information, it judges that the second other communication device permits the communication device to transmit during the TXOP period.

19. A communication device according to any one of claims 16 to 18, further comprising a determination means for determining whether or not the second other communication device permits transmission by the communication device during the TXOP period based on a signal received by the communication means, wherein the communication means receives a Clear To Send (CTS) frame transmitted from the second other communication device in response to a Request To Send (RTS) frame transmitted from the first other communication device requesting permission to transmit during the TXOP period, and wherein the communication control means, when the CTS frame received by the communication means includes predetermined information, determines that the CTS frame indicates that the second other communication device permits transmission by the communication device during the TXOP period.

20. The communication device according to any one of claims 16 to 18, further comprising a determination means for determining whether or not the second other communication device permits transmission by the communication device during the TXOP period based on a signal received by the communication means, wherein the communication means receives a Block ACK (BA) frame transmitted from the second other communication device in response to a data frame transmitted from the first other communication device to the second other communication device, and the communication control means determines whether or not the BA frame received by the communication means indicates that the second other communication device permits transmission by the communication device during the TXOP period.

21. A communication device as claimed in any one of claims 16 to 20, wherein the communication control means, when a signal received by the communication means indicates that the second other communication device authorises transmission by the communication device during the TXOP period, does not transmit a signal to the first other communication device during the TXOP period if the communication control means does not have uplink data for low latency communication to the first other communication device when access to the medium becomes available.

22. The communication device according to any one of claims 16 to 21, wherein the communication means transmits a transmission request to the first other communication device requesting transmission during the TXOP period, and receives, as a response to the transmission request, Enhanced Distributed Channel Access (EDCA) parameters to be used for accessing a medium when the communication device is permitted to transmit during the TXOP period.

23. A communications device as described in claim 22, further comprising a state control means for switching operation between a first state in which a medium access control (MAC) frame transmitted from another communications device is decoded and a second state which is a power saving mode in which a MAC frame transmitted from another communications device is not decoded, wherein the state control means switches the state of the communications device to the first state in the TXOP when the communications device receives the EDCA parameters in response to the transmission request.

24. A communications device conforming to the IEEE 802.11 series of standards, comprising: a communications means for communicating with a first other communications device during a transmission opportunity (TXOP) period reserved for receiving one or more data frames from the first other communications device; and a determination means for determining whether or not to permit transmission during the TXOP period by a second other communications device, wherein the communications means transmits a signal capable of specifying whether or not to permit transmission during the TXOP period by the second other communications device to other communications devices including at least the first other communications device.

25. The communication device according to claim 24, wherein the communication means notifies other communication devices including at least the first other communication device of a signal indicating whether or not to permit transmission by the second other communication device during the TXOP period via at least one of a Clear To Send (CTS) frame requesting reservation of the TXOP period, an occupancy request frame different from the CTS frame requesting reservation of the TXOP period, and a Block ACK (BA) frame to a data frame received from the first other communication device during the TXOP period.

26. A control method executed by a communication device compliant with IEEE 802.11 series standards, comprising: communicating with a first other communication device during a transmission opportunity (TXOP) period reserved by the communication device for transmitting one or more data frames to the first other communication device; receiving information from the first other communication device for specifying whether the first other communication device will accept a second other communication device different from the first other communication device to transmit one or more data frames to the communication device during the TXOP period; and when it is determined based on the received information that the first other communication device will accept the second other communication device to transmit the one or more data frames during the TXOP period, setting a waiting time before the communication device transmits at least one data frame addressed to the first other communication device during the TXOP period to be longer than the waiting time when it is determined that the first other communication device will not accept the second other communication device to transmit the one or more data frames during the TXOP period.

27. A control method executed by a communication device conforming to the IEEE 802.11 series of standards, comprising: receiving a signal transmitted from a first other communication device during a transmission opportunity (TXOP) period reserved for transmitting a data frame from the second other communication device to the second other communication device; and, if the received signal indicates that the second other communication device permits transmission by the communication device during the TXOP period, transmitting a signal to the first other communication device during the TXOP period.

28. A control method executed by a communication device conforming to the IEEE 802.11 series of standards, comprising: communicating with a first other communication device in a transmission opportunity (TXOP) period reserved for receiving one or more data frames from the first other communication device; determining whether or not to permit transmission by a second other communication device in the TXOP period; and notifying other communication devices, including at least the first other communication device, of a signal indicating whether or not to permit transmission by the second other communication device in the TXOP period.

29. A program for causing a computer to execute the control method according to any one of claims 26 to 28.

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