Communication device, control method, and program

Abstract

To provide a technique to improve convenience of a preemption operation.SOLUTION: A communication device conforming to the IEEE 802.11 series standard has communication means that communicates with first another communication device in a transmission opportunity (TXOP) period that is ensured for transmitting a data frame to the first another communication device, on the basis of a signal received from the first another communication device, determines whether the first another communication device permits transmission in a TXOP period for a second another communication device different from the first another communication device, and when determining that the first another communication device permits the transmission in the TXOP period for the second another communication device, sets a standby time before the communication device transmits any one of frames addressed to the first another communication device in the TXOP period, longer than a standby time when determining that the first another communication device does not permit the transmission in the TXOP period for the second another communication device.SELECTED DRAWING: Figure 14A

Description

Technical Field

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

Background Art

[0002] As a communication standard for wireless local area networks (hereinafter referred to as WLANs), the IEEE 802.11 series of standards is known. In the latest IEEE 802.11be standard, multi-link technology is used to achieve high peak throughput and low-latency communication in addition to high peak throughput (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Currently, the IEEE has established the IEEE802.11bn TG (Task Group) for the development of the successor standard to 802.11be, aiming to further improve reliability. Here, one of the considerations of the IEEE802.11bn TG is low-latency (LL) communication. In this LL communication, even during the period when the first communication device (TXOP holder) that has obtained the transmission opportunity (TXOP) and the second communication device (TXOP responder) are performing communication, a third communication device may interrupt and transmit. Such interrupt communication by the third communication device is called the Preemption operation. Even when the third communication device cannot meet the latency requirement of the LL communication if it waits for the expiration of the TXOP period to transmit, the latency requirement of the LL communication of the third communication device can be met by the transmission related to the Preempiont operation (Preemption transmission). On the other hand, since the communication between the first communication device that has obtained the transmission opportunity and the second communication device is delayed by the Preemption transmission, there has been a problem that it may not be appropriate to permit the Preemption transmission.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a technique for improving the convenience of the Preemption operation.

Means for Solving the Problems

[0006] In order to solve the above-described problems, the communication device of the present invention is a communication device compatible with the IEEE 802.11 series of standards, communication means for communicating with the first other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device; determination means for determining whether or not the first other communication device permits transmission during the TXOP period by a second other communication device different from the first other communication device based on a signal received from the first other communication device; When the determination means determines that the first other communication device permits the transmission by the second other communication device during the TXOP period, the communication control means sets the waiting time before transmitting any of the frames addressed to the first other communication device by the communication device during the TXOP period to be longer than the waiting time when the first other communication device determines that the transmission by the second other communication device during the TXOP period is not permitted. It is provided with.

Effect of the Invention

[0007] According to the present invention, a technique for improving the convenience of the Preemption operation can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 10

Figure 11

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Figure 13

Figure 14A

Figure 14B

Figure 15

Modes for Carrying Out the Invention

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

[0010] Using FIG. 1, the configuration of the system according to this embodiment will be described. The wireless communication system 1 includes an access point (AP) 101 and a distributed system (DS) 105.

[0011] The AP 101 is a wireless communication device that communicates with terminals (STAs) that can be located within the area indicated by a circle in FIG. 1. In the example of FIG. 1, it is assumed that three STAs 102 to 104 exist within the range (service area) connectable to the AP 101, but the number of STAs is not limited. The AP 101 manages a basic service set (BSS) that is a network composed of the AP 101 and the STAs 102 to 104.

[0012] The STAs 102 to 104 are wireless communication devices that connect to the AP 101 and communicate as clients. The STA may also be called a non-AP (non-access point) STA. In this embodiment, the AP 101 and the STAs 102 to 104 will be described as performing communication compliant with the IEEE 802.11 series standards.

[0013] DS105 is a network device that provides the distributed system access function (DSAF) to AP101, and can connect to other BSSs and external networks in addition to the BSS composed of AP101 and STAs 102 to 104. This access function (connection means) is provided via wired communication such as Ethernet (registered trademark) or telephone lines, or wireless communication 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) communication compliant with the IEEE802.11 series standards. In this case, the wireless channel used for WLAN communication between AP101 and DS105 may be the same as or different from the wireless channel used for communication between AP101 and STAs 102 to 104.

[0014] Figure 2 shows a hardware configuration diagram of the wireless communication device including AP101 and STAs 102 to 104 according to this embodiment. As an example of the hardware configuration, the wireless communication device has a storage unit 201, a control unit 202, a functional unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0015] The storage unit 201 is composed of a memory such as a ROM (read-only memory) or a RAM (random access memory), and stores programs for performing various operations described later, and various information such as communication parameters for wireless communication described later and explained. Note that, as the storage unit 201, in addition to ROM, RAM, etc., storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, DVDs, etc. may be used. Also, the storage unit 201 may include a plurality of memories.

[0016] The control unit 202 includes one or more processors and controls the operation of the entire wireless communication device by executing the programs stored in the storage unit 201. The processor includes at least one or more of a central processing unit (CPU), a micro processing unit (MPU), an ASIC (application specific integrated circuit), a DSP (digital signal processor), and an FPGA (field programmable gate array). Note that the control unit 202 may control the wireless communication device by the cooperation of the programs stored in the storage unit 201 and an operating system (OS). Also, the control unit 202 may include a plurality of processors such as a multi-core processor, and each processor may cooperate to control the wireless communication device. Further, the control unit 202 controls the functional unit 203 to execute predetermined processing for realizing the functions of the wireless communication device. For example, the wireless communication device can execute different processes depending on the role of the wireless communication device, such as executing the AP function when the wireless communication device is the AP 101 and executing the STA function when it is any one of the STAs 102 to 104. Also, the control unit 202 can execute processing for realizing different functions such as an imaging function, a printing function, and a projection function according to the hardware included in the functional unit 203.

[0017] The functional unit 203 is hardware for the wireless communication device to execute predetermined processing. 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 by being controlled by the control unit 202.

[0018] The input unit 204 includes input interfaces such as buttons for receiving various operations from the user, a microphone, and a pointing device. The output unit 205 includes output interfaces such as a display and a speaker for performing various outputs to the user. Here, the output by the output unit 205 includes at least one of display on the screen, audio output by the speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be realized by one module such as a touch panel. For example, the input unit 204 and the output unit 205 may be realized by a touch panel.

[0019] 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 capable of executing communication of wireless frames compliant with the IEEE802.11bn standard, which is a successor standard to the IEEE802.11be standard targeting a maximum transmission speed of 46.08 Gbps. Note that IEEE is an abbreviation for Institute of Electrical and Electronics Engineers. The IEEE802.11bn, which is a successor standard to IEEE802.11be, features high-reliability communication, low-latency communication, and improved throughput during congestion. Also, in 802.11bn, reducing power consumption in the AP is also one of the goals. The wireless frame communicated using the successor standard is also referred to as a UHR (Ultra High Reliability) PPDU. PPDU is an abbreviation for Physical Layer Protocol Data Unit. That is, the AP101 and STA102 to 104 having the communication unit 206 realize communication by exchanging UHR PPDUs with each other. Note that the name UHR is provided for convenience based on the goals to be achieved by the successor standard and the prominent features of the standard, and may have a different name when the standard formulation is completed. Similarly, the name IEEE802.11bn may have a different name when the standard formulation is completed. On the other hand, it should be noted that this specification and the appended claims are essentially applicable to all successor standards that are successor standards to the 802.11be standard. Also, although the AP101 and STA102 to 104 having the communication unit 206 are assumed to support communication (transmission and reception) of UHR PPDUs, in addition to this, they can also be configured to support communication of PPDUs of legacy standards that are standards prior to the UHR standard. Specifically, they can also be configured to support transmission and reception of PPDUs of standards such as IEEE802.11a / b / g / n / ac / ax / be.

[0020] Antenna 207 includes one or more antennas. In FIG. 2, only one antenna is shown for simplicity. Generally, the number of antennas included in antenna 207 is the number corresponding to the number of Spatial Streams.

[0021] Note that the communication unit 206 and the antenna 207 may include a plurality of communication units 206 and antennas 207 corresponding to the corresponding frequency bands (2.4 GHz band, 5 GHz band, 6 GHz band) and the number of corresponding streams.

[0022] FIG. 3 shows an example of the functional (software) configuration of the wireless communication device. The wireless communication device has, as a software configuration, a wireless LAN control unit 301, an Enhanced Distributed Channel Access (EDCA) control unit 302, and a priority EDCA control unit 303. Further, the wireless communication device has, as a 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.

[0023] The wireless LAN control unit 301 includes a circuit for transmitting and receiving wireless signals to and from other wireless LAN devices (for example, other APs and STAs) and a program for controlling them. The wireless LAN control unit 301 executes wireless LAN communication control such as frame generation, frame transmission, and reception of wireless frames from other wireless LAN devices according to the IEEE802.11 standard series.

[0024] After recognizing the idle state of the wireless medium, the EDCA control unit 302 performs transmission processing after the elapse of the predetermined inter-frame interval and the backoff counter time. EDCA is a priority control method defined by the IEEE802.11 standard. It classifies packets into four access categories (ACs), stores them in the transmission queue, and transmits the packets according to their respective priorities.

[0025] The priority EDCA control unit 303 performs transmission related to EDCA operation (Preemption transmission) during the Preemption declaration period, which will be described later, when the Preemption operation is possible.

[0026] 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 the situation where, within the period (TXOP period) allocated for communication between the AP 101, which is the TXOP holder, and one STA, which is the TXOP responder, another STA (Preemption STA) interrupts and transmits. 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.

[0027] The LL communication control unit 305 controls communication that is sensitive to (constrained by) delay and jitter, such as video communication and voice communication. When an application that requires communication sensitive to delay and jitter is executed, the LL communication control unit 305 performs transmission related to EDCA operation. In other words, for transmissions other than Preemption transmission, the LL communication control unit 305 controls the EDCA control unit 302 to access the wireless medium using normal EDCA parameters. 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.

[0028] The storage unit 306 is configured to include storage devices such as a ROM (read-only memory) and a RAM (random access memory) that store programs and various data executed by the wireless communication device.

[0029] The UI control unit 307 includes hardware such as a touch panel or buttons for receiving operations on the AP 101 and STAs 102 to 104 by a user (not shown) and programs for controlling them. Note that the UI control unit 307 also has functions for presenting information to the user, such as display of images or audio output. The antenna control unit 308 controls the antenna function.

[0030] <MAC Frame Structure> The structure of a Media Access Control (MAC) frame related to the Preemption operation will be described.

