JP2007151025A - Data collection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data collection system in which data are collected by radio between a master unit and a plurality of slave units and the time required for communication is shortened compatibly with prevention of interference by exchanging data only with slave units preceding and following in a transmission order using a preset channel. <P>SOLUTION: In a data collection system 1 of the present invention, a master unit P collects data from a plurality of slave units Cn by radio, a transmission order from a first slave unit C1 to a final slave unit CM is preset to the plurality of slave units Cn, each of the slave units Cn exchanges data only with slave units Cn-1 and Cn+1 preceding and following in the transmission order using a preset channel, respectively and the master unit P exchanges data only with the first slave unit C1 using a preset channel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data collection system that wirelessly collects data between a parent device and a plurality of child devices, and more particularly to a data collection system that achieves both a reduction in communication time and prevention of interference.

  In a data collection system that collects data between a single master unit and multiple slave units, data is conventionally collected by polling control by the master unit, and a unique address is assigned to the slave unit. When control data is received from the master unit, processing is executed based on the control data only when the destination address matches its own address, and no processing is executed unless the destination address matches. Was configured.

  When such a data collection system is installed in an existing facility, if the communication between devices is made wireless, it is possible to install it without cost because the construction of the communication line becomes unnecessary only by the power construction. .

As a conventional example of such a wireless communication network system, for example, Japanese Patent Laid-Open No. 2003-8626 (Patent Document 4) is known.
JP 2003-8626 A

  However, when all the slave units exist within the radio wave reach of the master unit, if each slave unit transmits without permission, even if each slave unit senses and transmits the carrier, The hidden terminal problem that cannot be received occurs. In order to avoid this, there is a method in which the master unit inquires each slave unit and only the specified slave unit responds, but all the slave units must be installed within the radio wave reach of the master unit. You can limit the range.

  In addition, there is a method to transmit information by installing wireless communication with at least the neighboring handset and communicating with the neighboring handset in order, but in order to avoid interference (hidden terminal problem) Since only one unit can transmit radio waves at a certain moment, the time required for communication as a system greatly increases.

  Furthermore, when 1: N multi-hop communication is used wirelessly, commands from the parent device can be transmitted to the child device in a time efficient manner, but the number of child devices that can communicate depends on the installation position of the child device. In contrast, the hidden terminal problem remains, which is not appropriate for the control system that collects the data of the handset.

  In addition, if the master unit controls the multi-hop to 1: 1 with the system configuration as shown in FIG. 28 and the sequence as shown in FIG. As can be seen from the sequence diagram, when a data request is made to any of the slave units, communication cannot be made to other slave units until it returns as a data response, resulting in an increase in communication time.

  An object of the present invention is to achieve both reduction in communication time and prevention of interference (hidden terminal problem) in a data collection system in which a parent device collects data from a plurality of child devices.

  In order to solve the above-described problem, a data collection system according to the present invention is a data collection system in which a parent device wirelessly collects data from a plurality of child devices, and the plurality of child devices includes a first child device. A transmission order is set in advance from the terminal to the terminal slave, and each slave transmits / receives data only to the slaves whose transmission order is different by using a channel preset according to the transfer direction. The device transmits / receives data only to / from the first child device using a preset channel.

  In the data collection system according to the present invention, a transmission order is preset for a plurality of slave units from the first slave unit to the terminal slave unit, and each slave unit uses a preset channel according to the transfer direction. Since data is transmitted / received only to the preceding and following slave units, and the master unit transmits / receives data only to the first slave unit using a preset channel, it is possible to prevent interference (hidden terminal problem). Communication time can also be greatly reduced.

  Embodiments of a data collection system according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration of a data collection system according to the present embodiment. As shown in FIG. 1, the data collection system 1 of the present embodiment is composed of a parent device P and a plurality of child devices C1 to CM.

  Here, the plurality of slave units C1 to CM have a transmission order set in advance from the first slave unit C1 to the terminal slave unit CM, and perform data transmission / reception only with the slave units whose transmission order is around. For example, the first child device C1 communicates only with the parent device P and the second child device C2, and the child device Cn located in the middle communicates only with the child devices Cn-1 and Cn + 1 whose transmission order is changed. The terminal slave CM communicates only with the slave CM-1.

  The base unit P transmits / receives data only to / from the first handset C1, and the base unit P sends a “data request” to the handset C1 in order to collect the information obtained by each handset C1 to CM. When transmitted, each of the slave devices C1 to CM transfers this “data request”. Then, each of the slave units C1 to CM that has received the “data request” returns a “data response”, and the master unit P receives this “data response” by the transfer of each slave unit, and each of the slave units C1 to CM receives the “data response”. Information is collected.

  In the data collection system 1 of this embodiment having such a configuration, the channels to be used and their order are determined by the procedure at the time of system startup, and the parent device P and each of the child devices C1 to CM recognize the contents.

  In addition, as a communication method used in the communication between the parent device P and the child devices C1 to CM described above, there are a plurality of wireless channels, the wireless channel can be switched, and the time is short. That's fine. For example, IEEE802.15.4. Further, wireless communication is limited to 1: 1.

  Next, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram illustrating the configuration of the data collection system according to the present embodiment.

  As shown in FIG. 2, the data collection system 21 of the present embodiment is composed of a parent device P and a plurality of child devices, here ten child devices C1 to C10, and the parent device P has ten child devices. This is a system for periodically collecting information generated or obtained in C1 to C10 within a predetermined time T.

  In this system, for example, those standardized by IEEE 802.15.4 are used for the PHY layer and the MAC layer as the wireless communication. That is, in 2.4 GHz band, 16 channels at 5 MHZ intervals, a maximum data transfer rate of 250 kbps, and a radio wave reach range of 10 m to 30 m. The radio channel switching time is 30 ms or less.

In addition, a peer-to-peer topology (one-to-one connection) is used, and a beacon function is not used. The case of not using ACK (Acknowledgement) for reception confirmation will be described in the present embodiment, but it may be used.

  Here, the frame format of the packet used in the data collection system 21 of the present embodiment is shown in FIG. As shown in FIG. 3, the packet used in the data collection system 21 of this embodiment has a configuration in which the MAC layer is added to the PHY layer, and the packet is included in the destination address DA and the source address SA. Destination address and source address are recorded. The transmission source address at which data is first transmitted is recorded in the SAO of the DATA part. In the DATA part, an area such as a command type area COM for recording “data request” and “data response” as commands, and an SAO for recording a transmission source address at which data is first transmitted (created). It is included.

