JP5979835B2 - Transmission device, transmission method, and program - Google Patents

Description

  The present invention relates to a transmission apparatus that transmits data.

  In recent years, wireless LANs (Local Area Networks) compliant with IEEE (Institut of Electrical and Electronics Engineers) 802.11n have been widely used. In addition, IEEE 802.11ac that is aiming for higher-speed communication than 802.11n is also being formulated. In these IEEE802.11 series, a CTS (Clear to Send) signal for regulating transmission of a data signal for a predetermined period by other apparatuses is defined. The data receiving apparatus can reduce interference in the receiving apparatus by transmitting the CTS signal before receiving the data signal.

  In addition, IEEE 802.11n and ac support a 40 MHz mode that uses a channel bandwidth twice that of the prior art for speeding up. In the 40 MHz mode, data signals are communicated using a 40 MHz channel bandwidth. However, even in the 40 MHz mode, control signals such as a beacon and the above-described CTS signal are communicated using a 20 MHz channel bandwidth called a basic channel.

  If such a wireless network (Basic Service Set, hereinafter referred to as BSS) that communicates in the 40 MHz mode is adjacent, even if the receiving apparatus transmits a CTS signal, interference may occur in the receiving apparatus. In other words, if the channel on which the receiving device transmits the CTS signal is different from the basic channel of the adjacent BSS, the device belonging to the adjacent BSS cannot receive the CTS signal and may transmit the data signal. is there. Here, since this data signal is transmitted with a 40 MHz bandwidth, the channel of the data signal transmitted by the device belonging to the adjacent BBS and the channel through which the receiving device receives the data signal may overlap, resulting in interference. is there.

  In order to solve this, a method in which the receiving apparatus switches the channel and transmits the CTS signal can be considered, but it takes much time to switch the channel and is not efficient. Therefore, Non-Patent Document 1 discloses a configuration in which a device different from a receiving device transmits a CTS signal to a basic channel of an adjacent BSS.

Jarkko Kneckt (Nokia), “Reserving STA”, 18 Jan 2011, https: // mentor. iee. org / 802.11 / dcn / 11 / 11-11-0127-01-00ac-reserving-sta. ppt

However, when a device different from the receiving device transmits a CTS signal, the CTS signal may not reach a device belonging to an adjacent BBS depending on the position of the device that transmits the CTS signal. In this case, a device belonging to an adjacent BSS cannot receive a CTS signal, and interference still occurs in the receiving device.
In order to solve the above problems, an object of the present invention is to reduce interference in a receiving device by causing a device existing in a common area of a plurality of networks to transmit a signal that suppresses data transmission of another device. And

  The transmission device of the present invention includes a first determination unit that determines a detection device that detects another wireless network that communicates using a second channel different from the first channel used for data transmission; When transmitting data to the receiving device in the first channel, whether or not a device different from the receiving device that is the transmission destination of the data is included in the detecting device determined by the first determining means. When it is determined by the second determination unit that determines that a device different from the reception device is included in the detection device, a signal for suppressing transmission of data is transmitted to the second determination unit. An instruction means for instructing the detection apparatus to transmit on the first channel, and a transmission for transmitting data on the first channel to the reception apparatus after the instruction by the instruction means And when the second determination unit determines that a device different from the reception device is not included as the detection device, the transmission unit does not issue an instruction by the instruction unit. Data is transmitted to the receiving device.

    An apparatus that exists in a common area of a plurality of networks and that is different from the receiving apparatus transmits a signal that suppresses data transmission of other apparatuses, and thus interference in the receiving apparatus can be reduced.

System configuration diagram in Embodiments 1 and 2 Functional block diagram of the AP in the first, second, and third embodiments Functional block diagram of STA in Embodiments 1, 2, and 3 Sequence diagram of OBSS Scan of STA in Embodiments 1, 2, and 3 Frame configuration diagram of OBSS report in Embodiments 1 and 2 The figure which shows the OBSS notification STA management database in Embodiment 1,2. The flowchart which AP implement | achieves in Embodiment 1 implement | achieves Sequence chart in the first embodiment The flowchart which AP implement | achieves in Embodiment 2 implement | achieves System configuration diagram in Embodiment 3 OBSS report frame configuration diagram in Embodiment 3 The figure which shows the OBSS notification STA management database in Embodiment 3. Flowchart realized by AP in Embodiment 3

<Embodiment 1>
FIG. 1 shows the configuration of a wireless LAN system compliant with the IEEE 802.11n standard. In the present embodiment, an example will be described in which interference is prevented from the AP 106 belonging to the BSS 109 when the AP 101 transmits data to the STA (station) 103 that is a communication apparatus belonging to the BSS 108.

