Communication apparatus, control method thereof, and storage medium

Abstract

The invention provides a communication apparatus, a control method thereof, and a storage medium. The invention provides a mechanism for reducing residual frequency difference and increasing synchronization precision between APs in distributed MIMO using slave triggering. The communication apparatus includes a transmission unit configured to transmit a radio frame including one or more repetitive signal intervals for detecting a frequency difference between the communication apparatus and another communication apparatus, a number of the repetitive signal intervals in the radio frame is determined based on a transmission mode used by the communication device and the other communication device.

Description

[0001] This application is a divisional application of an invention patent application with an application date of February 25, 2020, application number 202080031279.3 (international application number PCT / JP2020 / 007316), and invention name “Communication equipment, control method thereof, and storage medium”. Technical Field

[0002] The invention relates to communication equipment, a control method thereof and a storage medium. Background Art

[0003] In recent years, with the development of information communication technology, the use of the Internet has increased year by year, and in response to the increase in demand, various communication technologies are being developed. In particular, wireless local area network (wireless LAN) technology has achieved throughput improvement in Internet communication of packet data, audio, video, etc. through wireless LAN terminals, and various technical developments are still being actively carried out.

[0004] In the development of wireless LAN technology, many standardization works of IEEE (Institute of Electrical and Electronics Engineers) 802, which is a standardization body of wireless LAN technology, have played an important role. The standard of wireless LAN communication is known as IEEE802.11 standard, and there are standards such as IEEE802.11n / a / b / g / ac and IEEE802.11ax. For example, IEEE802.11ax achieves a high peak throughput of up to 9.6 gigabits per second (Gbps) using OFDMA (Orthogonal Frequency Division Multiple Access), and also improves the communication speed under congested conditions (PTL 1).

[0005] Recently, in order to further improve the throughput, a research group called IEEE802.11EHT (Extremely High Throughput) has been formed as a successor standard to IEEE802.11ax. Distributed MIMO is considered to be a measure to improve the throughput that EHT aims to achieve. The characteristic of distributed MIMO is that multiple APs operate in a collaborative manner, and as the number of available antennas increases, an increase in communication speed can be expected. A method of synchronizing multiple APs using a frame called a slave trigger is being proposed as a method of implementing distributed MIMO. In this method, the slave AP detects the frequency difference with respect to the slave trigger sent from the master AP, and performs frequency correction to synchronize with the master AP.

[0006] Reference List

[0007] Patent Literature

[0008] PTL 1: Japanese Patent Application Publication No. 2018-50133 Summary of the invention

[0009] Technical issues

[0010] In the above-mentioned distributed MIMO, synchronization between APs is necessary for multiple APs to perform cooperative operations. In the method using slave triggering, the slave AP detects the frequency difference for the slave trigger sent from the master AP and performs frequency correction to synchronize with the master AP. The frequency correction process is performed using the pilot signal included in the slave trigger. However, there is a problem that the synchronization accuracy between APs is reduced due to the occurrence of residual frequency differences caused by thermal noise, etc., thereby reducing communication performance.

[0011] The present invention has been made in view of the above-mentioned problems, and provides a technology capable of improving the synchronization accuracy between APs in distributed MIMO compared with the past.

[0012] Technical solutions to the problem

[0013] In order to solve this problem, the communication device of the present invention includes, for example, the following configuration. In other words,

[0014] A communication device that builds a wireless network by cooperating with other communication devices.

[0015] The communication device has a sending unit, which sends a frame for synchronization to the other communication device to cooperate with the other communication device, and

[0016] The sending unit comprises:

[0017] a setting unit that sets a value exceeding 4 as the number of repetitions of the EHT long training field (EHT-LTF) at a preset position of the EHT signal field (EHT-SIG-A) of the frame for synchronization; and

[0018] a generating unit, which generates a frame for synchronization, wherein the frame includes EHT-LTFs whose number is the set number of repetitions,

[0019] The sending unit sends the generated frame for synchronization to the other communication device.

