Communication device, method for controlling communication device, and program

Abstract

To determine a communication data rate so as to reduce delay due to communication errors.SOLUTION: A communication device receives, from one or more other communication devices wirelessly connected to the communication device, first information indicating an allowable delay time from data transmission by the one or more other communication devices to data reception completion by the communication device and a data length of data transmitted once by the one or more other communication devices, requested by the one or more other communication devices, determines a data rate used for communication with the one or more other communication devices based on the first information, and notifies the one or more other communication devices of second information about the determined data rate.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

[0002] In recent years, with the development of information and communication technology, the amount of Internet usage has been increasing year by year, and various communication technologies have been developed to meet the increasing demand. Among them, wireless LAN (Local Area Network) technology has realized an improvement in throughput in Internet communication such as packet data, voice, and video by wireless LAN terminals, and various technology developments are still actively carried out.

[0003] In the development of wireless LAN technology, a number of standardization efforts by the IEEE (Institute of Electrical and Electronics Engineers), a standardization body for wireless LAN technology, have played an important role. As one of the wireless LAN communication standards, the IEEE802.11 series is known. The IEEE802.11 series standards include standards such as IEEE802.11a / b / g / n / ac / ax standards. Patent Document 1 discloses that in the IEEE802.11ax standard, wireless communication by OFDMA (Orthogonal Frequency Division Multiple Access) is performed. In the IEEE802.11ax standard, high peak throughput is realized by performing wireless communication by OFDMA.

[0004] In recent years, as a new standard of the IEEE802.11 series, the formulation of the IEEE802.11be standard has been under consideration. In IEEE802.11be, in addition to realizing high-frequency utilization efficiency by using OFDMA as in IEEE802.11ax, technical studies on reducing latency for application to periodic control applications such as robot control have been conducted.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-50133 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In a wireless LAN system, automatic retransmission control is adopted as a mechanism for enhancing the reliability of wireless communication. As a method for realizing low-latency communication, it is conceivable to reduce the data transmission time by increasing the communication data rate (communication rate). However, as the communication data rate increases, data transmission errors (communication errors) are more likely to occur, and the delay time due to retransmission processing increases. Further, in a periodic control application such as robot control, if the communication data rate is set too low in order to suppress the occurrence of communication errors, there is a risk that the data transmission time will become longer than the transmission interval of control data.

[0007] The present invention has been made in view of the above problems, and an object thereof is to determine a communication data rate so as to reduce the delay due to communication errors. [Means for Solving the Problems]

[0008] As one means for achieving the above object, a communication device according to the present invention has the following configuration. That is, Operating as an access point defined in the IEEE802.11 standard series A communication device, wirelessly connected to the communication device Operating as a station defined in the IEEE802.11 standard series Receiving means for receiving first information indicating an allowable delay time from data transmission by the one or more other communication devices required by the one or more other communication devices to the communication device until completion of data reception by the communication device, and a data length of data transmitted by the one or more other communication devices at one time from the one or more other communication devices; determination means for determining a data rate to be used for communication with the one or more other communication devices based on the first information; and notification means for notifying the one or more other communication devices of second information regarding the determined data rate. wherein the second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and a number of spatial streams for realizing the data rate determined by the determining means .

Advantages of the Invention

[0009] According to the present invention, it becomes possible to determine the communication data rate so as to reduce the delay due to communication errors.

Brief Description of the Drawings

[0010]

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Figure 12

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0012] [Embodiment 1] (Network Configuration) FIG. 1 shows a configuration example of a wireless communication network in this embodiment. The wireless communication network 101 includes one access point (AP102) and one or more STAs (stations / terminal devices) (STA103, STA104). AP102 and STA103, 104 can be communication devices (be devices) compliant with the IEEE802.11be standard.

[0013] Each communication device can communicate in frequency bands of 2.4 GHz, 5 GHz, and 6 GHz bands. The frequency band used by each communication device is not limited to this, and for example, a different frequency band such as 60 GHz band may be used. Also, each communication device can communicate using any of bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. AP102 and STA103, STA104 can realize multi-user (MU) communication that multiplexes signals of a plurality of users (STAs) by performing OFDMA communication.