  The BSS 108 constructed by the AP 101 uses 36 ch (frequency channel) as a basic channel and 40 ch as a non-basic channel. Further, in the BSS 109 constructed by the AP 106, the basic channel is used as 48 ch, and the non-basic channel is used as 36 ch, 40 ch, and 44 ch. Here, the basic channel is a channel used for transmission of control signals (beacons and CTS signals). The non-basic channel is a channel used together with the basic channel so that each device transmits a data signal.

  FIG. 2A shows the hardware configuration of the AP 101. The control unit 201 includes a CPU and an MPU, and controls the entire AP 101 by executing a program stored in the storage unit 202. The storage unit 202 includes a ROM and a RAM, and stores various information such as a program executed by the control unit 201 and communication parameters. Various operations of the AP 101 described later are performed by the control unit 201 executing a program stored in the storage unit 202. The storage unit 202 stores not only memories such as ROM and RAM, but also flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, nonvolatile memory cards, DVDs, and the like. A medium may be used. The RF unit 203 includes an antenna and a circuit for transmitting / receiving a radio signal to / from another radio communication apparatus (STA).

  Next, FIG. 2B shows a software function block of the AP 101. The software function block of the present embodiment is realized when the control unit 201 reads a program stored in the storage unit 202. However, the present invention is not limited to this, and some or all of the software function blocks may be configured by hardware. Further, a plurality of software function blocks may be combined and realized as one software function block, or one software function block may be realized as a plurality of software function blocks. Further, these software function blocks realize not only the control unit 201 and the storage unit 202 but also the RF unit 203 depending on the case to realize the function.

  Reference numeral 251 denotes an STA specifying unit that specifies an STA that requests transmission of a Self-CTS signal when the AP 101 transmits a data signal. Here, the Self-CTS signal is a CTS signal that is transmitted with the destination set to the STA that has transmitted the signal.

  Reference numeral 252 denotes a channel specifying unit that specifies a frequency channel used when the STA specified by the STA specifying unit 251 transmits a Self-CTS signal. Reference numeral 253 denotes a STA wake-up unit that wakes up the STA that is in Power Save (power saving mode) conforming to the IEEE 802.11 series. Reference numeral 254 denotes a request unit that requests the STA specified by the STA specifying unit 251 to transmit a Self-CTS signal. Reference numeral 255 denotes a data transmission unit that transmits a data signal.

  Reference numeral 256 denotes an OBSS unit that performs processing related to the OBSS Scan conforming to the IEEE 802.11 series. Here, the OBSS (Overlapping Basic Service Set) Scan is a process for searching for another wireless network (in this case, the BSS 109 constructed by the AP 106) around the STA. A connection unit 257 performs processing for connecting the AP 101 and the STA.

  FIG. 3 shows the hardware configuration of the STA 102. Note that the STAs 103, 104, and 105 have the same hardware configuration. The control unit 301 includes a CPU and an MPU, and controls the entire STA 102 by executing a program stored in the storage unit 302. The storage unit 302 includes a ROM and a RAM, and stores various information such as programs executed by the control unit 301 and communication parameters. Various operations of the STA 102 described later are performed by the control unit 301 executing a program stored in the storage unit 302. The storage unit 302 stores not only memories such as ROM and RAM, but also flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, nonvolatile memory cards, DVDs, and the like. A medium may be used. The RF unit 303 includes an antenna and a circuit for transmitting and receiving wireless signals to and from other wireless communication devices (AP and STA).

  FIG. 4 is a sequence chart showing processing when the STA 103 connects to the AP 101 and executes OBSS Scan. The STAs 102, 104, and 105 execute the OBSS Scan in the same manner.

  First, the STA 103 transmits an authentication request (Authentication) to the AP 101 in order to participate in the BSS 108 (S401). When the AP 101 receives the authentication request, the connection unit 257 transmits the authentication response (Authentication) by permitting the authentication (S402). When the STA 103 receives the authentication response, the STA 103 transmits a connection request (Association Request) (S403). In the AP 101, the connection unit 257 transmits a connection response (Association Response) as a response to the connection request (Association Request) (S404). In this way, the STA 103 can participate (connect to the AP 101) in the BSS 108. Note that authentication in accordance with WPA or WPA2 may be performed after S404.