[0020] Advantageous Effects of the Invention

[0021] According to the present invention, the synchronization accuracy between APs in distributed MIMO can be increased to a higher level than before.

[0022] Other features and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings. Note that throughout the accompanying drawings, the same reference numerals designate the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0024] [ Figure 1 ]A diagram showing an example of a network configuration.

[0025] [ Figure 2 ]A diagram showing an example of the functional configuration of an AP.

[0026] [ Figure 3 ]A diagram showing an example of the hardware configuration of an AP.

[0027] [ Figure 4 ] shows a flowchart of the processing performed by the master AP.

[0028] [ Figure 5 ] shows a flowchart of the processing performed by the slave AP.

[0029] [ Figure 6 ] shows a sequence diagram of processing performed in a wireless communication network.

[0030] [ Figure 7 ]A diagram showing an example of the construction of a frequency difference detection unit.

[0031] [ Figure 8 ] is a diagram showing an example of a PHY frame structure of an EHT SU PPDU.

[0032] [ Fig. 9 ] A diagram showing an example of a PHY frame structure of an EHT ER PPDU.

[0033] [ Fig.10 ] A table showing the bit position and meaning of the subfields of EHT-SIG-A1 within a frame.

[0034] [ Fig.11 ] A table showing the bit position and meaning of the subfields of EHT-SIG-A2 within a frame.

[0035] [ Fig.12 ]A flowchart showing an example of processing of a master AP. DETAILED DESCRIPTION

[0036] Embodiments will be described in detail below with reference to the accompanying drawings. Note that the following embodiments are only specific examples of embodiments of the present invention and do not limit the present invention. Although multiple features are described in the embodiments, not all of these features are necessary for the present invention, and the multiple features can be combined arbitrarily. In addition, in the accompanying drawings, the same reference numerals are given to the same or similar parts, and their repeated description will be omitted.

[0037] [First embodiment]

[0038] [System structure]

[0039] Figure 1 An example of a network configuration according to the first embodiment is shown. Figure 1 The wireless communication system is a wireless network equipped with a plurality of APs (base stations; access points) 103 and 104 and a plurality of STAs (stations) 105 and 106.

[0040] AP 103 and 104 and STA 105 and 106 communicate according to the wireless communication method of IEEE802.11EHT standard. Circle 101 represents the range of arrival of the signal sent by AP 103, and circle 102 represents the range of arrival of the signal sent by AP 104. In addition, as shown in the figure, AP 103 and 104 can both communicate with STA 105 and 106. In addition, AP 103 and AP 104 can communicate similarly. AP 103 and AP 104 can perform distributed MIMO (hereinafter referred to as D-MIMO) communication. In other words, AP 103 and AP 104 can communicate with STA 105 and 106 by performing cooperative operation. AP 103 and 104 are connected by a backhaul line so that they can communicate with each other for cooperative operation, and are controlled by AP control device 107. Regarding AP control device 107, any one of multiple APs can have its function. Note that although in the present embodiment, it is assumed that AP 103 will operate as a master AP and AP 104 will operate as a slave AP, the method of setting which AP will operate as the master AP is not particularly important, and the AP control device 107 can set it in advance, or it can be set by operating a switch (not shown) arranged on each AP.

[0041] Notice, Figure 1 The configuration of the wireless communication network shown is only an example for explanation, and for example, a network including a large number of EHT devices and legacy devices (communication devices conforming to the IEEE802.11a / b / g / n / ax standards) in a wider area may be constructed. In addition, the arrangement of the communication devices is not limited to Figure 1 The arrangement shown in the figure and the following discussion are also applicable to various positional relationships of the communication devices. In addition, EHT can be understood as an abbreviation for Extremely High Throughput.

[0042] [AP structure]

[0043] Figure 2: is a functional block diagram of the APs 103 and 104. The APs 103 and 104 have a wireless LAN control unit 201, a frame generation unit 202, a frame control unit 203, and a UI (User Interface) control unit 204 as an example of the functional configuration thereof.

