Base radio device and wireless communication method

Abstract

To provide a base wireless device and a wireless communication method for realizing rapid wireless communication.SOLUTION: A base wireless device 14 includes: a plurality of transmission buffers 46A and 46B that store a plurality of signals destined for different destinations; a transmission processing unit that transmits the signals stored in the plurality of transmission buffers in a predetermined order regardless of whether the transmission is successful or not, and thereby transmits the signal to each of a plurality of remote wireless devices 16A to 16C; and a storage control unit that overwrites, on the successfully transmitted transmission buffer, a signal DPC to be transmitted to the transmission destination 16C different from the transmission destination 16B of a signal DPB stored in the transmission buffer 46B other than the successfully transmitted transmission buffer among the plurality of transmission buffers, if the transmission of a signal DPA stored in the transmission buffer 46A is successful.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a base radio device and a radio communication method. [Background technology]

[0002] Patent Document 1 discloses an FA system in which a PC and a controller are connected via a field network, in which wireless messages are sent and received. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5497730 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional systems do not always achieve rapid wireless communication.

[0005] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0006] A base radio device according to one aspect of the present invention is a base radio device that transmits and receives signals to and from a plurality of remote radio devices, and includes a plurality of transmission buffers that store a plurality of signals to be transmitted to the plurality of remote radio devices, the signals having different destinations; a transmission processing unit that transmits signals to each of the plurality of remote radio devices by transmitting the signals stored in the plurality of transmission buffers in a predetermined order regardless of whether the transmission is successful; and a memory control unit that, when the transmission of a signal stored in the transmission buffer is successful, overwrites the transmission buffer that has been successfully transmitted with a signal that is to be transmitted to a destination different from the destination of the signal stored in the transmission buffer other than the transmission buffer that has been successfully transmitted.

[0007] A wireless communication method according to another aspect of the present invention is a wireless communication method for transmitting and receiving signals between a base wireless device and a plurality of remote wireless devices, comprising the steps of: storing a plurality of signals to be transmitted to the plurality of remote wireless devices in a plurality of transmission buffers, the plurality of signals having different destinations; transmitting a signal to each of the plurality of remote wireless devices by transmitting the signals stored in the plurality of transmission buffers in a predetermined order regardless of whether the transmission is successful; and, if the transmission of the signal stored in the transmission buffer is successful, overwriting the transmission buffer whose transmission was successful with a signal to be transmitted to a destination different from the destination of the signal stored in the transmission buffer other than the transmission buffer whose transmission was successful. [Effects of the Invention]

[0008] According to the present invention, a base radio device and a radio communication method that can realize rapid radio communication can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 illustrates a wireless communication system according to one embodiment. [Figure 2] 1 is a block diagram illustrating a wireless communication system according to one embodiment. [Figure 3] 10 is a flowchart illustrating an example of the operation of a base radio device according to one embodiment. [Figure 4] 10 is a flowchart illustrating an example of the operation of a base radio device according to one embodiment. [Figure 5] 10 is a time chart illustrating an example of the operation of a base radio device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [One embodiment] A base radio device and a radio communication method according to an embodiment will be described below with reference to Figures 1 to 5. Figure 1 is a diagram showing a radio communication system according to this embodiment. Figure 2 is a block diagram showing a radio communication system according to this embodiment.

[0011] As shown in FIG. 1 , a wireless communication system 10 according to this embodiment may include a computer 12, a base radio device 14, and a remote radio device 16. The wireless communication system 10 may include multiple base radio devices 14. One computer 12 and multiple base radio devices 14 may be connected via a field bus 17. Pairing may be performed in advance between the base radio device 14 and the remote radio device 16. A synchronous connection may be established between the paired base radio device 14 and the remote radio device 16. Multiple remote radio devices 16 may be synchronously connected to one base radio device 14. The base radio device 14 may transmit and receive signals to and from multiple remote radio devices 16. Multiple networks 43 may be configured by synchronously connecting multiple remote radio devices 16 to each base radio device 14.

[0012] The computer 12 may monitor and control industrial equipment. For example, a programmable logic controller (PLC) may be used as the computer 12, but is not limited to this. As shown in FIG. 2 , the computer 12 may include, for example, a calculation unit 18 and a storage unit 19.