  An OBSS Scan Parameter Information Element (search parameter information element) compliant with the IEEE 802.11n standard is attached to the connection response (association response) in S404. The search parameter information element includes information related to the cycle for performing the OBSS Scan. Based on this information, the STA 103 periodically executes the OBSS Scan after participating in the BSS 108 (S405, S406).

  In OBSS Scan, all channels are scanned to search for surrounding BSSs (other wireless networks). Then, a BSS that uses the same channel as the channel used by the BSS 108 as a non-basic channel is found from the surrounding BSSs. Here, since BSS108 uses 36ch and 40ch, it searches for other BSSs using 36ch and 40ch as non-basic channels. Thereby, here, the AP 106 that constructs the BSS 109 is detected.

  After executing the OBSS Scan, the STA 103 notifies the AP 101 of the search result of the Scan using an OBSS Channel Report Management frame (OBSS report) compliant with IEEE802.11n (S407).

  FIG. 5 shows the frame structure of the OBSS report. Among the frame configurations, Number Of OBSS Channel describes the number of other BSSs detected by OBSS Scan. The OBSS Channel Report describes the number of basic channels used by other detected BSSs. Here, 1 is described in Number of OBSS Channel, and 48, which is a basic channel of BSS 109, is described in OBSS Channel Report.

  When the AP 101 receives the OBSS report notification from the STA 103, the OBSS unit 256 updates the OBSS notification STA management database shown in FIG. 6 (S408). That is, the OBSS report received from the STA 103 is analyzed, and the basic channel of another BSS that uses the same channel as the channel used by the BSS 108 as a non-basic channel and the STA that has notified the basic channel are stored.

  Here, since the STA 103 has notified 48 channels, which are the basic channels of the BSS 109, 1 is described as a flag in the items corresponding to the STA 103 and 48 channels in the database shown in FIG. On the other hand, since the STA 103 has not detected another BSS whose basic channel is a channel other than 48 ch, 0 is written in the corresponding item.

  Similarly, the STA 102, the STA 104, and the STA 105 execute the OBSS Scan. Here, the STA 102 cannot detect another BSS, and the STAs 104 and 105 detect the BSS 109. In this way, the database shown in FIG. 6 is constructed. According to this, it can be seen that the STAs 103, 104, and 105 detect other BSSs using 48 ch as a basic channel, and the STAs 102 do not detect other BSSs.

  When transmitting data to the STA 103, the AP 101 selects a STA that transmits a Self-CTS signal in order to prevent interference from other BSSs in the STA 103.

  FIG. 7 shows a flowchart in which the control unit 201 reads and implements a program stored in the storage unit 202 when selecting a STA that transmits a Self-CTS signal.

  First, the channel specifying unit 252 of the AP 101 determines a channel for transmitting the Self-CTS signal (S701). Here, the channel for transmitting the Self-CTS signal is a basic channel in another BSS that uses 36 ch or 40 ch as a non-basic channel used by the BSS 108. Here, it is determined that 48ch, which is a channel in which 1 is described in the database shown in FIG. 6, is a channel for transmitting a Self-CTS signal.

  Next, the STA specifying unit 251 specifies the STA that has notified 48ch as a result of the OBSS Scan (S702). Here, the STA 103, the STA 104, and the STA 105 are specified by referring to the database shown in FIG. Next, the STA specifying unit 251 confirms whether there is an STA other than the data transmission destination (here, the STA 103 which is the receiving apparatus) among the STAs specified in S702 (S703). If there is no STA other than the data transmission destination, the data transmission unit 255 transmits data to the STA 103 without transmitting the Self-CTS signal (S708). Here, the data transmission destination is the STA 103, and the STA 104 and the STA 105 exist as STAs other than the data transmission destination, so the process proceeds from S703 to S704.

  Next, the STA identifying unit 251 confirms whether there is a STA in Power Save (power saving mode) compliant with the IEEE802.11 series among the STAs confirmed in S703. If any of the confirmed STAs is not in Power Save, the process proceeds to S705. If any STA is in Power Save, the process proceeds to S706. Note that the STA that is in the normal mode may be detected in S704. In this case, if a STA that is in the normal mode is detected, the process proceeds to S705, and if a STA that is in the normal mode is not detected, the process proceeds to S706.

