JP2018170722A - Radio communication method and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve power saving operation at each node.SOLUTION: A radio communication method in an embodiment is a radio communication method of a tree-type network in which data is transmitted and received between nodes 3 arranged in 2 or more stages starting with a CS 2 as a root. The radio communication method includes periodically obtaining node information held by the nodes 3 and setting a communication period ratio R indicating the ratio of a communication period T1 to a basis period T at the nodes 3 on the basis of the node information obtained during each period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radio communication method and a radio communication system in a tree-type network for transmitting and receiving data between two or more nodes arranged with a collection control station as a root.

  2. Description of the Related Art In recent years, communication devices conforming to the IEEE 802.15.4 standard that are small, inexpensive, and capable of performing low-power digital wireless communication have been used in wireless networks. In a network compliant with the IEEE802.15.4 standard, as shown in FIG. 11, a tree type configured by a collection control station CS (Collection station) 71 and one or more nodes 72-1 to 72-4. The topology is adopted. In the tree topology, the lower node 72 transmits data to the higher node 72 and CS 71 as necessary (see, for example, Patent Documents 1 to 3).

  FIG. 12 shows an example of a time chart when data from lower nodes 72-3 and 72-4 is transmitted to the CS 71. Each of the CS 71 and each node 72 includes an active period (communication period T1 (unit: time t)) and a sleep period T2 (unit: time t) within a basic interval T (intermittent standby period (unit: time t)). Is assigned. Wireless communication can be performed in the communication period T1, and wireless communication cannot be performed in the sleep period T2 because the receiving side shifts to the sleep state. By intentionally providing the sleep period T2 within the basic interval T, power consumption can be reduced, and as a result, power consumption of the entire system can be suppressed.

  When data is transmitted from the node 72-3 to the CS 71, the node 72-3 is relayed from the node 72-1 to become the CS 71 path. In such a case, between the node 72-3 and the node 72-1, which is higher than the node 72-3, the upper node 72-1 is a master and the lower node 72-3 is a slave. Similarly, between the node 72-1 and the CS 71, the CS 71 as an upper node is a master and the lower node 72-1 is a slave. In such a relationship between the master and the slave, the higher order master determines the timing of the communication period T1 in the basic interval T, and the lower order slave matches the timing of the communication period T1 determined on the master side. Data will be transmitted.

  Under such rules, in FIG. 12, the node 72-3 first transmits the data D81 generated at the timing t91 in accordance with the communication period T1 of the node 72-1 as the master starting at the timing t92. The node 72-1 that has received the data D81 transmits the data D81 in accordance with the communication period T1 of the CS 71 as the master starting at the timing t93. As a result, the CS 71 can receive the data D81 within the communication period T1 set by itself.

  Similarly, when data is transmitted from the node 72-4 to the CS 71, the node 72-4 relays the node 72-1, and becomes a path of the CS 71. The node 72-4 transmits the data D82 generated at the timing t94 in accordance with the communication period T1 of the node 72-1 as the master starting at the timing t95. The node 72-1 that has received the data D82 transmits the data D82 in accordance with the communication period T1 of the CS 71 as the master that starts at timing t96. As a result, the CS 71 can receive the data D82 within the communication period T1 set by itself.

  The CS 71 can collect all data from each node 72 in the tree-type network based on the above-described wireless communication processing operation method.

JP-A-2015-198333 JP 2014-23085 A JP 2014-103580 A

  By the way, in the conventional tree-type topology described above, the power saving operation of each period T1 and T2 assigned to each node 72 is operated with a specification common to each node 72. For this reason, constant periods T1 and T2 are assigned to the node 72 regardless of the type of the node 72, the power supply status, and the like. Accordingly, there is a concern that the power saving effect cannot be obtained for each node 72.

  In particular, when nodes 72 using different power feeding methods such as dry cells and solar cells coexist, the power feeding state tends to change with time. For this reason, when nodes 72 with good power supply state and nodes 72 with poor power supply state coexist, there is a possibility that the operation of the entire wireless network may be difficult due to battery consumption of only some of the nodes 72. . Under such circumstances, it is desired to realize the power saving operation of each node 72.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is a tree type that transmits and receives data between two or more nodes arranged with a collection control station as a root. An object of the present invention is to provide a wireless communication method and a wireless communication system capable of realizing a power saving operation in each node in a network.