[0031] Figure 4(a) shows the structure of a MAC frame used in the IEEE 802.11 series standards. The MAC frame 400 includes Frame Control 401, Duration 402, Addresses 1 to 3 403 to 405, Sequence Control 406, and Address 4 407. The MAC frame 400 also includes QoS (Quality of Service) Control 408, HT (High Throughput) Control 409, Frame Body 410, and FCS (Frame Check Sequence) 411.

[0032] Frame Control 401 is a 2-octet (16-bit) field including sub-fields 412 to 422, which will be described later with reference to Figure 4(B), and includes frame control information.

[0033] Duration 402 is a 2-octet (16-bit) field, and by setting the MSB (Most Significant Bit: B15) to "1", it is possible to notify that a time such as the frame length or the length of the TXOP period is indicated. In this case, the 15 bits other than the MSB indicate the frame length or the length of the TXOP period as values from 0 to 32767 microseconds.

[0034] Address1~4 403, 404, 405, and 407 are 6-octet (42-bit) fields that store information indicating the addresses of wireless communication devices. Depending on the type (Type413) and subtype (Subtype414) of the MAC frame 400, the BSSID, source address, destination address, etc. are set. Note that depending on the type, the address fields used are different, and Address2~4 404, 405, and 407 may be omitted.

[0035] Sequence Control406 is a 0- or 2-octet field that indicates the sequence number of the data to be transmitted or the fragment number in the case of fragmentation.

[0036] QoS Control408 is a 0- or 2-octet field for performing QoS control of data frames. The BSR (Buffer Status Report) of standards prior to IEEE 802.11ax is stored in QoS Control408.

[0037] 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).

[0038] Frame Body410 is a variable-length field that stores various information elements (IE) when the type 422 of Frame Control401 is a management frame, that is, a beacon or a probe request / response.

[0039] FCS411 is a 4-octet field that stores a value for checking whether there are errors in the MAC header and data part. The MAC header consists of Frame Control401 to QoS Control408, and HT Control409 and Frame Body410 are called the MAC service data unit (MSDU).

[0040] Next, the details of Frame Control 401 will be described with reference to FIG. 4(b). Frame Control 401 includes Protocol Version 412, Type 413, Subtype 414, To DS 415, From DS 416, and More Fragment 417. Also, Frame Control 401 includes Retry 418, Power Management 419, More Data 420, Protected Frame 421, and +HTC 422.

[0041] Protocol Version 412 is a 2-bit field indicating the version of the protocol for which the MAC frame is transmitted, and is set to "0" in the case of an IEEE 802.11 frame.

[0042] Type 413 is a 2-bit field indicating whether the MAC frame is of the management, control, or data type.

[0043] Subtype 414 is a 4-bit field indicating the subtype that further classifies the type of management, control, or data indicated by Type 413.

[0044] To DS 415 is a 1-bit field indicating whether the destination of the MAC frame is DS 105. From DS 416 is a 1-bit field indicating whether the source of the MAC frame is DS 105.

[0045] More Fragment417 is a 1-bit field indicating whether the MAC frame is fragmented. Retry418 is a 1-bit field indicating whether the MAC frame is a retransmission. Power Management419 is a 1-bit field indicating whether it is in the power save mode. More Data420 is a 1-bit field indicating whether there is data for the STA in the power save mode. Protected Frame421 is a 1-bit field indicating whether the MSDU is encrypted. +HTC422 is a 1-bit field indicating whether the MAC frame 400 contains HT Control409. A frame that can set the bit "1" in +HTC422, that is, a frame that can contain HT Control409, is a QoS data, Management, or RTS (Request to Send) frame. Although there are more detailed conditions, the description is omitted here.

[0046] With reference to FIGS. 5A(a) to 5D(n), a configuration example of an action frame transmitted and received during a request or response of the Preemption operation according to this embodiment will be described.

[0047] The action frame 500 shown in FIG. 5A(a) is the same as the MAC frame 400 described with reference to FIG. 4(a), so the description is omitted. A MAC frame in which Type413 (bits B3 B2) in Frame Control401 is set to "00" and Subtype414 (bits B7 B6 B5 B4) is set to "1101" is an action frame which is a type of management frame.

[0048] FIG. 5A(b) shows a configuration example of the Frame Body410 of the action frame 500. The Frame Body410 of the action frame 500 includes Category501 and Action502. Category501 indicates that the MAC frame is an action frame. Category501 is a 1-octet field and Action502 is of variable length.

[0049] Figure 5A(c) shows the association between the codes set for Category 501 and their meanings. In IEEE 802.11be Draft 4.0, codes from "0" to "37" are defined in Figure 5A(c). For example, code "0" indicates "Spectrum management", code "3" indicates "Block ACK (BA)", code "36" indicates "Extremely High Throughput (EHT)", and code "37" indicates "Protected EHT". For each of these categories, the format of Action 502 is defined.

[0050] In this embodiment, a new code "38" is defined as the value of Category 507 for "UHR" to enable the transmission and reception of control signals related to the Preemption operation. However, the Action Details related to the Preemption operation may also be defined in the Action Details of the existing value of Category 507, for example, code "37". This means diverting the reserved value of the EHT category for UHR. Specifically, the Action 502 for EHT consists of a 1-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 that is a reserved value in EHT is assigned to the control signal related to the Preemption operation. Then, the field configuration of the detailed information for the action corresponding to the type value is defined. With this mechanism, the reserved value of the EHT category can be diverted for the transmission of the control signal related to the Preemption operation for UHR. Note that the specific type of action and the corresponding detailed information may be configured in the same way as the type of action and the detailed information of the UHR category described later.

[0051] Figure 5B(d) shows the configuration of the Frame Body set to the code "38" indicating that the value of Category501 is UHR. In the action field for UHR, Action502 includes an Action Value508 that stores a type value indicating the type of 1-octet action, and a variable-length Action Details509 that stores detailed information for the action corresponding to the type value. Since Action Value508 is an action value for UHR, it is also called the UHR Action Value.

[0052] Figure 5B(e) is a diagram showing the definition of the association between the values set in Action Value508 and their meanings. When "0" is set as the Action Value, it indicates a permission request (Preemption request) 510 to request permission for the Preemption operation. When "1" is set as the Action Value, it indicates a response (Preemption response) 511 to the permission request for the Preemption operation.

[0053] Figure 5B(f) shows the configuration of the action frame for a permission request when "0" is set in Action Value508, that is, for the Preemption operation. The permission request is sent from the STA to the AP101.

[0054] In the action field for the Preemption request, Action502 includes an Action Value508 with the code set to "0", a Dialog Token512, and a Multi-Link Element513.

[0055] Dialog Token512 is a 1-octet field. Dialog Token512 is a field for distinguishing each request when there are multiple requests.

[0056] The Multi-Link Element 513 is a field that is also used in the action frame, which will be described later with reference to FIG. 5B(g). The Preemption operation can also be executed in the Multi-Link configuration of IEEE 802.11be. Therefore, it is defined as a multi-link element. The Multi-Link Element 513 includes common information (Common Info) and a profile sub-element for each STA, as will be described later with reference to FIG. 5C(h).

[0057] FIG. 5B(g) shows the configuration of an action frame for a response to a permission request when the Action Value is set to "1", that is, for the Preemption operation. The permission request is sent from the AP 101 to the STA.

[0058] In the action field for the response to the permission request shown in FIG. 5B(g), Action 502 includes an Action Value 508 whose code is set to "1". Also, Action 502 includes a Dialog Token 514, a Status Code 515, and a Multi-Link Element 516.

[0059] The Dialog Token 514 is a 1-octet field. The Dialog Token 514 is a field for distinguishing each request when there are multiple requests.

[0060] Status Code 515 is a 2-octet field and is defined in IEEE 802.11. When AP101 accepts a request for permission to perform the Preemption operation, it sets "0 (SUCCESS)". If the request is not accepted, it indicates non-permission (rejection) with a value reserved in the conventional standard. For example, AP101 can determine permission or rejection of the Preemption operation under predetermined conditions, such as when the number of STAs capable of performing the Preemption operation within the BSS is determined. Note that in this embodiment, as will be described later, the Preemption operation can also be permitted or rejected by an STA operating as a TXOP responder. The structure of the MAC frame transmitted by the STA to permit or reject the Preemption operation will be described later with reference to FIGS. 6A, 6B, and 7.

[0061] Multi-Link Element 516 is the same as Multi-Link Element 513 in FIG. 5B(f), so the description thereof is omitted.

[0062] FIG. 5C(h) shows a configuration example of the common information (Common Info) included in Multi-Link Elements 513 and 516. The common information includes a Commn Info Length 517 and an AP MLD MAC Address 518. The Commn Info Length 517 is a 1-octet field, and the AP MLD MAC Address 518 is a 6-octet field.

[0063] Figure 5C(i) shows the configuration of the profile sub-elements for each STA included in the Multi-Link Elements 513 and 516. The profile sub-elements for each STA include a Subelement ID 519, a Length 520, a STA Control 521, and a STA Profile 522. The Subelement ID 519 is a 1-octet field, the Length 520 is a 2-octet field, and the STA Control 521 is a 2-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 as a response to the preemption permission request is the priority EDCA parameter for performing preemption transmission during the TXOP period.

[0064] Figure 5C(j) shows a configuration example of the STA Control 521. The STA Control 521 includes a 4-bit Link ID 523, and the remaining 12 bits are reserved. The Link ID 523 is an identifier of the link that requests the preemption operation.

[0065] Figure 5D(k) shows a configuration example of the EDCA parameter set element included in the STA Profile 522 of Figure 5C(i). Since the EDCA parameter set element conforms to the IEEE 802.11-2020 standard, for items with the same meaning and usage as in the conventional standard, only the field name is noted.

[0066] The EDCA parameter set element includes Element ID524, Length525, QoS Info526, and Update EDCA Info527, each of which is a 1-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 4-octet field. Parameter record 528 is the AC_BE Parameter Record, and parameter record 529 is the AC_BK Parameter Record. Parameter record 530 is the AC_VI Parameter Record, and parameter record 531 is the AC_VO Parameter Record.

[0067] As shown in FIG. 5D(l), each of the parameter records 528 to 531 includes ACI / AIFSN (Arbitration Inter Frame Space Number) 532, ECWmin / ECWmax 533, and TXOP Limit 534.

[0068] ACI / AIFSN 532 is a 1-octet field and includes four sub-fields as described later with reference to FIG. 5D(m).

[0069] ECWmin / ECWmax 533 is a 1-octet field and is used to calculate the contention window for collision avoidance during EDCA access and is defined by the following formula.