  Assume that the packet transfer time (including the waiting time after transmission and the waiting time after reception) is the same for the base unit and the handset, and that each radio channel has no noise reduction and can communicate without retransmission.

  The parent device P and each of the child devices C1 to C10 each have a unique address, and are manually set by a 5-bit dip switch provided for each. For example, the address of the parent device is 10000 (binary), the address of the child device C1 is 00001 (binary), the child device C2 is 0010 (binary), and the address of the child device C10 at the end farthest from the parent device is 01010. (Binary) is set.

  Accordingly, each of the slave units C1 to C10 can recognize the number of the slave unit as viewed from the master unit based on the value of the dip switch, and also recognizes the addresses of the slave units adjacent to itself. be able to.

  In addition, the channels used are ten types of 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20, and are used in the following order.

CH (0) = 11
CH (i) = CH (1), CH (2), CH (3), CH (4), CH (5), CH (6), CH (7), CH (8), CH (9) ( i = 1-9)
= 12, 13, 14, 15, 16, 17, 18, 19, 20
In each of the slave units C1 to C10, a communication partner and a wireless channel used for the communication are determined in advance, and the same wireless channel is not used. For example, the parent device P and the child device C1 transmit and receive via the channel CH (0), that is, the channel 11, and the child device C1 and the child device C2 transmit and receive via CH (1), that is, the channel 12. In short, the slave unit Cn transmits / receives to / from the slave unit Cn−1 via the channel CH (n−1) and transmits / receives to / from the slave unit Cn + 1 via the channel CH (n).

  Next, data collection processing by the data collection system 21 of this embodiment will be described based on the sequence diagram of FIG. 4 and the flowcharts of FIGS. 5 and 6. 4 is a sequence diagram of data collection processing performed between the parent device P and the child devices C1 to C10, FIG. 5 is a flowchart of data collection processing in the parent device P, and FIG. 6 is a data collection processing in the child devices C1 to C10. It is a flowchart of.

  First, the base unit P performs a startup process for performing the data collection process, sets i to 0 (S501), and performs other processes necessary for performing the data collection process (S502). .

  On the other hand, each of the slave units C1 to C10 also executes the activation process, sets i to a preset number N from itself (S601), and waits for reception on the channel CH (n-1) (S602).

  Next, for the purpose of collecting the information generated or obtained in each of the slave units C1 to C10, that is, the data, the master unit P sends a data request to each of the slave units C1 to C10 to the master unit P. Is transmitted to the first handset C1 through the preset channel CH (0) (S100-1, S503).

  Since the child device C1 is waiting for reception on the channel CH (0), when receiving a “data request” addressed to its own address (S603), the received data request is a data request to all the child devices. (S604), if it is not a data request for all the slave units, another process is performed (S605), and the process returns to step S602 to repeat the above-described process.

  If it is a data request to all the slave units, if it is not the terminal slave unit C10 (S606), the source address SA is rewritten to its own address (S607), and the destination address DA is changed to the terminal side. The address of the child device Cn + 1, that is, the child device C2 is rewritten (S608), and the data request is transferred to the child device 2 through the channel CH (n), that is, CH (1) (S100-2, S609).

The child device C1 to which the data request has been transferred prepares information detected by the sensor or the like, that is, data from itself (S610), and the channel CH (n-1) as the “data response”, and CH (0) in the child device C1. To the base unit P (S101-1, S611).

  On the other hand, after transmitting the data request, base unit P waits (S504), sets i to i + 1 (S505), and waits for reception on channel CH (0) (S506).

  When a packet is received from the child device C1 through the channel CH (0), it is determined whether or not the destination is the own address (S507). If the destination is not the own address, the process returns to step S506 and continues to wait for reception. Is the self address, it is determined whether or not the command type COM of the received signal is “data response” (S508).

  If the command type COM is not “data response”, another process is performed (S509), and the process returns to step S502. If it is “data response”, the received data is processed (S510). It is determined whether or not the “data response” is a data response from the terminal unit C10 at the end (S511).

  If it is not a data response from the terminal handset C10, the process returns to step S504 to continue receiving “data responses” from other handset.

  On the other hand, the child device C1 that has transmitted the data response to the parent device P in step S611 sets i to i + 1 (S612) and waits for reception on the channel CH (1) (S613).

  When a “data response” packet is received from the child device C2 (S102-1), it is determined whether or not the destination is the own address (S614). If the signal is not addressed to the own address, the process returns to step S613. Subsequently, the channel CH (1) is in a waiting state for reception, and if it is a “data response” addressed to its own address, the received “data response” packet is transmitted to the parent device P on the channel CH (0) (S102). -2, S615).

  At this time, the child device C1 rewrites the transmission source address SA to its own address and rewrites the transmission destination address DA to the address of the parent device P for transmission. However, since the data contents are not rewritten, the data of the child device C2 is recorded as the data contents.

  When the “data response” sent from the child device C2 is transmitted to the parent device P, the child device C1 determines whether i has reached the maximum number of child devices M, here 10 (S616). If i is not 10, the process returns to step S612 to wait for reception, and if i is 10, the process returns to step S602.

  When the processing similar to the processing performed in the above-described child device C1 is executed in each of the child devices C2 to C9 and a data request is transmitted to the terminal child device C10 (S100-10, S606), The slave C10 waits (S617), and then prepares information detected by a sensor, that is, data from itself (S618). When the prepared data is transmitted as a “data response” to channel C9 via channel CH (9) (S110-1, S619), the process returns to step S602 and the above-described processing is repeated.

  When the “data response” packet is transmitted in the slave unit C10 in this way, the same processing as that performed in the slave unit C1 is executed in each of the slave units C2 to C9, and “ The “data response” packet is transferred to the parent device P.

  When the base unit P determines that the “data response” packet received in step S511 is a packet (S110-10) from the terminal unit C10, the current data collection process is terminated, and the process proceeds to step S502. The process described above is repeated to return and collect new data.