[0044] The wireless LAN control unit 201 may be configured to include one or more antennas 205 and circuits for transmitting / receiving wireless signals (radio frames) to / from other wireless LAN devices, and a program for controlling these. The wireless LAN control unit 201 performs communication control of the wireless LAN based on the frame generated by the frame generation unit 202 in accordance with the IEEE802.11 series of standards.

[0045] The frame generation unit 202 generates a frame to be transmitted by the wireless LAN control unit 201 based on an instruction of the frame control unit 203. Although the details will become clear by the description given later, in the case where the frame to be transmitted is a slave trigger for D-MIMO, the frame control unit 203 of the AP 103 as the master performs the following settings on the frame generation unit 202.

[0046] · In the preset position of the EHT signal field (EHT-SIG-A) of the frame (refer to Fig. 9 and Fig.10 ), set a value greater than 4 as the number of repetitions of the EHT long training field (EHT-LTF).

[0047] · Executes an instruction for generating EHT-LTFs whose number is the set number of repetitions.

[0048] The frame generation unit 202 generates a slave trigger for D-MIMO according to the instruction.

[0049] Note that the frame generation unit 202 may create frames independently of instructions from the frame control unit 203 .

[0050] The UI control unit 204 accepts the user (not shown) of the APs 103 and 104 to input the input unit 304 ( Figure 3 ) operations, and performs control for transmitting control signals corresponding to these operations to each structural element, or for output unit 305 ( Figure 3 ) output (including display, etc.) control.

[0051] Figure 3The hardware configuration of APs 103 and 104 in this embodiment is shown. As an example of its hardware configuration, APs 103 and 104 have a storage unit 301, a control unit 302, a function unit 303, an input unit 304, an output unit 305, and a communication unit 306, and one or more antennas 205.

[0052] The storage unit 301 is composed of both or one of a ROM and a RAM, and stores various information such as programs for performing various operations described later and communication parameters for wireless communication. Note that in addition to memories such as ROM and RAM, a storage medium such as a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, or a DVD can be used as the storage unit 301.

[0053] The control unit 302 is composed of, for example, a processor such as a CPU or an MPU, an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), etc. Here, CPU is an acronym for a Central Processing Unit, and MPU is an acronym for a Micro Processing Unit. The control unit 302 controls the entire AP 103 and 104 by executing a program stored in the storage unit 301. Note that the control unit 302 can control the entire AP 103 and 104 by cooperation of an OS (Operating System) and a program stored in the storage unit 301.

[0054] In addition, the control unit 302 performs predetermined processing such as imaging, printing, and projection by controlling the function unit 303. The function unit 303 is hardware of the APs 103 and 104 for performing predetermined processing. For example, in the case where the APs 103 and 104 are imaging devices represented by digital cameras, the function unit 303 is an imaging unit and performs imaging processing. In addition, for example, in the case where the APs 103 and 104 are image forming devices represented by printers, the function unit 303 is a printing unit and performs printing processing. In addition, for example, in the case where the APs 103 and 104 are projection devices represented by projectors, the function unit 303 is a projection unit and performs projection processing. The data to be processed by the function unit 303 may be data stored in the storage unit 301, or may be data transmitted from the STA or other APs via the communication unit 306 described later.

[0055] The input unit 304 accepts various operations from the user. The output unit 305 performs various outputs for the user. Here, the output of the output unit 305 includes at least one of display on the screen, audio output of the speaker, vibration output, etc. Note that both the input unit 304 and the output unit 305 can be implemented by a module such as a touch panel.

[0056] The communication unit 306 performs control of wireless communication conforming to the IEEE802.11EHT standard (including modulation and coding processing), control of wireless communication conforming to Wi-Fi, and control of IP (Internet Protocol) communication. In addition, the communication unit 306 performs transmission / reception of radio signals for wireless communication by controlling one or more antennas 205. In this case, MIMO (Multi Input Multi Output) communication using spatial streams can be performed. APs 103 and 104 transmit content such as image data, document data, and video data with other communication devices via the communication unit 306. Note that Figure 3 The functions of the various configuration elements shown in the drawings may be partially implemented by software.