  Here, it is assumed that the STA 104 is in Power Save and the STA 105 is not in Power Save. If neither STA 104 nor STA 105 is in Power Save, any STA is selected and the processing from S705 onward is similarly performed.

  If there is an STA that is not in Power Save, the request unit 254 sends a Self-CTS signal transmission request to an STA that is not in Power Save (here, the STA 105) (S705). Here, the 48ch specified in S701 is requested to transmit a Self-CTS signal. After the request unit 254 requests the STA 105 to transmit the Self-CTS signal, the data transmission unit 255 transmits data to the STA 103 (S708).

  FIG. 8 shows a sequence chart representing the above processing.

  First, the AP 101 selects a STA that transmits a Self-CTS signal (S801). This corresponds to a series of processes of S701 to S704. When the AP 101 selects the STA that transmits the Self-CTS signal, the AP 101 transmits a transmission request for the Self-CTS signal to the selected STA, that is, the STA 105 (S802).

  The AP 101 transmits data to the STA 103 after requesting the transmission of the Self-CTS signal (S803). On the other hand, when the STA 105 receives the transmission request for the Self-CTS signal, the STA 105 transmits the Self-CTS signal to 48ch (S804). The Self-CTS signal transmitted to 48 ch is received by the AP 106 and STA 107 operating with 48 ch as a basic channel. Upon receiving the Self-CTS signal, the AP 106 and the STA 107 suppress data transmission for a predetermined period (NAV period) designated by the Self-CTS signal.

  Next, the case where both the STA 104 and the STA 105 are in power save will be described. In this case, any STA of STA 104 and STA 105 is woken up from the power save (S706), and a Self-CTS signal transmission request is sent to the STA that has woken up (S707). Thereafter, data is transmitted to the STA 103 (S708). The processing of S707 and S708 is the same as S705 and S708 when there is an STA in Power Save in S704.

  As described above, before the AP 101 transmits data to the STA 103, the Self-CTS signal is transmitted to the STA 104 or 105 existing in the common area (AP 101 and AP 106) of the BSS 108 and the BSS 109. Thereby, possibility that interference will arise in STA103 can be reduced.

  In addition, when there is an STA in the power save, the STA in the power save is prevented from being woken up as much as possible, so that it can be operated while maintaining the power saving operation of the STA in the power save.

  In the above-described embodiment, if there is no STA other than the transmission destination in S703, the AP transmits data without transmitting any Self-CTS to any communication device in the network. However, the present invention is not limited to this, and the STA that is the receiving apparatus may transmit the Self-CTS. Thereby, although a time loss occurs until data reception, the possibility of interference in the receiving apparatus can be further reduced.

<Embodiment 2>
In the second embodiment, a STA that transmits a Self-CTS signal is selected by a method different from that in the first embodiment. Note that a description of the same points as in the first embodiment will be omitted.

  FIG. 9 shows a flowchart realized by the control unit 201 reading the program stored in the storage unit 202 when the AP 101 selects the STA that transmits the Self-CTS signal in the second embodiment.

  First, a case where the AP 101 transmits data to the STA 102 will be described.

  The OBSS unit 256 first checks whether or not the data transmission destination STA (here, the STA 102) has detected another BSS by the OBSS Scan (S901). Here, referring to the database shown in FIG. 6, since STA102 describes 0 in all channels, it can be seen that STA102 has not detected another BSS.

  As described above, when the transmission destination STA has not detected another BSS, the data transmission unit 255 transmits data without requesting transmission of the Self-CTS signal (S906).

  Next, a case where the AP 101 transmits data to the STA 103 will be described.

  Similarly, the OBSS 256 confirms whether or not the transmission destination STA, that is, the STA 103 has detected another BSS by the OBSS Scan (S901). From the database shown in FIG. 6, since the STA 103 has 1 for 48 ch, it can be seen that another BSS is detected.

  As described above, when the transmission destination STA detects another BSS, the channel identifying unit 252 identifies the channel for transmitting the Self-CTS signal (S902). Since the processing of S902, S903, and S904 is the same as S701, S702, and S703 in the first embodiment, detailed description thereof is omitted. Here, 48 ch is specified as a channel for transmitting the Self-CTS signal. Also, STAs 103 to 105 are specified as STAs that have notified 48ch as a result of OBSS Scan.

