Access point and wireless terminal device

Abstract

An access point according to an embodiment includes a communication circuit and a processor. The communication circuit is configured to transmit and receive wireless signals using a plurality of subcarriers. The processor is constituted to: establish a link with a plurality of wireless terminal devices using a communication circuit; set a plurality of units RU in which a plurality of subcarriers are grouped; allocate an application for each of the plurality of units RU on the basis of quality requirements received from the plurality of wireless terminal devices; and notify the plurality of wireless terminal devices about information on the allocated applications by using a trigger frame that indicates the transfer period of a frame in the uplink direction.

Description

Access point and wireless terminal device

[0001] The embodiments relate to an access point and a wireless terminal device.

[0002] A wireless LAN (Local Area Network) is known as a communication system that wirelessly connects an access point and a wireless terminal device. By using a wireless LAN, a wireless terminal device can access a network via an access point within its communication area. Furthermore, the R-TWT (restricted target wake time) function is known as a method for transmitting and receiving low-latency traffic between an access point and a wireless terminal device. An access point using the R-TWT function sets a service period at a period corresponding to the required latency of the low-latency traffic and notifies the wireless terminal device of the set service period using a beacon signal. The access point then prioritizes transmission and reception of low-latency traffic during the periodically set service period. This can reduce the delay and jitter of the low-latency traffic.

[0003] IEEE802.11be D4.0, “35.3 Multi-link operation, 35.8 Restricted TWT (R-TWT)”, p489-p580, p611-p616, July 2023

[0004] However, low-latency traffic can include not only low-latency traffic that occurs periodically but also low-latency traffic that occurs aperiodically. It is desirable for a communication system to be able to satisfy the required delay for low-latency traffic that occurs aperiodically. It is also desirable for a communication system to be able to satisfy the quality requirements for traffic other than aperiodic low-latency traffic that has quality requirements.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide an access point and a terminal that can satisfy traffic quality requirements.

[0006] An access point according to an embodiment includes a communication circuit and a processor. The communication circuit is configured to transmit and receive wireless signals using a plurality of subcarriers. The processor is configured to establish links with a plurality of wireless terminal devices using the communication circuit, set a plurality of units into which the plurality of subcarriers are grouped, assign a purpose to each of the plurality of units based on quality requirements received from the plurality of wireless terminal devices, and notify the plurality of wireless terminal devices of information about the assigned purposes using a trigger frame that indicates a transfer period for uplink frames.

[0007] According to the embodiment, it is possible to provide an access point and a wireless terminal device that can satisfy traffic quality requirements.

[0008] FIG. 1 is a block diagram showing an example of the configuration of a communication system according to an embodiment. FIG. 2 is a schematic diagram showing an example of an RU assigned to a 20 MHz band. FIG. 3 is a schematic diagram showing an example of a format of a radio frame used in the communication system according to an embodiment. FIG. 4 is a schematic diagram showing an example of a format of a trigger frame used in the communication system according to an embodiment. FIG. 5 is a block diagram showing an example of the hardware configuration of an access point according to an embodiment. FIG. 6 is a block diagram showing an example of the hardware configuration of a wireless terminal device according to an embodiment. FIG. 7 is a block diagram showing an example of the functional configuration of an access point according to an embodiment. FIG. 8 is a block diagram showing an example of the configuration of a channel access function of an access point according to an embodiment. FIG. 9 is a block diagram showing an example of the functional configuration of a wireless terminal device according to an embodiment. FIG. 10 is a block diagram showing an example of the configuration of a channel access function of a wireless terminal device according to an embodiment. FIG. 11 is a time chart showing an example of a downlink data transfer method using OFDMA in the communication system according to an embodiment. FIG. 12 is a time chart showing an example of an uplink data transfer method using OFDMA in the communication system according to an embodiment. FIG. 13 is a schematic diagram showing an example of the configuration of an OFDMA frame transfer period in the communication system according to an embodiment. Fig. 14 is a flowchart showing an example of a negotiation method for allocation of RUs by a quality management unit of an access point according to the embodiment. Fig. 15 is a flowchart showing an example of a method for managing communication quality by a quality management unit of an access point according to the embodiment. Fig. 16 is a flowchart showing an example of a method for allocating RUs by a resource control unit of an access point according to the embodiment. Fig. 17 is a flowchart showing an example of a method for generating a trigger frame by a frame processing unit of an access point according to the embodiment. Fig. 18 is a flowchart showing an example of a method for generating an OFDMA frame by a frame processing unit of an access point according to the embodiment. Fig. 19 is a flowchart showing an example of a method for transmitting an OFDMA frame in the downlink direction by a transceiver unit of an access point according to the embodiment.FIG. 20 is a flowchart showing an example of a method for transmitting downlink aperiodic low latency traffic by a transceiver unit of an access point according to the embodiment. FIG. 21 is a flowchart showing an example of a method for negotiating allocation of application-specific RUs by a quality management unit of a wireless terminal device according to the embodiment. FIG. 22 is a flowchart showing an example of a method for managing communication quality by a quality management unit of a wireless terminal device according to the embodiment. FIG. 23 is a flowchart showing an example of a method for acquiring and updating RU allocation information by a resource control unit of a wireless terminal device according to the embodiment. FIG. 24 is a flowchart showing an example of a method for processing downlink frames by a frame processing unit of a wireless terminal device according to the embodiment. FIG. 25 is a flowchart showing an example of a method for processing uplink frames by a frame processing unit of a wireless terminal device according to the embodiment. FIG. 26 is a flowchart showing an example of a method for receiving downlink frames by a transceiver unit of a wireless terminal device according to the embodiment. FIG. 27 is a flowchart showing an example of a method for transmitting uplink OFDMA frames by a transceiver unit of a wireless terminal device according to the embodiment. FIG. 28 is a flowchart showing an example of a method for transmitting uplink aperiodic low latency traffic by a transceiver unit of a wireless terminal device according to the embodiment.

[0009] Hereinafter, embodiments will be described with reference to the drawings. The embodiments illustrate devices and methods for embodying the technical ideas of the invention. The drawings are schematic or conceptual. In the following description, components having the same function and configuration are assigned common reference symbols. Furthermore, when multiple components having the same function and configuration are to be distinguished from one another, a hyphen and a number are added to the end of the reference symbol.

[0010] <1> Configuration First, the configuration of a communication system 1 according to the embodiment will be described.

[0011] <1-1> Configuration of communication system 1 Fig. 1 is a block diagram showing an example of the configuration of a communication system 1 according to an embodiment. As shown in Fig. 1, the communication system 1 includes an access point (hereinafter also referred to as "AP") 10 and at least one wireless terminal apparatus 20. In the example shown in Fig. 1, three wireless terminal apparatuses 20-1, 20-2, and 20-3 are wirelessly connected to the access point 10.

[0012] The access point 10 is a base station of a wireless LAN. The access point 10 is configured to establish links with a plurality of wireless terminal devices 20 and to be able to communicate wirelessly with each of the wireless terminal devices 20 with which the link is established. The access point 10 is also connected to a network NW and is configured to be able to communicate with a server (not shown) on the network NW. The access point 10 and the network NW may be connected wirelessly or by wire.

[0013] The wireless terminal device 20 is a wireless terminal such as a smartphone or a PC (Personal Computer). The wireless terminal device 20 is configured to be able to communicate with a server on the network NW via a wirelessly connected access point 10. Hereinafter, the wireless terminal devices 20-1, 20-2, and 20-3 that have established a link with the access point 10 will also be referred to as "STA#1," "STA#2," and "STA#3," respectively.

[0014] The wireless communication between the access point 10 and the wireless terminal device 20 complies with, for example, the IEEE 802.11 standard. The IEEE 802.11 standard has wireless communication functions based on the OSI (Open Systems Interconnection) reference model. In the OSI reference model, wireless communication functions are divided into seven layers (Layer 1: Physical Layer, Layer 2: Data Link Layer, Layer 3: Network Layer, Layer 4: Transport Layer, Layer 5: Session Layer, Layer 6: Presentation Layer, and Layer 7: Application Layer). The data link layer includes a Logical Link Control (LLC) sublayer and a Media Access Control (MAC) sublayer. The LLC sublayer forms LLC packets by adding a Destination Service Access Point (DSAP) header, a Source Service Access Point (SSAP) header, etc. to data input from an upper application. The MAC layer forms MAC frames by adding a MAC header to the LLC packets. In this specification, the processing for the MAC sublayer of the first and second layers will be mainly described, and the processing for other layers will not be described.

[0015] The access point 10 and the wireless terminal device 20 each support Orthogonal Frequency Division Multiple Access (OFDMA) as a wireless communication method. OFDMA is a method that combines Orthogonal Frequency Division Multiplexing (OFDM) and Time Division Multiple Access (TDMA). OFDM is a method that divides a channel bandwidth allocated for wireless communication into multiple subcarriers (tones). OFDM achieves narrowband subcarriers by orthogonalizing the phases of subcarriers allocated to adjacent frequencies and overlapping portions of the frequency bands. TDMA is a multiplexing method that divides a carrier used for communication into fixed periods and assigns STAs to each period. OFDMA, which is a combination of OFDM and TDMA, divides the right to use each subcarrier by time and assigns it to different STAs. OFDMA can finely change the allocation of subcarriers according to the radio wave conditions of each STA, thereby improving the efficiency of radio wave usage. In OFDMA, subcarriers are allocated to multiple STAs in units of resource units (RUs), which are groups of subcarriers that make up one channel. In OFDMA, data can be transmitted in parallel in units of RUs.

[0016] FIG. 2 is a schematic diagram showing an example of RUs allocated to a 20 MHz band. (A) of FIG. 2 illustrates a case where nine 26-tone RUs #1 to #9, each consisting of 26 subcarriers, are allocated to the 20 MHz band. In this case, one of the nine 26-tone RUs #1 to #9 is allocated to each STA. (B) of FIG. 2 illustrates a case where four 52-tone RUs #1 to #4, each consisting of 52 subcarriers, are allocated to the 20 MHz band. In this case, one of the four 52-tone RUs #1 to #4 is allocated to each STA. (C) of FIG. 2 illustrates a case where two 106-tone RUs #1 and #2, each consisting of 106 subcarriers, are allocated to the 20 MHz band. In this case, one of the two 52-tone RUs #1 and #2 is allocated to each STA. Note that an RU may be configured with other numbers of subcarriers. For example, an RU may be configured with more than 106 subcarriers. Furthermore, multiple types of RUs, each with a different number of subcarriers, may be assigned to a channel bandwidth allocated to wireless communication. The maximum number of RUs varies depending on the channel bandwidth allocated to wireless communication.