[0013] The calculation unit 18 may include a processor such as a CPU (Central Processing Unit). That is, the calculation unit 18 may include a processing circuit. The calculation unit 18 is provided with a control unit 20. The calculation unit 18 may also include components other than the control unit 20, but for simplicity of explanation, components other than the control unit 20 will be omitted here. The control unit 20 is responsible for overall control of the computer 12. The control unit 20 may monitor and control industrial equipment. The control unit 20 may be realized by the calculation unit 18 executing a program stored in the memory unit 19. Note that at least a portion of the control unit 20 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a portion of the control unit 20 may be an electronic circuit including discrete devices.

[0014] The storage unit 19 may include a volatile memory (not shown) and a non-volatile memory (not shown). Examples of the volatile memory include a random access memory (RAM). Examples of the non-volatile memory include a read-only memory (ROM) and a flash memory. Data and the like may be stored in the volatile memory. Programs, tables, maps, and the like may be stored in the non-volatile memory. At least a part of the storage unit 19 may be included in a processor, an integrated circuit, or the like as described above. The storage unit 19 may further include a hard disk drive (HDD), a solid state drive (SSD), or the like.

[0015] The computer 12 is provided with an input / output interface 21 for realizing a fieldbus connection. The computer 12 can communicate with the base radio device 14 via the fieldbus 17.

[0016] The base radio device 14 includes, for example, a calculation unit 22 and a storage unit 23.

[0017] The calculation unit 22 may include a processor such as a CPU. That is, the calculation unit 22 may include a processing circuit. The calculation unit 22 may include a control unit 24, an acquisition unit 25, a transmission / reception processing unit 26, and a storage control unit 28. The calculation unit 22 may include other components, but for simplicity of explanation, these other components are omitted here. The control unit 24, the acquisition unit 25, the transmission / reception processing unit 26, and the storage control unit 28 may be realized by the calculation unit 22 executing a program stored in the storage unit 23. The control unit 24 is responsible for overall control of the base radio device 14. Note that at least a portion of the control unit 24, the acquisition unit 25, the transmission / reception processing unit 26, and the storage control unit 28 may be realized by an integrated circuit such as an ASIC or an FPGA. At least a portion of the control unit 24, the acquisition unit 25, the transmission / reception processing unit 26, and the storage control unit 28 may be electronic circuits including discrete devices.

[0018] The storage unit 23 may include a volatile memory (not shown) and a non-volatile memory (not shown). Examples of the volatile memory include RAM. Examples of the non-volatile memory include ROM and flash memory. Data and the like may be stored in the volatile memory. Programs, tables, maps, and the like may be stored in the non-volatile memory. At least a portion of the storage unit 23 may be provided in the processor, integrated circuit, etc. described above.

[0019] The base radio device 14 is provided with an input / output interface 29 for realizing a fieldbus connection. The base radio device 14 can be connected to the computer 12 by the fieldbus 17 as described above.

[0020] The base radio device 14 is provided with a communication unit 30 for performing wireless communication. The base radio device 14 can perform wireless communication with the remote radio device 16 using the communication unit 30.

[0021] The remote wireless device 16 may be provided in each of a plurality of devices 44 (see FIG. 1 ) included in the industrial facility. Such devices 44 may include, but are not limited to, sensors, valves, etc. The remote wireless device 16 may include, for example, a calculation unit 32 and a storage unit 34.

[0022] The calculation unit 32 may include a processor such as a CPU. That is, the calculation unit 32 may include a processing circuit. The calculation unit 32 may include a control unit 35 and a transmission / reception processing unit 37. The calculation unit 32 may include components other than these components, but for simplicity of explanation, these components will be omitted here. The control unit 35 and the transmission / reception processing unit 37 may be implemented by the calculation unit 32 executing a program stored in the storage unit 34. The control unit 35 is responsible for overall control of the remote radio device 16. Note that at least a portion of the control unit 35 and the transmission / reception processing unit 37 may be implemented by an integrated circuit such as an ASIC or FPGA. At least a portion of the control unit 35 and the transmission / reception processing unit 37 may be implemented by an electronic circuit including discrete devices.