[0070] CWmin = 2 ECWmin -1 CWmax = 2 ECWmax -1 Here, CWmin indicates the lower limit value of the contention window, and CWmax indicates the upper limit value of the contention window. In the conventional standard, the range of CWmin and CWmax is such that the minimum value is 0 and the maximum value is 32767. At this time, for each access category, priority control is realized by providing a difference in the range indicated by the default value or the value notified by the beacon.

[0071] In one example, both CWmin and CWmax are set to 0. This setting makes the backoff counter 0 (zero), and after the time corresponding to AIFSN after SIFS (Short IFS) has elapsed, the access right is acquired, enabling access control suitable for LL communication.

[0072] TXOP Limit534 is a field with a length of 2 octets and represents the restricted time for one access right, with the unit being 32 microseconds. In the conventional standard, AC_VI is defined as 4.096 milliseconds and AC_VO as 2.080 milliseconds. Also, TXOP Limit = 0 has a special meaning and indicates that only one MSDU (MAC service data unit) or MMPDU (MAC management protocol data unit) can be transmitted.

[0073] Figure 5D(m) shows an example of the structure of ACI / AIFSN532. ACI / AIFSN532 includes a 4-bit AIFSN535, a 1-bit ACM (Admission Control Mandatory) 536, a 2-bit ACI (Access Category Index) 537, and a 1-bit reserved field.

[0074] AIFSN535 indicates the number of slots (time) until the backoff control is activated after SIFS during EDCA access. In the conventional standard, the minimum value was 2, but in this embodiment, 0 or 1 can be specified. Also, the slot time, which is also called aSlotTime, has its value defined by each physical layer in the IEEE802.11 standard. For example, in OFDM used since 802.11n, it is 9 microseconds in the 5 or 6 GHz band and 9 or 20 microseconds in the 2.4 GHz band.

[0075] ACI537 is associated with four access categories as shown in FIG. 5D(n). For example, when ACI537 is set to "0", it indicates that the access category is "AC_BE", that is, best effort communication is performed.

[0076] Note that the STA Profile522 for the Preempt response may include information indicating non - permission of requests instead of the EDCA parameters themselves. For example, a new ID indicating non - permission of requests can be added to the Element ID524.

[0077] FIG. 6A(a) is a table of combinations of Type413 and Subtype414 in the header of the MAC frame shown in FIG. 4(b). The table includes a combination 601 of Type and Subtype indicating control frame extension when Type413 is set to "01" and Subtype414 is set to "0110". When Type413 and Subtype414 in the header of the MAC frame are set to combination 601, the following 4 bits are interpreted as the Control Frame Extension field.

[0078] Figure 6A(b) is a diagram showing details of control frame extension values in a 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, when the control frame extension value is 1100, it indicates pRTS, and when it is 1101, it indicates pCTS. A frame with the control frame extension value set to pRTS (pRTS frame) is treated as an occupancy request frame transmitted to secure a TXOP period. A frame with the control frame extension value set to pCTS (pCTS frame) is treated as an occupancy response frame that is a response to an occupancy request frame. In Figure 6A(b), according to the convention of IEEE 802.11 standard notation, the Bit numbers are shown in descending order from left to right. That is, a MAC frame with the Type field set to "01", the Subtype field set to "0110", and the Control Frame Extension field set to "1100" is called a pRTS frame. Similarly, a MAC frame with the Type field set to "01", the Subtype field set to "0110", and the Control Frame Extension field set to "1101" is called a pCTS frame.

[0079] Figure 6B(c) shows the frame structure of the pRTS frame. The pRTS frame is an occupancy request frame that requests the securing of a transmission opportunity for STAs within a BSS and is also a control frame indicating a period during which a Preemption operation is possible. Further, it is interpreted as a permission request signal that requests permission for the Preemption operation to the destination of the pRTS.

[0080] The pRTS frame includes Frame Control 604, Duration 605, Receiver Address (RA) 606, Transmitter Address (TA) 607, and FCS 608.

[0081] Frame Control 604 is the same as Frame Control 401 in the MAC frame structure of FIG. 4(A). Duration 605 is the period during which preemption operation is possible, and is sometimes 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 source 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. 4(a).

[0082] Here, in this embodiment, after notifying the preemption declaration period 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.

[0083] FIG. 6B(d) shows the structure of the pCTS frame. As described above, the pCTS frame is a control frame indicating that the TXOP responder permits the preemption operation for the STA within the BSS. The pCTS frame includes Frame Control 609, Duration 605, RA 611, and FCS 612.

[0084] Frame Control 609 is the same as Frame Control 401 in the MAC frame structure of FIG. 4(a). 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 the 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. 4(a).

[0085] In addition, in this embodiment, when the TXOP responder does not permit the Preemption operation, the receiving station of the pRTS shall return a conventional CTS frame. In this way, by switching between transmitting a pCTS frame and a conventional CTS frame in response to the pRTS frame, the TXOP responder can notify the terminal group including the TXOP holder whether the Preemption operation is permitted or not.

[0086] However, the TXOP responder may also notify whether the Preemption operation is permitted by including information indicating whether the Preemption operation is permitted in the CTS frame. For example, when RA611 is the broadcast address, it may indicate that the Preemption operation is permitted, and when RA611 is the address of the TXOP holder, it may indicate that the Preemption operation is rejected. That is, information capable of specifying whether the Preemption operation is permitted may be included in any of the Frame Control 609, Duration 610, and RA611 of the CTS frame.

[0087] In addition, information indicating whether the Preemption operation is permitted may be included in the pCTS frame which is the occupancy response. Similar to the case of using the CTS frame for notification, information capable of specifying whether the Preemption operation is permitted may be included in any of the Frame Control 609, Duration 610, and RA611 of the pCTS frame. Alternatively, unlike FIG. 6A(b), two types of pCTS frames may be defined as the occupancy response pCTS frame. For example, it can be realized by defining a value that permits the Preemption operation and a value that rejects the Preemption operation for the control frame extension value.

[0088] In addition, the TXOP responder according to this embodiment may include information indicating whether the Preemption operation is permitted in the Block ACK (BA) that notifies the reception of the data frame.

[0089] Figure 7(a) shows the structure of the BA frame. In the description of the BA frame, items with the same meaning and usage as in the conventional standard are only named.

[0090] Frame Control 701 is the same as Frame Control 401 in the MAC frame structure of Figure 4(A). As shown in Figure 5A(c), by setting the value of Frame Control 401, it can be indicated that the MAC frame is a BA frame.

[0091] Duration 702, RA 703, and TA 704 are the same as Duration 605 - TA 607 described in Figure 6B(c), so the description is omitted. The details of the 2-octet field BA Control 705 will be described later with reference to Figure 7(b). The variable-length field BA Information 706 may include, in addition to information related to BA in this embodiment, a 1-bit field indicating whether the TXOP responder permits the Preemption operation. FCS 707 is the same as the FCS in the MAC frame structure of Figure 4(A).

[0092] Figure 7(b) shows the structure of BA Control 705 in Figure 7(a). BA Control 705 includes Preemption 708, Multi-Traffic Identifier (TID) 709, Compressed Bitmap 710, GCR Mode 711, Reserved 712, and TID_INFO 713.

[0093] Preemption 708 is a field indicating whether to permit the Preemption operation. When permission is given, 1 is set, and when rejection is given, 0 is set. 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 standard of IEEE 802.11, so the description is omitted.

[0094] Alternatively, as shown in Fig. 7(a), whether or not to permit Preempt may be indicated by the value of BA Information 706.

[0095] As described above, in this embodiment, the TXOP responder can indicate permission / denial of the Preemption operation not only by transmitting a pCTS frame but also by transmitting a BA frame. Therefore, a STA permitted to perform the Preemption operation may monitor the BA from other terminals without entering the Power Save mode during the Preempt declaration period to determine the permission / denial of the Preemption operation.

[0096] Fig. 8 is a flowchart showing an example of the processing executed by the control unit 202 of the AP 101. Unless otherwise specified, the description will be made assuming that the main body of the operation is the AP 101.

[0097] In S800, the control unit 202 starts the processing. For example, it is started during control processing other than data frame transmission and can be executed at any timing except during the Preemption operation period. For example, it is started at the start of processing for generating beacons transmitted at a predetermined interval or when a MAC frame is received from a STA.

[0098] In S801, the control unit 202 determines the normal state EDCA parameters (normal EDCA parameters). The normal state means a state that is not during the Preemption operation period. If the default value of the EDCA parameters is set in the wireless communication system or is specified by the standard, the processing in S801 may be omitted.

[0099] In S802, the control unit 202 determines the policy for the Preemption operation. Here, the first parameter of the policy is the number of wireless communication devices capable of the Preemption operation. The range of this value is from 0 to the number of connectable devices. The second parameter of the policy is the setting of access conditions when the number of wireless communication devices capable of the Preemption operation is 2 or more. Specifically, when a request is received from the STA even in a state where the limit value of the number of connectable devices due to the Preemption operation has been reached, conditions such as rejecting it or canceling the Preemption operation of the wireless communication device with the lowest priority are set. Here, the priority can be arbitrarily determined, for example, by the type of the wireless communication device (XR / AR / VR / MR related to virtual reality, game console, others). The policy for the Preemption operation may be selected from among the policy candidates predefined by the operator of the AP101, or may be determined according to the communication environment such as the packet loss rate and the number of packet collisions. Also, the policy for the Preemption operation may be determined according to the state of the AP101, such as the buffer state and the load state of the AP101.

[0100] In S803, the control unit 202 detects the transmission timing of the 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 when the process of S801 is omitted, the control unit 202 may transmit a beacon signal not including the normal EDCA parameters in S803.

[0101] In S805, the control unit 202 determines whether a frame transmitted from any STA is 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 with the process to S806. If it is determined that a frame conforming to the conventional standard, that is, a frame that is not a Preemption operation request, has been received (No in S805), the process proceeds to S810.

[0102] At S806, it is checked whether there is another STA for which preemption operation has been permitted at S805. If there is another STA for which preemption operation has been permitted (Yes at S806), the control unit 202 advances the process to S807; otherwise, the process advances to S809.

[0103] At S807, the control unit 202 determines whether a hidden terminal state has occurred in the wireless communication system. If it has not occurred, the process advances to S809. If a hidden terminal state has occurred (Yes at S807), the control unit 202 advances the process to S808. The determination as to whether a hidden terminal state has occurred at S807 is based on the report of the number of recognized terminals from each STA. The report of the number of recognized terminals is made from each STA to the AP101 at regular intervals and includes information indicating that each STA has detected a signal transmitted from another STA. Thereby, the AP101 can specify whether each of the STAs connected to the AP101 has detected each other. The AP101 stores the number of recognized terminals of each STA from the received report of the number of recognized terminals. Based on the report of the number of recognized terminals, the AP101 can detect that any one STA has not detected any other STA connected to the AP, that is, that STA cannot detect a signal transmitted from another STA within the wireless communication system. In such a case, the AP101 determines that a hidden terminal state has occurred. On the other hand, when all STAs have detected each other's STAs connected to the AP101, it can be determined that a hidden terminal state has not occurred. Note that in the report of the number of recognized terminals, the STA reports the other recognized STAs as the number of recognized terminals. However, as an example, the identifier of the recognized STA may be included in the report to the AP101.