[0017] (Radio Frame Format) FIG. 3 is a schematic diagram showing an example of a radio frame format used in the communication system 1 according to the embodiment. As shown in FIG. 3, the radio frame includes a preamble and a MAC frame. The preamble is located at the beginning of the radio frame and includes a bit string indicating the start position of the radio frame. The MAC frame includes, for example, a MAC header, a payload, and an FCS (Frame Check Sequence) field. The MAC header stores information such as the frame type and data length. The payload stores information according to the frame type and includes an LLC packet when data (traffic) is transmitted. The FCS field stores an error detection code used to detect errors in the MAC header and payload. In the communication system 1, the access point 10 can control the transmission of uplink data (traffic) by the STA by using a trigger frame. The format of the trigger frame will be described below.

[0018] 4 is a schematic diagram showing an example of the format of a trigger frame used in the communication system 1 according to the embodiment. As shown in FIG. 4, the multiple fields included in the trigger frame include, for example, a frame control field, a duration field, a first address field (RA: Receiver Address), a second address field (TA: Transmitter Address), a common information field, a user information list field, a padding field, and an FCS (Frame Check Sequence) field. In this example, the set of the frame control field, duration field, and address field corresponds to the MAC header, and the set of the common information field, user information list field, and padding field corresponds to the payload.

[0019] The frame control field stores various control information. For example, the frame control field includes information indicating the frame type of the wireless frame. The duration field indicates the planned period for using the wireless link. The first address field and the second address field indicate the BSSID (Basic Service Set Identifier), source address, destination address, sender terminal address, receiver terminal address, etc. The common information field indicates information shared among multiple STAs. The user information list field indicates information assigned to each STA. The padding is an area for adjusting the data length of the wireless frame.

[0020] The common information field includes, for example, a trigger type subfield, an uplink (UL) bandwidth subfield, and a maximum frame length subfield. The trigger type subfield indicates the type of trigger frame. The UL bandwidth subfield indicates the channel bandwidth available for frame transmission. The maximum frame length subfield indicates the maximum length of a frame that can meet the delay requirement of aperiodic low-latency traffic, which will be described later.

[0021] The User Information List field includes, for example, an AID (Terminal Identifier) ​​subfield and an RU Allocation subfield. The allocation of an RU to each STA can be specified by the information of the STA specified by the AID subfield and the location of the RU indicated by the RU Allocation subfield. In other words, the STA can recognize that an RU has been allocated to itself by the AID subfield. The STA can then recognize the settings of the RU allocated to itself by the RU Allocation subfield.

[0022] The RU assignment subfield includes, for each RU, information regarding, for example, RU usage, RU identifier, and access category. The RU usage includes information such as whether the RU is dedicated to the access category indicated, whether it is shared with a higher priority access category, whether transmission can start midway through an OFDMA frame, and whether it is dedicated to a specific wireless terminal device 20 (indicated by the AID). The OFDMA frame is assigned to a subcarrier based on the RU assignment and corresponds to a MAC frame that is the target of transmission / reception using OFDMA. The RU identifier indicates the RU to which the assignment is made. The access category is, for example, aperiodic low latency, deterministic periodic low latency, video, voice, best effort, etc. In the following, the access category may be abbreviated as "AC."

[0023] <1-2> Hardware Configuration of Communication System 1 The hardware configuration of the communication system 1 according to the embodiment will be described below.

[0024] <1-2-1> Hardware Configuration of Access Point 10 Fig. 5 is a block diagram showing an example of the hardware configuration of the access point 10 according to the embodiment. As shown in Fig. 5, the access point 10 includes, for example, a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a wireless communication module 14, and a wired communication module 15.

[0025] The CPU 11 is an integrated circuit capable of executing various programs and controls the overall operation of the access point 10. The ROM 12 is, for example, a non-volatile semiconductor memory and stores programs and control data for controlling the access point 10. The RAM 13 is, for example, a volatile semiconductor memory and is used as a work area for the CPU 11. The wireless communication module 14 is configured to be able to send and receive wireless signals via an antenna and is a circuit used for sending and receiving data, etc. with the wireless terminal device 20. The wired communication module 15 is a circuit used for sending and receiving data, etc. via wired signals and is configured to be connectable to the network NW.

[0026] The access point 10 may have other hardware configurations. For example, the access point 10 may be wirelessly connected to the network NW. In this case, the wired communication module 15 may be omitted from the access point 10. The antenna may be built into the access point 10 or may be externally connected. The CPU 11 may be called a "processor." The wireless communication module 14 may be called a "communication circuit."

[0027] <1-2-2> Hardware Configuration of Wireless Terminal Device 20 Fig. 6 is a block diagram showing an example of the hardware configuration of the wireless terminal device 20 according to the embodiment. As shown in Fig. 6, the wireless terminal device 20 includes, for example, a CPU 21, a ROM 22, a RAM 23, a wireless communication module 24, a display 25, and a storage 26.

[0028] The CPU 21 is an integrated circuit capable of executing various programs and controls the overall operation of the wireless terminal device 20. The ROM 22 is, for example, a non-volatile semiconductor memory and stores programs and control data for controlling the wireless terminal device 20. The RAM 23 is, for example, a volatile semiconductor memory and is used as a work area for the CPU 21. The wireless communication module 24 is configured to be able to send and receive wireless signals via an antenna and is a circuit used to send and receive data to and from the access point 10. The display 25 displays, for example, a graphical user interface (GUI) corresponding to application software. The storage 26 is a non-volatile storage device and stores, for example, system software for the wireless terminal device 20.

[0029] The wireless terminal device 20 may have other hardware configurations. For example, if the wireless terminal device 20 is an IoT (Internet of Things) terminal or the like, the display 25 may be omitted from the wireless terminal device 20. The display 25 may function as an input interface for the wireless terminal device 20. The antenna may be built into the wireless terminal device 20 or may be externally connected. The CPU 21 may be called a "processor." The wireless communication module 24 may be called a "communication circuit."

[0030] <1-3> Functional Configuration of Communication System 1 The functional configuration of the communication system 1 according to the embodiment will be described below.

[0031] <1-3-1> Functional Configuration of Access Point 10 Fig. 7 is a block diagram showing an example of the functional configuration of the access point 10 according to the embodiment. As shown in Fig. 7, the access point 10 functions as a computer including, for example, an LLC processing unit 110, a link management unit 120, a frame processing unit 130, and a transceiver unit 140. The LLC processing unit 110 performs processing of the LLC sublayer of layer 2 and layers 3 to 7. The link management unit 120, the frame processing unit 130, and the transceiver unit 140 perform processing of the MAC sublayer of layer 2. The transceiver unit 140 also performs processing of layer 1.

[0032] The LLC processing unit 110 generates LLC packets by adding DSAP headers, SSAP headers, etc. to data received from the network NW. The LLC processing unit 110 then inputs the generated LLC packets to the frame processing unit 130. The LLC processing unit 110 also extracts data from the LLC packets input from the frame processing unit 130. The LLC processing unit 110 then transmits the extracted data to the network NW.

[0033] The link management unit 120 manages the state of the link between the access point 10 and the wireless terminal device 20. The link management unit 120 can perform association processing and authentication processing in response to a connection request from the wireless terminal device 20. MAC frames including information related to the link, OFDMA, etc. are input and output between the link management unit 120 and the frame processing unit 130. The link management unit 120 includes a quality management unit 121 and a resource control unit 122.

[0034] The quality management unit 121 exchanges quality requirements, which may include the required delay, throughput, packet arrival rate, etc., of aperiodic low-latency traffic (hereinafter referred to as "aperiodic low-latency traffic"), with the wireless terminal device 20. The quality management unit 121 then requests the resource control unit 122 to provide the required application-specific RUs in accordance with the quality requirements received from the wireless terminal device 20. Application-specific RUs are RUs allocated for different traffic purposes. Application-specific RUs may include dedicated RUs, high-priority RUs, etc. Dedicated RUs are RUs allocated for aperiodic low-latency traffic regardless of the presence or absence of traffic. High-priority RUs are RUs allocated to predetermined high-priority traffic. High-priority traffic is associated with, for example, a category having a priority of access category VI or higher. Information such as Preferred_AC may be added to application-specific RUs. Preferred_AC indicates the access category for which transmission is prioritized in the associated RU.

[0035] The resource control unit 122 determines the allocation of RUs to uplink / downlink OFDMA frames. Then, the resource control unit 122 notifies the frame processing unit 130 of the determined RU allocation. Hereinafter, information related to the RU allocation will also be referred to as "RU allocation information." The RU allocation information may include information related to the allocation of application-specific RUs when application-specific RUs are requested by the quality management unit 121.

[0036] The frame processing unit 130 generates a MAC frame by adding a MAC header to the LLC packet input from the LLC processing unit 110 based on the RU allocation notified by the resource control unit 122. The frame processing unit 130 then outputs the generated MAC frame to the transceiver unit 140. The frame processing unit 130 can also output a trigger frame generation instruction to the transceiver unit 140 based on information received from the link management unit 120. The frame processing unit 130 also outputs the MAC frame input from the transceiver unit 140 to the LLC processing unit 110, the quality management unit 121, the resource control unit 122, etc., depending on the type of MAC frame. The frame processing unit 130 may extract an LLC packet from the MAC frame and output the extracted LLC packet to the LLC processing unit 110, etc.

[0037] The transceiver 140 performs carrier sensing based on CSMA / CA for each link and transmits a MAC frame using the link that has acquired the transmission right. When transmitting a MAC frame, the transceiver 140 generates a wireless frame by adding a preamble or the like to the MAC frame input from the frame processor 130. The transceiver 140 then converts the generated wireless frame into a wireless signal (wireless medium) and radiates (transmits) it via an antenna. The transceiver 140 can assign and transmit OFDMA frames to subcarriers based on RU assignment. The transceiver 140 can transmit trigger frames for uplink OFDMA frames. The transceiver 140 also converts wireless signals received via the antenna into wireless frames. The transceiver 140 then extracts the MAC frame from the converted wireless frame and outputs it to the frame processor 130.