  As described above, in the data collection system 21 according to the present embodiment, the transmission order is set in advance from the first slave unit C1 to the terminal slave unit C10 in the plurality of slave units C1 to C10, Data is transmitted / received only to the slave units whose transmission order is changed using a preset channel, and the master unit P is configured to transmit / receive data only to the first slave unit C1 using a preset channel. Therefore, after transferring the data request, the slave unit Cn only needs to execute a simple procedure of repeating transmission on the channel CH (n-1) and reception on the channel CH (n), and the number of slave units If only the channel is used, interference (hidden terminal problem) can be surely prevented, and the communication time can be greatly shortened.

  Next, a second embodiment of the present invention will be described with reference to the drawings. However, the configuration of the data collection system according to the present embodiment is the same as that of the first embodiment shown in FIG.

  In the system of the present embodiment, as in the first embodiment, for example, wireless communication that is standardized by IEEE 802.15.4 is used for the PHY layer and the MAC layer. This standard uses the 2.4 GHz band as described above, and the band overlaps with the wireless LAN. However, the communication of the present embodiment is intermittent data transmission, and since the packet length of the PHY layer is as short as 114 bytes at the maximum, there is very little possibility of interference.

  Similarly to the first embodiment, a peer-to-peer topology (one-to-one connection) is used and the beacon function is not used, but an ACK for reception confirmation is returned after data reception.

  Further, the frame format of the packet used in the data collection system of the present embodiment is the same as that of the first embodiment shown in FIG. As the channels to be used, 11 types of 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 21 are used in the following order.

CH (0) = 11
CH (i) = CH (1), CH (2), CH (3), CH (4), CH (5), CH (6), CH (7), CH (8), CH (9), CH (10), (i = 1 to 10)
= 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
Next, data collection processing by the data collection system of this embodiment will be described with reference to the sequence diagram of FIG. 7 and the flowcharts of FIGS. 7 is a sequence diagram of data collection processing performed between the parent device P and the child devices C1 to C10, FIG. 8 is a flowchart of data collection processing in the parent device P, and FIG. 9 is a data collection processing in the child devices C1 to C10. It is a flowchart of.

  First, the master unit performs a startup process for performing a data collection process, sets i to 0 (S801), and performs other processes necessary for performing the data collection process (S802).

  On the other hand, each of the slave units C1 to C10 also executes a start-up process, sets i to the preset number N (S901), and waits for reception on the channel CH (0) (S902).

  Next, for the purpose of collecting information generated or obtained in each slave unit, that is, data, the master unit P sends a “data request” to the master unit P so that each slave unit sends data to the first slave unit. It transmits on the channel CH (0) preset in the machine C1 (S100-1, S803).

  Since the child device C1 is waiting for reception on the channel CH (0), when receiving the “data request” addressed to its own address (S903), the child device C1 takes in the packet and transmits an acknowledgment ACK to the parent device P (S904). ).

  Base unit P determines whether or not reception confirmation ACK has been received (S804), and if not received, determines whether or not to retransmit (S805). If not, returns to step S802 and returns to step S802. When the above processing is repeated and retransmitted, after waiting (S806), the process returns to step S803 to retransmit the data request.

  On the other hand, the slave unit C1 determines whether or not the received data request is a data request to all the slave units (S905). If it is not a data request for all the slave units, another process is performed (S906), step Returning to S902, the above-described processing is repeated.

  If it is a data request to all the slave units, if it is not the terminal slave unit C10 (S907), the source address SA is rewritten to its own address (S908), and the destination address DA is changed to the terminal side. The address is rewritten to the address of the child device, that is, the child device C2 (S909), and the data request is transferred to the child device C2 through the channel CH (0) (S100-2, FIG. 9: S910).

  The child device C1 having transferred the data request determines whether or not the reception confirmation ACK from the child device C2 has been received (S911). When the child device C1 receives the information, the child device C1 detects information detected by a sensor or the like, that is, data from itself. Is prepared (S912), and is transmitted to the parent device P as a "data response" on the preset channel CH (1) (S101-1, S913).

  On the other hand, when receiving the acknowledgment ACK from the child device C1 in step S804, the parent device P waits (S807), sets i to i + 1 (S808), and changes the channel from channel CH (0) to channel CH ( Switching to 1) and waiting for reception (S809).

  When a signal is received from the slave unit C1 through the channel CH (1), it is determined whether or not the destination is the own address (S810). If the destination is not the own address, the process returns to step S809 and continues to wait for reception. Is the own address, a reception confirmation ACK is transmitted to the child device C1 (S811), and it is determined whether or not the command type COM of the received packet is “data response” (S812).

  If the command type COM is not “data response”, another process is performed (S813), and the process returns to step S802. If the command type COM is “data response”, the received data is processed (S814). It is determined whether the “response” is a “data response” from the terminal unit C10 at the end (S815).

  If it is not a data response from the terminal child device C10, the process returns to step S807 to continue receiving data responses from other child devices.

  On the other hand, the child device C1 that has transmitted “data response” to the parent device P in step S913 determines whether or not a reception confirmation ACK has been received from the parent device P (S914). It is determined whether or not (S915). When retransmitting, after waiting (S916), the process returns to step S913 to retransmit the “data response”.

  If the reception confirmation ACK is received from the parent device P in step S914 and if the “data response” is not retransmitted in step S915, i is set to i + 1 (S917), and the channel is channel CH (2). To wait for reception (S918).

  When a “data response” packet is received from the child device C2 (S102-1), it is determined whether or not the destination is the own address (S919). If the packet is not addressed to the own address, the process returns to step S918. Subsequently, the channel CH (2) is in a reception waiting state, and if it is a “data response” addressed to its own address, a reception confirmation ACK is transmitted to the child device C2 (S920), and the received “data response” packet is transmitted. Transmission is performed to the parent device P through the channel CH (2) (S102-2, S921).

  At this time, the child device C1 rewrites the transmission source address SA to its own address and rewrites the transmission destination address DA to the address of the parent device P for transmission. However, since the data contents are not rewritten, the data of the child device C2 is recorded as the data contents.

  When the “data response” sent from the child device C2 is transmitted to the parent device P in this way, the child device C1 determines whether or not the reception confirmation ACK from the parent device P has been received (S922), and has not been received. In this case, it is determined whether or not to retransmit (S923).