[0104] In S808, the control unit 202 determines the STA that permits the Preemption operation in accordance with the policy determined in S802. This policy can be arbitrarily determined for each wireless communication system, such as "giving priority to permitting the Preemption operation to the STA whose device type is a game machine" as described above. In another example, the policy may be to permit the Preemption operation in the order in which the Preemption operation requests are transmitted. For example, if the setting is not to permit the Preemption operation when the hidden terminal state occurs, it may be determined that the Preemption operation is not permitted to any STA. This can prevent a STA that could not detect the transmission from the STA operating as a TXOP Responder by carrier sense from executing a Preemption transmission and causing a collision. In this example, it is described that the Preemption operation is permitted to the STA that has transmitted the Preemption request.

[0105] In S809, the control unit 202 determines the priority EDCA parameters to be used when accessing the medium in accordance with the policy. Note that when the Preemption operation is not permitted to the STA that has transmitted the Preemption request in S808, the process of S809 may be omitted. In one example, S809 may include determining the Arbitrate Inter Frame Spacing Number (AIFSN). In the present embodiment, the priority EDCA parameters shall include an AIFSN with a value greater than 0.

[0106] In one example, in S809, the control unit 202 may determine the priority EDCA parameters based on other STAs that have permitted the Preemption operation. For example, when the priority is determined based on the traffic type of the STA and it is determined that the priority is lower than that of other STAs that have already permitted the Preemption operation, parameters inferior to the priority EDCA parameters notified to other STAs may be notified. Inferior parameters are, for example, parameters including a large AIFSN. In this way, by allowing access to the medium with different EDCA parameters among the STAs that permit the Preemption operation, it is possible to prevent transmissions from a plurality of STAs from colliding, and the convenience of the Preemption operation can be improved.

[0107] In S810, the control unit 202 responds to the Preemption permission request. The response to the Preemption permission request (Preemption response) includes information indicating permission and the priority EDCA parameters when the Preemption operation is permitted. Also, when the Preemption operation is not permitted, only information indicating that, or the same normal EDCA parameters as the EDCA parameters in the normal state are included. Here, permission / non - permission is assumed to be indicated by the Status Code 515 shown in FIG. 5B(g).

[0108] In S811, if control processing other than the response to the preemtion request is necessary, the control unit 202 executes that processing. That is, the processing in S811 may be omitted. After the processing in S811, the control unit 202 ends the processing shown in FIG. 8 (S812).

[0109] FIGS. 9A and 9B are flowcharts showing examples of the processing of the AP101 executed in the downlink communication from the AP101 to the STA. The processing in FIGS. 9A and 9B will be described as being executed by the control unit 202 of the AP101.

[0110] S901 is the starting point of downlink processing. When a data frame addressed to the connected STA is recognized, the processes in FIGS. 9A and 9B are started. This data is generated by a communication device on DS105, another STA within the BSS, or an application of AP101. In this example, it is described that AP101 receives downlink data addressed to STA102 from DS105.

[0111] In S902, the control unit 202 checks whether there is a STA that has permitted the Preemption operation. If there is no permitted STA (No in S902), the control unit 202 executes the same processing as before (S903). That is, the control unit 202 performs the RTS / CTS procedure as necessary during the TXOP period, includes the data in a physical layer protocol data unit (PPDU), and aggregates and transmits a plurality of PPDUs. Since there is no STA that has permitted the Preemption operation, in S903, transmission by the Preemption operation is not executed during the TXOP period. The maximum length of the PPDU transmitted from AP101 to STA102 in S903 is referred to as the "normal PPDU length".

[0112] If there is a permitted STA (Yes in S902), the control unit 202 proceeds to S904 and transmits a pRTS frame to STA102, which is the destination of the data frame, that is, the TXOP responder. By receiving the pRTS frame, STA102 recognizes that it is requested to permit the Preemption operation. Therefore, STA102 determines whether to permit the Preemption operation according to the policy and transmits a response that can specify whether to permit it.

[0113] Subsequently, the control unit 202 advances the process to S905 and determines whether a pCTS frame has been received. If the AP101 has received a pCTS frame (Yes in S905), the control unit 202 advances the process to S906. If the AP101 has not received a pCTS frame (No in S905), the control unit 202 advances the process to S918. As described above, pCTS is a response signal transmitted when the TXOP responder permits the Preemption operation. Therefore, the AP101 executes the processes after S906 as the processes when it determines that the Preemption operation has been permitted by the TXOP responder.

[0114] In S906, the control unit 202 determines the maximum length (first length) of the PPDU transmitted during the period when the Preemption operation is permitted. The first length is determined to be shorter compared to the maximum length (second length) of the PPDU transmitted when the Preemption operation is not permitted in order to give a transmission opportunity to STAs other than the TXOP responder earlier by the Preemption operation.

[0115] In this embodiment, the first length and the second length are determined as prescribed values within the wireless communication system. In one example, the first length is set shorter than the second length at 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 time equal to or less than half of the remaining time of the TXOP period.

[0116] Note that in S906, it is only necessary to make a change to the PPDU for giving a transmission opportunity to STAs other than the TXOP responder earlier by the Preemption operation, and any change can be made.

[0117] For example, it is also possible to simply shorten the length of any PPDU transmitted from AP101 to STA102 during the TXOP period. For example, the maximum length of the PPDU transmitted from AP101 to STA102 in the first half of the TXOP period may be shortened, and the maximum length of the PPDU transmitted in 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, since shorter PPDUs are transmitted in the first half, the number of inter-data-frame intervals increases. As a result, the opportunity for transmission by the Preemption operation can be increased.

[0118] In S907, the control unit 202 determines the IFS within the period for permitting the Preemption operation. The value of the IFS can be arbitrarily determined by AP101 according to the policy. For example, if the policy is "always transmit the first PPDU", it is set to SIFS. At this time, the AIFSN of the STA that has requested the Preemption operation shall not be 0. As a result, since the SIFS ends in a shorter time than the backoff time of the STA that has requested the Preemption operation has elapsed, AP101 can obtain the opportunity to transmit the PPDU. On the other hand, if the policy is "it is not necessary to always transmit the first PPDU", the value of the IFS may be set to a different value such as DIFS (Distributed Coordination Function IFS).

[0119] When the TXOP responder determines that transmission by the Preemption operation is permitted, the AP101 according to this embodiment sets the waiting time so as to increase the waiting time before transmitting any of the frames communicated with the STA102 during the TXOP period. That is, when the Preemption operation is permitted, the AP101 increases the waiting time before transmitting any frame as compared with the case where the Preemption operation is not permitted. For example, when the STA102 does not permit transmission by the Preemption operation, all inter-frame intervals are set to SIFS, while when the STA102 permits transmission by the Preemption operation, at least one inter-frame interval is set to DIFS. As a result, the STAs 103 and 104 that have requested the Preemption operation can detect the idle state of the medium and execute transmission by the Preemption operation. Note that the inter-frame interval when transmission by the Preemption operation is permitted only needs to be greater than SIFS and is not limited to DIFS.

[0120] Also, in this embodiment, the AP101 sets the waiting time before transmitting a frame addressed to the 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.

[0121] Also, setting the waiting time to be long before transmitting any of the data frames addressed to STA102 within the TXOP period includes the case where AP101 does not transmit any of the data frames addressed to STA102 during the TXOP period. For example, when the Preemption operation is not permitted, it is assumed that after the first data frame, a waiting time of SIFS is placed and the second data frame is transmitted. Here, when the Preemption operation is permitted, by not transmitting the first data frame, the waiting time until the second data frame is transmitted may be set to two SIFS and the length of the first data frame. This can also cause transmission due to the Preemption operation.

[0122] S908 is a process during the IFS period. In S908, the control unit 202 monitors whether the medium remains idle for the time determined in S907. If the medium remains idle and the IFS period has elapsed, the control unit 202 proceeds with the process to S909. On the other hand, if the medium does not remain idle and the IFS time has not elapsed, such as when receiving a PPDU from STA103 that requested a Preemption operation before the IFS elapsed, a predetermined process is executed, such as transmitting a BA after the transmission of STA103 ends.

[0123] In S909, the control unit 202 transmits the downlink data frame received in S901 to the destination STA, in this example, the TXOP responder. In S910, the control unit 202 receives a BA for the data frame transmitted in S909 from the TXOP responder.

[0124] In S911, the control unit 202 checks the remaining time of the TXOP, that is, the remaining time of the period in which the Preemption operation is permitted. This is based on the time specified in the pRTS frame transmitted in S904 and the time specified in the pCTS frame received in S905.

[0125] If there is remaining TXOP period (Yes in S911), the control unit 202 proceeds with the process to S912. If it is determined that there is no remaining TXOP period (No in S911), the control unit 202 ends the downlink process shown in FIGS. 9A and 9B.

[0126] In S912, the control unit 202 checks whether the TXOP responder permits the Preemption operation. This is done by the AP101 determining whether the TXOP responder permits the Preemption operation based on the received pCTS frame or CTS frame. If the control unit 202 determines that the Preemption operation is permitted (Yes in S912), the control unit 202 proceeds with the process to S913. If the control unit 202 determines that the Preemption operation is rejected (No in S912), the control unit 202 proceeds with the process to S915.

[0127] 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 with the process to S914.

[0128] In S914, the control unit 202 sets the length of the PPDU as the normal PPDU length and proceeds with the process to S919. That is, when the BA frame indicates that the Preemption operation is not permitted, the waiting time before the frame addressed to the TXOP responder is transmitted is set longer in S914 and S919 than the waiting time when the Preemption operation is permitted.

[0129] In S915, the control unit 202 checks whether the BA frame received in S910 indicates permission for the Preemption operation. If the control unit 202 determines that the BA indicates permission for the Preemption operation (Yes in S915), the control unit 202 advances the process to S916. On the other hand, if the control unit 202 determines that the BA indicates rejection of the Preemption operation (No in S915), the control unit 202 advances the process to S919.

[0130] In S916, the control unit 202 sets the length of the PPDU to a length shorter than the normal PPDU length and advances the process to S907. The process of S916 is the same as the process of S906.