[0014] In addition, AP102, STA103, and STA104 may be able to perform MIMO (Multiple-Input and Multiple-Output) communication. In this case, AP102, STA103, and STA104 have multiple antennas, and one of them sends different signals from each antenna using the same frequency channel. The receiving side simultaneously receives all the signals that have arrived from multiple streams using multiple antennas, separates the signals of each stream, and decodes them. In this way, by performing MIMO communication, AP102, STA103, and STA104 can communicate more data in the same time compared to the case where MIMO communication is not performed. Also, AP102 can establish a wireless link with STA103 and STA104 through connection processes such as an association process that complies with the IEEE802.11 series of standards. Note that the configuration of the wireless communication network shown in FIG. 1 is merely an example for explanation. For example, a network including a large number of be devices, ax devices, and legacy devices (devices compliant with the IEEE802.11a / b / g / n / ac standards) in an even wider area may be configured. Also, AP102, STA103, and STA104 may be compatible with legacy standards (IEEE802.11a / b / g / n / ac standards) that are standards prior to IEEE802.11ax. Also, they may be compatible with other communication standards such as Bluetooth (registered trademark), NFC (Near Field Communication), UWB (Ultra Wide Band), Zigbee, and MBOA (Multi Band OFDM Alliance). UWB includes wireless USB, wireless 1394, Winet, etc. Also, they may be compatible with the communication standards of wired communication such as wired LAN.

[0015] Specific examples of the AP102 include, but are not limited to, a wireless LAN router, a PC, etc. The AP102 may be any communication device capable of performing OFDMA communication with other communication devices. Also, the AP102 may be an information processing device such as a wireless chip capable of performing wireless communication compliant with the IEEE802.11be standard. Specific examples of the STA103 and STA104 include, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, etc. The STA103 and STA104 may be any communication devices capable of performing OFDMA communication with other communication devices. The STA103 and STA104 may be an information processing device such as a wireless chip capable of performing wireless communication compliant with the IEEE802.11be standard. Also, the network in FIG. 1 is a network composed of one AP and two STAs, but the number of APs and STAs is not limited to this. Note that an information processing device such as a wireless chip has an antenna for transmitting the generated signal.

[0016] (Hardware Configuration of AP and STA) FIG. 2 shows an example of the hardware configuration of the AP102. Note that the STA103 and STA104 have the same hardware configuration as the AP102, and in that case, the communication partner device can be the AP102. As an example of the hardware configuration, the AP102 has a storage unit 201, a control unit 202, a functional unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0017] The storage unit 201 is composed of one or more memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores computer programs for performing various operations described later, as well as various information such as communication parameters for wireless communication. Note that as the storage unit 201, in addition to memories such as ROM and RAM, storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs may be used. Further, the storage unit 201 may include a plurality of memories and the like.

[0018] The communication unit 206 controls wireless communication compliant with the IEEE802.11be standard. In addition to the IEEE802.11be standard, the communication unit 206 may control wireless communication compliant with other IEEE802.11 series standards or wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive signals for wireless communication generated by the control unit 202. The AP 102 may have a plurality of communication units 206. When the AP 102 having a plurality of communication units 206 establishes a plurality of links in multi-link communication, at least one link is established per communication unit 206. Alternatively, the AP 102 may establish a plurality of links using one communication unit 206. In this case, the communication unit 206 switches the frequency channels operating in a time-division manner to execute communication via a plurality of links. Note that when the AP 102 supports communication standards such as the NFC standard and the Bluetooth standard in addition to the IEEE802.11be standard, it may control wireless communication compliant with these communication standards. Further, when the AP 102 can execute wireless communication compliant with a plurality of communication standards, it may have a configuration in which communication units and antennas corresponding to the respective communication standards are provided separately. The AP 102 communicates data such as image data, document data, and video data with the STAs 103 and 104 via the communication unit 206. Note that the antenna 207 may be configured separately from the communication unit 206 or may be configured as one module together with the communication unit 206.

[0019] Antenna 207 is an antenna capable of communication in frequency bands such as the 2.4 GHz band, 5 GHz band, and 6 GHz band. In this embodiment, AP102 is assumed to have one antenna, but it may have different antennas for each frequency band. Further, when AP102 has a plurality of antennas, it may have a communication unit 206 corresponding to each antenna.

[0020] (Function configuration of STA) FIG. 3 shows a functional configuration example of STA103 and STA104. Here, STA103 will be described as an example, but STA104 has the same functional configuration as STA103. As an example of the functional configuration, STA103 includes a frame transmission / reception unit 301 and a transmission information frame generation unit 302.

[0021] The frame transmission / reception unit 301 controls the transmission and reception of frames such as MAC (Media Access Control) frames (management frames, control frames, or data frames). Further, in this embodiment, the frame transmission / reception unit 301 controls the reception of trigger frames included in control frames. Also, the frame transmission / reception unit 301 manages the transmission of all data and can determine whether to end the transmission of all data.

[0022] The transmission information frame generation unit 302 generates a frame for notifying AP102 of the transmission information of data to be UL-MU (Uplink Multi-User) transmitted. The transmission information can include information regarding the allowable delay time, data length, allowable error rate, and power consumption required by AP102. Also, the transmission information can be stored within the MAC frame.