In the case of resending, after waiting (S924), the process returns to step S921 and resends. For example, although the slave unit C2 in the area A in FIG. 7 transmits a “data response” packet on the channel CH (5) (S105-4-1), the slave unit C1 does not receive the packet and receives the data from the slave unit C1. Since the reception confirmation ACK was not received, it is retransmitted (S105-4-2). Similarly, in the area A, the slave units C3 to C7 are also retransmitted (S106-4-2 to S110-4-2).

  When the reception confirmation ACK is received in step S922 or not retransmitted in step S923, it is determined whether i is the maximum number M of slave units, here 10 (S925), and i becomes 10. If not, the process returns to step S917 to wait for reception on the next channel. If i is 10, the process returns to step S902 to repeat the above-described processing.

  Further, if the reception confirmation ACK of the “data request” transmitted in step S911 is not received, it is determined whether or not to retransmit (S926), and if retransmitted, wait (S927), and then go to step S910. Go back and resend “data request”.

  If not retransmitted, data indicating that the handset C2 is “no response” on the channel CH (0) is prepared (S928), and the handset C1 sends a “no response response” to the base unit P on the channel CH (1). ] Packet is transmitted (S929).

Then, handset C1 determines whether or not a reception confirmation ACK has been received (S930), and if not received, determines whether or not to retransmit (S931). In step S932), the process returns to step S929 to retransmit the “no response response” packet.

  If the reception confirmation ACK is received in step S930 and if it is determined not to retransmit in step S931, the process returns to step S902 and the above-described processing is repeated.

  When the processing similar to the processing performed in the above-described child device C1 is executed in each of the child devices C2 to C9 and a “data request” is transmitted to the terminal child device C10 (S100-10, S907). ), The child device C10 waits (S933), prepares information detected by the sensor, that is, data from itself (S934), and sends a “data response” packet on the preset channel CH (10). It transmits to the subunit | mobile_unit C9 (S110-1, S935).

  Then, handset C10 determines whether or not a reception confirmation ACK has been received (S936), and if not received, determines whether or not to retransmit (S937). In step S938, the process returns to step S935 to retransmit the “data response” packet.

  If reception confirmation is received in step S936 and if it is determined not to retransmit in step S937, the process returns to step S902 and the above-described processing is repeated.

  When the “data response” packet is transmitted in the slave unit C10 in this way, the same processing as that performed in the slave unit C1 is executed in each of the slave units C2 to C9, and “ The “data response” packet is transferred to the parent device P.

  If the base unit P determines that the “data response” packet received in step S815 is the packet from the terminal unit C10 (S110-10), the current data collection process is terminated, and the process proceeds to step S802. The process described above is repeated to return and collect new data.

  In this way, in the data collection system of this embodiment, each of the slave units C1 to C10 switches the radio channel to time division based on the reception of the “data request”, so that the radio channel to be used at a certain time is multiplexed. The amount of data per unit time as a system can be increased. As a result, the time required for communication as a system can be shortened.

  Furthermore, by limiting wireless communication to 1: 1 and communicating with a predetermined partner on a predetermined channel, it is possible to limit the number of slave units that transmit on a channel at a certain time to one. Interference (hidden terminal problem) can be prevented.

  In addition, communication reliability can be improved by transmitting / receiving ACK as reception confirmation. Further, if the next operation (transmission or reception waiting) is started after the ACK is received, the data collection time of the entire system can be shortened.

  Embodiment 3 of the present invention will be described below with reference to the drawings. However, the configuration of the data collection system according to the present embodiment is the same as that of the first embodiment shown in FIG.

  In the system of the present embodiment, for example, 2.4 GHz band, direct spread offset-QPSK modulation (2 Mchips / sec), 16 channels at 5 MHz intervals, a maximum data transfer rate of 250 kbps, and a radio wave coverage of 10 m to 30 m are used. It shall be. The radio channel switching time is 30 ms or less. Further, as a network configuration, it is assumed that the parent device P performs only one-to-one communication between the child device C1 and the child devices other than the child device C1 communicate with each other. Although it is similar to IEEE802.15.4, the frame format and sequence (communication procedure) of a packet are simplified. A reception confirmation ACK notifying that a beacon, handshake, or data has been received is not used here.

  Here, the frame format of the packet used in the data collection system of the present embodiment is shown in FIG. As shown in FIG. 10, in the packet format used in the data collection system of this embodiment, a MAC layer is added to the PHY layer, and “data request” and “data response” as commands are distinguished from the DATA part. A command type area COM is included. In this embodiment, the transmission source address SA is communicated in a procedure that is not rewritten by each slave unit so that the transmission source address that transmitted the data first remains until the end. This is because the wireless multi-hop is limited to 1: 1, that is, the number of slave units that can be transmitted and received is limited to one by one, so that it is not necessary to rewrite the source address SA at the time of transfer. Thereby, it is possible to omit the SAO that describes the source address that transmitted the data first.

Next, the channels used in the data collection system of this embodiment are 11, 12,
Six types of 15, 18, 21, and 24 are used in the following order.

CH (0) = 11
CH (i) = CH (1), CH (2), CH (3), CH (4), CH (5), CH (6), CH (7), CH (8), CH (9), CH (10) (i = 1 to 10)
= 12, 15, 18, 21, 24, 12, 15, 18, 21, 24
Next, data collection processing by the data collection system of the present embodiment will be described based on the sequence diagram of FIG. 11 and the flowcharts of FIGS. 12 and 13. 11 is a sequence diagram of data collection processing performed between the parent device P and the child devices C1 to C10, FIG. 12 is a flowchart of data collection processing in the parent device P, and FIG. 13 is a flowchart of data collection processing in the child device. is there.

  First, the base unit P performs a start-up process for performing the data collection process, sets i to 0, sets j to 0 (S1201), and other items necessary for performing the data collection process. Processing is performed (S1202).

  On the other hand, each of the slave units C1 to C10 also performs a startup process, sets i to a preset number N from itself, sets j to 1 (S1301), and waits for reception on channel CH (0). (S1302).

  Next, for the purpose of collecting information generated or obtained in each slave unit, that is, data, the master unit P sends a “data request” to the master unit P so that each slave unit sends data to the first slave unit. It transmits with channel CH (0) previously set to the machine C1 (S100-1, S1203). FIG. 14 shows the frame format of the “data request” packet transmitted at this time.