[0131] In S918, the control unit 202 determines whether a CTS frame has been received. If a CTS is received, the control unit 202 advances the process to S919. In S919, the IFS is set to SIFS, and the process is advanced to S908.

[0132] Note that in this embodiment, it is described that the Preemption operation is permitted when a pCTS frame is received, and the Preemption operation is rejected when a CTS frame is received. However, when the information in the pCTS frame indicates whether to permit or reject the Preemption operation, different processes may be executed in S905 and S918. For example, after S904, if the information in the pCTS frame permits the Preemption operation, the process may be advanced to S906, and if the Preemption operation is not permitted, the process may be advanced to S919.

[0133] In other words, S906 may be executed as the process when the received pCTS permits the Preemption operation, and S919 may be executed as the process when the received pCTS rejects the Preemption operation. Similarly, as described above, when the information in the CTS frame indicates whether to permit the Preemption operation, or when the information in other frames indicates whether to permit the Preemption operation, the processes in FIGS. 9A and 9B may be replaced and executed.

[0134] In S918, when the CTS is not received (No in S918), the control unit 202 advances the process to S920. The process of S920 is executed when the TXOP responder fails to receive the pRTS frame, or when the TXOP holder fails to receive the pCTS frame or the CTS frame. Therefore, in S920, the control unit 202 determines the necessity of retransmitting the pRTS frame. If the pRTS frame is to be retransmitted (Yes in S920), the process returns to S904, and if not, the process shown in FIGS. 9A and 9B is terminated as a downlink process failure (S921). One example of not retransmitting the pRTS frame is when the limit value of the number of retransmissions of the pRTS frame is reached.

[0135] <Example of TXOP Responder Processing> FIG. 10 is a flowchart showing an example of the processing of 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 STA102 operating as a TXOP responder executing a program at the start of the TXOP period (S1000).

[0136] In S1001, the control unit 202 receives a pRTS frame for which STA102 is the destination. In S1001, based on the received pRTS signal, it can be recognized that a request is made to permit transmission by a Preemption operation by an STA different from STA102 and AP101 within the TXOP period assigned to STA102. In S1002, the control unit 202 determines whether to permit or reject transmission by a Preemption operation by an STA different from STA102 and AP101.

[0137] When permitting transmission by an STA different from STA102 and AP101 during the TXOP period (Yes in S1002), the control unit 202 advances the process to S1003 and transmits a pCTS signal indicating permission for transmission by the Preemption operation. Although the destination of the pCTS frame is AP101, other terminals that detect the pCTS signal can recognize that transmission by the Preemption operation is permitted, and the Preemption operation becomes possible.

[0138] On the other hand, when not permitting transmission by the Preemption operation (No in S1002), the control unit 202 advances the process to S1004 and transmits a CTS frame indicating non - permission, that is, rejection of transmission by the Preemption operation. Although the destination of the CTS frame is AP101, other STAs that detect the CTS frame can recognize that transmission by the Preemption operation is rejected. In one example, when STA102 recognizes that data should be received continuously without interruption before receiving the PPDU, that is, there is a time limit (timeout) for data reception, the CTS frame can be transmitted. For example, STA102 can recognize that there is a time limit for data reception based on the application executed by STA102.

[0139] In S1005, the control unit 202 of STA102 receives a PPDU (data frame) from AP101. In S1006, the control unit 202 determines whether there is a subsequent PPDU. When the control unit 202 determines that the reception of the data frame has ended, that is, determines not to continue receiving the data frame (No in S1006), the process advances to S1010; otherwise, the process advances to S1007. In S1010, STA102 transmits a BA conforming to the conventional standard, that is, a BA that does not indicate whether to permit transmission by the Preemption operation, to AP101 and ends the downlink reception in FIG. 10.

[0140] In S1007, the control unit 202 determines whether to change the state of permitting or rejecting transmission by the Preemption operation. That is, in S1007, after the determination in S1002, it is determined whether there is a change in permitting or rejecting the Preemption operation. If it is determined to change the state of permitting or rejecting transmission by the Preemption operation (Yes in S1007), the control unit 202 advances the process to S1008; otherwise, it advances the process to S1009.

[0141] In S1008, a BA indicating whether to permit or reject transmission by the Preemption operation is transmitted. In one example, after determining to permit transmission by the Preemption operation in S1002, when an application for performing low-latency communication is executed, transmission by the Preemption operation can be rejected. In another example, after determining to reject transmission by the Preemption operation in S1002, as a result of receiving at least one PPDU and analyzing the data, a BA frame indicating permission for transmission by the Preemption operation can be transmitted in S1008. Also, even when a pCTS frame is transmitted in S1003, STA102 may determine that after receiving one or more PPDUs and analyzing the data, it should receive the downlink data without interruption. In such a case, STA102 can transmit a BA frame rejecting transmission by the Preemption operation. This means canceling the permission for transmission by the Preemption operation by the pCTS frame transmitted in S1003. Also, after transmitting a BA frame in S1008, as a result of executing the process of S1007 again and determining to change the state of permitting or rejecting Preemption, a BA specifying a state different from the previous one can be transmitted. Note that within the TXOP period, BA frames indicating permission or rejection of transmission by this Preemption operation can be transmitted without limitation.

[0142] In S1009, the control unit 202 transmits a BA frame (conventional BA frame) that does not include information on permission or rejection of the Preemption operation. After the processing of S1008 or S1009, the control unit 202 returns the processing to S1005.

[0143] FIG. 11 is a flowchart showing an example of processing executed by a STA that requests transmission by the Preemption operation. In this example of processing, it is assumed that STAs 103 and 104 request transmission by the Preemption operation. The processing shown in FIG. 11 is realized by the control unit 202 of STAs 103 and 104 executing a program. In one example, the processing shown in FIG. 11 is executed when traffic with a delay requirement occurs, such as when an application that performs low-latency communication is executed in the normal state after STAs 103 and 104 are connected to the AP101.

[0144] In S1101, the control unit 202 transmits a Preemption request to the AP101 and receives a Preemption response. Subsequently, in S1102, the control unit 202 determines whether the Preemption response received from the AP101 permits transmission by the Preemption operation. If it is determined that the Preemption response received from the AP101 permits transmission by the Preemption operation (Yes in S1102), the control unit 202 proceeds with the processing to S1103, and if not, the processing proceeds to S1104.

[0145] 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 the Preemption operation is not permitted, and the channel access parameters are set so that STA103 and 104 do not transmit during a TXOP period in which they are not TXOP responders. In one example, after the process of S1104, the control unit 202 may wait for a predetermined time and execute the process shown in FIG. 11 again.

[0146] FIG. 12 is a flowchart showing the details of the process of S1200. S1200 is realized by the control unit 202 of STA103 or 104 executing a program following the process of S1103 in FIG. 11. In the following description, it is assumed that the control unit 202 of STA103 executes the process of FIG. 12. Note that the process of FIG. 12 is executed before the Preemption declaration period.

[0147] In S1201, the control unit 202 receives a pRTS frame from AP101. In S1202, the control unit 202 sets a timer for the period during which the Preemption operation is to be performed based on the received pRTS frame. The time of this timer is the Duration included in the pRTS frame.

[0148] Here, during the period defined by Duration, the TXOP responder may permit the Preemption operation. Therefore, when the control unit 202 functions as a state control unit that controls the state of the STA103, the STA103 that requests the Preemption operation maintains the normal state (the first state) during the TXOP period and does not transition to the power-saving mode (the 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 the information of a MAC frame such as a decoded BA frame is not analyzed.

[0149] 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 a pCTS frame has been detected. If a pCTS frame has been detected (Yes in S1204), the control unit 202 advances the process to S1205; otherwise, the process advances to S1207.

[0150] In S1205, the control unit 202 updates the timer for the period during which the Preemption operation is performed according to the value of Duration in the pCTS frame.

[0151] In S1206, the control unit 202 determines that the state of the STA103 is a state in which the Preemption operation is permitted. In this state, access is performed according to the priority EDCA parameters included in the Preemption response, rather than the normal EDCA parameters or the default EDCA parameters included in the beacon signal transmitted from the AP101. Here, the default EDCA parameters are parameters used when accessing the medium outside the Preemption declaration period.

[0152] The process of S1207 is the process when STA103 detects a CTS frame or does not detect anything after the SIFS, which is the inter-frame interval after the pRTS frame. The control unit 202 determines that the Preemption operation is not permitted. In this case, the control unit 202 performs the conventional operation, that is, it does not perform media access using the priority EDCA parameters included in the Preemption response during the Preemption declaration period.

[0153] After the process of S1206 or S1207, the control unit 202 of STA103 advances the process to the process during the Preemption declaration period of S1208.

[0154] FIG. 13 is a flowchart showing an example of the process executed by the control units 202 of STA103 and 104 that requested transmission by the Preemption operation during the Preemption declaration period. In this example, it is assumed that STA103 executes the process of FIG. 13. The process shown in FIG. 13 is assumed to be executed by starting the Preemption declaration period timer following S1206 or S1207 in FIG. 12.

[0155] In S1301, the control unit 202 determines whether the uplink data of the LL communication is staying in the buffer. If it is determined that the uplink data of the LL communication is staying (Yes in S1301), the control unit 202 advances the process to S1302 and determines whether the Preemption operation is permitted. If it is determined that the uplink data of the LL communication is not staying (No in S1301), the control unit 202 does not perform data transmission and advances the process to S1308.

[0156] If it is determined that the Preemption operation is permitted (Yes in S1302), the control unit 202 advances the process to S1303 and determines whether it has obtained the access right for Preemption transmission. If it is determined that the Preemption operation is not permitted (No in S1302), the control unit 202 advances the process to S1306.

[0157] In S1303, the control unit 202 performs carrier sense during the contention window specified from the priority EDCA parameters included in the Preemption response, and determines that the access right has been acquired when it is determined that the medium is in the idle state. If the access right can be acquired (Yes in S1303), the control unit 202 advances the process to S1304 and transmits the LL data to the AP101. A UHR PPDU can be used for the radio frame of the transmission. If it is determined that the access right cannot be acquired (No in S1303), the control unit 202 advances the process to S1306.

[0158] After performing the transmission by the Preemption operation in S1304, the control unit 202 advances the process to S1305, receives a BA frame from the AP101, and advances the process to S1308. In S1308, the control unit 202 compares the value of Duration included in the received pRTS frame with the elapsed time of 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 shifts to the normal state. If it has not expired (No in S1308), the process returns to S1301.

[0159] In S1306, the control unit 202 determines whether downlink communication from the AP101 to the STA102 (TXOP responder) is occurring. If it is determined that the downlink communication is occurring (Yes in S1306), the control unit 202 advances the process to S1307.