[0038] The transceiver 140 may also be referred to as an "STA function." The conversion process from radio frames to radio signals performed by the transceiver 140 includes, for example, any of convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform, OFDM (Orthogonal Frequency Division Multiplexing) modulation, and frequency conversion. The conversion process from radio signals to radio frames performed by the transceiver 140 includes, for example, any of frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. The access point 10 may include multiple transceivers 140 that handle different channels.

[0039] (Channel Access Function of Access Point 10) Fig. 8 is a block diagram showing an example of the configuration of the channel access function of the access point 10 according to the embodiment. As shown in Fig. 8, the transceiver 140 includes, for example, a classification unit 141, queues 142A, 142B, 142C, and 142D, carrier sense execution units 143A, 143B, 143C, and 143D, and an internal collision management unit 144.

[0040] The classification unit 141 classifies MAC frames input from the frame processing unit 130 into multiple access categories: VO (Voice), VI (Video), BE (Best Effort), BK (Background), and RT (Real Time) based on the traffic type (TID: Traffic IDentifier) ​​included in the MAC header. The classification unit 141 then inputs MAC frames corresponding to the access categories VO, VI, BE, and BK to queues 142A, 142B, 142C, and 142D, respectively. The queues 142A, 142B, 142C, and 142D buffer MAC frames corresponding to the access categories VO, VI, BE, and BK, respectively. The queues 142A, 142B, 142C, and 142D are associated with carrier sense execution units 143A, 143B, 143C, and 143D, respectively.

[0041] Each of the carrier sense execution units 143A, 143B, 143C, and 143D executes carrier sense based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) in accordance with preset access parameters. The access parameters are set for each access category. For example, the access parameters are set so that the transmission of wireless signals is prioritized in the order of "VO," "VI," "BE," and "BK." Each of the carrier sense execution units 143A, 143B, 143C, and 143D halts acquisition of the transmission right if the channel state during carrier sense is busy, and acquires the transmission right for a MAC frame if the channel state remains idle for a predetermined period of time. After acquiring the transmission right, the carrier sense execution unit 143 retrieves a MAC frame from the associated queue 142 and outputs the retrieved MAC frame to the internal collision management unit 144.

[0042] The internal collision management unit 144 prevents transmission collisions when multiple carrier sense execution units 143 simultaneously acquire the right to transmit. Specifically, when multiple MAC frames are input simultaneously, the internal collision management unit 144 prioritizes and outputs MAC frames of higher priority access categories. The MAC frames output from the internal collision management unit 144 are converted into wireless frames after a preamble is added, and then transmitted via an antenna.

[0043] Furthermore, when a MAC frame input from the frame processing unit 130 is classified as the access category RT, the classification unit 141 performs carrier sensing and then inputs the MAC frame to the internal collision management unit 144 without passing through each queue 142. MAC frames classified as the access category RT are, for example, high-priority frames such as trigger frames and aperiodic low-latency traffic. High-priority frames undergo carrier sensing without passing through each queue 142 and are prioritized over other traffic types, so they are processed with less latency than other traffic. When transmitting a high-priority frame, the transceiver 140 may temporarily suspend carrier sensing in each carrier sense execution unit 143. When a dedicated RU is assigned, the transceiver 140 may transmit traffic of the access category RT using the dedicated RU without performing carrier sensing. The transceiver 140 may generate a trigger frame based on information notified by the frame processing unit 130.

[0044] Access parameters used in carrier sensing in the transceiver 140 of the access point 10 include, for example, CW (contention window) min, CWmax, AIFS (arbitration interframe space), and TXOP (transmission opportunity) Limit. The contention window is a parameter used to determine the transmission wait time for collision avoidance. CWmin and CWmax indicate the minimum and maximum values ​​of the contention window, respectively. AIFS (arbitration interframe space) indicates a fixed transmission wait time set for each access category for collision avoidance control with a priority control function. TXOP corresponds to the channel occupancy time. TXOPLimit indicates the upper limit of TXOP. The shorter the CWmin and CWmax, the easier it is for the queue 142 to obtain the transmission right. The smaller the AIFS, the higher the priority of the queue 142. The larger the value of TXOPLimit, the greater the amount of data transmitted with one transmission right. The access parameters may be referred to as Enhanced Distributed Channel Access (EDCA) parameters.

[0045] The access point 10 may have other functional configurations as long as it is capable of performing the operations described below. For example, the channel access function of the access point 10 may be implemented in the frame processing unit 130, rather than in the transceiver unit 140. The transmission priority may be determined based on the required delay of aperiodic low-latency traffic, the traffic priority (SCS: Stream Classification Service), and the traffic type. The access point 10 may acquire a transmission right to forward both uplink traffic and downlink traffic. In this case, the access point 10 uses OFDMA frames to transmit downlink traffic and trigger frames to transmit uplink traffic. The access point 10 may acquire a transmission right using common access parameters for uplink and downlink traffic, and transmit OFDMA frames and trigger frames alternately.

[0046] <1-3-2> Functional Configuration of Wireless Terminal Device 20 FIG. 9 is a block diagram showing an example of the functional configuration of the wireless terminal device 20 according to the embodiment. As shown in FIG. 9, the wireless terminal device 20 functions as a computer including, for example, an application execution unit 200, an LLC processing unit 210, a link management unit 220, a frame processing unit 230, and a transceiver unit 240. The application execution unit 200 performs processing corresponding to layer 7. The LLC processing unit 210 performs processing for the LLC sublayer of layer 2 and layers 3 to 7. The link management unit 220, the frame processing unit 230, and the transceiver unit 240 perform processing for the MAC sublayer of layer 2. The transceiver unit 240 also performs processing for layer 1.

[0047] The application execution unit 200 executes an application based on data input from the LLC processing unit 210. The application execution unit 200 also inputs data to the LLC processing unit 210. For example, the application execution unit 200 can display application information on the display 25. The application execution unit 200 can also operate based on operations on an input interface.

[0048] The LLC processing unit 210 generates LLC packets by adding DSAP headers, SSAP headers, etc. to data received from the network NW. The LLC processing unit 210 then inputs the generated LLC packets to the frame processing unit 230. The LLC processing unit 210 also extracts data from the LLC packets input from the frame processing unit 230. The LLC processing unit 210 then transmits the extracted data to the application execution unit 200.

[0049] The link management unit 220 manages the state of the link between the access point 10 and the wireless terminal device 20. The link management unit 220 transmits a connection request to the access point 10 and can execute association processing and authentication processing. MAC frames including information related to the link, OFDMA, etc. are input and output between the link management unit 220 and the frame processing unit 230. The link management unit 220 includes a quality management unit 221 and a resource control unit 222.

[0050] The quality management unit 221 exchanges quality requirements, which may include the required delay of aperiodic low-latency traffic, with the access point 10. The quality management unit 221 can measure the actual delay value of the aperiodic low-latency traffic and notify the access point 10. The resource control unit 222 acquires RU allocation information notified from the access point 10. Then, based on the acquired RU allocation information, it notifies the frame processing unit 230 of the allocation of RUs.

[0051] Frame processing unit 230 generates a MAC frame by adding a MAC header to the LLC packet input from LLC processing unit 210 based on the RU allocation notified by resource control unit 222. Frame processing unit 230 then outputs the generated MAC frame to transceiver unit 240. Frame processing unit 230 outputs the MAC frame input from transceiver unit 240 to LLC processing unit 210, quality management unit 221, resource control unit 222, etc., depending on the type of MAC frame. Frame processing unit 230 may extract an LLC packet from the MAC frame and output the extracted LLC packet to LLC processing unit 210, etc.

[0052] The transceiver 240 performs carrier sensing based on CSMA / CA for each link and transmits a MAC frame using the link that has acquired the transmission right. When transmitting a MAC frame, the transceiver 240 generates a wireless frame by adding a preamble or the like to the MAC frame input from the frame processor 230. The transceiver 240 then converts the generated wireless frame into a wireless signal (wireless medium) and radiates (transmits) it via an antenna. The transceiver 240 can assign the OFDMA frame to a subcarrier based on the RU assignment and transmit it. The transceiver 240 also converts the wireless signal received via the antenna into a wireless frame. The transceiver 240 then extracts the MAC frame from the converted wireless frame and outputs it to the frame processor 230.

[0053] The transceiver 240 may also be referred to as an "STA function." One link is formed by a pair of the STA function of the access point 10 and the STA function of the wireless terminal device 20. The conversion process from wireless frames to wireless signals performed by the transceiver 240 includes, for example, any of convolutional coding, interleaving, subcarrier modulation, inverse fast Fourier transform, OFDM modulation, and frequency conversion. The conversion process from wireless signals to wireless frames performed by the transceiver 240 includes, for example, any of frequency conversion, OFDM demodulation, fast Fourier transform, subcarrier demodulation, deinterleaving, and Viterbi decoding. The wireless terminal device 20 may include multiple transceivers 240 that handle different channels.

[0054] 10 is a block diagram showing an example of the configuration of the channel access function of the wireless terminal device 20 according to the embodiment. As shown in Fig. 10, the transceiver 240 includes, for example, a classification unit 241, queues 242A, 242B, 242C, and 242D, carrier sense execution units 243A, 243B, 243C, and 243D, and an internal collision management unit 244.

[0055] The classification unit 241 classifies MAC frames input from the frame processing unit 230 into a plurality of access categories VO, VI, BE, BK, and RT based on the traffic type included in the MAC header. The classification unit 241 then inputs MAC frames corresponding to the access categories VO, VI, BE, and BK to queues 242A, 242B, 242C, and 242D, respectively. The queues 242A, 242B, 242C, and 242D buffer MAC frames corresponding to the access categories VO, VI, BE, and BK, respectively. The queues 242A, 242B, 242C, and 242D are associated with carrier sense execution units 243A, 243B, 243C, and 243D, respectively.