  Since the child device C1 is waiting for reception on the channel CH (0), when receiving the “data request” addressed to its own address (S1303), the received “data request” is received from all the child devices. It is determined whether or not it is a data request (S1304). If it is not a data request for all the slave units, another process is performed (S1305), and the process returns to step S1302 to repeat the above-described process.

  If it is a “data request” to all the slave units, the timer is initialized to t = 0 (S1306), and if it is not the terminal slave unit C10 itself (S1307), the destination address DA is set to the termination side. (S1308) When the timer reaches time t = tr1 + tcd + ts0 (tr1: standby time after reception, tcd: channel switching dummy time, ts0: transmission preparation time) (S1309) Then, the data request packet as shown in FIG. 15 is transferred to the child device C2 through the channel CH (0) (S100-2, S1310). However, the channel switching dummy time tcd is a time provided for the purpose of matching the timing with other slave units, although the actual channel is not changed, and reception and transmission are switched within this time. When the transmission / reception switching time is short, tr1 may be extended within the time tcd.

  Then, after transmitting the “data request” to the child device C2, it waits on the channel CH (0) until the waiting time ts1 after transmission elapses, that is, until the timer reaches time T1 = tr1 + tcd + ts0 + ts1 (S1311) After the channel switching time tc, the channel is switched to channel CH (i), and the slave C1 is switched to channel CH (1) (S1312), and information detected by the sensor or the like, that is, data from itself is prepared (S1313).

  Then, when the transmission preparation time ts0 has elapsed, that is, when the timer has elapsed the time t = T1 + tc + ts0 (S1314), it is transmitted to the parent device P as a “data response” through the preset channel CH (1) (S101-1, S1315). The frame format of the “data response” packet transmitted at this time is shown in FIG.

  On the other hand, if the base unit P transmits a “data request” in step S1203, the timer is started (S1204), and when the timer has elapsed time T1 (S1205), i is set to i + 1 (S1206) and the channel is set to channel CH. Switch from (0) to channel CH (1) and wait for reception (S1207).

  When a signal is received from the slave unit C1 through the channel CH (1), it is determined whether or not the destination is the own address (S1208). If the destination is not the own address, the process returns to step S1207 and waits for reception. In the case of an address, it is determined whether or not the command type COM of the received signal is “data response” (S1209).

  If the command type COM is not “data response”, another process is performed (S1210), and the process returns to step S1202. If it is “data response”, the received data is processed (S1211).

  On the other hand, the slave unit C1 that has transmitted “data response” to the master unit P in step S1315 sets i to i + 1 when the timer has passed T2 = T1 + tc + ts0 + ts1 (ts1: standby time after transmission) (S1316), j Is set to j + 1 (S1317), and the channel is switched to channel CH (2) to wait for reception (S1318).

  When receiving a “data response” packet as shown in FIG. 17 from the slave unit C2 (S102-1), it is determined whether or not the destination is the own address (S1319), and the signal is not addressed to the own address. After that, the process returns to step S1318, and the channel CH (2) continues to wait for reception. On the other hand, if it is a “data response” addressed to its own address, when the timer has passed the time t = T1 + tc + ts0 + j × (ts1 + tc + tr0 + tr1 + tcd + ts0) and (tr0: reception preparation time) (S1320), the received “data response” packet is transmitted. It transmits to base unit P through channel CH (2) (S102-2, S1321).

  At this time, the child device C1 rewrites the transmission destination address DA of the packet to the address of the parent device P as shown in FIG. However, since the data contents are not rewritten, the data of the child device C2 is recorded as the data contents.

  When the “data response” sent from the child device C2 is transmitted to the parent device P in this way, this time, when the timer has passed the time t = T2 + j × (tc + tr0 + tr1 + tcd + ts0 + ts1) (S1322), i is the maximum number of child devices M, where Then, it is determined whether or not 10 (S1323). If i is not 10, the process returns to step S1317 to wait for reception on the next channel, and if i is 10, It returns to S1302 and repeats the process mentioned above.

  On the other hand, the parent device P that has performed the data processing of the “data response” received in step S1211, determines whether or not the received “data response” is a data response from the terminal child device C10 (S1212). If it is not a data response from the terminal unit C10 at the end, after the timer has elapsed time t = T1 + tc + ts0 + ts1 + j × (tc + ts0 + ts1 + tcd + tr0 + tr1) (S1213), j is set to j + 1 (S1214) and the process returns to step S1206. Continue to receive “data response” from the machine.

  When the processing similar to the processing performed in the above-described child device C1 is executed in each of the child devices C2 to C9 and a “data request” is transmitted to the terminal child device C10 (S100-10, FIG. 13: S1307), the slave unit C10 prepares information detected by the sensor, that is, data from itself (S1324). When the transmission preparation time ts0 has elapsed, that is, when the timer has elapsed time t = T1 + tc + ts0 (S1325), A packet of “data response” is transmitted to the child device C9 through the preset channel CH (10) (S110-1, S1326), and the process returns to step S1302 to repeat the above-described processing.

  When the “data response” packet is transmitted in the slave unit C10 in this way, the same processing as that performed in the slave unit C1 is executed in each of the slave units C2 to C9, and “ The “data response” packet is transferred to the parent device P.

  If the base unit P determines that the “data response” packet received in step S1212 is a packet (S110-10) from the terminal unit C10, the current data collection process is terminated, and the process proceeds to step S1202. The process described above is repeated to return and collect new data.

  However, in the sequence diagram shown in FIG. 11 described above, the transmission preparation time ts0 and the reception preparation time tr0 are equal, the standby time ts1 after transmission is equal to the standby time tr1 after reception, and the channel switching time tc. And the channel switching dummy time tcd are also equal. When the data is long and becomes a plurality of packets, or when ACK for reception confirmation is used, processing is performed within the waiting time ts1 after transmission and the waiting time tr1 after reception. Also, when retransmission is performed, the transmission is terminated within the waiting time ts1 after transmission.

  Here, a specific example of communication time by the data collection system of the above-described embodiment will be described. Consider a case where 10 data per second (average 100 bytes, maximum 500 bytes), 11 bytes other than the DATA part in the frame format of FIG. 10, and channel switching time 30 ms.