[0160] In S1307, the control unit 202 updates the permission state of the Preemption operation according to the content of the BA frame from STA102 (TXOP responder). That is, even if the Preemption operation is rejected in the CTS frame, when the BA frame received in S1307 indicates that the Preemption operation is permitted, STA103 determines that it is in the permitted state when executing the process of S1302 again. Thus, the STA that executes the Preemption operation can detect that the permission or rejection state of the Preemption operation by STA102, which is the TXOP responder, has changed during the Preemption declaration period. Here, the reason why the BA frame transmitted from the TXOP responder can be detected is that the pCTS frame can be detected in S1204. When the access right by the Preemption operation cannot be obtained in the state where downlink communication is not occurring, the control unit 202 advances the process to S1308.

[0161] Hereinafter, several embodiments will be shown with reference to the operation sequences of DS105, AP101, and STA102 to 104.

[0162] <Example 1> FIGS. 14A and 14B show the operation sequences of the first embodiment according to the present embodiment. In the following description, the reference numerals in FIGS. 8 to 13 are shown in parentheses in correspondence with the reference numerals in FIGS. 14A and 14B.

[0163] In F1400 (S801), AP101 determines the EDCA parameters in the normal state. In F1401 (S804), AP101 transmits a beacon signal. In the examples of FIGS. 14A and 14B, it is assumed that STA102 to 104 receive the beacon signal.

[0164] In F1402 (S1101), STA103 transmits a Preemption request to AP101. Thus, AP101 can detect that STA103 is requesting permission for transmission by the Preemption operation.

[0165] In F1403 (S805), AP101 analyzes the preemption response and determines EDCA parameters (priority EDCA parameters) for the preemption operation according to the policy. In this case, in the case of a policy that accepts the preemption operation, the EDCA parameters will be superior to the EDCA parameters notified in the beacon. Here, the superior parameters mean parameters that, when determining the contention window, can be expected to enable media access in a shorter time compared to the case of determining according to the inferior parameters. Parameters that enable media access in a shorter time refer to at least any one of having a smaller CWmin, having a smaller CWmax, and having a smaller (CWmax - CWmin) / 2.

[0166] In F1404 (S809), AP101 returns the preemption response to STA103. Thereby, STA103 can obtain the EDCA parameters for accessing the medium when performing the preemption operation.

[0167] In F1405 (S1101), STA104 sends a preemption request to AP101. In F1406 (S806 - S808), AP101 analyzes the preemption response and determines the priority EDCA parameters according to the policy. In this case, in the case of a policy that performs priority control in the order of arrival when the number of STAs requesting the preemption operation is 2 or more, parameters that are superior to the EDCA parameters notified in the beacon and inferior to the EDCA parameters notified to STA103 may be notified. Thereby, during the preemption declaration period, the possibility of multiple STAs colliding when transmitting by the preemption operation can be reduced. In F1407 (S809), AP101 returns the preemption response to STA104. In this embodiment, it is assumed that STA103 and STA104 are not in a hidden terminal state with respect to each other.

[0168] At F1408, data is transmitted from DS105 to AP101 for STA102. At F1409 (S901), AP101 detects that downlink data for STA102 has occurred.

[0169] At F1410 (S904), AP101 transmits a pRTS frame to STA102. At F1411 (S1003), STA102 transmits a pCTS frame as a response to the pRTS frame received at F1410 to AP101. Here, STA103 and STA104 may or may not be able to recognize this pCTS frame.

[0170] In F1412 (S906, S907), AP101 executes a process of not inducing transmission to STA103 or STA104 by the Preemption operation. Here, as a process of not inducing Preempt, AP101 sets the value of IFS to SIFS. The process of F1412 is executed, for example, at the time of the first PPDU transmission to STA102. At this time, STA102 can determine whether to continue the permission state of the Preemption operation based on the PPDU in order to recognize the attributes (transmission source) and content of the data in the subsequent PPDUs from the content of the PPDU.

[0171] At F1413 (S1301), data for LL communication occurs at STA103, and at F1414 (S1301), data for LL communication occurs at STA104. That is, STA103 and 104 determine that transmission by the Preemption operation is necessary at F1413 and F1414. Assume that the generation timing of these LL communication data has a property that cannot be predicted (scheduled). In this sequence, it is assumed that the data for LL communication occurs before the start of IFS, which is the inter-frame interval after transmission from AP101 to STA102.

[0172] In F1415 (S909), after the pCTS frame, AP101 transmits a PPDU after the expiration of the SIFS. At this time, STA103 and STA104 cannot acquire the access right because the IFSs of STA103 and STA104 are larger than the SIFS, that is, the AIFSN is not 0.

[0173] In F1416 (S910), STA102 transmits a BA frame to AP101. This BA frame is assumed not to include information that can identify whether to permit the conventional BA frame, that is, the Preemption operation. AP101 determines that STA102, which has received the BA frame transmitted in F1416, is in a state where the Preemption operation is permitted.

[0174] In F1417 (S907 and S908), AP101 performs a process of inducing transmission by the Preemption operation. The process of inducing transmission by the Preemption operation is to refrain from transmitting a PPDU even after the expiration of the SIFS after receiving the BA frame. This non - transmission control is performed until the time corresponding to the AIFSN for Preemption notified by AP101 to STA103 has elapsed. Thereby, AP101 can give an opportunity for transmission by the STA that requests the Preemption operation during the Preemption declaration period.

[0175] In F1418 (S1303), STA103 acquires the access right. Here, in the Preemption operation, it is assumed that STA103 sets CWmin and CWmax to 0 (zero) and does not execute the subtraction of the back - off counter.

[0176] In F1419 (S1304), STA103 transmits a PPDU containing LL communication data to AP101. In F1420 (S1305), AP101 transmits a BA frame for the PPDU transmitted in F1419 to STA103.

[0177] In this sequence, it is assumed that the AIFNS of STA104 is N greater than the AIFS of STA103, and STA104 and STA103 are not in a hidden terminal relationship. This prevents a collision caused by STA104 transmitting during the transmission of STA103.

[0178] The processing from F1421 to F1424 is the same as that from F1412 and from F1415 to F1417. However, it is assumed that there is no queued LL data in STA103, and the LL data of F1414 is queued in STA104. Also, at F1424, it is assumed that the medium remains idle until the time corresponding to the AIFSN for preemption notified by AP101 to STA104 has elapsed.

[0179] At F1425 (S1303), STA104 acquires the access right. At F1426 (S1304), STA104 transmits a PPDU including LL data. At F1427 (S1305), AP101 transmits a BA frame to STA104. The description of F1428 to F1430 is omitted because it is the same as that of F1412 and from F1415 to F1416.

[0180] At F1431, the preemption declaration period specified by the Duration of pRTS ends, and the processing of FIGS. 14A and 14B ends.

[0181] As described above, in this embodiment, by differentiating (prioritizing) the AIFSN of the EDCA parameters notified when permitting the preemption operation for a plurality of terminals, collisions due to the preemption operation can be avoided. Thereby, flexible priority control can be performed, and the convenience in the preemption operation can be improved.

[0182] <Example 2> Example 2 will be described with reference to FIGS. 14A and 14B. The description of up to F1422 is omitted because it is the same as that of Processing Example 1.

[0183] In Embodiment 2, at F1423, STA102 transmits a BA frame including information that does not permit the Preemption operation to AP101. In this case, the process proceeds to F1431 without the processes from F1425 to F1427 occurring.

[0184] In this way, after the TXOP responder permits the Preemption operation by the pCTS frame, the permission of the Preemption operation can be cancelled during the Preemption declaration period specified by the Duration included in the pCTS frame. Thereby, it is possible to flexibly respond to changes in the situation of the TXOP responder, and the convenience in the Preemption operation can be improved.

[0185] <Embodiment 3> Referring to FIGS. 14A and 14A, Embodiment 3 will be described. Note that the description of the processing up to F1410 is the same as that in Processing Example 1, and thus will be omitted.

[0186] At F1411, STA102 transmits a CTS frame instead of a pCTS frame to AP101. In this case, the processes from F1418 to F1420 or from F1425 to F1427 do not occur, and the process proceeds to F1431.

[0187] In this way, the TXOP responder can reject the Preemption operation by the CTS frame, and the Preemption operation can be executed reflecting the intention of the TXOP responder. Thereby, the convenience in the Preemption operation can be improved.

[0188] <Embodiment 4> In Embodiment 1, at any timing after F1412, AP101 notifies the end of the Preemption declaration period. This is possible in the following two ways.

[0189] The first method is that the AP101 sends a Preemption response indicating that it does not permit the Preemption operation to the STA at F1404 or F1407. This is indicated by the Status Code or the EDCA parameter. This is not a direct response to the Preemption request, but a response by an unsolicited response action frame.

[0190] The second method is that the AP101 transmits a CF-End (RA is the 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 executed at the discretion of the AP101 or upon request from the TXOP holder. Here, this request can be realized by the reserved field (7 bits) of the BA frame.

[0191] 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, and the convenience of the Preemption operation can be improved.

[0192] <Example 5> Referring to FIG. 15, the processing when the timing at which the AP101 induces the Preemption operation is close to the generation timing of the LL data at the STA will be described.

[0193] At F1500, it is assumed that the STA103 operates with AIFSN = 1, and at F1501, it is assumed that the STA104 operates with AIFSN = 2. That is, it is assumed that the STA103 has more favorable access parameters than the STA104.

[0194] At F1502, data for LL communication is generated at STA104. At F1503, a PPDU is transmitted from AP101 to STA102. At this time, AP101 performs access control so as not to cause a Preemption operation on STA103 or STA104. At F1504, a BA frame is transmitted from STA102 to AP101.

[0195] At F1505, AP101 starts a process of inducing transmission related to the Preemtion operation. In this case, in order to target STA104, AP101 refrains from transmitting from AP101 for two slots (equivalent to two aSlotTime) after SIFS.

[0196] At F1506, SIFS elapses, and at F1507, one slot after SIFS elapses.

[0197] Here, it is assumed that LL data is generated at STA103 at F1508. In this embodiment, STA103 does not perform transmission by the Preemption operation even if there is no LL communication data at the time of AIFSN elapse and LL communication data is generated by the next slot time elapse. Therefore, at F1509, STA103 refrains from media access.

[0198] At F1510, two slots after SIFS elapse. As a result, at F1511, STA104 acquires the access right, and at F1512, STA104 transmits a PPDU (LL data). At F1513, AP101 transmits a BA frame to STA104.

[0199] In this way, by STA103 refraining from media access at F1509, a collision with F1512 transmitted by other STAs is prevented. Here, the transmission timing of each STA including AP101 is determined in slot units, and transmission is not started in the middle of a slot.