[0057] [STA structure]

[0058] The functional configuration and hardware configuration of the STAs 105 and 106 are respectively similar to the above-mentioned functional configurations of the APs 103 and 104 ( Figure 2 ) and hardware configuration ( Figure 3 ) is the same. In other words, each of the STAs 105 and 106 may be configured to include a wireless LAN control unit 201, a frame generation unit 202, a frame control unit 203, and a UI control unit 204 as functional configurations, and to include a storage unit 301, a control unit 302, a functional unit 303, an input unit 304, an output unit 305, a communication unit 306, and one or more antennas 205 as hardware configurations.

[0059] [Processing Flow]

[0060] Next, we will refer to Figures 4 to 6 The flow of processing to be performed by the AP 103 constructed as described above and the Figure 1 Here, an example of an operation in which the APs 103 and 104 perform data transmission by D-MIMO to the STA 105 by cooperative operation will be described. Figure 4 and Figure 5104. The control unit 302 of each of the APs 103 and 104 performs calculation and processing of information and control of each hardware by executing a control program stored in the storage unit 301, thereby realizing Figure 4 and Figure 5 In addition, Figure 6 A sequence diagram showing a process to be performed in a wireless communication system.

[0061] exist Figure 6 In the sequence diagram of , AP 103 and 104 perform D-MIMO transmission of the data frame. When performing D-MIMO transmission of the data frame, AP 104 as a slave AP must be synchronized with AP 103 as a master AP. For this synchronization process, AP 103 sends a slave trigger to AP 104 before the data frame is sent. Although in this embodiment, it is assumed that the slave trigger is sent based on the trigger frame of the IEEE802.11ax standard, the present invention is not limited to this. Note that it is assumed that CSI (channel state information) for AP 103 and 104 to perform D-MIMO transmission to STA 105 is acquired in advance.

[0062] AP 103 as a master transmits a slave trigger to AP 104 (step S401; F601). AP 104 as a slave detects a frequency difference from the received slave trigger and corrects the frequency to synchronize with AP 103 (step S501).

[0063] (Specific example of synchronization processing)

[0064] Here, we will refer to Figure 7 The frequency correction process is described. Figure 7 201 is a block diagram showing an example of the configuration of the frequency difference detection unit 701. The frequency difference detection unit 701 is included in the wireless LAN control unit 201.

[0065] The frequency difference detection unit 701 detects the frequency difference using a repetitive signal section included in the received signal. In the IEEE802.11 standard, STF (Short Training Field) and LTF (Long Training Field) are specified as repetitive signals.

[0066] The communication unit 306 of AP 104 generates an in-phase wave detection axis signal (hereinafter referred to as I signal) and an orthogonal wave detection axis signal (hereinafter referred to as Q signal) by orthogonally demodulating the wireless signal received via antenna 205, and generates a signal P(t) to be provided to the frequency difference detection unit 701.

[0067] The frequency difference detection unit 701 supplies the input signal P(t) to the multiplication unit 702 and the delay unit 703. Here, if the frequency difference between the AP 103 and the AP 104 is set to Δf, P(t) can be expressed by the following expression (1).

[0068] P(t)=I(t)+j×Q(t) ∝ exp(j×2×π×(f-Δf)×t) ... (1)

[0069] The delay unit 703 generates a delayed signal P(tT), which is the input signal P(t) delayed by a repetitive signal period T, and outputs it to the complex conjugation unit 704.

[0070] STF and LTF are designed so that T = n / f. Therefore, the delayed signal P(tT) can be expressed by the following equation (2) and will be a signal with a phase lead of Δθ = 2×π×Δf×T of the input signal P(t).

[0071] P(tT)∝exp(j×2×π×(f-Δf)×(tT))=exp(j×2×π×(f-Δf)×tj×2×π×f×T+j×2×π×Δf×T)

[0072] =exp(j×2×π×(f-Δf)×t+j×Δθ) ... (2)

[0073] The complex conjugation unit 704 generates a complex conjugate signal P*(tT) of the delayed signal P(tT) and outputs it to the multiplication unit 702.