  First, when the time that can be spent for one transmission or reception is calculated, it can be calculated as 1 s ÷ (10 units + reserve 1) = 90.9 ms. If the channel switching time 30 ms is subtracted from here, 90.9 ms-30 ms = 60.9 ms becomes the fixed time (tr0 + tr1 + tcd + ts0 + ts1) in a certain channel.

  When the “data request” is a packet of 11 bytes + 1 bytes = 12 bytes, the time taken to transmit the “data request” is 12 bytes × 8 bits ÷ 250 kbps = 0.38 ms.

  Further, when the DATA portion of the “data response” packet is 3 bytes + 100 bytes, and the total becomes 11 bytes + 3 bytes + 100 bytes = 114 bytes, the time taken to transmit the “data response” is 114 bytes × 8 bits ÷ 250 kbps = 3.65 ms. Furthermore, in addition to this time, it takes 5 ms to analyze the packet after reception and prepare for the next operation, so the time required to transfer is 3.65 ms + 5 ms + 3.65 ms = 12.3 ms. This is sufficiently smaller than the fixed time 60.9 ms in the channel.

  Therefore, in this embodiment, asynchronous communication is systematically, but the transfer time of the “data request” for starting the timer of each slave unit is sufficiently shorter than other times. Further, in consideration of performing a predetermined operation every predetermined time, and ignoring it after a certain time (tr0 + tr1 + tcd + ts0) when not receiving (when there is no response), the next operation is considered in FIG. Processing can be executed in the sequence shown.

  Next, a case where data does not fit in one transmission packet will be described. In such a case, the data is divided and the divided data is transmitted continuously. For example, it is possible by preparing a bit field indicating that packets are continuous in the frame format of the packet.

  When the data of the slave unit Cn is 500 bytes at the maximum, the data is continuously transmitted in five times. The packet length per “data response” is 11 bytes + 3 bytes + 500 bytes / 5 = 114 bytes. This transmission time is 114 bytes × 8 bits ÷ 250 kbps = 3.65 ms. Even if the “data response” is transmitted five times continuously, it is 3.65 ms × 5 times = 18.25 ms, and a fixed time ( tr0 + tr1 + tcd + ts0 + ts1) = 60.9 ms.

  As described above, in the data collection system of this embodiment, the master unit P starts the timer based on the transmission of the “data request”, and each of the slave units C1 to C10 sets the timer based on the reception of the “data request”. By activating each of them and operating at a fixed time in a certain channel, communication can be performed without an acknowledgment ACK.

  Further, the slave unit Cn is set to start a timer when receiving a “data request” and to perform a predetermined operation at a predetermined time from this point. In addition, it is set to send the “data response” from itself after the “data request” transfer is executed first, and the transfer time of the “data request” for starting the timer is sufficient for the entire system. Short. Considering these points, the difference in timing between each slave unit Cn is only the transfer time of “data request”, and the master unit P and each slave unit Cn can be operated almost in synchronization.

  Furthermore, since the master unit P and each slave unit Cn are operating in synchronization with each other while switching channels in a time-sharing manner, the required number of radio channels is only M (the number of slave units) / 2 + 1. In IEEE 802.15.4, 16 channels can be used, so that up to 30 slave units can be connected if the response time allows.

  On the contrary, when there are 10 slave units, the required number of channels may be 6, so that it is possible to perform communication without using a defective channel in advance.

  Also, assuming that one communication is one step, in this embodiment, the number of steps “2 × M (number of slave units) +1” is required, and the channel change time (tc) × M is implemented in this step. In the example, 30 ms × 10 units = 300 ms is added.

  However, in the case of the conventional system shown in the configuration diagram of FIG. 28 and the sequence diagram of FIG. 29 in which 1: 1 communication is performed wirelessly and time-division multiplex communication is not performed, 110 steps are required if there are 10 slave units. there were. On the other hand, in this embodiment, since 2 × 10 + 1 = 21 steps, it can be significantly shortened. Further, the time increase of the radio channel change time tc × the number of units (300 ms in the present embodiment) is slight compared to the increase in the number of steps.

  Further, in the data collection system of this embodiment, the source address SA is not rewritten at the time of transfer, so the source address that transmitted the data first remains to the end, and the SAO that describes the actual source address is omitted. can do. As a result, the packet length can be shortened accordingly, and the data collection time as a system can be shortened.

  Next, a fourth embodiment of the present invention will be described. However, since the configuration of the data collection system according to the present embodiment and the data collection processing performed by the parent device and the child device are the same as those of the third embodiment, detailed description thereof is omitted.

  In the data collection system of this embodiment, the fixed time of the channel is set so as to become longer as the transmission order becomes a later slave unit and as the channel order becomes later.

  In the above-described third embodiment, each of the slave units C1 to C10 starts a timer based on the reception of the “data request” and performs a predetermined operation at a predetermined time, so that each of the slave units C1 to C10 is synchronized. I was going to take. However, the synchronization was shifted only for the communication time of the packet transmitted and received by each slave unit. Also, the reception processing operation may be delayed depending on the state of the slave unit.

  Therefore, in the third embodiment, as the terminal becomes a terminal on the terminal side, the synchronization shift with the parent increases, and the possibility that transmission / reception cannot be performed increases. In addition, even when the time has elapsed since the timer was started, as the time has passed since the timer was started, the difference in synchronization with the parent device has increased, and the possibility of being unable to transmit and receive has increased.

  Therefore, in this embodiment, the interval of the fixed time of each channel is increased as it becomes a terminal on the terminal side, and further, when the time elapses after the timer is started, it increases as time elapses. I have to.

  In the third embodiment described above, the intervals of T3-T2, T4-T3,..., T11-T10 are all equal as shown in FIG. 11, but in this embodiment, the waiting time after reception as shown in FIG. The time tr1 and the waiting time ts1 after transmission are set to increase by time ta as the terminal becomes a slave unit on the end side and further after the timer starts. Thus, in this embodiment, T3′−T2 <T4′−T3 ′ <... <T10′−T9 ′ <T11′−T10 ′.

  As described above, in the data collection system of the present embodiment, it becomes possible to consider the transfer time of the “data request” that is the timing difference between the slave units, and the fixed time in the channel is terminated. It can be made longer as the slave unit becomes closer and as time passes after the timer starts. This can reduce the possibility that transmission / reception will not be possible at the end side slave unit when the timer has started, and improve the accuracy of synchronization between the master unit and each slave unit. Communication reliability can be maintained even without a reception confirmation ACK.