[0200] As a modification of this embodiment, the case where F1511 to F1513 are not executed is shown by the dashed-dotted line in FIG. 15. STA103 acquires the access right (F1515) at F1514 after the slot time of the normal AIFSN that is not the Preemption operation has elapsed. As a result, STA103 can transmit the LL data to AP101.

[0201] In this way, by restricting the medium access timing of the Preemption operation to the AIFSN slot unit, the possibility of collision is reduced, the usage efficiency of the wireless medium is improved, and the convenience of the Preemption operation is improved.

[0202] <Other Embodiments> The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiment to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0203] The disclosure of this embodiment includes the following communication device, its control method, and program.

[0204] (Item 1) A communication device compatible with the IEEE 802.11 series of standards, communication means for communicating with the first other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device; determination means for determining whether or not the first other communication device permits transmission by a second other communication device different from the first other communication device during the TXOP period based on a signal received from the first other communication device; When the determination means determines that the first other communication device permits the transmission by the second other communication device during the TXOP period, a waiting time before transmitting any one of the frames addressed to the first other communication device by the communication device during the TXOP period is set to be longer than the waiting time when it is determined that the first other communication device does not permit the transmission by the second other communication device during the TXOP period. A communication control means; A communication device comprising:

[0205] (Item 2) The communication means transmits a permission request for requesting permission for the transmission by the second other communication device during the TXOP period to the first other communication device, receives a response to the permission request from the first other communication device, The determination means determines whether the first other communication device permits the transmission by the second other communication device during the TXOP period based on the response received by the communication means. The communication device according to Item 1.

[0206] (Item 3) The communication means transmits an occupancy request frame for requesting the securing of the TXOP period as the permission request, The determination means when receiving a Clear To Send (CTS) frame as a response to the occupancy request frame, determines that the first other communication device does not permit the transmission by the second other communication device during the TXOP period, when receiving an occupancy response frame different from the CTS frame as a response to the occupancy request frame, determines that the first other communication device permits the transmission by the second other communication device during the TXOP period. The communication device according to Item 2.

[0207] (Item 4) The communication means transmits an occupancy request frame for requesting the securing of the TXOP period as the permission request, and receives an occupancy response frame as a response to the occupancy request frame, When the determination means determines that the received occupancy response frame contains predetermined information, the determination means determines that the first other communication device permits the second other communication device to transmit during the TXOP period, as described in item 2 of the communication device.

[0208] (Item 5) The occupancy request frame and the occupancy response frame are the communication devices according to item 3 or 4, wherein at least one of the Type field, Subtype field, and Control Frame Extension field of the Request To Send (RTS) frame or Clear To Send (CTS) frame and the Medium Access Control (MAC) frame is different.

[0209] (Item 6) The communication means transmits a Request To Send (RTS) frame as the permission request and receives a Clear To Send (CTS) frame as the response. When the determination means determines that the received CTS frame contains predetermined information, the determination means determines that the first other communication device permits the second other communication device to transmit during the TXOP period, as described in item 2 of the communication device.

[0210] (Item 7) When the determination means receives a Block ACK (BA) frame as a response to a data frame transmitted to the first other communication device within the TXOP period by the communication means, the determination means determines whether the first other communication device permits the second other communication device to transmit during the TXOP period based on the received BA frame, as described in any one of items 1 to 6 of the communication device.

[0211] (Item 8) The communication means receives a transmission request for requesting transmission during the TXOP period by the second other communication device from the second other communication device. As a response to the transmission request, when transmission by the second other communication device during the TXOP period is permitted, transmit Enhanced Distributed Channel Access (EDCA) parameters used for accessing the medium to the second other communication device. The communication device according to any one of items 1 to 7.

[0212] (Item 9) The communication device according to item 8, wherein the EDCA parameter includes an Arbitration Inter Frame Space Number (AIFSN) having a value greater than 0.

[0213] (Item 10) When the determination means determines that the first other communication device permits the transmission by the second other communication device during the TXOP period, the communication control means 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 determination means determines that the first other communication device does not permit the transmission by the second other communication device during the TXOP period. The communication device according to any one of items 1 to 9.

[0214] (Item 11) When the determination means determines that the first other communication device permits the transmission by the second other communication device during the TXOP period, the communication control means controls the frame length of the data frame so that the number of intervals between data frames transmitted from the communication device to the first other communication device during the TXOP period is larger than when the determination means determines that the first other communication device does not permit the transmission by the second other communication device during the TXOP period. The communication device according to any one of items 1 to 10.

[0215] (Item 12) The communication control means When the determination means determines that the first other communication device does not permit the transmission during the TXOP period by the second other communication device, set all the inter-frame intervals before the frame transmitted from the communication device to the first other communication device to Short Inter Frame Space (SIFS). The communication device according to any one of items 1 to 11, wherein when the determination means determines that the first other communication device permits the transmission during the TXOP period by the second other communication device, set the inter-frame interval before transmitting any one of the frames addressed to the first other communication device from the communication device to be greater than SIFS.

[0216] (Item 13) When the communication control means determines that the first other communication device permits the transmission during the TXOP period by the second other communication device, set the waiting time before transmitting any one of the frames addressed to the first other communication device by the communication device within the TXOP period to have a larger inter-frame interval than the waiting time before the first other communication device accesses the medium during the TXOP period. The communication device according to any one of items 1 to 12.

[0217] (Item 14) The communication means receives information capable of specifying whether each of the other communication devices connected to the communication device is mutually detected. When the communication control means determines that the first other communication device permits the transmission during the TXOP period by the second other communication device, and when a predetermined condition regarding whether each of the other communication devices connected to the communication device is mutually detected is satisfied, set the waiting time before any one 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 is determined that the first other communication device does not permit the transmission by the second other communication device. The communication device according to any one of items 1 to 13.

[0218] (Item 15) The determination means further determines whether to permit transmission by the second other communication device during the TXOP period, When the communication means determines not to permit transmission by the second other communication device during the TXOP period, the communication device notifies the second other communication device that the communication device does not permit transmission during the TXOP period. The communication device according to any one of items 1 to 14.

[0219] (Item 16) A communication device compatible with the IEEE 802.11 series of standards, Communication means for detecting a signal transmitted from the second other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame from the first other communication device to the second other communication device; Determination means for determining, based on the signal detected by the communication means, whether the second other communication device permits transmission by the communication device during the TXOP period; When the determination means determines that the second other communication device permits transmission by the communication device during the TXOP period, the communication control means detects a period during which a frame is not transmitted to the second other communication device during the TXOP period and controls the communication means to transmit a signal to the first other communication device. A communication device comprising:

[0220] (Item 17) The communication means receives a response transmitted from the second other communication device as a response to an occupancy request frame requesting permission for transmission during the TXOP period transmitted from the first other communication device, When the determination means receives an occupancy response frame different from a Clear To Send (CTS) frame as a response to the occupancy request frame by the communication means, the determination means determines that the second other communication device permits transmission by the communication device during the TXOP period. The communication device according to item 16.

[0221] (Item 18) The communication means receives an occupancy response frame transmitted from the second other communication device as a response to an occupancy request frame that requests permission for transmission during the TXOP period transmitted from the first other communication device, The determination means, when determining that the occupancy response frame received by the communication means includes predetermined information, determines that the second other communication device permits transmission by the communication device during the TXOP period, according to the communication device described in item 16.

[0222] (Item 19) The communication means receives a Clear To Send (CTS) frame transmitted from the second other communication device as a response to a Request To Send (RTS) frame that requests permission for transmission during the TXOP period transmitted from the first other communication device, The determination means, when determining that the CTS frame received by the communication means includes predetermined information, determines that the second other communication device permits transmission by the communication device during the TXOP period, according to the communication device described in item 16.

[0223] (Item 20) The communication means receives a Block ACK (BA) frame transmitted from the second other communication device as a response to a data frame transmitted from the first other communication device to the second other communication device, The determination means determines whether the second other communication device permits transmission by the communication device during the TXOP period based on the BA frame received by the communication means. The communication device according to any one of items 16 to 19.

[0224] (Item 21) The communication control means determines that the second other communication device permits the transmission by the communication device during the TXOP period, and when access to the medium becomes possible, if there is no uplink data for low-latency communication to the first other communication device, it does not transmit a signal to the first other communication device during the TXOP period. The communication device according to any one of items 16 to 20.

[0225] (Item 22) The communication means transmits a transmission request for requesting transmission during the TXOP period to the first other communication device, As a response to the request for transmission, it receives Enhanced Distributed Channel Access (EDCA) parameters used to access the medium when transmission by the communication device during the TXOP period is permitted. The communication device according to any one of items 16 to 21.

[0226] (Item 23) It further has state control means for switching the operation between a first state for decoding a Medium Access Control (MAC) frame transmitted from another communication device and a second state which is a power-saving mode for not decoding a MAC frame transmitted from another communication device, The state control means sets the state of the communication device to the first state during the TXOP when it receives the EDCA parameters as a response to the transmission request. The communication device according to item 22.

[0227] (Item 24) A communication device corresponding to the IEEE 802.11 series of standards, Communication means for communicating with the first other communication device during a Transmission Opportunity (TXOP) period secured for receiving a data frame from the first other communication device, Determination means for determining whether to permit transmission by the second other communication device during the TXOP period, Comprising, The communication means transmits, to other communication devices including at least the first other communication device, a signal capable of specifying whether to permit transmission by the second other communication device during the TXOP period.

[0228] (Item 25) The communication means according to item 24 notifies, to other communication devices including at least the first other communication device, whether to permit transmission by the second other communication device during the TXOP period via at least any one of: a Clear To Send (CTS) frame requesting securing of the TXOP period; an occupancy request frame different from the CTS frame and requesting securing of the TXOP period; and a Block ACK (BA) frame for a data frame received from the first other communication device during the TXOP period.

[0229] (Item 26) A control method executed by a communication device compliant with the IEEE 802.11 series of standards, the method including: communicating with a first other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device; determining, based on a signal received from the first other communication device, whether the first other communication device permits transmission by a second other communication device different from the first other communication device during the TXOP period; when it is determined that the first other communication device permits transmission by the second other communication device during the TXOP period, setting a waiting time before any one of the frames transmitted from the communication device to the first other communication device within the TXOP period to be longer than the waiting time when it is determined that the first other communication device does not permit transmission by the second other communication device during the TXOP period. A control method including the above.

[0230] (Item 27) A control method executed by a communication device compliant with the IEEE 802.11 series of standards, the method including: Receiving a signal from the second other communication device during a transmission opportunity (TXOP) period reserved for transmitting a data frame from the first other communication device to the second other communication device; Based on the received signal, determining whether the second other communication device permits transmission by the communication device during the TXOP period; When it is determined 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; A control method including the above.