[0074] The multiplication unit 702 performs complex multiplication on the input signal P(t) and the complex conjugate signal P*(tT), and outputs the multiplication result to the frequency error calculation unit 705. The multiplication result is represented by Expression (3).

[0075] P(t)×P*(tT)∝exp(-j×Δθ)...(3)

[0076] The frequency error calculation unit 705 calculates the Δθ by performing ARCTAN calculation on the input multiplication result, and obtains the frequency difference Δf. The communication unit 306 corrects the frequency in the subsequent transmission / reception processing based on the Δf obtained in the frequency difference detection unit 701. The frequency correction method can be implemented by multiplying exp(j×2×π×Δf×t) with the I signal and the Q signal. Alternatively, such a structure can be adopted so that the oscillation source is constructed by a variable control oscillator, and its frequency is corrected by Δf. Note that the obtained frequency difference Δf has a noise component caused by thermal noise, etc. In order to suppress this noise component, averaging processing is effective. For example, the noise component can be suppressed by obtaining an average value within the range of the repetitive signal period T. In addition, the noise component can be further suppressed by increasing the number of repetitions of the repetitive signal and obtaining the average value of multiple repetitive signals. As described later, in the present embodiment, in the slave trigger of the D-MIMO transmission requiring high-precision synchronization, the synchronization accuracy is improved by increasing the number of LTFs.

[0077] Description will be returned to Figure 6 , AP 103 and AP 104 perform D-MIMO transmission of data frames to STA 105 at synchronized timing (steps S402, S502, and F602).

[0078] (Frame structure)

[0079] exist Figure 8 and Fig. 9 An example of the structure of a PHY (physical) frame of a PPDU specified by the IEEE802.11EHT standard transmitted through the above sequence is shown in FIG. Note that PPDU is an abbreviation of a physical layer (PHY) protocol data unit. Although it is assumed that Figure 8 and Fig. 9 Any PHY frame shown in the figure sends a slave trigger, but a PHY frame separately designated for the slave trigger may be constructed.

[0080] Figure 8 An example of the structure of a PHY frame of an EHT SU PPDU which is a PPDU for single-user (SU) communication (between an AP and a single AP / STA) is shown. Fig. 9 An example of the structure of a PHY frame of an EHT ER PPDU which is a PPDU for communication in an extended range (communication range) is shown. The EHT ER PPDU is used for communication between an AP and a single AP / STA.

[0081] There are STF (Short Training Field), LTF (Long Training Field) and SIG (Signal Field) as Figure 8 and Fig. 9 The information contained in the PPDU. Figure 8In the example of , the header of the PPDU includes L (Legacy)-STF 801, L-LTF 802 and L-SIG 803 which are backward compatible with the IEEE802.11a / b / g / n / ax standards. In addition, EHT-SIG-A 805, EHT-STF 806 and EHT-LTF 807 for the EHT standard are commonly included in each PPDU.

[0082] L-STF 801 is used for PHY frame signal detection, automatic gain control (AGC) and timing detection, etc. L-LTF 802 arranged immediately after L-STF 801 is used for high-precision frequency / time synchronization, CSI acquisition, etc. L-SIG 803 arranged immediately after L-LTF 802 is used for sending control information, and the control information includes information on data transmission rate and PHY frame length. Legacy devices that comply with IEEE802.11a / b / g / n / ax standards can decode data in the above-mentioned various legacy fields (L-STF 801, L-LTF 802 and L-SIG 803). Various legacy fields are similarly included in Fig. 9 In the PPDU shown.

[0083] After the above L-STF 801, L-LTF 802 and L-SIG 803, Figure 8 The frame of the EHT SU PPDU shown includes RL-SIG 804, EHT-SIG-A 805, EHT-STF 806, EHT-LTF 807, a data field 808, and a packet extension 809. Among them, RL-SIG 804 may be omitted. EHT-SIG-A 805 is arranged after L-SIG 803, EHT-STF 806 is arranged immediately after EHT-SIG-A 805, and EHT-LTF 807 is arranged immediately after EHT-STF 806. Note that the fields from L-STF 801, L-LTF 802, L-SIG 803, RL-SIG 804, EHT-SIG-A 805, EHT-STF 806 to EHT-LTF 807 are referred to as "preambles".