[0023] The storage unit 34 may include a volatile memory (not shown) and a non-volatile memory (not shown). Examples of the volatile memory include RAM. Examples of the non-volatile memory include ROM and flash memory. Data and the like may be stored in the volatile memory. Programs, tables, maps, and the like may be stored in the non-volatile memory. At least a portion of the storage unit 34 may be provided in the processor, integrated circuit, etc. described above.

[0024] The remote radio device 16 is provided with a communication unit 42 for performing wireless communication. The remote radio device 16 can perform wireless communication with the base radio device 14 using the communication unit 42.

[0025] As described above, the base radio apparatus 14 may be provided with the transmission / reception processing unit 26. The transmission / reception processing unit 26 may be provided with a transmission processing unit 26A and a reception processing unit 26B. The transmission processing unit 26A processes signal transmission. The reception processing unit 26B processes signal reception. As described above, the remote radio apparatus 16 may be provided with the transmission / reception processing unit 37. The transmission / reception processing unit 26 and the transmission / reception processing unit 37 control the processing of signal transmission and reception between the remote radio apparatus 16 and the base radio apparatus 14. Frequency hopping communication may be performed between the base radio apparatus 14 and the remote radio apparatus 16 that are synchronously connected. That is, signals may be transmitted and received between the base radio apparatus 14 and the remote radio apparatus 16 that are synchronously connected by switching the hopping frequency at a predetermined hopping period Tfh(n) (see FIG. 5 ).

[0026] As described above, the base radio device 14 may be provided with an acquisition unit 25. The acquisition unit 25 may sequentially acquire signals (data packets) supplied from the computer 12. The signals supplied from the computer 12 may include information indicating the remote radio device 16 to which the signals are to be sent.

[0027] As described above, the base radio device 14 may be provided with a storage unit 23. The storage unit 23 may be provided with a standby buffer 45. The acquisition unit 25 sequentially stores a plurality of signals supplied from the computer 12 in the standby buffer 45. The standby buffer 45 may store the signals acquired by the acquisition unit 25 in chronological order.

[0028] The storage unit 23 may further include multiple transmit buffers 46A, 46B. The transmit buffers 46A, 46B may temporarily store signals to be transmitted to the remote radio device 16. When describing a buffer in general, the reference symbol 46 is used, and when describing an individual buffer, the reference symbols 46A, 46B are used. The multiple transmit buffers 46 may store multiple signals to be transmitted to the multiple remote radio devices 16. The multiple transmit buffers 46 may store multiple signals having different destinations. That is, when a signal is stored in the transmit buffer 46B, a signal to be transmitted to a destination different from the destination of the signal stored in the transmit buffer 46B is stored in the transmit buffer 46A. When a signal is stored in the transmit buffer 46A, a signal to be transmitted to a destination different from the destination of the signal stored in the transmit buffer 46A is stored in the transmit buffer 46B.

[0029] Regardless of whether the transmission is successful or not, the transmission processing unit 26A transmits the signals stored in the plurality of transmission buffers 46 in a predetermined order. The transmission processing unit 26A transmits the signals stored in the plurality of transmission buffers 46 in a predetermined order, thereby transmitting the signals to each of the plurality of remote radio devices 16.

[0030] When the remote radio device 16 receives a signal from the base radio device 14, the remote radio device 16 transmits a reception completion notification to the base radio device 14 indicating that the signal has been received. The transmission of the signal from the base radio device 14 to the remote radio device 16 and the transmission of the reception completion notification from the remote radio device 16 to the base radio device 14 are performed within one hopping period. If the reception processing unit 26B receives a reception completion notification within the hopping period in which the signal was transmitted from the base radio device 14 to the remote radio device 16, the control unit 24 determines that the transmission of the signal to the remote radio device 16 was successful. If the reception processing unit 26B does not receive a reception completion notification within the hopping period in which the signal was transmitted from the base radio device 14 to the remote radio device 16, the control unit 24 determines that the transmission of the signal to the remote radio device 16 failed.