[0056] Each of the carrier sense execution units 243A, 243B, 243C, and 243D executes carrier sense based on CSMA / CA in accordance with preset access parameters, similar to the transceiver unit 140 of the access point 10. Each of the carrier sense execution units 243A, 243B, 243C, and 243D halts acquisition of the transmission right if the channel state at the time of carrier sense is busy, and acquires the transmission right for the MAC frame if the channel state has been idle for a predetermined period of time. The carrier sense execution unit 243 that has acquired the transmission right extracts a MAC frame from the associated queue 242 and outputs the extracted MAC frame to the internal collision management unit 244.

[0057] The internal collision management unit 244 prevents transmission collisions when multiple carrier sense execution units 243 simultaneously acquire the right to transmit. Specifically, when multiple MAC frames are input simultaneously, the internal collision management unit 244 prioritizes and outputs MAC frames of higher priority access categories. The MAC frames output from the internal collision management unit 244 are converted into wireless frames after a preamble is added, and then transmitted via an antenna.

[0058] Furthermore, when a MAC frame input from the frame processing unit 230 is classified as the access category RT, the classification unit 241 performs carrier sensing and then inputs the MAC frame to the internal collision management unit 244 without passing through each queue 242. MAC frames classified as the access category RT are, for example, aperiodic low-latency traffic. Since carrier sensing is performed on the aperiodic low-latency traffic without passing through each queue 242 and the aperiodic low-latency traffic is prioritized over other traffic types, the aperiodic low-latency traffic is processed with less latency than other traffic. When transmitting aperiodic low-latency traffic, the transceiver unit 240 may temporarily suspend carrier sensing in each carrier sense execution unit 243. When a dedicated RU is assigned, the transceiver unit 240 may transmit traffic of the access category RT using the dedicated RU without performing carrier sensing.

[0059] The access parameters used in carrier sensing in the transceiver 240 of the wireless terminal device 20 are, for example, CWmin, CWmax, AIFS, and TXOPLimit, similar to those used in the transceiver 140 of the access point 10. The shorter the CWmin and CWmax, the easier it is for the queue 242 to obtain a transmission right. The smaller the AIFS, the higher the priority of the queue 242. The larger the value of TXOPLimit, the larger the amount of data transmitted with one transmission right.

[0060] Note that the wireless terminal device 20 may have other functional configurations as long as it is capable of executing the operations described below. For example, the channel access function of the wireless terminal device 20 may be implemented in the frame processing unit 230, rather than in the transceiver unit 240. The transmission priority may be determined based on the required delay of the aperiodic low-latency traffic, the priority of the traffic, and the traffic type. When transmitting uplink traffic based on a trigger frame transmitted by the access point 10, the wireless terminal device 20 transmits the traffic using an RU corresponding to the RU allocation information notified by the access point 10. The wireless terminal device 20 transmits uplink aperiodic low-latency traffic using a dedicated RU. The wireless terminal device 20 transmits uplink high-priority traffic using a high-priority RU. Furthermore, when multiple wireless terminal devices 20 use a common dedicated RU, the wireless terminal device 20 may perform carrier sensing based on CSMA / CA and then transmit the aperiodic low-latency traffic using the dedicated RU in order to avoid collisions with the aperiodic low-latency traffic of the other wireless terminal devices 20. Similarly, when multiple wireless terminal devices 20 use a common high-priority RU, the wireless terminal device 20 may transmit the high-priority traffic using the high-priority RU in accordance with carrier sensing based on CSMA / CA, predetermined terminal priorities, or a scheduling method by the access point 10 in order to avoid collisions with the high-priority traffic of the other wireless terminal devices 20. In other words, when a dedicated RU and / or a high-priority RU is shared by multiple STAs or multiple traffic flows, a random access method may also be used in combination.

[0061] <2> Operation Next, the operation of the communication system 1 according to the embodiment will be described.

[0062] <2-1> Overview of OFDMA Below, as an overview of OFDMA in the communication system 1 according to the embodiment, the flow of communication in the downlink direction, the flow of communication in the uplink direction, and the OFDMA frame transfer period set for these communications will be described in order.

[0063] (Downlink Data Transfer Method) FIG. 11 is a time chart showing an example of a downlink data transfer method using OFDMA in the communication system 1 according to the embodiment. FIG. 11 illustrates a case where downlink data (traffic) is transferred between an access point 10 (AP) and three wireless terminal devices 20 (STAs #1 to #3). As shown in FIG. 11, when downlink traffic occurs, the AP transmits a MU-RTS (multi-user request to send) to each of STAs #1 to #3 in a batch. The MU-RTS is a frame for reserving channels between the AP and multiple STAs when the AP starts transferring downlink traffic to multiple STAs. The MU-RTS includes, for example, RU allocation information.

[0064] Each STA that receives the MU-RTS transmits a CTS (clear to send) to the AP if it is able to receive downlink traffic. When the AP receives a CTS from each of STAs #1 to #3, it uses the associated RU (i.e., at least one subcarrier) to transmit data #1 to #3 stored in OFDMA frames to STAs #1 to #3, respectively. In Figure 11, the period used to transmit the OFDMA frames from the AP to each STA is shown as the "OFDMA frame transfer period."

[0065] Then, after transmitting an OFDMA frame to each of STAs #1 to #3, the AP transmits a MU-BAR (multi-user block acknowledgment request) to each of STAs #1 to #3 in a batch. The MU-BAR is a frame that the AP uses to request multiple STAs to transmit a response in a batch. Each STA that receives the MU-BAR transmits a BA (block acknowledgment) to the AP in accordance with the reception result of the OFDMA frame. The AP recognizes that the transmission of each of data #1 to #3 was successful based on the reception of the BA from each STA. This causes the communication system 1 to terminate downlink data transfer using OFDMA.

[0066] During the OFDMA frame transfer period in the downlink data transfer, the start time of transmission and the time required for transmission of each of the data #1 to #3 may be different. The AP may transmit the RTS and BAR separately for each STA. The timing at which the AP receives the CTS from each STA may be different. The timing at which the AP receives the BA from each STA may be different. The RU used for transmitting the OFDMA frame may be assigned for each traffic or for each STA.

[0067] (Uplink Data Transfer Method) Fig. 12 is a time chart showing an example of an uplink data transfer method using OFDMA in the communication system 1 according to the embodiment. Fig. 12 illustrates a case where uplink data is transferred between an access point 10 (AP) and three wireless terminal devices 20 (STA#1 to #3). As shown in Fig. 12, when uplink traffic occurs, the AP transmits a trigger frame to each of STA#1 to #3 in a batch.

[0068] Each STA that receives the trigger frame transmits data to the AP using the associated RU (i.e., at least one subcarrier) based on the RU allocation information stored in the trigger frame. In this example, STAs #1 to #3 transmit data #1 to #3 stored in OFDMA frames to the AP, respectively. In Figure 12, the period used to transmit the OFDMA frames from each STA to the AP is shown as an "OFDMA frame transfer period."

[0069] Then, after receiving OFDMA frames from each of STAs #1 to #3, the AP transmits an M-BA (multi-STA BA) to each of STAs #1 to #3 all at once. The M-BA is a type of BA, and is a frame that the AP uses to notify multiple STAs that data reception has been successful. Each STA recognizes that it has successfully transmitted each of data #1 to #3 based on receiving the M-BA from the AP. This causes the communication system 1 to end uplink data transfer using OFDMA.

[0070] During the OFDMA frame transfer period during uplink data transfer, the start time of transmission and the time required for transmission of each of Data #1 to #3 may be different. The AP may transmit a trigger frame and a BA individually to each STA. The timing at which each STA receives a trigger frame from the AP may be different. The timing at which each STA receives a BA from the AP may be different. The RU used to transmit the OFDMA frames may be assigned to each traffic or each STA.

[0071] (Configuration of OFDMA Frame Transfer Period) Fig. 13 is a schematic diagram showing an example of the configuration of an OFDMA frame transfer period in the communication system 1 according to the embodiment. Fig. 13 illustrates a case where an OFDMA frame transfer period to which a usage-specific RU is assigned starts after a certain time (IFS: interframe space) has elapsed since the wireless terminal device 20 received a trigger frame. The horizontal axis indicates the time axis. As shown in Fig. 13, the OFDMA frame transfer period has a configuration in which, for example, the usage-specific RU has multiple transfer periods TP divided in the time axis direction, and an IFS is inserted between adjacent transfer periods TP.

[0072] Each transfer period TP is set shorter than the required delay of aperiodic low-latency traffic. Each transfer period TP is used to transfer frames associated with RU #1 to RU #4. In this example, the four RUs #1 to #4 are set as application-specific RUs. RU #1 is assigned a dedicated RU associated with aperiodic low-latency traffic (Dedicated). RU #2 is assigned a high-priority RU associated with high-priority traffic (High Priority). RU #3 is assigned an RU that does not limit the STA functions that can use the RU (Any). RU #4 is assigned an RU associated with STA1 (STA1). In this case, the user information list field of the trigger frame stores, for example, the following information (1) to (4): (1) AID = AID1 (dedicated RU and can be sent en route), RU = RU1, AC = aperiodic low delay. (2) AID = AID2 (high priority: AC lower limit specified), RU = RU2, AC = AC_VI. (3) AID = AID0 (anything is possible), RU = RU3, AC = AC_BE. (4) AID = STA1, RU = RU4, AC = AC_BE.

[0073] The setting (1) designates RU1 as a dedicated RU for aperiodic low-latency traffic. The setting (2) designates RU2 as an RU capable of transmitting traffic of an access category having a priority of AC_VI or higher. Note that in (1) to (4), the setting associated with the AID may be other settings. Multiple STAs may be associated with the AID. The category indicated by AC indicates Preferred_AC. In this way, the access point 10 can designate the use of the RU by a combination of AID, RU assignment, and Preferred_AC in a trigger frame that triggers an uplink OFDMA frame.

[0074] As described above, in this example, multiple subcarriers are grouped, and multiple RUs are configured, including dedicated RUs associated with low-latency traffic and high-priority RUs associated with high-priority traffic. In the OFDMA frame transfer period, the divided transfer periods TP are arranged consecutively with IFSs inserted. The number of transfer periods TP included in the OFDMA frame transfer period may vary depending on the required delay of the aperiodic low-latency traffic. Multiple dedicated RUs or multiple high-priority RUs may be assigned to each transfer period TP. The combination of application-specific RUs assigned to each transfer period TP may be changed as appropriate depending on the quality requirements from the wireless terminal device 20.