[0023] Here, the transmission information will be described in more detail. The allowable delay time indicates the maximum data transmission time allowed by STA103 when the time from data transmission by STA103 to the completion of data reception by AP102 is regarded as the data transmission time. The data length indicates the length of data transmitted once by STA103 in response to one trigger frame. The allowable error rate indicates the maximum error rate allowed by the system. The information regarding power consumption indicates whether power consumption is prioritized (whether power-saving communication is requested). A user using the system can input each piece of information regarding the allowable delay time, data volume, allowable error rate, and power consumption into STA103 in advance via a UI (User Interface) such as the input unit 204. The transmission information frame generation unit 302 can set the input information in the MAC frame. Examples of sub-fields indicating each piece of information (value) will be described later with reference to FIG. 5.

[0024] The frame for notifying the transmission information may be a MAC frame. Alternatively, the frame for notifying the transmission information may be a new frame created using the Reserved Subtype value of the extended frame or the Reserved Element ID of the Element. Thus, the frame for notifying the transmission information is not limited to a frame of a specific format.

[0025] FIG. 5 shows a configuration example of a MAC frame for notifying transmission information. The MAC frame is a frame conforming to the HE (High Efficiency) format. Configure the Control List field 521 in the A-Control field 511 included in the HT Control field 501 of the MAC frame shown in FIG. 5 as follows. That is, a new ID is created by using the value (= 7 to 14) reserved as the Control ID value shown in the table included in FIG. 5 for the value of the Control ID field 531. Correspondingly, in the Control Information field 532, a Delay Time sub-field 541 indicating the allowable delay time, a Data Length sub-field 542 indicating the data length, an Error Rate sub-field 543 indicating the allowable error rate, and a Power Consumption sub-field 544 indicating information regarding power consumption are set.

[0026] (Functional Configuration of AP) FIG. 4 shows a functional configuration example of the AP102. As an example of the functional configuration, the AP102 includes a frame transmission / reception unit 401, a data rate determination unit 402, and a trigger frame generation unit 403. The frame transmission / reception unit 401 controls the transmission and reception of frames such as MAC frames (management frames, control frames, or data frames). Also, in this embodiment, the frame transmission / reception unit 401 controls the transmission of trigger frames included in control frames. Further, the frame transmission / reception unit 401 can determine whether an error has occurred in the communication.

[0027] The data rate determination unit 402 determines the data rate (communication rate) to be used in the UL-MU communication with the STA103 and STA104 that have established a wireless link (are wirelessly connected) based on the transmission information included in the frame received by the frame transmission / reception unit 401. Details of this data rate determination method will be described later.

[0028] The trigger frame generation unit 403 generates a trigger frame including information (parameters) for realizing the data rate determined by the data rate determination unit 402. The generated trigger frame is transmitted by the frame transmission / reception unit 401 to the STAs 103 and 104. The STAs 103 and 104 that have received the trigger frame can perform UL-MU transmission by OFDMA based on the content of the trigger frame. As will be described later, the trigger frame is divided into two types: a normal trigger frame and a retransmission trigger frame.

[0029] Fig. 6 shows a configuration example of a trigger frame. The trigger frame includes a Common Info field 601 that contains information common to a plurality of STAs multiplexed by OFDMA, and User Info fields 602-1 to 602-N (collectively referred to as User Info field 602) that contain unique information for each STA multiplexed by OFDMA. For example, information (parameters) for realizing the data rate determined by the data rate determination unit 402 can be set in the UL BW (Uplink Bandwidth) subfield 611 and the GI And HE-LTF Type subfield 612 within the Common Info field 601, and in the RU Allocation subfield 621, the UL HE-MCS subfield 622, the UL DCM subfield 623, and the SS Allocation / RA-RU information subfield 624 within the User Info field 602. The UL BW subfield 611 can indicate the frequency bandwidth. The GI And HE-LTF Type subfield 612 can indicate the length of the guard interval. The guard interval refers to the interval inserted between transmitted symbols (bits). The RU Allocation subfield 621 can indicate the allocation of resource units (RUs). The UL HE-MCS subfield 622 and the UL DCM subfield 623 can indicate the MCS (Modulation and Coding Scheme). The SS Allocation / RA-RU information subfield 624 can indicate the number of spatial streams. The trigger frame with each piece of information set is transmitted to STA103 and STA104.

[0030] (Processing of STA) Next, the processing executed by the STAs 103 and 104 configured as described above will be described. FIG. 7 is a flowchart showing the processing executed by the STAs 103 and 104 according to the present embodiment. Here, the STA 103 will be described as an example, but the STA 104 can also perform the same processing. Further, this processing flow can be implemented when the STA 103 starts communication by the control unit 202 reading and executing the computer program stored in the storage unit 201.