[0031] As described above, the base radio device 14 may be provided with a storage control unit 28. The storage control unit 28 stores signals to be transmitted to the remote radio device 16 in the transmission buffer 46. The storage control unit 28 stores multiple signals, each with a different destination, in the multiple transmission buffers 46. If the transmission of a signal stored in a transmission buffer 46 is successful, the storage control unit 28 performs the following process. That is, in this case, the storage control unit 28 overwrites the successfully transmitted transmission buffer 46 with a signal that is to be transmitted to a destination different from the destination of the signal stored in a transmission buffer 46 other than the successfully transmitted transmission buffer 46. For example, if the transmission of a signal stored in transmission buffer 46A is successful, the storage control unit 28 performs the following control. That is, in this case, the storage control unit 28 overwrites the transmission buffer 46A with a signal that is to be transmitted to a destination different from the destination of the signal stored in transmission buffer 46B other than the transmission buffer 46A among the multiple transmission buffers 46. If the transmission of the signal stored in transmission buffer 46B is successful, the storage control unit 28 performs the following control. In other words, in such a case, the storage control unit 28 overwrites the transmission buffer 46B with a signal to be transmitted to a destination different from the destination of the signal stored in the transmission buffer 46A other than the transmission buffer 46B among the multiple transmission buffers 46.

[0032] The storage control unit 28 stores in the transmission buffer 46 a signal selected from the signals stored in the standby buffer 45 according to its priority. For example, the older the signal was acquired, the higher the priority may be. That is, the priority of a signal acquired by the acquisition unit 25 at an older time may be higher than the priority of a signal acquired by the acquisition unit 25 at a more recent time.

[0033] The operation of the base radio device 14 according to this embodiment will now be described with reference to Figure 3. Figure 3 is a flow chart showing an example of the operation of the base radio device according to this embodiment. The basic operations relating to the transmission of signals are shown in Figure 3.

[0034] In step S1, the storage control unit 28 provided in the base radio device 14 stores a plurality of signals having different destinations in a plurality of transmission buffers 46.

[0035] In step S2, the transmission processing unit 26A provided in the base radio device 14 transmits, in a predetermined order, the signals stored in the plurality of transmission buffers 46. The process shown in Fig. 3 can be repeated.

[0036] The operation of the base radio device 14 according to this embodiment will be explained below with reference to Fig. 4. Fig. 4 is a flowchart showing an example of the operation of the base radio device according to this embodiment. Fig. 4 shows an example of the operation depending on whether the transmission of the signal stored in the transmission buffer 46 is successful or not.

[0037] In step S11, the control unit 24 determines whether the transmission of the signal stored in the transmission buffer 46A was successful. If the transmission of the signal stored in the transmission buffer 46A was successful (YES in step S11), the process proceeds to step S12. If the transmission of the signal stored in the transmission buffer 46A was unsuccessful (NO in step S11), the process proceeds to step S13.

[0038] In step S12, the storage control unit 28 overwrites the transmission buffer 46A with a new signal. That is, the storage control unit 28 overwrites the transmission buffer 46A with a signal to be transmitted to a destination different from the destination of the signal stored in the transmission buffer 46B. When step S12 is completed, the process proceeds to step S13.

[0039] In step S13, the control unit 24 determines whether the transmission of the signal stored in the transmission buffer 46B was successful. If the transmission of the signal stored in the transmission buffer 46B was successful (YES in step S13), the process proceeds to step S14. If the transmission of the signal stored in the transmission buffer 46B was unsuccessful (NO in step S13), the process shown in FIG. 4 is completed.

[0040] In step S14, the storage control unit 28 overwrites the transmission buffer 46B with a new signal. That is, the storage control unit 28 overwrites the transmission buffer 46B with a signal to be transmitted to a destination different from the destination of the signal stored in the transmission buffer 46A. When step S14 is completed, the processing shown in Fig. 4 is completed. The processing shown in Fig. 4 can be performed repeatedly.

[0041] The operation of the base radio device 14 according to this embodiment will be explained below with reference to Fig. 5. Fig. 5 is a time chart showing an example of the operation of the base radio device according to this embodiment.

[0042] 5 shows an example in which signals (data packets) DPA to DPC are stored in the waiting buffer 45. The signal DPA is a signal transmitted to remote radio device 16A of the multiple remote radio devices 16. The signal DPB is a signal transmitted to remote radio device 16B of the multiple remote radio devices 16. The signal DPC is a signal transmitted to remote radio device 16C of the multiple remote radio devices 16. When describing signals in general, the symbol DP is used, and when describing individual signals, the symbols DPA to DPC are used.