  In order to solve the above-described problems, the present inventors periodically exchange node information of nodes in a tree-type network that transmits and receives data between two or more nodes arranged with a collection control station as a root. Invented a wireless communication method and system for setting a communication period ratio indicating a ratio of a communication period to an intermittent standby period in a node based on node information acquired in each period.

  The wireless communication method according to claim 1 is a wireless communication method in a tree-type network in which data is transmitted and received between two or more nodes arranged with a collection control station as a root, and node information of the node is periodically transmitted. The communication period ratio indicating the ratio of the communication period to the basic interval in the node is set based on the node information acquired in each cycle.

  According to a second aspect of the present invention, in the wireless communication method according to the first aspect, the synchronization signal periodically transmitted from the node is acquired, and the node information included in the synchronization signal acquired in each cycle is acquired. The frequency of transmitting the synchronization signal of the node and the communication period ratio are set based on the above.

  According to a third aspect of the present invention, there is provided the wireless communication method according to the first or second aspect, wherein the node information has a contribution ratio indicating a ratio of a remaining battery level when the node information is acquired with respect to a maximum value of the battery. And the communication period ratio is set higher as the contribution rate becomes higher.

  According to a fourth aspect of the present invention, in the wireless communication method according to the third aspect, the first node having the first contribution rate is specified as a lower rank of the second node having the second contribution rate higher than the first contribution rate. It is characterized by doing.

  According to a fifth aspect of the present invention, in the wireless communication method according to the first or second aspect, the node information is obtained from the node information for the type of device used for the node, the power supply method, and the maximum value of the battery. At least one of the contributions indicating the ratio of the remaining battery level, and based on the node information or information on the determination generated by the collection control station or a node higher than the node, A determination is made as to whether or not the node receives the data, and the timing for starting a sleep period in which the data is not received is controlled according to the determination.

  The wireless communication system according to claim 6 is a wireless communication system in a tree-type network that transmits and receives data between two or more nodes arranged with a collection control station as a root, and periodically transmits node information of the nodes. An acquisition means for acquiring, and a setting means for setting a communication period ratio indicating a ratio of a communication period to a basic interval in the node based on the node information acquired in each cycle.

  According to the present invention having the above-described configuration, the communication period ratio is set based on periodically acquired node information. For this reason, a communication period can be allocated based on a different kind, power supply condition, etc. for every node. Thereby, it is possible to realize a power saving operation in each node.

  Further, according to the present invention having the above-described configuration, the frequency of transmitting the node synchronization signal is set based on the node information. For this reason, it is possible to control the frequency of transmitting the synchronization signal, and it is possible to further enhance the power saving effect in each node.

  Moreover, according to this invention which consists of an above-described structure, a communication period ratio is set according to the contribution rate of a battery. For this reason, it is possible to establish fairness in the network by setting a higher communication period ratio for a node having a higher contribution rate. Further, even when nodes with good power supply state and nodes with poor power supply state coexist, the relative battery consumption of each node can be made uniform. As a result, it is possible to avoid a situation where the operation of the entire wireless network becomes difficult to continue due to battery consumption of only some nodes, and it is possible to continue stable operation.

  Further, according to the present invention having the above-described configuration, a node with a high contribution rate is designated as a higher rank, and a node with a low contribution rate is designated as a lower rank. For this reason, an operation mode in which many data frames are relayed preferentially to a node having a good power supply state is formed in an autonomous and distributed manner. This makes it possible to continue more stable management.

  Further, according to the present invention having the above-described configuration, the timing for starting the sleep period in which no data is received is controlled according to the determination based on the node information. For this reason, the sleep period of each node can be further controlled according to the necessity of data. As a result, the power saving effect at each node can be further improved.