[0075] <2-2> Operation of Access Point 10 Below, detailed operation of the access point 10 according to the embodiment will be described, focusing on the functional configuration of the access point 10 shown in Fig. 7. It is assumed that communication between each functional configuration of the access point 10 and the STA is performed via the frame processing unit 130, the transceiver unit 140, etc. as appropriate.

[0076] <2-2-1> Operation of the Quality Control Unit 121 First, the operation of the quality control unit 121 of the access point 10 will be described.

[0077] 14 is a flowchart showing an example of a negotiation method for allocation of application-specific RUs by the quality control unit 121 of the access point 10 (AP) according to the embodiment. For example, when aperiodic low-latency traffic or high-priority traffic occurs after a link is established between the AP and a STA, the quality control unit 121 starts the processing of the flowchart shown in FIG. 14 (START).

[0078] First, the quality management unit 121 acquires quality requirements from the STA (S101). The quality requirements are generated by the quality management unit 221 of the wireless terminal device 20. The frame type for transferring the quality requirements is not particularly limited. Traffic associated with the quality requirements includes aperiodic low latency traffic, deterministic periodic traffic, video traffic, etc. The quality requirements for aperiodic low latency traffic include information on the delay time required to transfer the aperiodic low latency traffic. The quality requirements for deterministic periodic traffic include information on the period of the deterministic periodic traffic. The quality requirements for video traffic include information on the video quality of the video traffic.

[0079] Next, the quality management unit 121 receives a request for allocation of a usage-specific RU (S102). The request for allocation of a usage-specific RU is generated by the quality management unit 221 of the wireless terminal device 20. There are no particular limitations on the frame type for transferring the request for allocation of a usage-specific RU.

[0080] Next, the quality management unit 121 determines whether application-specific RUs can be allocated (S103). Based on the quality requirements of the aperiodic low-latency traffic, the quality management unit 121 determines whether dedicated RUs can be allocated by, for example, determining whether the remaining number of configurable dedicated RUs exceeds the number of configurable dedicated RUs. The number of configurable dedicated RUs may be preset by the AP or may be changed depending on the number of STAs connected to the AP or the allocation of RUs. Based on the quality requirements of the deterministic periodic traffic, the quality management unit 121 determines whether necessary RUs can be allocated to match the deterministic period. Based on the quality requirements of the video traffic, the quality management unit 121 determines whether necessary RUs can be allocated to match the video quality. Note that the quality management unit 121 may allocate RUs necessary for transmitting traffic to a specific wireless terminal device 20, or may acquire buffer status from the wireless terminal device 20 each time and allocate RUs based on the acquired status.

[0081] If it is determined in the process of S103 that a usage-specific RU can be allocated (S103: YES), the quality management unit 121 transmits an affirmative response to the STA (S104). Then, the quality management unit 121 requests the resource control unit 122 to allocate a usage-specific RU (S105). When allocating a usage-specific RU, the quality management unit 121 may set a high-priority RU. For example, the quality management unit 121 sets a high-priority RU when there are insufficient resources for the allocated usage-specific RU. Then, the quality management unit 121 notifies the resource control unit 122 and the frame processing unit 130 of the required delay for the aperiodic low-latency traffic to determine whether or not frame division is necessary (S106). Thereafter, the quality management unit 121 ends the series of processes shown in FIG. 14 (END).

[0082] If it is determined in the process of S103 that the usage-specific RU cannot be allocated (S103: NO), the quality control unit 121 transmits a negative response to the STA (S107). Then, the quality control unit 121 ends the series of processes in FIG. 14 (END).

[0083] 15 is a flowchart showing an example of a method for managing communication quality by the quality management unit 121 of the access point 10 (AP) according to the embodiment. The quality management unit 121 starts the processing of the flowchart shown in FIG. 15 (START) after, for example, completing the transfer of aperiodic low latency traffic using a dedicated RU.

[0084] First, the quality control unit 121 acquires the actual delay measurement value of the aperiodic low-delay traffic from the STA (S111). The actual delay measurement value is calculated by the STA. There are no particular limitations on the frame type for transferring the actual delay measurement value.

[0085] Next, the quality management unit 121 evaluates whether the "requested delay > actual measured delay" (S112). If the actual measured delay is greater than the requested delay, this indicates that the delay time when transferring aperiodic low-delay traffic does not satisfy the requirements requested by the STA.

[0086] In the process of S112, if the "requested delay > actual delay" does not hold (S112: NO), the quality management unit 121 requests the resource control unit 122 to increase the allocation of dedicated RUs (S113). That is, the quality management unit 121 requests the resource control unit 122 to increase the allocation of dedicated RUs based on the communication quality. Then, the quality management unit 121 ends the series of processes in FIG. 15 (END).

[0087] In the process of S112, if the "request delay>actual delay measurement value" (S112: YES), the quality management unit 121 ends the series of processes in FIG. 15 (END).

[0088] The quality management unit 121 may execute the processes of S112 and S113 each time it acquires a delay measurement value from a STA, or may execute the processes periodically. When the quality management unit 121 acquires delay measurement values ​​multiple times, it may compare the required delay with a parameter based on the average, minimum, or maximum of the acquired delay measurement values, jitter, or other actual measurement values ​​in the process of S112. The quality management unit 121 may also determine whether or not to increase the allocation of dedicated RUs based on the use of a high-priority RU. The reason for this is that the use of a high-priority RU indicates that the originally assigned application-specific RU has competed with another wireless terminal device 20.

[0089] <2-2-2> Operation of the Resource Control Unit 122 Next, the operation of the resource control unit 122 of the access point 10 will be described.

[0090] 16 is a flowchart showing an example of a method for allocating an RU by the resource control unit 122 of the access point 10 (AP) according to the embodiment. After a link between the AP and a STA is established, the resource control unit 122 starts the process of the flowchart shown in FIG. 16 in response to a request for allocation of an RU from the STA (START).

[0091] First, the resource control unit 122 checks whether allocation of a usage-specific RU has been requested (S121). The request for allocation of a usage-specific RU may be generated by the quality management unit 121. The frame type for transferring the RU allocation request is not particularly limited.

[0092] If allocation of usage-specific RUs is requested in the processing of S121 (S121: YES), the resource control unit 122 allocates usage-specific RUs in response to the request (S122). The resource control unit 122 then allocates traffic to the remaining RUs (S123). The resource control unit 122 then notifies the frame processing unit 130 of information about the allocated RUs (S124). Thereafter, the resource control unit 122 ends the series of processing shown in FIG. 16 (END).

[0093] If allocation of application-specific RUs is not requested in the process of S121 (S121: YES), the resource control unit 122 allocates traffic to all RUs (S122). Then, the resource control unit 122 proceeds to the process of S124 and notifies the frame processing unit 130 of information about the allocated RUs. Thereafter, the resource control unit 122 ends the series of processes shown in FIG. 16 (END).

[0094] The resource control unit 122 may increase the allocation of application-specific RUs in the process of S122 in the order of 26-tone, 52-tone, 106-tone, ... based on a request from the quality management unit 121. In allocations other than application-specific RUs, the resource control unit 122 may perform channel estimation with the STAs, and if an RU suitable for each STA is available, may preferentially allocate the RU suitable for each STA. If traffic having a required delay exists other than aperiodic low latency traffic, the resource control unit 122 may preferentially allocate RUs to that traffic. Furthermore, the resource control unit 122 may allocate RUs for each OFDMA frame based on the buffer accumulation status of downlink traffic and uplink traffic.

[0095] <2-2-3> Operation of the Frame Processing Unit 130 Next, the operation of the frame processing unit 130 of the access point 10 will be described.

[0096] 17 is a flowchart showing an example of a method for generating a trigger frame by the frame processing unit 130 of the access point 10 (AP) according to the embodiment. For example, when traffic occurs after a link is established between the AP and a STA, the frame processing unit 130 starts the processing of the flowchart shown in FIG. 17 (START).

[0097] First, the frame processing unit 130 generates a MAC frame for each traffic stream to be simultaneously transmitted by OFDMA (S131). In the process of S131, the frame processing unit 130 may generate multiple MAC frames according to the number of traffic streams to be simultaneously transmitted. Furthermore, when generating the MAC frames, a MAC header and the like are added.

[0098] Next, the frame processing unit 130 checks whether the generated MAC address frame corresponds to aperiodic low latency traffic (S132). The process of S132 is executed for each of the multiple MAC frames generated in the process of S131.

[0099] If it is confirmed in the process of S132 that the frame corresponds to aperiodic low-latency traffic (S132: YES), frame processing unit 130 outputs the generated MAC frame together with RU allocation information to transceiver unit 140 (S133). The RU allocation information in the process of S133 includes allocation information for RUs other than dedicated RUs. Then, frame processing unit 130 ends the series of processes in FIG. 17 (END).

[0100] If it is determined in the process of S132 that the traffic does not correspond to aperiodic low latency traffic, i.e., that the traffic being processed is traffic other than aperiodic low latency traffic (S132: NO), frame processing unit 130 outputs the generated MAC frame together with RU allocation information and required delay to transceiver unit 140 (S134). The RU allocation information in the process of S134 includes allocation information for dedicated RUs. Then, frame processing unit 130 ends the series of processes shown in FIG. 17 (END).

[0101] 18 is a flowchart showing an example of a method for generating an OFDMA frame by the frame processing unit 130 of the access point 10 (AP) according to the embodiment. For example, when the frame processing unit 130 is notified by the STA that uplink traffic has occurred, the frame processing unit 130 starts the processing of the flowchart shown in FIG. 18 (START).

[0102] First, the frame processor 130 checks whether a usage-specific RU is allocated (S141). For example, the frame processor 130 checks whether a RU for transmitting aperiodic low latency traffic between an AP and a STA is allocated.