[0084] The EHT-SIG-A 805 includes information such as EHT-SIG-A1 and EHT-SIG-A 2 required for receiving the PPDU. Fig.10 and Fig.11 , a group of subfields constituting EHT-SIG-A1 included in EHT-SIG-A 805 and a group of subfields constituting EHT-SIG-A 2 are respectively shown.

[0085] EHT-STF 806 after EHT-SIG-A805 is the abbreviation of EHT Short Training Field, and its main purpose is to improve automatic gain control in MIMO transmission. EHT-LTF 807 is the abbreviation of EHT Long Training Field, and is used for the above-mentioned frequency difference correction and propagation channel estimation. Data field 808 includes various data modulated according to the modulation method represented in the above-mentioned EHT-SIG-A1.

[0086] In this embodiment, the EHT-SIG-A1 ( Fig.10 ) in the GI+LTF size subfield of the EHT-LTF, and set the number of repetitions to be greater than 4×EHT-LTF. Note that although it is assumed that Fig.10 6×EHT-LTF or 8×EHT-LTF is set in the embodiment, but the present invention is not limited thereto, and a configuration capable of setting 5×EHT-LTF and 16×EHT-LTF may be adopted. In the present embodiment, the number of repetitions of EHT-LTF is set to a number exceeding 4 in order to improve the synchronization accuracy in the transmission of the slave trigger via noise suppression through averaging.

[0087] As mentioned above, Fig. 9 The EHT ER PPDU shown in is a PPDU used when it is desired to extend the communication range, and is used for communication between an AP and a single AP / STA. The EHT ER PPDU includes an L-STF 901, an L-LTF 902, an L-SIG 903, an RL-SIG 904, an EHT-SIG-A 905, an EHT-STF 906, an EHT-LTF 907, a data field 908, and a packet extension 909. Among them, the RL-SIG 904 is not required. The L-LTF 902 is arranged immediately after the L-STF 901, the L-SIG 903 is arranged immediately after the L-LTF 902, the EHT-SIG-A 905 is arranged after the L-SIG 903, the EHT-STF 906 is arranged immediately after the EHT-SIG-A 905, and the EHT-LTF 907 is arranged immediately after the EHT-STF 906. Note that the fields from L-STF 901, L-LTF 902, L-SIG 903, RL-SIG 904, EHT-SIG-A 905, EHT-STF 906 to EHT-LTF 907 are referred to as "preambles". Figure 8 The EHT SU PPDU shown has the same content, so the description of these information will be omitted. Note that in EHT-SIG-A 905, similar to Figure 8For an EHT SU PPDU of 4× ...

[0088] As described above, if the frame structure of the EHT SU PPDU and the EHT ER PPDU, which are PPDUs used in the IEEE 802.11 EHT standard, represented in this embodiment is used, the EHT LTF can be transmitted with a repetition number exceeding 4. In other words, the synchronization accuracy can be improved by setting a larger repetition number for the EHT LTF when transmitting a slave trigger, thereby improving the communication performance in D-MIMO transmission.

[0089] Note that although Figure 8 and Fig. 9 The frame structure backward compatible with the IEEE802.11a / b / g / n / ax standard is shown, but if there is no need to ensure backward compatibility, the L-STF and L-LTF fields can be omitted. Instead, the EHT-STF and EHT-LTF can be inserted.

[0090] In addition, although in the present embodiment, it is assumed that the number of repetitions of the EHT LTF triggered by the slave is increased, the present invention is not limited thereto, and in a transmission mode requiring high-precision synchronization, a configuration in which the number of repetitions is increased in any frame may be adopted. For example, since a transmission error due to a frequency difference is more likely to occur in a high-order modulation such as 1048QAM, a configuration in which the number of repetitions of the EHT LTF of the high-order modulation data frame is set may be adopted.