  In S904, since the STA 104 and the STA 105 correspond to STAs other than the transmission destination here, the request unit 254 requests one of the STAs to transmit the Self-CTS signal (S905). Then, after the request unit 254 makes a transmission request for the Self-CTS signal, the data transmission unit 255 transmits data to the STA 103.

  As described above, when data is transmitted to an STA in which no other BSS is detected, that is, there is no possibility of causing interference with the other BSS, the transmission of the Self-CTS signal should be requested. Without sending data. Thereby, the transmission request | requirement of the Self-CTS signal at the time of data transmission and the overhead which transmits a Self-CTS signal can be reduced.

  In the above-described embodiment, if there is no STA other than the transmission destination in S904, the AP transmits data without transmitting any Self-CTS to any communication device in the network. However, the present invention is not limited to this, and the STA that is the receiving apparatus may transmit the Self-CTS. Thereby, although a time loss occurs until data reception, the possibility of interference in the receiving apparatus can be further reduced.

<Embodiment 3>
The present embodiment is different from the first embodiment in the selection process of the OBSS report notified by the STA, the OBSS notification STA management database managed by the AP 101, and the STA that transmits the Self-CTS signal in the AP 101. Note that description of points that are the same as those of the first embodiment is omitted.

  The system configuration in this embodiment is shown in FIG.

  The AP 1001 configures the BSS 1007 in a 20 MHz mode conforming to IEEE 802.11ac, and uses 36 ch as a basic channel. The STA 1002, the STA 1003, and the STA 1004 are STAs conforming to IEEE 802.11ac, and participate in the BSS 1007 formed by the AP 1001.

  The AP 1005 configures the BSS 1008 in an 80 MHz mode conforming to IEEE 802.11ac, and uses 48 ch as a basic channel and 44 ch, 40 ch, and 36 ch as non-basic channels. BSSID is 1.

  The AP 1006 configures the BSS 1009 in an 80 MHz mode conforming to IEEE 802.11ac, and uses 48 ch as a basic channel and 44 ch, 40 ch, and 36 ch as non-basic channels. The BSSID is 2.

  The AP 1001, the STA 1002, the STA 1003, and the STA 1004 are assumed to exist within the communication range of each other. Similarly, the STA 1002, the STA 1003, and the AP 1006 exist within the communication range of each other. Similarly, the STA 1004 and the AP 1005 exist within the communication range of each other. On the other hand, the other devices do not exist within the communication range of each other. For example, AP 1001 and AP 1006 and STA 1002 and AP 1005 cannot communicate with each other.

  In the present embodiment, when the AP 1001 transmits data to the STA 1002, the STA 1002 reduces interference from other BSSs.

  First, the STA 1002, the STA 1003, and the STA 1004 perform the OBSS Scan. The processing at this time is the same as the sequence chart shown in FIG. However, the frame configuration of the OBSS report transmitted in S407 is different.

  The frame structure of the OBSS report in this embodiment is shown in FIG. The OBSS BSSID describes the BSSID of another BSS that uses the same channel as the channel on which the BSS 1007 is operating as a non-basic channel. In addition, a channel used by the other BSS as a basic channel is described in the OBSS Channel. When a plurality of other BSSs are found, the OBSS BSSID and the OBSS Channel are stored as a pair for each BSSID.

  FIG. 12 shows an OBSS notification STA management database that is managed after the AP 1001 receives an OBSS report from the STA 1002, STA 1003, and STA 1004. In the database of this embodiment, the BSSID notified by each STA is stored in addition to the basic channels of other BSSs. Since the STA 1002 can detect the AP 1006 with 48 ch as a basic channel, the STA 1002 and 48 ch items store 2 as the BSSID of the AP 1006.

  Similarly, since the STA 1003 can detect the AP 1006, the BSSID 2 of the AP 1006 is stored. Since the STA 1004 can be detected by the AP 1005, 1 that is the BSSID of the STA 1004 is stored.

  FIG. 13 shows a flowchart of processing in which the AP 1001 selects a STA that transmits a Self-CTS signal.

  The channel specifying unit 252 specifies the channel for transmitting the Self-CTS signal based on the data transmission destination (that is, the STA 1002 that is the receiving apparatus) and the database shown in FIG. 12 (S1301). Here, since the channel and BSSID notified by the STA 1002 are 48ch and 2 from FIG. 12, the channel and BSSID are channel information for transmitting the Self-CTS signal.