[0103] If it is determined in the process of S141 that a usage-specific RU has been allocated (S141: YES), the frame processing unit 130 generates usage-specific RU allocation information based on the notification from the resource control unit 122 and stores it in the RU allocation subfield (S142). The frame processing unit 130 then calculates the maximum frame length based on the required delay and stores it in the maximum frame length subfield (S143). The maximum frame length information corresponds to, for example, the maximum frame length that can satisfy the required delay of aperiodic low-latency traffic. Note that the maximum frame length information may be associated with a value smaller than the maximum frame length that can satisfy the required delay of aperiodic low-latency traffic. The frame processing unit 130 then adds a MAC header and other information to generate a trigger frame and outputs it to the transceiver unit 140 (S144). The frame processing unit 130 then terminates the series of processes shown in FIG. 18 (END).

[0104] If it is confirmed in the process of S141 that no usage-specific RUs have been allocated (S141: NO), frame processing unit 130 generates RU allocation information based on the notification from resource control unit 122 and stores it in the RU allocation subfield (S146). The RU allocation information generated by the process of S146 does not include information about usage-specific RUs. Frame processing unit 130 then proceeds to the process of S144, where it adds a MAC header and the like to generate a trigger frame and outputs it to transceiver unit 140. Thereafter, frame processing unit 130 ends the series of processes shown in FIG. 18 (END).

[0105] As described above, the frame processing unit 130 can notify the STA of the allocation of RUs in uplink OFDMA by transmitting a trigger frame to the STA. Note that the RU allocation information and maximum frame length information stored in the trigger frame may be generated by the link management unit 120.

[0106] (When Receiving an Uplink Frame) When frame processing unit 130 receives a frame from transceiver unit 140, it performs processing such as MAC header processing. Then, frame processing unit 130 outputs information contained in the processed frame to network NW or the like via LLC processing unit 110 or the like. If the received frame contains data, frame processing unit 130 outputs the received frame to network NW. Furthermore, if the received frame is a request for allocation of a usage-specific RU from an STA or a report on communication quality (e.g., actual delay measurement value, etc.), frame processing unit 130 outputs the received frame to quality management unit 121. In this way, frame processing unit 130 can select an appropriate output destination to output the received frame depending on the type of uplink frame.

[0107] <2-2-4> Operation of the Transceiver Unit 140 Next, the operation of the transceiver unit 140 of the access point 10 will be described.

[0108] (Method of transmitting OFDMA frames in the downlink direction) Fig. 19 is a flowchart showing an example of a method of transmitting OFDMA frames in the downlink direction by the transceiver 140 of the access point 10 (AP) according to the embodiment. When a MAC frame or the like corresponding to downlink traffic is input, the transceiver 140 starts the processing of the flowchart shown in Fig. 19 (start).

[0109] First, the transmitting / receiving unit 140 associates the MAC frame input from the frame processing unit 130 with the subcarrier based on the RU allocation information (S151). The transmitting / receiving unit 140 may associate the input MAC frame with the subcarrier based on information notified by the frame processing unit 130, the link management unit 120, etc., or may associate the MAC frame with the subcarrier based on information stored in the RU allocation subfield.

[0110] Next, the transmitting / receiving unit 140 calculates the required transmission time (S152). The required transmission time can be estimated based on the size of the MAC frame to be transmitted, the number of sub-channels used to transmit the MAC frame, and the like.

[0111] Next, the transmitting / receiving unit 140 evaluates whether the "request delay>transmission required time" (S153).

[0112] If the "requested delay > required transmission time" is not satisfied in the process of S153 (S153: NO), the transceiver 140 divides the frame (S154). The period for transmitting the divided frames corresponds to the transfer period TP shown in FIG. 13. The transceiver 140 then adds a preamble including RU allocation information to each divided frame (S155). The transceiver 140 then transmits the divided frames continuously using the allocated RUs, with a waiting period (IFS) between frames (S156). The transceiver 140 then ends the series of processes shown in FIG. 19 (END).

[0113] In the process of S153, if the "required delay > required transmission time" (S153: YES), the transceiver 140 transmits the frame using the assigned RU (S157). Note that when the process of S157 is executed, it is possible to satisfy the required delay of aperiodic low-latency traffic without dividing the frame. Thereafter, the transceiver 140 ends the series of processes in FIG. 19 (END).

[0114] Note that the "transmission" in the processes of S155 and S156 includes generating a wireless frame by adding a preamble to a MAC frame and wireless signal processing. Acquisition of the transmission right in the transceiver 140 is based on, for example, CSMA / CA. If the transceiver 140 detects upstream traffic during an IFS (waiting period) of an OFDMA frame transfer period, the transceiver 140 is configured to postpone transmission of the divided frames until reception of the upstream traffic is complete.

[0115] (Method for transmitting aperiodic low latency downlink traffic) Fig. 20 is a flowchart showing an example of a method for transmitting aperiodic low latency downlink traffic by the transceiver 140 of the access point 10 (AP) according to the embodiment. For example, when a MAC frame corresponding to the aperiodic low latency downlink traffic is input, the transceiver 140 starts the processing of the flowchart shown in Fig. 20 (start).

[0116] First, the transmitting / receiving unit 140 associates the input MAC frame with the subcarriers of the dedicated RU (S161). The transmitting / receiving unit 140 may associate the input MAC frame with the subcarriers based on information notified by the frame processing unit 130, the link management unit 120, etc., or based on information stored in the RU allocation subfield.

[0117] Next, the transmitting / receiving unit 140 adds a preamble to the MAC frame (S162). A radio frame is generated by the process of S162. The transmitting / receiving unit 140 then checks the communication status (S163). In the process of S163, the transmitting / receiving unit 140 checks, for example, the communication status of each of the multiple RUs.

[0118] If it is determined in the process of S163 that a downlink OFDMA frame is being transmitted, the transceiver 140 transmits aperiodic low-latency traffic using the assigned dedicated RU (S164). For example, if the transceiver 140 is transmitting downlink traffic using an RU other than the dedicated RU, the transceiver 140 transmits the generated low-latency traffic to one of multiple STAs using the dedicated RU in parallel with transmitting the downlink traffic. Thereafter, the transceiver 140 ends the series of processes shown in FIG. 20 (END).

[0119] If it is determined in step S163 that an uplink OFDMA frame is being received, the transceiver 140 waits until the completion of OFDMA frame reception or the end of a waiting period (step S165). Upon detecting the completion of OFDMA frame reception or the end of a waiting period, the transceiver 140 proceeds to step S164 and transmits aperiodic low-latency traffic using the assigned dedicated RU. The transceiver 140 then terminates the series of processes shown in FIG. 20 (end).

[0120] As described above, the transmitting / receiving unit 140 performs processing according to the transmission status when it receives aperiodic low-latency traffic from the frame processing unit 130. It is preferable that the processing of S164 be performed promptly in order to reduce the delay of the aperiodic low-latency traffic.

[0121] (Method of Receiving Upstream Traffic, etc.) When the transceiver 140 receives a wireless signal via an antenna, it performs wireless signal processing. The transceiver 140 then extracts a MAC frame from the wireless signal through the wireless signal processing and outputs the extracted MAC frame to the frame processing unit 130. In this way, the transceiver 140 can receive upstream traffic, etc.

[0122] <2-3> Operation of Wireless Terminal Device 20 Below, detailed operation of the wireless terminal device 20 according to the embodiment will be described, focusing on the functional configuration of the wireless terminal device 20 shown in Fig. 9. It is assumed that communication between each functional configuration of the wireless terminal device 20 and the access point 10 is performed via the frame processing unit 230, the transceiver unit 240, etc. as appropriate.

[0123] <2-3-1> Operation of the Quality Management Unit 221 First, the operation of the quality management unit 221 of the wireless terminal device 20 will be described.

[0124] 21 is a flowchart showing an example of a negotiation method for allocation of application-specific RUs by the quality control unit 221 of the wireless terminal device 20 (STA) according to the embodiment. For example, when the occurrence of traffic requiring low latency, such as aperiodic low latency traffic, is scheduled after a link is established between the AP and the STA, the quality control unit 221 starts the processing of the flowchart shown in FIG. 21 (start).

[0125] First, the quality management unit 221 notifies the AP of quality requirements (S201). The quality requirements are transferred from an upper layer along with traffic such as aperiodic low-latency traffic. The quality requirements for aperiodic low-latency traffic include, for example, data rate and required delay. The quality requirements for deterministic low-latency traffic include, for example, data rate and traffic generation period. The quality requirements for video traffic include, for example, data rate and required delay. Next, the quality management unit 221 transmits a request for allocation of application-specific RUs to the AP (S202). Note that the quality management unit 221 may transmit a set of the quality requirements and the request for allocation of application-specific RUs all at once to the AP. Then, the quality management unit 221 waits until it receives a response from the AP (S203).

[0126] Upon receiving a response from the AP, the quality control unit 221 determines whether or not a usage-specific RU has been allocated based on the AP's response (S204). For example, if a positive response is received, the quality control unit 221 determines that a usage-specific RU has been allocated. On the other hand, if a negative response is received, the quality control unit 221 determines that a usage-specific RU has not been allocated. Thereafter, the quality control unit 221 ends the series of processes shown in FIG. 21 (END).

[0127] If the allocation of a usage-specific RU is confirmed in the processing of S204, the wireless terminal device 20 can transmit aperiodic low-latency traffic, etc., using the usage-specific RU until the allocation of the usage-specific RU is released. After receiving a negative response, the quality management unit 221 may retry the processing of S201 to S204 after a predetermined time has elapsed. If a usage-specific RU is not allocated, the quality management unit 221 may notify the application that it is difficult to meet the required delay.

[0128] (Method for Managing Communication Quality) Fig. 22 is a flowchart showing an example of a method for managing communication quality by the quality management unit 221 of the wireless terminal device 20 (STA) according to the embodiment. For example, when aperiodic low latency traffic occurs after a link is established between the AP and the STA, the quality management unit 221 starts the processing of the flowchart shown in Fig. 22 (start).

[0129] First, the quality control unit 221 waits until the transmission of the aperiodic low latency traffic is completed (S211).

[0130] When the transmission of the aperiodic low-latency traffic is completed, the quality control unit 221 measures the actual delay value of the aperiodic low-latency traffic (S212). The actual delay value corresponds to, for example, the time required from the generation of the aperiodic low-latency traffic (from the input to the buffer) until the transmission of the aperiodic low-latency traffic is completed.