[0031] First, the transmission information frame generation unit 302 of the STA 103 generates a frame including transmission information. In the present embodiment, the transmission information frame generation unit 302 includes at least the allowable delay time and the data length requested from the AP 102 in the transmission information. The frame transmission / reception unit 301 notifies (transmits) the transmission information including the allowable delay time and the data length to the AP 102 by transmitting the frame to the AP 102 (S701). Subsequently, the frame transmission / reception unit 301 of the STA 103 receives a trigger frame (S702), and based on the information regarding the data rate determined by the AP 102 included in the trigger frame, generates and transmits data (S703). Further, there are two types of trigger frames: a normal trigger frame and a retransmission trigger frame, and the frame transmission / reception unit 301 executes data transmission or retransmission according to the type of the trigger frame.

[0032] After the completion of the processing in S703, the frame transmission / reception unit 301 of the STA 103 determines whether to end the communication (S704). If the transmission of all data is completed and there is no data to be continuously transmitted, the frame transmission / reception unit 301 determines to end the communication (Yes in S704) and ends the processing. If there is data to be continuously transmitted, the frame transmission / reception unit 301 determines not to end the communication (No in S704), and the processing returns to S702 and the repetitive processing is performed.

[0033] (Processing of the AP) Next, the processing executed by the AP102 configured as described above will be explained. FIG. 8 is a flowchart showing the processing executed by the AP102 according to the present embodiment. Note that this processing flow can be implemented by the control unit 202 reading and executing a computer program stored in the storage unit 201 when determining the data rate used by the AP102.

[0034] First, the frame transmission / reception unit 401 of the AP102 receives a frame including transmission information including an allowable delay time and a data length from the wirelessly connected STAs 103 and 104 (S801). Subsequently, the data rate determination unit 402 calculates a required data rate for each STA from the received allowable delay time and data length (S802). The required data rate can be obtained by dividing the data length by the allowable delay time. Subsequently, the data rate determination unit 402 determines one or more data rates that satisfy the required data rate for each STA calculated in S802 as rate candidates (S803).

[0035] Here, the processing of S803 will be specifically explained. The 802.11 standard has a table showing the theoretical data rate (the theoretical value of the data rate) for each resource unit (RU), frequency bandwidth, and number of spatial streams. FIG. 9 shows an example of a table showing the theoretical data rate for a given RU (26 - tone), frequency bandwidth (20 MHz), and number of spatial streams (N = 1). The theoretical data rate is a data rate that can be used by the AP102 for communication with one or more STAs. Also, in the table, the relationship between the length of the guard interval (GI) and the MCS (MCS index) that can achieve each data rate is shown. Each MCS has a modulation method (Modulation) and a coding rate (R) associated with it. In the present embodiment, it is assumed that the AP102 has a table similar to the table shown in FIG. 9. The data rate determination unit 402 of the AP102 determines one or more data rates that are equal to or higher than the required data rate calculated in S802 from the table shown in FIG. 9 as rate candidates.

[0036] When the process of S803 is completed, from the perspective of the error rate, the data rate determination unit 402 of AP102 determines to use the lowest data rate among the rate candidates determined in S803 (S804). The lower the data rate, the lower the error rate for the data can be. Next, the trigger frame generation unit 403 of AP102 generates a normal trigger frame including information regarding the data rate determined to be used in S804. Specifically, the trigger frame generation unit 403 generates a normal trigger frame including information (information on at least any one of the frequency bandwidth, GI, RU, MCS, and the number of spatial streams) for realizing the data rate determined to be used in S804. Then, the frame transceiver unit 401 of AP102 transmits the generated trigger frame to STA103 and STA104 and starts UL-MU communication (S805).

[0037] After the start of UL-MU communication, the frame transceiver unit 401 of AP102 determines whether an error has occurred in the communication (S806). When the frame transceiver unit 401 correctly receives data, it determines that no error has occurred (No in S806), and the process returns to S805 to repeatedly transmit the trigger frame. When the frame transceiver unit 401 detects an error in the data, or determines that data cannot be received (a certain time has elapsed without receiving data) despite transmitting the trigger frame, it determines that an error has occurred (Yes in S806), and the process proceeds to S807.

[0038] In S807, the frame transmission / reception unit 401 of AP102 determines whether errors have occurred continuously for a certain number of times or more. The number of times used for the determination can be arbitrarily set by the user. When the frame transmission / reception unit 401 determines that errors have occurred continuously for a certain number of times or more (Yes in S807), it terminates the communication. When the frame transmission / reception unit 401 determines that the number of consecutive errors is less than the certain number of times (No in S807), the process proceeds to S808. In S808, the trigger frame generation unit 403 of AP102 generates a trigger frame for data retransmission, and the frame transmission / reception unit 401 transmits the trigger frame for data retransmission to at least the STA that is the target of the error occurrence. Thereby, AP102 can prompt the target STA to retransmit the data. After that, the process returns to S806, and AP102 repeatedly determines whether an error has occurred in the communication.