[0043] The transmission buffer 46 stores a signal selected according to priority from among the signals stored in the standby buffer 45. The time when the signal DPA was acquired by the acquisition unit 25 is earlier than the time when the signal DPB was acquired by the acquisition unit 25. The time when the signal DPB was acquired by the acquisition unit 25 is earlier than the time when the signal DPC was acquired by the acquisition unit 25. Therefore, the priority of the signal DPA is higher than the priority of the signal DPB. Also, the priority of the signal DPB is higher than the priority of the signal DPC. Therefore, the storage control unit 28 stores the signal DPA in the transmission buffer 46A. Also, the storage control unit 28 stores the signal DP in the transmission buffer 46B. B Since the number of transmit buffers 46 is two, the number of signals that can be stored simultaneously in the multiple transmit buffers 46 is two. For this reason, the signal DPC is not stored in the transmit buffer 46 at this stage.

[0044] The signals DP stored in the multiple transmission buffers 46 are transmitted in a predetermined order. In the hopping period Tfh(1), the signal DPA stored in the transmission buffer 46A is transmitted. Specifically, the signal DPA is transmitted from the base radio device 14 to the remote radio device 16A. An example in which the transmission of the signal DPA fails in the hopping period Tfh(1) is shown in FIG. 5.

[0045] In the hopping period Tfh(2) following the hopping period Tfh(1), the signal DPB stored in the transmission buffer 46B is transmitted. Specifically, the signal DPB is transmitted from the base radio device 14 to the remote radio device 16B. An example in which the transmission of the signal DPB fails in the hopping period Tfh(2) is shown in FIG. 5.

[0046] In the hopping period Tfh(3) next to the hopping period Tfh(2), the signal DPA stored in the transmission buffer 46A is transmitted. Specifically, the signal DPA is transmitted from the base radio device 14 to the remote radio device 16A. FIG. 5 shows an example in which the transmission of the signal DPA is successful in the hopping period Tfh(3). If the transmission of the signal DPA stored in the transmission buffer 46A is successful, the signal DPC is overwritten in the transmission buffer 46A.

[0047] In the hopping period Tfh(4) following the hopping period Tfh(3), the signal DPB stored in the transmission buffer 46B is transmitted. Specifically, the signal DPB is transmitted from the base radio device 14 to the remote radio device 16B. An example in which the transmission of the signal DPB fails in the hopping period Tfh(4) is shown in FIG. 5.

[0048] In the hopping period Tfh(5) next to the hopping period Tfh(4), the signal DPC stored in the transmission buffer 46A is transmitted. Specifically, the signal DPC is transmitted from the base radio device 14 to the remote radio device 16C. An example in which the transmission of the signal DPC is successful in the hopping period Tfh(5) is shown in FIG. 5.

[0049] In the hopping period Tfh(6) following the hopping period Tfh(5), the signal DPB stored in the transmission buffer 46B is transmitted. Specifically, the signal DPB is transmitted from the base radio device 14 to the remote radio device 16B. FIG. 5 shows an example in which the transmission of the signal DPB is successful in the hopping period Tfh(6). In this way, the transmission of the signal DP can be performed sequentially.

[0050] If there is only one transmission buffer 46, the signal DPC cannot be transmitted until the transmission of the signal DPB is successful or until the number of retries for transmitting the signal DPB has reached a predetermined number. In contrast, in this embodiment, multiple transmission buffers 46 are provided, so the signal DPC can be transmitted even if the transmission of the signal DPB has failed. Therefore, as shown in FIG. 5, the signal DPC can be transmitted successfully before the transmission of the signal DPB is successful. In this way, according to this embodiment, rapid wireless communication can be achieved.

[0051] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

[0052] For example, in the above embodiment, the number of transmission buffers 46 is two, but the present invention is not limited to this. The number of transmission buffers 46 may be three or more.

[0053] The above embodiment can be summarized as follows.