[0131] Then, the quality control unit 221 notifies the AP of the measured delay actual value (S213). After that, the quality control unit 221 ends the series of processes in FIG.

[0132] The measured delay value transmitted in the process of S213 may be an average value of a plurality of measured delay values, jitter during transmission of aperiodic low-delay traffic, or a maximum delay calculated based on the measured delay value and a predetermined percentage. The process of S213 may be executed based on a request from the AP, or may notify the AP when the measured delay value exceeds the required delay. The quality management unit 221 can determine whether resources appropriate for the required delay are allocated by the series of processes in FIG. 22.

[0133] <2-3-2> Operation of Resource Control Unit 222 Next, the operation of the resource control unit 222 of the wireless terminal device 20 will be described.

[0134] 23 is a flowchart showing an example of a method for acquiring and updating RU allocation information by the resource control unit 222 of the wireless terminal device 20 (STA) according to the embodiment. After a link between the AP and the STA is established, for example, when the resource control unit 222 receives RU allocation information from the AP, the resource control unit 222 starts the processing of the flowchart shown in FIG. 23 (START).

[0135] First, the resource control unit 222 checks whether the received RU allocation information includes allocation information for RUs by usage (S221).

[0136] In the process of S221, if it is confirmed that there is usage-specific RU allocation information (S221: YES), the resource control unit 222 checks whether there is a difference with the RU allocation information it manages (S222).

[0137] If it is determined in the process of S222 that there is a difference with the managed RU allocation information (S222: YES), the resource control unit 222 updates the managed RU allocation information (S223). Then, the resource control unit 222 notifies the frame processing unit 230 of the updated RU allocation information (S224). Thereafter, the resource control unit 222 ends the series of processes in FIG. 23 (END).

[0138] If it is not confirmed in the processing of S221 that there is allocation information for RUs for specific uses (S221: NO), or if it is confirmed in the processing of S222 that there is no difference from the RU allocation information managed (S222: NO), the resource control unit 222 checks whether there is RU allocation information for its own station, i.e., whether there is RU allocation information for traffic other than aperiodic low-latency traffic for its own station (S225).

[0139] In the process of S225, if it is confirmed that there is RU allocation information for the own station (S225: YES), the resource control unit 222 proceeds to the process of S224 and notifies the RU allocation information to the frame processing unit 230. Thereafter, the resource control unit 222 ends the series of processes in FIG. 23 (END).

[0140] In the process of S225, if it is confirmed that there is no RU allocation information for the own station (S225: NO), the resource control unit 222 ends the series of processes in FIG. 23 (END).

[0141] <2-3-3> Operation of Frame Processing Unit 230 Next, the operation of frame processing unit 230 of wireless terminal device 20 will be described.

[0142] 24 is a flowchart showing an example of a method for processing a downlink frame by the frame processing unit 230 of the wireless terminal device 20 (STA) according to the embodiment. For example, when the frame processing unit 230 receives a frame from the transceiver unit 140 after a link is established between the AP and the STA, the frame processing unit 230 starts the processing of the flowchart shown in FIG. 24 (START).

[0143] First, the frame processing unit 230 executes processing such as MAC header processing (S231).

[0144] Next, frame processing unit 230 checks the frame type (S232). If data is received, the data included in the processed frame is output to the upper layer (S233). If a response to a usage-specific RU allocation request from the AP is received, frame processing unit 230 outputs the response content to quality control unit 221 (S234). If a trigger frame is received, frame processing unit 230 extracts RU allocation information from the RU allocation subfield and notifies resource control unit 222 (S235). Thereafter, frame processing unit 230 ends the series of processes shown in FIG. 24 (END).

[0145] 25 is a flowchart showing an example of a method for processing uplink frames by the frame processing unit 230 of the wireless terminal device 20 (STA) according to the embodiment. For example, when uplink traffic occurs after a link is established between the AP and the STA, the frame processing unit 230 starts the processing of the flowchart shown in FIG. 25 (START).

[0146] First, the frame processing unit 230 receives traffic from an upper layer (S241). The traffic in S241 may be aperiodic low-latency traffic or other traffic.

[0147] Next, frame processing unit 230 generates a MAC frame by adding a MAC header, etc. (S242). The MAC frame generated by the processing of S242 includes data corresponding to aperiodic low latency traffic or data corresponding to other traffic.

[0148] Next, frame processing unit 230 outputs the generated MAC frame to transceiver unit 240 together with the RU allocation information input from resource control unit 222 (S243). This RU allocation information may or may not include application-specific RU allocation information based on the RU allocation status between the AP and multiple STAs. After that, frame processing unit 230 ends the series of processes in FIG. 25 (END).

[0149] <2-3-4> Operation of the Transceiver Unit 240 Next, the operation of the transceiver unit 240 of the wireless terminal device 20 will be described.

[0150] 26 is a flowchart showing an example of a method for receiving a downlink frame by the transceiver 240 of the wireless terminal device 20 (STA) according to the embodiment. For example, when the transceiver 240 receives a wireless signal, the transceiver 240 starts the processing of the flowchart shown in FIG. 26 (START).

[0151] First, the transmitting / receiving unit 240 executes radio signal processing (S251). By the processing of S251, the transmitting / receiving unit 240 acquires a radio frame from the radio signal.

[0152] Next, the transmitting / receiving unit 240 checks whether or not an OFDMA frame has been received (S252). In the process of S252, the transmitting / receiving unit 240 checks, for example, the frame type.

[0153] If it is confirmed in the process of S252 that an OFDMA frame has been received (S252: YES), the transceiver 240 extracts RU allocation information from the preamble and outputs it to the resource control unit 222 (S253). Then, if the transceiver 240 detects an RU corresponding to its own station from the RU allocation field, it performs reception processing for that RU. That is, the transceiver 240 extracts a MAC frame from the RU allocated to its own station and outputs it to the frame processing unit 230 (S254). Thereafter, the transceiver 240 ends the series of processes shown in FIG. 26 (END).

[0154] If it is not confirmed in the processing of S252 that an OFDMA frame has been received, that is, if the received frame is a normal wireless frame and not an OFDMA frame (S252: NO), the transmitting / receiving unit 240 proceeds to the processing of S254, extracts the MAC frame, and outputs it to the frame processing unit 230. Thereafter, the transmitting / receiving unit 240 ends the series of processing in FIG. 26 (END).

[0155] If it is confirmed in the processing of S252 that the trigger frame has been received, the transmitting / receiving unit 240 outputs the received trigger frame to the frame processing unit 230. If it is confirmed in the processing of S252 that a response has been received from the AP, the transmitting / receiving unit 240 outputs the received response to the frame processing unit 230.

[0156] 27 is a flowchart showing an example of a method for transmitting an OFDMA frame in the uplink direction by the transceiver 240 of the wireless terminal device 20 (STA) according to the embodiment. When a MAC frame corresponding to uplink traffic is input, the transceiver 240 starts the process of the flowchart shown in FIG. 27 (START).

[0157] First, the transmitting / receiving unit 240 associates the input MAC frame with the subcarrier based on the RU allocation information (S261). The transmitting / receiving unit 240 may associate the input MAC frame with the subcarrier based on information notified by the frame processing unit 230, the link management unit 220, etc., or based on information stored in the RU allocation subfield.

[0158] Next, the transmitting / receiving unit 240 evaluates whether "maximum frame length>frame length" holds (S262).

[0159] If the maximum frame length is not greater than the frame length in the process of S262 (S262: NO), the transmitting / receiving unit 240 divides the frame (S263). The period for transmitting the divided frames corresponds to the transfer period TP shown in FIG. 13. The transmitting / receiving unit 240 then uses the assigned RU to continuously transmit the divided frames, providing a waiting period (IFS) between frames (S264). Thereafter, the transmitting / receiving unit 240 ends the series of processes shown in FIG. 27 (END).

[0160] If the maximum frame length is greater than the frame length in the process of S262 (S262: YES), the transmitter / receiver 140 transmits the frame using the assigned RU (S265). Note that when the process of S265 is executed, it is possible to satisfy the required delay of aperiodic low-latency traffic without dividing the frame. Thereafter, the transmitter / receiver 240 ends the series of processes shown in FIG. 27 (END).

[0161] Note that the "transmission" in the processes of S264 and S265 includes generating a wireless frame by adding a preamble to a MAC frame and wireless signal processing. Acquisition of the transmission right in the transceiver unit 240 is based on, for example, CSMA / CA. When the transceiver unit 240 detects downstream traffic during an IFS (waiting period) of an OFDMA frame transfer period, the transceiver unit 240 is configured to postpone transmission of the divided frames until reception of the downstream traffic is complete.

[0162] (Method for transmitting uplink aperiodic low latency traffic) Fig. 28 is a flowchart showing an example of a method for transmitting uplink aperiodic low latency traffic by the transceiver 240 of the wireless terminal device 20 (STA) according to the embodiment. For example, when a MAC frame corresponding to the uplink aperiodic low latency traffic is input, the transceiver 240 starts the processing of the flowchart shown in Fig. 28 (start).

[0163] First, the transmitting / receiving unit 240 adds a preamble and the like to a MAC frame (S271). By the process of S271, a wireless frame is generated.

[0164] Next, the transmission / reception unit 140 checks the communication state (S272). If it is confirmed in the process of S272 that a downlink OFDMA frame is being received, the transmission / reception unit 240 waits until reception of the OFDMA frame is completed or a waiting period is detected (S273). Then, upon detecting completion of reception of the OFDMA frame or a waiting period, the transmission / reception unit 240 proceeds to the process of S274. If it is confirmed in the process of S272 that an uplink OFDMA frame is being transmitted, the transmission / reception unit 240 proceeds to the process of S274.

[0165] In the process of S274, the transceiver 240 checks whether a dedicated RU has been assigned. If it is confirmed in the process of S274 that a dedicated RU has not been assigned (S274: NO), the transceiver 240 transmits aperiodic low latency traffic in another RU or in the next frame (S275). This "other RU" corresponds to, for example, a high-priority RU. This "next frame" corresponds to the next transmission period TP or the next OFDMA frame transmission period. When the process of S275 ends, the transceiver 240 ends the series of processes in FIG. 28 (END).