[0091] Furthermore, a configuration may be adopted such that, when the AP 103 as the master transmits a slave trigger, it is determined whether it is a D-MIMO slave trigger and the number of repetitions of the LTF is decided accordingly. Fig.12 The processing procedure (of the control unit 302) of the AP 103 which is the master device in this case is shown. A description will be given below with reference to this figure.

[0092] In step S1201, the control unit 302 determines whether to send a D-MIMO slave trigger. In the case where the determination in step S1201 is "yes", the control unit 302 advances the processing to step S1202, and generates a slave trigger in which the number of repetitions of LTF is more than 4 times (which can be 6 or 8). In addition, in the case where the determination in step S1201 is "no" (the frame to be sent is not a slave trigger), the control unit 302 advances the processing to step S1203, and generates a frame as follows, in which the number of repetitions of LTF is set to any number that can be set in the GI+LTF size subfield. Then, in step S1204, the control unit 302 sends the generated frame by controlling the communication unit 306. Note that in the processing of steps S1202 and S1203, the number of repetitions of the slave-triggered LTF can be set to a value greater than that of other frames. For example, when the number of repetitions of the slave-triggered LTF is set to 6, the number of repetitions of the LTF of other frames that do not require synchronization accuracy is set to 2. Therefore, the number of repetitions of the LTF of each frame can be flexibly set according to the required synchronization accuracy.

[0093] (Other embodiments)

[0094] The present invention can be implemented by the following processing: providing a program for implementing one or more functions of the above-mentioned embodiment to a system or device via a network or storage medium, and causing one or more processors in a computer of the system or device to read out and execute the program. The present invention can also be implemented by a circuit (such as an ASIC) for implementing one or more functions.

[0095] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, the claims are made to disclose the scope of the present invention.

[0096] This application claims the benefit of Japanese Patent Application No. 2019-085799, filed on April 26, 2019, which is hereby incorporated by reference herein in its entirety.

Claims

1. A communication device, comprising: a transmitting unit configured to transmit a radio frame including one or more repeated signal intervals for detecting a frequency difference between the communication device and other communication devices, The number of the repeated signal intervals in the radio frame is determined based on the transmission modes used by the communication device and the other communication devices.

2. The communication device according to claim 1, in, The communication device operates as an access point, and Herein, in a case where the communication device transmits the radio frame to the other communication device operating as an access point, the number of the repeated signal sections in the radio frame is set to be not less than 4.

3. The communication device according to claim 1, in, The communication device operates as an access point, and Wherein, when the communication device performs distributed multiple-input multiple-output (MIMO) communication, the number of the repeated signal sections in the radio frame is set to be no less than 4.

4. The communication device according to claim 1, in, The sending unit sends the radio frame according to IEEE 802.11 series standards.

5. The communication device according to claim 1, in, A value indicating that the number of the repetitive signal intervals is greater than 4 can be set in the GI+LTF size subfield of the radio frame.

6. A method for controlling a communication device, comprising: transmitting a radio frame including one or more repeated signal intervals for detecting a frequency difference between the communication device and another communication device, The number of the repeated signal intervals in the radio frame is determined based on a transmission mode used by the communication device and the other communication devices.

7. The control method according to claim 6, in, The communication device operates as an access point, and Herein, in a case where the communication device transmits the radio frame to the other communication device operating as an access point, the number of the repeated signal sections in the radio frame is set to be not less than 4.

8. The control method according to claim 6, in, The communication device operates as an access point, and Wherein, when the communication device performs distributed multiple-input multiple-output (MIMO) communication, the number of the repeated signal sections in the radio frame is set to be no less than 4.

9. The control method according to claim 6, in, The transmitted radio frames are radio frames according to the IEEE802.11 series of standards.

10. A storage medium storing a program which, when executed by one or more processors, causes a communication device to: transmitting a radio frame including one or more repeated signal intervals for detecting a frequency difference between the communication device and another communication device, in, The number of the repeated signal intervals in the radio frame is determined based on a transmission mode used by the communication device and the other communication devices.

Images