[0039] Note that in the processing flow of FIG. 8, AP102 received the allowable delay time and the data length from STA103 and STA104 and calculated the required data rate (S802). Instead of this, AP102 may receive the information on the required data rate from STA103 and STA104 and determine the data rate to be used. In that case, the process of S802 in FIG. 8 is omitted, and STA103 and STA104 may transmit a frame including the information on the required data rate in S701 of FIG. 7. Specifically, in S701 of FIG. 7, the transmission information frame generation unit 302 of STA103 / STA104 calculates the required data rate from the allowable delay time and the data length, generates a frame including the transmission information including the required data rate, and the frame transmission / reception unit 301 may transmit the frame to AP102.

[0040] Also, when AP102 is connected to STA103 and STA104, it may determine the data rate to be used for each of STA103 and STA104, or it may commonly determine one data rate. In the latter case, for example, in S803, AP102 determines, as rate candidates, one or more data rates that are equal to or higher than the higher of the two required data rates calculated in S802, and in S804, it may determine the lowest data rate among the rate candidates. Similarly, when the required data rates are notified from STA103 and STA104, AP102 determines, as rate candidates, one or more data rates that are equal to or higher than the higher required data rate, and in S804, it may determine the lowest data rate among the rate candidates.

[0041] Thus, in this embodiment, AP102 determines the data rate to be used for communication so as to satisfy the required data rate based on the allowable delay time and data length notified from STA103 and STA104. Thereby, it is possible to reduce the occurrence of errors and realize low-latency communication.

[0042] [Embodiment 2] In Embodiment 1, from the perspective of the error rate, AP102 determines to use the lowest data rate among the rate candidates that satisfy the required data rate calculated from the allowable delay time and data length. However, in cases where there are multiple terminal devices, such as in the example of the network composed of one AP102 and two STA103 and STA104 shown in FIG. 1, there may be cases where a higher data rate is desirable from the perspective of frequency utilization efficiency. Therefore, in this embodiment, an embodiment of determining the data rate to be used for communication while considering frequency utilization efficiency will be described. Note that descriptions of the same features as those in Embodiment 1 will be omitted.

[0043] (Processing of STA) FIG. 10 is a flowchart showing the processes executed by STA103 and STA104 according to this embodiment. Here, STA103 will be described as an example, but STA104 can also perform the same processes. Also, this process flow can be implemented when STA103 starts communication by the control unit 202 reading and executing the computer program stored in the storage unit 201. In the flowchart of FIG. 10, the same or similar processes as those in the flowchart of FIG. 7 described in Embodiment 1 are given the same reference numerals, and duplicate explanations are omitted.

[0044] First, the transmission information frame generation unit 302 of STA103 generates a frame including transmission information. In this embodiment, the transmission information frame generation unit 302 includes at least the allowable delay time, data length, and allowable error rate requested from AP102 in the transmission information. The frame transmission / reception unit 301 notifies AP102 of the transmission information including the allowable delay time, data length, and allowable error rate by transmitting the frame to AP102 (S1001). Subsequently, the frame transmission / reception unit 301 of STA103 determines whether there is a data rate that satisfies the request based on the notified transmission information (S1002). The frame transmission / reception unit 301 of STA103 can determine whether there is a data rate that satisfies the request based on the response frame from AP102. Details will be described later in the explanation of the process of AP102 in this embodiment with reference to FIG. 11.

[0045] When the frame transmission / reception unit 301 of STA103 receives a response frame from AP102 indicating that there is no data rate that satisfies the request based on the transmission information (No in S1002), it ends the process without transmitting the data. Otherwise, when the frame transmission / reception unit 301 of STA103 determines that there is a data rate that satisfies the request based on the transmission information (Yes in S1002), the process proceeds to the process of S702. The subsequent processes are the same as those in FIG. 7.

[0046] (Processing of AP) FIG. 11 is a flowchart showing the processing executed by the AP102 according to the present embodiment. Note that this processing flow can be implemented by the control unit 202 reading and executing a computer program stored in the storage unit 201 when determining the data rate used by the AP102. In the flowchart of FIG. 11, the same or similar processes as those in the flowchart of FIG. 8 described in Embodiment 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0047] First, the frame transmission / reception unit 401 of the AP102 receives a frame including transmission information including an allowable delay time, a data length, and an allowable error rate from the STA103 and the STA104 (S1101). After the subsequent processes of S802 and S803, the data rate determination unit 402 of the AP102 determines whether the number of rate candidates determined in S803 is one (S1102). If the determined rate candidate is one (Yes in S1102), the process proceeds to S805, and the subsequent processes are the same as those in FIG. 8. If the determined rate candidates are plural (No in S1102), the process proceeds to S1103.