[0231] (Item 28) A control method executed by a communication device compatible with the IEEE 802.11 series of standards, Communicating with the first other communication device during a transmission opportunity (TXOP) period reserved for receiving a data frame from the first other communication device; Determining whether to permit transmission by the second other communication device during the TXOP period; Notifying at least other communication devices including the first other communication device whether to permit transmission by the second other communication device during the TXOP period; A control method including the above.

[0232] (Item 29) A program for causing a computer to execute the control method according to any one of Items 26 to 28.

[0233] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Explanation of Signs

[0234] 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 communication device compliant with the IEEE 802.11 series of standards, comprising: communication means for communicating with a first other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device; determination means for determining, based on a signal received from the first other communication device, whether the first other communication device permits transmission by a second other communication device different from the first other communication device during the TXOP period; communication control means for setting, when the determination means determines that the first other communication device permits transmission by the second other communication device during the TXOP period, a waiting time before transmitting any one of the frames addressed to the first other communication device by the communication device during the TXOP period to be longer than a waiting time when it is determined that the first other communication device does not permit transmission by the second other communication device during the TXOP period; A communication device comprising the above.

2. The communication means: transmits a permission request to the first other communication device, requesting permission for transmission by the second other communication device during the TXOP period; receives a response to the permission request from the first other communication device; The determination means determines, based on the response received by the communication means, whether the first other communication device permits transmission by the second other communication device during the TXOP period. The communication device according to Claim 1.

3. The communication means transmits an occupancy request frame requesting securing of the TXOP period as the permission request; The determination means: determines that the first other communication device does not permit transmission by the second other communication device during the TXOP period when receiving a Clear To Send (CTS) frame as a response to the occupancy request frame; determines that the first other communication device permits transmission by the second other communication device during the TXOP period when receiving an occupancy response frame different from the CTS frame as a response to the occupancy request frame. The communication device according to Claim 2.

4. The communication means transmits an occupancy request frame requesting securing of the TXOP period as the permission request, and receives an occupancy response frame as a response to the occupancy request frame. The communication device according to claim 2, wherein when the determination means determines that the received occupancy response frame includes predetermined information, the determination means determines that the first other communication device permits transmission by the second other communication device during the TXOP period.

5. The communication device according to claim 3 or 4, wherein at least one of the Type field, Subtype field, and Control Frame Extension field of the Request To Send (RTS) frame or Clear To Send (CTS) frame and the media access control (MAC) frame is different between the occupancy request frame and the occupancy response frame.

6. The communication means transmits a Request To Send (RTS) frame as the permission request and receives a Clear To Send (CTS) frame as the response. The communication device according to claim 2, wherein when the determination means determines that the received CTS frame includes predetermined information, the determination means determines that the first other communication device permits transmission by the second other communication device during the TXOP period.

7. The communication device according to claim 1, wherein when the determination means receives a Block ACK (BA) frame as a response to a data frame transmitted to the first other communication device within the TXOP period by the communication means, the determination means determines, based on the received BA frame, whether the first other communication device permits transmission by the second other communication device during the TXOP period.

8. The communication means receives a transmission request for requesting transmission by the second other communication device during the TXOP period from the second other communication device, and transmits Enhanced Distributed Channel Access (EDCA) parameters used to access the medium when transmission by the second other communication device is permitted during the TXOP period to the second other communication device as a response to the transmission request. The communication device according to claim 1.

9. The communication device according to claim 8, wherein the EDCA parameters include an Arbitration Inter Frame Space Number (AIFSN) having a value greater than 0.

10. When the communication control means determines, as determined by the determination means, that the first other communication device permits transmission by the second other communication device during the TXOP period, the maximum length of the data frame transmitted from the communication device to the first other communication device during the TXOP period is set shorter than when the determination means determines that the first other communication device does not permit transmission by the second other communication device during the TXOP period. The communication device according to claim 1, characterized in that.

11. When the communication control means determines, as determined by the determination means, that the first other communication device permits transmission by the second other communication device during the TXOP period, the number of data frame intervals transmitted from the communication device to the first other communication device during the TXOP period is increased compared to when the determination means determines that the first other communication device does not permit transmission by the second other communication device during the TXOP period. The communication device according to claim 1, characterized in that the frame length of the data frame is controlled so that.

12. The communication control means, When the determination means determines that the first other communication device does not permit transmission by the second other communication device during the TXOP period, all the frame intervals before the frame transmitted from the communication device to the first other communication device are set to Short Inter Frame Space (SIFS), When the determination means determines that the first other communication device permits transmission by the second other communication device during the TXOP period, the frame interval before transmitting any of the frames addressed to the first other communication device from the communication device is set larger than SIFS. The communication device according to claim 1.

13. When the communication control means determines that the first other communication device permits transmission by the second other communication device during the TXOP period, the waiting time before transmitting any of the frames addressed to the first other communication device by the communication device within the TXOP period is set to have a larger frame interval than the waiting time before the first other communication device accesses the medium during the TXOP period. The communication device according to claim 1.

14. The communication means receives information capable of specifying whether each of the other communication devices connected to the communication device is mutually detected, The communication control means is a case where it is determined that the first other communication device permits transmission by the second other communication device during the TXOP period, and when a predetermined condition regarding whether or not each of the other communication devices connected to the communication device is mutually detected is satisfied, the waiting time before any one of the frames transmitted from the communication device to the first other communication device during the TXOP period is set to be longer than the waiting time in the case where it is determined that the first other communication device does not permit transmission by the second other communication device. The communication device according to claim 1.

15. The determination means further determines whether or not to permit transmission by the second other communication device during the TXOP period. The communication means, when it is determined that the communication device does not permit transmission by the second other communication device during the TXOP period, notifies that the communication device does not permit transmission by the second other communication device during the TXOP period. The communication device according to claim 1.

16. A communication device corresponding to the IEEE 802.11 series of standards, communication means for detecting a signal transmitted from the second other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame from the first other communication device to the second other communication device; determination means for determining, based on the signal detected by the communication means, whether or not the second other communication device permits transmission by the communication device during the TXOP period; communication control means for controlling the communication means to transmit a signal to the first other communication device by detecting a period during which a frame is not transmitted to the second other communication device during the TXOP period when the determination means determines that the second other communication device permits transmission by the communication device during the TXOP period; A communication device comprising:

17. The communication means receives a response transmitted from the second other communication device as a response to an occupancy request frame requesting permission for transmission during the TXOP period transmitted from the first other communication device. The determination means determines that the second other communication device permits the transmission by the communication device during the TXOP period when receiving an occupancy response frame different from a Clear To Send (CTS) frame as a response to the occupancy request frame by the communication means, according to the communication device of claim 16.

18. The communication means receives an occupancy response frame transmitted from the second other communication device as a response to an occupancy request frame requesting permission for transmission during the TXOP period transmitted from the first other communication device, The determination means determines that the second other communication device permits the transmission by the communication device during the TXOP period when determining that the occupancy response frame received by the communication means includes predetermined information, according to the communication device of claim 16.

19. The communication means receives a Clear To Send (CTS) frame transmitted from the second other communication device as a response to a Request To Send (RTS) frame requesting permission for transmission during the TXOP period transmitted from the first other communication device, The determination means determines that the second other communication device permits the transmission by the communication device during the TXOP period when determining that the CTS frame received by the communication means includes predetermined information, according to the communication device of claim 16.

20. The communication means receives a Block ACK (BA) frame transmitted from the second other communication device as a response to a data frame transmitted from the first other communication device to the second other communication device, The determination means determines whether the second other communication device permits the transmission by the communication device during the TXOP period based on the BA frame received by the communication means. The communication device according to claim 16.

21. When the communication control means determines that the second other communication device permits the transmission by the communication device during the TXOP period and access to the medium becomes possible, if there is no uplink data for low-latency communication to the first other communication device during the TXOP period, the communication control means does not transmit a signal to the first other communication device during the TXOP period, according to the communication device of claim 16.

22. The communication means transmits a transmission request requesting transmission during the TXOP period to the first other communication device. The communication device according to claim 16, wherein, in response to the request for transmission, when transmission by the communication device during the TXOP period is permitted, an Enhanced Distributed Channel Access (EDCA) parameter used to access the medium is received.

23. Further comprising state control means for switching operations between a first state for decoding a Medium Access Control (MAC) frame transmitted from another communication device and a second state which is a power saving mode for not decoding a MAC frame transmitted from another communication device, The state control means sets the state of the communication device to the first state in the TXOP when the EDCA parameter is received as a response to the transmission request. The communication device according to claim 22.

24. A communication device corresponding to the IEEE 802.11 series of standards, Communication means for communicating with a first other communication device during a transmission opportunity (TXOP) period secured for receiving a data frame from the first other communication device, Determination means for determining whether to permit transmission by a second other communication device during the TXOP period, Comprising: The communication means transmits a signal capable of specifying whether to permit transmission by the second other communication device during the TXOP period to other communication devices including at least the first other communication device.

25. The communication means notifies other communication devices including at least the first other communication device whether 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 securing of the TXOP period, an occupancy request frame different from the CTS frame and requesting securing of the TXOP period, and a Block ACK (BA) frame for a data frame received from the first other communication device during the TXOP period. The communication device according to claim 24.

26. A control method executed by a communication device corresponding to the IEEE 802.11 series of standards, Communicating with a first other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame to the first other communication device, Determining whether the first other communication device permits transmission by a second other communication device different from the first other communication device during the TXOP period based on a signal received from the first other communication device; When it is determined that the first other communication device permits transmission by the second other communication device during the TXOP period, setting a waiting time before any one of the frames transmitted from the communication device to the first other communication device within the TXOP period to be longer than the waiting time when it is determined that the first other communication device does not permit transmission by the second other communication device during the TXOP period; A control method including the above.

27. A control method executed by a communication device compatible with the IEEE 802.11 series of standards, Receiving a signal from a second other communication device during a transmission opportunity (TXOP) period secured for transmitting a data frame from a first other communication device to the second other communication device; Determining whether the second other communication device permits transmission by the communication device during the TXOP period based on the received signal; When it is determined 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; A control method including the above.

28. A control method executed by a communication device compatible with the IEEE 802.11 series of standards, Communicating with the first other communication device during a transmission opportunity (TXOP) period secured for receiving a data frame from the first other communication device; Determining whether to permit transmission by a second other communication device during the TXOP period; Notifying at least other communication devices including the first other communication device of whether to permit transmission by the second other communication device during the TXOP period; A control method including the above.

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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