[0054] The base radio device (14) is a base radio device that transmits and receives signals to and from a plurality of remote radio devices (16), and includes: a plurality of transmission buffers (46A, 46B) that store a plurality of signals to be transmitted to the plurality of remote radio devices, the plurality of signals having different transmission destinations; a transmission processing unit (26A) that transmits a signal to each of the plurality of remote radio devices by transmitting the signals stored in the plurality of transmission buffers in a predetermined order regardless of whether the transmission is successful; and a storage control unit (28) that, when the transmission of a signal (DPA) stored in the transmission buffer (46A) is successful, overwrites the transmission buffer (46A) that has been successfully transmitted with a signal (DPC) that is to be transmitted to a destination (16C) different from the destination (16B) of a signal (DPB) stored in a transmission buffer (46B) other than the transmission buffer (46A) that has been successfully transmitted. If there is only one transmission buffer, another signal cannot be transmitted until the transmission of one signal is successful or until the number of retries for the transmission of one signal has reached a predetermined number. In contrast, in this configuration, multiple transmission buffers are provided, so that even if the transmission of one signal fails, the transmission of another signal can be performed. Therefore, the transmission of another signal can be successful before the transmission of one signal is successful. With this configuration, rapid wireless communication can be achieved.

[0055] The system may further include a standby buffer (45) for storing a plurality of signals supplied from a computer (12) connected via a field bus (17), and the storage control unit may store in the transmission buffer a signal selected from the signals stored in the standby buffer according to priority. With this configuration, signals can be transmitted accurately.

[0056] The wireless communication method is a wireless communication method for transmitting and receiving signals between a base wireless device and multiple remote wireless devices, and includes the steps of: storing multiple signals to be transmitted to the multiple remote wireless devices in multiple transmission buffers (S1); transmitting signals to each of the multiple remote wireless devices by transmitting the signals stored in the multiple transmission buffers in a predetermined order regardless of whether the transmission is successful; and, if the transmission of the signal stored in the transmission buffer is successful, overwriting the transmission buffer that was successfully transmitted with a signal that is to be transmitted to a destination different from the destination of the signal stored in the transmission buffer other than the transmission buffer that was successfully transmitted (S11 to S14). [Explanation of symbols]

[0057] 10: Wireless communication system 12: Computer 14: Base radio equipment 16, 16A-16C: Remote radio equipment 17: Field bus 18, 22, 32: Calculation unit 19, 23, 34: Memory unit 20, 24, 35: Control unit 21, 29: Input / output interface 25: Acquisition unit 26, 37: Transmission and reception processing section 26A: Transmission processing section 26B: Reception processing unit 28: Storage control unit 30, 42: Communication unit 43: Network 44: Equipment 45: Waiting buffer 46A, 46B: Transmit buffer DPA~DPC: Signal Tfh(1)~Tfh(6), Tfh(n): hopping period

Claims

1. A base radio device that transmits and receives signals to and from a plurality of remote radio devices, a plurality of transmit buffers for storing a plurality of signals to be transmitted to a plurality of said remote radio devices, the signals having different destinations; a transmission processing unit that transmits signals stored in the plurality of transmission buffers in a predetermined order, regardless of whether the transmission is successful, to each of the plurality of remote wireless devices; a storage control unit that, when the transmission of the signal stored in the transmission buffer is successful, overwrites the transmission buffer that has been successfully transmitted with a signal that is to be transmitted to a destination different from the destination of the signal stored in the transmission buffer other than the transmission buffer that has been successfully transmitted among the plurality of transmission buffers; a waiting buffer for storing a plurality of signals supplied from a computer connected by a field bus; Equipped with The storage control unit stores in the transmission buffer a signal selected from the signals stored in the waiting buffer according to priority.

2. A wireless communication method for transmitting and receiving signals between a base wireless device and a plurality of remote wireless devices, comprising: a storing step of storing a plurality of signals to be transmitted to a plurality of said remote radio devices, the plurality of signals having different destinations, in a plurality of transmit buffers; transmitting signals to each of the plurality of remote wireless devices by transmitting the signals stored in the plurality of transmit buffers in a predetermined order, regardless of whether the transmission is successful; When the transmission of the signal stored in the transmission buffer is successful, overwriting the transmission buffer from which the transmission was successful with a signal to be transmitted to a destination different from the destination of the signal stored in the transmission buffer other than the transmission buffer from which the transmission was successful; and The method further includes the step of storing a plurality of signals provided from a computer connected by the field bus in a waiting buffer; In the storing step, a signal selected according to priority from the signals stored in the waiting buffer is stored in the transmission buffer.

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