It is a schematic diagram which shows the example of the radio | wireless communications system to which this invention is applied. It is a figure which shows the specific example of the control assistance terminal in the case of assigning one node as a controlled terminal. It is a time chart at the time of the uplink data communication between nodes other than a control assistance terminal. It is a figure which shows the 1st example of the communication period ratio in 1st Embodiment. It is a figure which shows the 2nd example of the communication period ratio in 1st Embodiment. It is a figure which shows the 3rd example of the communication period ratio in 1st Embodiment. (A)-(c) is a figure which shows the example of the communication period in 2nd Embodiment. It is a figure which shows the example which increases the time ratio of a communication period within the basic interval in 3rd Embodiment, and shortens a sleep period in the part. It is a time chart in the case of transmitting emergency control data from a collection control station in a third embodiment to a certain node. It is a time chart in the case of performing very urgent uplink data communication from the node of the controlled terminal in the third embodiment toward the collection control station. 1 is a diagram illustrating an example of a network that conforms to the IEEE 802.15.4 standard. FIG. It is a figure for demonstrating the problem of a prior art.

First Embodiment Hereinafter, a wireless communication method as a first embodiment of the present invention will be described in detail. FIG. 1 is a schematic diagram illustrating an example of a wireless communication system 1 according to the present embodiment. The wireless communication system 1 includes, as wireless communication terminals, nodes 3-1, 3-2, 3-3, and 3-4 having a collection control station (collectively referred to as CS) 2 as a root. A type topology is adopted. In this wireless communication system 1, a lower node 3 performs uplink data communication toward a higher node 3 and CS2. In the wireless communication system 1, the higher order node 3 and CS 2 perform downlink data communication toward the lower order node 3.

  CS2 is the highest-level master device, and collects data transmitted from each of the nodes 3-1 to 3-4 by uplink data communication. The CS 2 also plays a role as a central control unit for controlling the entire wireless communication system 1 and performs downlink data communication of control data to a specific node 3.

  The node 3 is a generic name for devices capable of transmitting and receiving data such as data transmission and relay, and is a communication device compliant with the IEEE 802.15.4 standard, for example. The node 3 is embodied as a sensor that senses predetermined data and transmits the data wirelessly, and for example, a mobile phone, a smartphone, a tablet terminal, a wearable terminal, a notebook personal computer (PC), and the like It may be embodied as a terminal device capable of wireless communication. The node 3 may include a control system such as an actuator. In such a case, for example, it is embodied as a device that can perform control for stopping a valve, control a robot, or perform control for stopping gas. If the node 3 is embodied as an actuator including a control system, various control operations are executed based on the control data transmitted from the CS 2 via the other nodes 3 via the downlink data. It becomes.

  In this embodiment, as shown in the wireless communication system 1 shown in FIG. 1, four nodes 3-1, 3-2, 3-3, 3-4, 3-5 are arranged under CS2. The case will be described as an example, but the present invention is not limited to this. That is, the node 3 arranged in the lower link of the CS 2 may have a tree structure configured by any branching pattern as long as the data is collected by the CS 2, and any number of one or more nodes 3 may be used. It may be constituted by.

  In the wireless communication system 1 of the present embodiment, for example, the CS 2 and the controlled terminal and all the nodes 3 arranged on these routes may be specified as the control support terminal. In the example shown in FIG. 2, when the node 3-4 is assigned as a controlled terminal, CS2, the node 3-1, and the node 3-4 are specified as the control support terminal. In the present embodiment, the communication method is common between the wireless communication between the control support terminals and the wireless communication between other routes, and for example, the communication methods may be different from each other.

  FIG. 3 shows an example of a time chart when relaying data from the node 3-5 to the node 3-2 and communicating data to the CS 2 between the nodes 3. CS2 and each of the nodes 3-2 and 3-5 have an active period (communication period T1 (unit: time t)) and a sleep period T2 within a basic interval T (intermittent standby period (unit: time t)). (Unit: time t) is assigned. Wireless communication can be performed in the communication period T1, and wireless communication cannot be performed in the sleep period T2 because the receiving side shifts to the sleep state. By intentionally providing the sleep period T2 within the basic interval T, power consumption can be reduced, and as a result, power consumption of the entire system can be suppressed.

  When data is transmitted from the node 3-5 to the CS 71, the upper node 3-2 is the master and the lower node 3 is between the node 3-5 and the higher node 3-2. -5 is the slave relationship. Similarly, between the node 3-2 and CS2, CS2 as an upper node is a master and the lower node 3-2 is a slave. In such a relationship between the master and the slave, the upper master assigns the timing of the communication period T1 within the basic interval T, and the lower slave assigns the data in accordance with the timing of the communication period T1 assigned on the master side. Will be sent.