  Next, a fifth embodiment of the present invention will be described. However, since the configuration of the data collection system according to the present embodiment and the data collection processing performed by the parent device and the child device are the same as those of the third embodiment, detailed description thereof is omitted.

  In the data collection system of this embodiment, data can be collected by limiting the slave units by the master unit.

  Here, FIG. 20 shows a frame format of a packet used in the data collection system of this embodiment. As shown in FIG. 20, in the packet frame format used in the present embodiment, the command type COM is recorded as “limited data request” when a data request is made by limiting the slave units, and the DATA part is recorded in the DATA section. An OJ section for limiting the target slave units is set. Each slave unit is assigned to each bit of the OJ section in the DATA section, and “1” requests a reply, and “0” does not request a reply. For example, in the case of the bit string of FIG. 20, only the slave unit 1, the slave unit 5, and the slave unit 7 are required to return a “data response”.

  Next, FIG. 21 shows a sequence diagram of data collection processing by the data collection system of the present embodiment. As shown in FIG. 21, when each slave unit receives a “limited data request”, it starts a timer and switches channels in a preset order based on this “limited data request”.

  The master unit and each slave unit can recognize which slave unit has the “data response” by analyzing the OJ bit of the “limited data request” received first, so there is no reception for a certain period of time. If no acknowledgment ACK is returned, there is no need to send a “no response”. Further, since the master unit recognizes at which timing the “data response” is received, it waits for reception at the corresponding timing.

  In addition, the response from the slave unit to the “limited data request” is not a normal “data response” but a “limited data response” which is another command type, and the OJ portion is eliminated from the data response packet. Good.

  As described above, in the data collection system according to the present embodiment, since it is possible to limit the slave units to which data is requested in the packet frame format, data is collected only from an arbitrary slave unit instead of all the slave units. It becomes possible to do.

  Furthermore, since each slave unit receives and transmits a “limited data request”, each slave unit can recognize from which slave unit there is a response, that is, at what timing. Can be determined as a system. In particular, when there is no need for transfer, it is possible to reduce the probability of radio wave interference if transmission is not performed even if the channel is switched as shown in FIG.

  In addition, except for the case of inquiring to the terminal slave unit, the response time can be obtained in a shorter time than when all the slave units are requested to reply.

  Next, a sixth embodiment of the present invention will be described. However, since the configuration of the data collection system according to the present embodiment and the data collection processing performed by the parent device and the child device are the same as those of the third embodiment, detailed description thereof is omitted.

  In the data collection system of this embodiment, a no-response response is transmitted when there is no reception for a certain period of time or when a reception confirmation ACK is not returned.

  Here, FIG. 22 shows a sequence diagram of data collection processing by the data collection system of the present embodiment. As shown in FIG. 22, each slave unit Cn waits for reception on a preset channel CH (i) until reception. At this time, if the signal is not received within the fixed reception time (tr0 + tr1) in a certain channel (S220), the fact that it has not been received is regarded as a “no response”, and the child device Cn− on the parent device side at the next timing and channel. 1 is transmitted (S221).

  In this “no response response” packet, since the source address SA is the child device Cn that generated this “no response”, it is indicated that there is no response from the child device Cn + 1. It can be recognized by each slave unit closer to the master unit than Cn and slave unit Cn.

  In addition, the master unit P can detect which slave unit cannot communicate with which channel by receiving and analyzing the “no response”.

  At this time, since at least one cycle time T, all the slave units are waiting to receive CH (0), the master unit P can individually inquire about the cause of the slave unit. Sending a restart command or removing the cause of no response.

  Further, when waiting for reception on CH (0), for example, if a time limit of 2T is provided for each slave unit, if nothing is received on channel CH (0) until time 2T, If the process returns to the process for re-determining the use channel and the use order (included in the start-up process), a state in which no control from the parent device P can be avoided.

  As described above, in the data collection system according to the present embodiment, when there is no reception for a certain period of time or when a reception confirmation ACK is not returned, the child device Cn on the parent device side at the timing when the child device Cn should transmit normal data. Since the “no response” is transmitted to −1, the parent device P can detect which child device cannot communicate with which channel by receiving and analyzing the “no response”. In addition, the base unit P determines a new use channel and order, and notifies each slave unit, so that communication can be performed without using a defective channel even when data collection is being performed. Communication problems can be reduced.

  Next, a seventh embodiment of the present invention will be described. However, since the configuration of the data collection system according to the present embodiment and the data collection processing performed by the parent device and the child device are the same as those of the third embodiment, detailed description thereof is omitted.

  In the data collection system of this embodiment, after transmitting data, the reception confirmation ACK cannot be received within a fixed time in a preset channel, and data that cannot be confirmed is stored in a memory. The transmission is performed on the next channel.

  Here, FIG. 23 shows a sequence diagram of data collection processing by the data collection system of the present embodiment. FIG. 23 shows a case in which the “data response” (S103-1), which is data transmitted from the child device C3, has failed in transferring from the child device C2 to the child device C1 (S103-2). In this embodiment, a case will be described in which the channel is changed every fixed time and the reception confirmation ACK is set to be returned.

  First, if the handset C1 cannot receive a packet from the handset C2 on the channel CH (3), that is, the channel 18, for a certain time tr0 (reception preparation time) + tr1 (waiting time after reception), the time is further increased. After a lapse of tcd (channel switching dummy time) + ts0 (transmission preparation time), a “no response” is transmitted to base unit P through channel CH (3) (S113-1).

  At this time, the child device C2 recognizes that the transmission has failed by not receiving the reception confirmation ACK from the child device C1, and stores the failed packet (S103-2) shown in FIG. 24 in the memory in the child device C2. accumulate.

  Then, handset C1 changes the channel to CH (4), that is, channel 21 after time tc (channel switching time), and waits for reception (t = T4). Then, the child device C1 receives the “data response” (S104-3) that is the data of the child device C4 from the child device C2, and returns a reception confirmation ACK to the child device C2.

  At this time, since the handset C2 could not communicate with the handset C1 on the channel CH (3) but could communicate on the next channel CH (4), the transmission stored in the memory in the handset C2 The data that failed to be transmitted is transmitted with a new command type “stored data response” to the child device C1 using the channel format shown in FIG. 25 through the channel CH (4).