[0166] If it is determined in the process of S274 that a dedicated RU has been allocated (S274: YES), the transmitting / receiving unit 240 checks whether the dedicated RU is in use (S276).If it is determined in the process of S276 that the dedicated RU is in use (S276: YES), the transmitting / receiving unit 240 proceeds to the process of S275.

[0167] If it is confirmed in the process of S276 that the dedicated RU is not in use (S276: NO), the transceiver 240 evaluates whether the transmission of the radio frame created in the process of S271 can be completed within the current OFDMA frame transfer period or within the transfer period TP. Specifically, the transceiver 240 compares the remaining frame time of the RU with the required time for the data to be transmitted. If the transceiver 240 determines that the transmission cannot be completed, it waits until the next uplink OFDMA frame to transmit. To ensure that the radio frame is transmitted in the next uplink OFDMA frame, the transceiver 240 may transmit the RU allocation request using the remaining time of the OFDMA frame transfer period.

[0168] If it is determined in the process of S277 that the transmission can be completed (S277: YES), the transmitting / receiving unit 240 transmits the aperiodic low latency traffic using the allocated dedicated RU (S278). After that, the transmitting / receiving unit 240 ends the series of processes in FIG. 28 (END).

[0169] If it is determined in the process of S277 that transmission cannot be completed (S277: NO), the transceiver 240 transmits the aperiodic low latency traffic in the next frame (S279). At this time, the transceiver 240 may notify the AP of the transmission status of the aperiodic low latency traffic by transmitting a BSR (Buffer Status Report) to the AP. Thereafter, the transceiver 240 ends the series of processes shown in FIG. 28 (END).

[0170] As described above, when the transceiver 240 receives aperiodic low-latency traffic from the frame processor 230, it performs processing according to the transmission status. It is preferable that the processing of S275, S278, and S279 be performed promptly to reduce the delay of the aperiodic low-latency traffic. When performing the processing of S278, if the dedicated RU is shared with other wireless terminal devices 20, the transceiver 240 transmits when no signal is detected in the dedicated RU by CSMA / CA. On the other hand, when a signal is detected by carrier sense, the transceiver 240 performs CSMA / CA again in the high-priority RU, and transmits when a signal is no longer detected by carrier sense.

[0171] <3> Advantages of the embodiment According to the communication system 1 according to the embodiment described above, it is possible to satisfy the traffic quality requirements. The advantages of the embodiment will be described in detail below.

[0172] In OFDMA, for downlink data transmission, an access point generates multiple RUs by grouping subcarriers and assigns them to multiple STAs. Then, the access point transmits data in parallel to the multiple STAs using the multiple RUs. For uplink data transmission, the access point also assigns an RU to each STA and notifies it via a trigger frame. Then, each STA transmits data using the assigned RU.

[0173] The communication system 1 according to the embodiment sets application-specific RUs when allocating RUs to traffic or STAs. The application-specific RUs include dedicated RUs that are allocated (reserved) for aperiodic low-latency traffic regardless of whether traffic is present or not. When aperiodic low-latency traffic occurs in the communication system 1, traffic traveling in the same direction as the transmission direction of the OFDMA frame is promptly transmitted using the dedicated RU. Even when traffic traveling in the same direction as the transmission direction of the OFDMA frame is transmitted using a dedicated RU in response to the occurrence of traffic, interference with other traffic can be suppressed. Therefore, the communication system 1 according to the embodiment can suppress delay and jitter in aperiodic low-latency traffic occurring in the same direction as the transmission direction of the OFDMA frame.

[0174] On the other hand, traffic in the opposite direction to the transmission direction of the OFDMA frame may not be accurately received due to interference between adjacent RUs, even if a dedicated RU is not used. In response to this, the communication system 1 according to the embodiment divides the RUs in the period during which the OFDMA frame is transmitted along the time axis and inserts a waiting period (IFS) between the divided and adjacent RUs. The communication system 1 then checks the presence or absence of traffic in the IFS, taking into account the presence of traffic in the opposite direction when the OFDMA frame has a longer delay than the required delay of the aperiodic low-latency traffic. The communication system 1 then transmits traffic in the opposite direction to the transmission direction of the OFDMA frame using the dedicated RU during the IFS or after the transmission of the OFDMA frame is completed. Furthermore, the communication system 1 is configured to postpone the transmission of traffic by other RUs when transmission of reverse traffic via the dedicated RU begins. As a result, the communication system 1 can suppress delay and jitter in aperiodic low-latency traffic even if the traffic is in the opposite direction to the transmission direction of the OFDMA frame.

[0175] As described above, the communication system 1 according to the embodiment can suppress delay and jitter low not only for periodic traffic but also for aperiodic low-latency traffic. Therefore, the communication system 1 according to the embodiment can meet the required delay of aperiodic low-latency traffic. Furthermore, the communication system 1 according to the embodiment can set application-specific RUs for traffic other than aperiodic low-latency traffic. As a result, the communication system 1 according to the embodiment can improve the efficiency of communication using OFDMA and meet traffic quality requirements.

[0176] <4> Others In the above embodiment, a dedicated RU is used to transfer aperiodic low-latency traffic, but this is not limiting. A dedicated RU may also be used to transfer periodically occurring low-latency traffic. Even when transferring periodically occurring low-latency traffic, delay and jitter can be suppressed by using a dedicated RU.

[0177] In the above embodiments, the flowcharts used to explain the operations are merely examples. The order of the processes of each operation described in the embodiments may be changed as far as possible, and other processes may be added. The wireless frame formats described in the embodiments are merely examples. The wireless frames used in the communication system 1 may be in other formats as long as they can execute the operations described in the embodiments. A wireless communication standard other than the IEEE 802.11 standard may be used for wireless communication between the access point 10 and the wireless terminal device 20. "RU" may also be called a "unit."

[0178] In the communication system 1, the CPU 11 included in the access point 10 and the CPU 21 included in the wireless terminal device 20 may each be other circuits. For example, the access point 10 and the wireless terminal device 20 may each be equipped with an MPU (Micro Processing Unit) or the like instead of a CPU. Each of the processes described in the embodiments may be realized by dedicated hardware. The processes of the access point 10 and the wireless terminal device 20 may be a mixture of processes executed by software and processes executed by hardware, or may be only one of them.

[0179] The access point 10 may establish a multilink with the wireless terminal device 20 using multiple channels. Each of the access point 10 and the wireless terminal device 20 may include multiple transceivers (STA functions) corresponding to the multiple channels, respectively. In the multilink, one or multiple STA functions may be assigned to one traffic type. The association between traffic and the STA function is set, for example, so that the traffic volume (data volume) is equalized among the multiple links constituting the multilink. Traffic of similar types (priority / non-priority, etc.) may be collected in a specific link constituting the multilink.

[0180] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention.

[0181] 1...Communication system 10...Access point 20, 20-1, 20-2, 20-3...Wireless terminal device 11, 21...CPU 12, 22...ROM 13, 23...RAM 14, 24...Wireless communication module 15...Wired communication module 25...Display 26...Storage 200...Application execution unit 110, 210...LLC processing unit 120, 220...Link management unit 121, 221...Quality management unit 122, 222...Resource control unit 130, 230...Frame processing unit 140, 240...Transmission / reception unit 141, 241...Classification unit 142, 142A, 142B, 142C, 142D, 242, 242A, 242B, 242C, 242D...Queue 143, 143A, 143B, 143C, 143D, 243, 243A, 243B, 243C, 243D...Carrier sense execution unit 144, 244...Internal collision management unit

Claims

1. An access point comprising: a communication circuit configured to transmit and receive radio signals using a plurality of subcarriers; and a processor configured to establish links with a plurality of wireless terminal devices using the communication circuit, set a plurality of units into which the plurality of subcarriers are grouped, assign a use to each of the units based on quality requirements received from the plurality of wireless terminal devices, and notify the plurality of wireless terminal devices of information on the assigned use using a trigger frame that indicates a transfer period of an uplink frame.

2. The access point of claim 1, wherein the plurality of units includes a first unit associated with low-latency traffic, and the processor, when low-latency traffic is generated, checks the communication status of the plurality of units, and when a downlink frame is being transmitted, transmits the generated low-latency traffic to one of the plurality of wireless terminal devices using the first unit, and when an uplink frame is being received, transmits the generated low-latency traffic to one of the plurality of wireless terminal devices using the first unit during a waiting period in the transfer period or after the transfer period is completed.

3. The access point of claim 2, wherein the plurality of units further includes a second unit associated with high priority traffic corresponding to an access category having a higher priority than the first access category, and the processor is configured to transmit high priority traffic to one of the plurality of wireless terminal devices using the second unit when high priority traffic occurs, and to receive low latency traffic from one of the plurality of wireless terminal devices via the second unit when the first unit is in use during the transfer period.

4. The access point according to claim 1, wherein the trigger frame includes, for each unit, information regarding the unit's purpose, the unit's identifier, and an access category.

5. A wireless terminal device comprising: a communication circuit configured to transmit and receive wireless signals using a plurality of subcarriers; and a processor configured to establish a link with an access point using the communication circuit, notify the access point of quality requirements for traffic to be transmitted, and set a plurality of application-specific units into which the plurality of subcarriers are grouped based on receipt of a trigger frame from the access point indicating a transfer period for uplink frames.

6. The wireless terminal device of claim 5, wherein the plurality of units includes a first unit associated with low-latency traffic, and the processor, when low-latency traffic is generated, checks the communication status of the plurality of units, and when a first frame in the uplink direction is being transmitted, transmits the generated low-latency traffic to the access point using the first unit, and when a second frame in the downlink direction is being received, transmits the generated low-latency traffic to the access point using the first unit during a waiting period for reception of the second frame or after reception of the second frame is completed.

7. The wireless terminal device of claim 6, wherein the plurality of units further includes a second unit associated with high priority traffic corresponding to an access category having a higher priority than the first access category, and the processor is configured to transmit to the access point using the second unit when high priority traffic occurs, and to transmit low latency traffic via the second unit when the first unit is in use during the transfer period.

8. The wireless terminal device according to claim 5, wherein when the processor detects a preamble of a frame received from the access point that corresponds to the own station, it performs reception processing for a unit among the plurality of units that is specified by the preamble.

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