[0048] In S1103, the data rate determination unit 402 of the AP102 determines whether two or more STAs are connected. If two or more STAs are connected (Yes in S1103), the process proceeds to the process of S1104. If less than two STAs are connected (No in S1103), the process proceeds to the process of S804, and the subsequent processes are the same as those in FIG. 8. In the present embodiment, the AP102 is connected to the STA103 and the STA104, and the process proceeds to S1104.

[0049] In S1104, the data rate determination unit 402 of AP102 acquires the SNR (Signal-to-Noise Radio) as the transmission quality in the transmission paths between AP102 and STA103 and STA104 respectively. The SNR can be obtained from the CSI (Channel State Information) reports from each STA, but the acquisition method is not limited to this. For example, alternatively, the SNR may be obtained by a frame including a Channel Measurement Feedback Element or a newly defined frame.

[0050] After the processing of S1104 is completed, the data rate determination unit 402 of AP102 calculates the error rate for each data rate of the rate candidates determined in S803 using the acquired SNR. The relationship between the error rate and the SNR for each data rate will be described later. Then, the data rate determination unit 402 determines whether there is a data rate among the rate candidates that satisfies the allowable error rate received (acquired) in S1101, that is, whether there is a data rate for which the calculated error rate is less than or equal to the allowable error rate (S1105). If there is a data rate among the rate candidates that satisfies the allowable error rate (if there is a data rate for which the calculated error rate is less than or equal to the allowable error rate) (Yes in S1105), the process proceeds to S1106. Otherwise (No in S1105), the process proceeds to S1107.

[0051] Here, the relationship between the error rate and the SNR for each data rate will be described. For each modulation method that realizes each data rate, the relationship between the error rate Pb and the SNR is expressed by the following formula. · When the modulation method is BPSK (Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying), TIFF0007699459000001.tif643 is obtained. ·When the modulation method is QAM (Quadrature Amplitude Modulation), TIFF0007699459000002.tif1160However, M is the number of symbols: TIFF0007699459000003.tif461k is the number of bits per symbol: TIFF0007699459000004.tif535is. Also, in common in Expressions (1) and (2), Q(x) represents the probability that a single sample obtained from a random process with a Gaussian probability density function having a mean of zero and a variance of 1 is x or more, and is represented by the following Expression (5). TIFF0007699459000005.tif982

[0052] Note that in the present embodiment, the above expression is stored in advance in the storage unit 201 of the AP102, and the data rate determination unit 402 calculates the error rate for each data rate using the expression. Alternatively, the data rate determination unit may be configured to calculate the error rate for each data rate by other means. For example, the storage unit 201 of the AP102 has a table showing the error rate with respect to the SNR for each data rate, and after calculating the allowable error rate in S1105, the data rate determination unit 402 may refer to the table and read out the data rate that is equal to or lower than the allowable error rate.

[0053] In S1107 that proceeds when the answer in S1105 is No, the frame transmission / reception unit 401 of the AP102 transmits a response frame indicating that there is no data rate that satisfies the request by the transmission information to the STA103 and the STA104. Thereby, the AP102 notifies the STA103 and the STA104 that there is no data rate rate that satisfies the allowable error rate. The frame to be used may be a newly created management frame or control frame, or a frame to which a newly created Element ID is assigned.

[0054] If it proceeds to S1106 when the answer is Yes in S1105, the data rate determination unit 402 of AP102 determines to use the highest data rate among the data rates (data rates equal to or lower than the allowable error rate) that satisfy the allowable error rate. The processing after S1106 is the same as that in FIG. 8. However, when AP102 determines No in S806, the process returns to S1104. By doing so, even when the wireless propagation environment of the transmission path changes dynamically, such as when the distance between AP102 and STA103 and STA104 fluctuates, the error rate can be calculated each time, and the data rate to be used can be appropriately determined. However, this is an exemplary processing flow. For example, when the wireless propagation environment of the transmission path is static, since the SNR is unlikely to change significantly, when AP102 determines No in S806, the process may return to S805. By doing so, the process of repeatedly obtaining the SNR by AP102 and determining the data rate to be used can be omitted, and the processing load can be reduced.

[0055] Furthermore, in FIG. 11, when AP102 determines No in S1105, it proceeds to S1107, transmits a response frame indicating that there is no data rate that satisfies the request by the transmission information, and ends the communication. However, without ending the communication, the process may proceed to S804. By doing so, AP102 can communicate at the data rate that satisfies the requested data rate and has the lowest error rate. In that case, the processing step S1001 of STA103 and STA104 in FIG. 10 is omitted, and the operation is the same as that in FIG. 5 of Embodiment 1.

[0056] As described above, in this embodiment, AP102 determines the data rate to be used in consideration of the number of STAs connected to AP102. Thereby, even in a network environment where there are a plurality of connected STAs, AP102 can respond flexibly, satisfy the error rate allowable by the STA, and improve the frequency utilization efficiency.