  Here, only when the command type is “accumulated data response”, if the DATA unit is set to include the address SAO of the slave that first transmitted the data, the packet that failed to be transmitted (S103-2) ), That is, the slave device C3 can be the SAO of “stored data response”, and the sender address SA of the “stored data response” can be the slave device C2 (S123-1, FIG. 25).

  Then, the child device C1 returns a reception confirmation ACK to the “accumulated data response”, so that the child device C2 recognizes that the transmission of the packet (S103-2) that has failed to be transmitted has been successfully transmitted on another channel. The data is deleted from the memory.

  In the next step, the slave unit C1 transmits a “data response” (S104-4), which is data of the slave unit C4, to the master unit P, and the content of the data generated by the slave unit C2 is the slave unit C3. The “accumulated data response” (S123-2), which is the data of, is transmitted in the frame format of FIG.

  On the other hand, the base unit P receives and analyzes the “stored data response” packet shown in FIG. 26 to confirm that communication cannot be performed on the channel CH (3) between the handset C2 and the handset C1. Can be detected.

  As described above, in the data collection system of this embodiment, when the “data response” cannot be transmitted, the data is stored in the memory and transmitted through another channel. Even if there is a channel whose communication status has deteriorated during implementation, data can be collected. Further, the base unit P can accumulate and analyze the situation to control the entire system so as not to use the channel.

  Next, an eighth embodiment of the present invention will be described. However, since the configuration of the data collection system according to the present embodiment and the data collection processing performed by the parent device and the child device are the same as those of the third embodiment, detailed description thereof is omitted.

  In the data collection system of the present embodiment, emergency information can be transmitted from the slave unit when the sensor detects abnormal data on the slave unit side.

  Here, FIG. 27 shows a sequence diagram of data collection processing by the data collection system of the present embodiment. In FIG. 27, a case will be described in which the child device C6 wants to send an “emergency response” to the parent device P as emergency information. The slave C6 transfers the transmission data from the “data response” to the “emergency response” to the slave C5 at the next timing to transfer the “data response” (S116-1). The child device C6 thereafter performs a normal operation, receives the “data response” from the child device C7, and transfers it to the child device C5. Further, the packet replaced with the “emergency response” is also transferred to the parent device P in the same manner as a normal packet.

  In this way, in the data collection system of this embodiment, in the system in which the parent device P originally inquires each child device and collects data of each child device (based on polling), each child device transmits spontaneously. However, if the slave unit replaces the “data response” with an “emergency response” as necessary, the master unit P receives the “emergency response” within one period T of data collection, Can be recognized.

  Further, since the slave unit does not make a call at an arbitrary timing, it is possible to prevent interference.

  Furthermore, after performing the processing based on the received “emergency response”, the master unit can return to the normal sequence at any timing.

  The data collection system of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. Can do.

It is a block diagram which shows the structure of the data collection system which concerns on the Example of this invention. It is a block diagram which shows the structure of the data collection system which concerns on Example 1 of this invention. It is a figure which shows the frame format of the packet used with the data collection system which concerns on Example 1 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 1 of this invention. It is a flowchart which shows the data collection process by the main | base station of the data collection system which concerns on Example 1 of this invention. It is a flowchart which shows the data collection process by the subunit | mobile_unit of the data collection system which concerns on Example 1 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 2 of this invention. It is a flowchart which shows the data collection process by the main | base station of the data collection system which concerns on Example 2 of this invention. It is a flowchart which shows the data collection process by the subunit | mobile_unit of the data collection system which concerns on Example 2 of this invention. It is a figure which shows the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 3 of this invention. It is a flowchart which shows the data collection process by the main | base station of the data collection system which concerns on Example 3 of this invention. It is a flowchart which shows the data collection process by the subunit | mobile_unit of the data collection system which concerns on Example 3 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 3 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 4 of this invention. It is a figure which shows the frame format of the packet used with the data collection system which concerns on Example 5 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 5 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 6 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 7 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 7 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 7 of this invention. It is a figure which shows an example of the frame format of the packet used with the data collection system which concerns on Example 7 of this invention. It is a sequence diagram which shows the data collection process by the data collection system which concerns on Example 8 of this invention. It is a block diagram which shows the structure of the polling system of the conventional wireless connection. It is a sequence diagram which shows the data collection process by the polling system of the conventional wireless connection.

Explanation of symbols

1,21 Data collection system P Master unit C1 to C10, Cn Slave unit

Claims (10)

A data collection system in which a master unit wirelessly collects data from a plurality of slave units,
The plurality of slave units have a transmission order set in advance from the first slave unit to the terminal slave unit, and each slave unit uses a channel set in advance according to the transfer direction, and the transmission order is changed. Send and receive data only to the machine,
The data collection system, wherein the master unit transmits / receives data only to / from the first slave unit using a preset channel. A data collection system in which a master unit wirelessly collects data from a plurality of slave units,
The plurality of slave units have a preset transmission order from the first slave unit to the terminal slave unit, and each slave unit uses the preset plurality of channels in a preset order. Sends and receives data only with the slave unit
The base unit performs data transmission / reception only with the first handset using a plurality of preset channels in a preset order.   3. The data collection system according to claim 1, wherein the master unit and the plurality of slave units return a reception confirmation when receiving data.   4. The data collection system according to claim 2, wherein the master unit and the plurality of slave units use a plurality of channels set in advance for each fixed time in a preset order.   5. The data collection system according to claim 4, wherein the fixed time is set to become longer as the transmission order becomes a later slave unit and as the channel order becomes later. .   The data collection system according to any one of claims 1 to 5, wherein the parent device transmits an instruction only for a specific child device.   The data collection according to any one of claims 1 to 6, wherein a transmission source address recorded in the data is not changed from an address of a parent device or a child device that transmitted data first. system.   When the plurality of slave units do not receive the data within the fixed time, the plurality of slave units notify the master unit or the slave unit whose transmission order is on the master unit side that the slave unit has not responded. The data collection system according to any one of claims 4 to 7.   The plurality of slave units store the transmitted data and transmit it on another channel when the reception confirmation cannot be received even after the fixed time has elapsed after the transmission of the data. The data collection system according to any one of claims 4 to 8.   The data collection system according to any one of claims 1 to 9, wherein the plurality of slave units transmit emergency information instead of the data.

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