  Next, the STA identification unit 251 identifies the STA that has notified the similar OBSS report based on the identified channel and BSSID (S1302). Here, STA 1002 and STA 1003, which are STAs that have notified channel 48ch and BSSID2, are specified.

  Then, the STA identification unit 251 confirms whether there is an STA other than the transmission destination (here, STA 1002) among the STAs identified in S1302 (S1303). If there is no STA other than the transmission destination at this time, the data transmission unit 255 transmits data to the STA 1002 without transmitting the Self-CTS signal (S1305). Here, since the STA 1003 exists as a STA other than the transmission destination, the process proceeds to S1304.

  Then, of the STAs identified in S1302, the request unit 254 requests Self-CTS signal transmission from STAs other than the transmission destination (here, STA1003) (S1304). In this Self-CTS signal transmission request, it is requested to transmit the Self-CTS signal to 48ch. After the request, the data transmission unit 255 transmits data to the STA 1002 (S1305).

  According to the present embodiment, the Self-CTS signal can be transmitted to other STAs existing in the communication range of other BSSs that are likely to cause interference in the STA of the data transmission destination. For example, the STA 1002 notifies the AP 1001 of the presence of the BSS 1009, while the BSS 1008 cannot be detected. Therefore, the Self-CTS signal is transmitted to other STAs existing within the communication range of the BSS 1009 that is likely to cause interference in the STA 1002. That is, in the receiving device, a device that can transmit a CTS signal to another network that is more likely to cause interference is determined, and the CTS signal is transmitted to the device, thereby reducing the possibility of interference in the receiving device. be able to.

  In Embodiments 1 to 3 described above, the Self-CTS signal is used as a signal for causing other devices to suppress data transmission. However, the present invention is not limited to this, and an RTS signal defined in the IEEE 802.11 series is used. You may do it. Note that RTS is an abbreviation for Request to Send.

101, 106, 1001, 1005, 1006 AP
102, 103, 104, 105, 107, 1002, 1003, 1004 STA
108, 109 BSS

Claims (7)

A transmitting device,
First determination means for determining a detection device that detects another wireless network that communicates using a second channel different from the first channel used for data transmission;
Whether or not a device different from the receiving device that is the transmission destination of the data is included in the detection device determined by the first determination unit when transmitting data to the receiving device in the first channel Second determination means for determining
When it is determined by the second determination means that a device different from the reception device is included in the detection device, the detection is performed so that a signal for suppressing transmission of data is transmitted in the second channel. Instruction means for instructing the device;
Transmission means for transmitting data on the first channel to the receiving device after the instruction by the instruction means;
When the second determination unit determines that a device different from the reception device is not included as the detection device, the transmission unit transmits data to the reception device without performing an instruction by the instruction unit. A transmission apparatus characterized by transmitting   2. The transmission apparatus according to claim 1, wherein the signal for suppressing transmission of data is a CTS signal or an RTS signal defined in the IEEE802.11 series.   The transmission device according to claim 1, wherein the second channel is a frequency channel used for communication of a wireless network detected by the detection device. When the first determination unit determines a plurality of the detection devices, the detection device not operating in the power saving mode for periodically reducing power consumption used for communication among the plurality of detection devices. A third determination means for determining;
The instructing unit instructs the detection apparatus that is determined not to operate in the power saving mode by the third determining unit to transmit a signal for suppressing transmission of the data. The transmission device according to any one of claims 1 to 3.   5. The transmission apparatus according to claim 1, wherein each of the first channel and the second channel is a frequency channel. 6. A method for controlling a transmitting device , comprising:
A first determination step of determining a detection device that detects a wireless network for communication using a second channel different from the first channel used when transmitting data;
A second determination step of determining whether the detection device includes a device different from the reception device to which the data is transmitted when transmitting data to the reception device in the first channel;
An instruction step for instructing the detection apparatus to transmit a signal for suppressing data transmission in the second channel when it is determined that the detection apparatus includes a device different from the reception device. When,
A transmission step of transmitting data on the first channel to the receiving device after the instruction;
When it is determined that a device different from the reception device is not included as the detection device, the control method includes transmitting data to the reception device without performing an instruction in the instruction process.   A program for causing a computer to operate as the transmission device according to any one of claims 1 to 5.

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