[0057] [Embodiment 3] In the above embodiment, an example was described in which the AP102 operates to determine the data rate to be used appropriately from the perspective of frequency utilization efficiency or error rate, taking into account the connected STAs. On the other hand, considering the perspective of power consumption, since power consumption greatly depends on the data transmission time, the higher the data rate, the more power is saved. Therefore, in this embodiment, a use case in which power saving is given top priority is assumed, and an embodiment for determining the data rate used for communication considering power saving will be described. Note that descriptions of the same features as in Embodiments 1 and 2 are omitted.

[0058] (Processing of STA) The processing of STA103 and STA104 is the same as that of FIG. 10 described in Embodiment 2. However, it is assumed that the transmission information transmitted in S1001 includes at least information regarding the allowable delay time, data length, allowable error rate, and power consumption required by the AP102. As described above, the information regarding power consumption indicates whether to prioritize power consumption (whether to request power-saving communication).

[0059] (Processing of AP) FIG. 12 is a flowchart showing the processing executed by the AP102 according to this embodiment. This processing flow can be implemented by the control unit 202 reading and executing the computer program stored in the storage unit 201 when determining the data rate used by the AP102. In the flowchart of FIG. 12, the same or similar processing as the flowchart of FIG. 8 described in Embodiment 1 or the flowchart of FIG. 11 described in Embodiment 2 is assigned the same reference number, and duplicate descriptions are omitted.

[0060] First, the frame transceiver 401 of the AP102 receives a frame including transmission information including information regarding the allowable delay time, data length, allowable error rate, and power consumption from the STA103 and STA104 (S1201). After the processing of S802 and S803 and then in S1102, when there are multiple rate candidates determined in S803 (No in S1102), the processing proceeds to S1202.

[0061] In S1202, the data rate determination unit 402 of the AP102 determines whether the information regarding the power consumption included in the transmission information indicates prioritizing the power consumption. When the information regarding the power consumption indicates prioritizing the power consumption (Yes in S1202), the process proceeds to S1104. When the information regarding the power consumption indicates not prioritizing the power consumption (No in S1202), the process proceeds to S804. In either case, the subsequent processing is the same as that in FIG. 11.

[0062] Thus, in this embodiment, the AP102 can respond even in a network environment where power saving is desired, and can perform more power-saving operations while satisfying the error rate acceptable to the STA.

[0063] [Other Embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in a computer of the system or device read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0064] The invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0065] 101 Network, 102 AP, 103, 104 STA

Claims

A communication device operating as an access point defined in the IEEE 802.11 standard series, comprising: receiving means for receiving first information indicating an allowable delay time from data transmission by one or more other communication devices operating as stations defined in the IEEE 802.11 standard series wirelessly connected to the communication device to data reception completion by the communication device and a data length of data transmitted by the one or more other communication devices, which is requested by the one or more other communication devices; determining means for determining a data rate to be used for communication with the one or more other communication devices based on the first information; notifying means for notifying the one or more other communication devices of second information regarding the determined data rate; wherein the communication device further comprises: the second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and a number of spatial streams for realizing the data rate determined by the determining means. The communication device is characterized by this. Claim 2 The communication device according to claim 1, further comprising storage means for storing a plurality of data rates that can be used for communication with the one or more other communication devices, wherein: the determining means: calculates a required data rate by the one or more other communication devices from the allowable delay time and the data length; determines one or more data rates equal to or higher than the required data rate from the plurality of data rates; and determines the lowest data rate among the determined one or more data rates as the data rate to be used for communication with the one or more other communication devices. A communication device operating as an access point defined in the IEEE 802.11 standard series, comprising: receiving means for receiving first information indicating a required data rate requested by one or more other communication devices operating as stations defined in the IEEE 802.11 standard series wirelessly connected to the communication device; determining means for determining a data rate to be used for communication with the one or more other communication devices based on the first information; notifying means for notifying the one or more other communication devices of second information regarding the determined data rate; wherein the communication device further comprises: The second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and the number of spatial streams in order to realize the data rate determined by the determination means. A communication device characterized by this.

4. The communication device further includes storage means for storing a plurality of data rates that can be used for communication with the one or more other communication devices. The determination means determines one or more data rates equal to or higher than the required data rate from the plurality of data rates. The communication device according to claim 3, wherein the lowest data rate among the determined one or more data rates is determined as the data rate used for communication with the one or more other communication devices.

5. The communication device further includes determination means for determining whether one other communication device or a plurality of other communication devices are wirelessly connected to the communication device. The first information further indicates an allowable error rate required by the one or more other communication devices. When it is determined by the determination means that the plurality of other communication devices are wirelessly connected. The determination means determines, among the determined one or more data rates, the data rate used for communication with the plurality of other communication devices based on a signal-to-noise ratio between the plurality of other communication devices and the communication device and the allowable error rate. The communication device according to claim 2 or 4, characterized by this.

6. The determination means calculates an error rate at the determined one or more data rates based on the signal-to-noise ratio. The communication device according to claim 5, wherein the highest data rate among the one or more data rates at which the error rate is equal to or lower than the allowable error rate is determined as the data rate used for communication with the plurality of other communication devices.

7. When it is determined by the determination means that one other communication device is wirelessly connected, the determination means determines, among the determined one or more data rates, the lowest data rate as the data rate used for communication with the one other communication device. The communication device according to claim 5 or 6, characterized by this.

8. The first information further indicates an allowable error rate required by the one or more other communication devices and whether the one or more other communication devices require power-saving communication. When the first information indicates a request for power-saving communication, The determination means determines, among the determined one or more data rates, a data rate to be used for communication with the one or more other communication devices based on a signal-to-noise ratio and the allowable error rate between the one or more other communication devices and the communication device. The communication device according to claim 2 or 4.

9. The determination means Based on the signal-to-noise ratio, calculates an error rate for each of the determined one or more data rates, Among the one or more data rates, determines the highest data rate at which the error rate is equal to or less than the allowable error rate as the data rate to be used for communication with the one or more other communication devices. The communication device according to claim 8.

10. The notification means notifies the one or more other communication devices of the second information in a trigger frame. The communication device according to any one of claims 1 to 9.

11. When the second information causes the one or more other communication devices to retransmit data, the second information is notified to the one or more other communication devices using a data retransmission trigger frame for causing the one or more other communication devices to retransmit the data. The communication device according to any one of claims 1 to 10.

12. A communication device operating as a station defined in the IEEE 802.11 standard series, Transmission means for transmitting first information to another communication device operating as an access point defined in the IEEE 802.11 standard series, Receiving means for receiving second information regarding a data rate to be used for communication with the other communication device, determined by the other communication device based on the first information, from the other communication device, The first information indicates an allowable delay time from data transmission by the communication device to completion of data reception by the other communication device and the data length of data transmitted by the communication device at one time, or indicates a required data rate calculated by the communication device from the allowable delay time and the data length, The second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and the number of spatial streams for realizing a data rate determined by the other communication device, and is characterized by a communication device.

13. The communication device according to claim 12, wherein the first information further indicates at least one of an allowable error rate required by the communication device and whether the communication device requires power-saving communication.

14. The communication device according to claim 12 or 13, wherein when the communication device retransmits data, the second information is notified using a data retransmission trigger frame that causes the communication device to retransmit the data.

15. A control method for a communication device operating as an access point defined in the IEEE 802.11 standard series, a receiving step of receiving first information indicating an allowable delay time from data transmission by the one or more other communication devices to completion of data reception by the communication device and a data length of data transmitted by the one or more other communication devices at one time, which are required by the one or more other communication devices operating as stations defined in the IEEE 802.11 standard series wirelessly connected to the communication device; a determining step of determining a data rate to be used for communication with the one or more other communication devices based on the first information; a notifying step of notifying the one or more other communication devices of second information regarding the determined data rate; and having The second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and the number of spatial streams for realizing the data rate determined by the determining step, and is characterized by a control method.

16. A control method for a communication device operating as an access point defined in the IEEE 802.11 standard series, a receiving step of receiving first information indicating a required data rate required by the one or more other communication devices from the one or more other communication devices operating as stations defined in the IEEE 802.11 standard series wirelessly connected to the communication device; A determining step of determining a data rate to be used for communication with the one or more other communication devices based on the first information; A notifying step of notifying the one or more other communication devices of second information regarding the determined data rate; comprising: The second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and a number of spatial streams for realizing the data rate determined in the determining step. A control method characterized by this.

17. A control method for a communication device operating as a station defined in the IEEE 802.11 standard series, A transmitting step of transmitting first information to another communication device operating as an access point defined in the IEEE 802.11 standard series; A receiving step of receiving, from the other communication device, second information regarding a data rate to be used for communication with the other communication device, which is determined by the other communication device based on the first information. The first information indicates an allowable delay time from data transmission by the communication device to completion of data reception by the other communication device and the data length of data transmitted by the communication device at one time, which are required by the communication device, or indicates a required data rate calculated by the communication device from the allowable delay time and the data length. The second information includes a frequency bandwidth, a length of a guard interval, information on allocation of resource units, information on an MCS (Modulation and Coding Scheme), and a number of spatial streams for realizing the data rate determined by the other communication device. A control method characterized by this.

18. A program for causing a computer to function as the communication device according to any one of Claims 1 to 14.

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