  Under such rules, as shown in FIG. 3, the node 3-5 first matches the data D21 generated at the timing t11 with the communication period T1 starting at the timing t12 of the node 3-2 as the master. Send. The node 3-2 that has received the data D21 transmits the data D21 in accordance with the communication period T1 of the CS2 as the master that starts at the timing t13. As a result, the CS 2 can receive the data D21 within the communication period T1 set by itself.

  In the wireless communication system 1 of the present embodiment, node information of the node 3 is periodically acquired (acquisition means), and a communication period ratio R (basic interval T in the node 3) is acquired based on the node information acquired in each cycle. Is set (setting means).

  In the acquisition means, for example, the CS 2 acquires the node information transmitted from the node 3. In the setting means, for example, the CS 2 sets a communication period ratio R and transmits the communication period ratio R to the node 3. The node 3 assigns a communication period T1 corresponding to the received communication period ratio R.

  The node 3 has node information including at least one of the type of device used for the node 3, the power supply method, and the contribution rate indicating the power supply status. The type of device includes, in addition to the terminal device that embodies the node 3, for example, information related to a device that can perform control for stopping the valve and the like, and includes communication frequency required for the device and the like. The power supply method is a method used to supply power to a terminal device or the like that embodies the node 3, and includes information on a power supply method from, for example, a solar battery, a dry battery, or an external power supply. The contribution rate indicates the ratio of the remaining battery value to the maximum value of the battery used in the terminal device or the like that embodies the node 3.

  In the wireless communication system 1 of the present embodiment, a different communication period ratio R is set for each node 3 based on the node information. The node information is included in the synchronization signal B that is periodically transmitted from the node 3 as necessary. The synchronization signal B includes the communication period ratio R set in the node 3 at the timing of transmitting the synchronization signal B in addition to the node information. The CS 2 acquires the synchronization signal B periodically transmitted from the node 3, and sets the communication period ratio R based on the node information included in the synchronization signal B acquired in each cycle. For this reason, the communication period T1 corresponding to each node 3 can be allocated. Thereby, it is possible to realize a power saving operation in the node 3. Note that the period at which CS2 acquires the synchronization signal B is arbitrary.

  In the wireless communication system 1 of the present embodiment, for example, for information included in node information, information with high communication frequency, or information with a good power supply state (for example, an environment where power supply is easy, battery consumption is low, etc.). Thus, the communication period ratio R is set to be high. For example, in FIG. 4, the communication frequency is high or the power supply state is good in the order of the node 3-1, the node 3-2, and the node 3-3. For this reason, the communication period ratio R1 of the node 3-1 is the highest, the communication period ratio R2 of the node 3-2 is next highest, and the communication period ratio R3 of the node 3-3 is the lowest. As described above, by setting the communication period ratio R based on the node information, it is possible to set the communication period ratio R suitable for each node 3 and to realize the power saving operation in the node 3. It becomes. The communication period ratio R may be set in two or more stages using one threshold, for example, or may be set in three or more stages such as a 100 minute ratio.

  In the wireless communication system 1 of the present embodiment, the frequency of transmitting the synchronization signal B in addition to the communication period ratio R may be set based on, for example, node information. For example, the communication period ratio R2 at the node 3-2 is lower than the communication period ratio R1 at the node 3-1. For this reason, power consumption in the node 3-2 can be suppressed by reducing the frequency of transmitting the synchronization signal B in the node 3-2 compared to the node 3-1. Thus, by setting the frequency of transmitting the synchronization signal B in proportion to the communication period ratio R, the frequency of transmitting the synchronization signal B can be controlled, and the power saving effect at the node 3 can be further increased. It becomes possible to raise.

  The communication period ratio R is set based on, for example, the type of device included in the node information. Each node 3 may have different communication frequencies depending on the type of device. Therefore, by setting the communication period ratio R based on the type of device, it is possible to realize a power saving operation in each node 3.

  As a type of device, for example, when a terminal device having a relatively excellent communication function such as a PC is used as the node 3-1, and a control device for stopping a valve is used as the node 3-3, the control device is a terminal device. The communication frequency may be less than that. For this reason, power consumption can be suppressed by setting a value lower than the communication period ratio R1 of the node 3-1 as the communication period ratio R3 of the node 3-3. In addition, in the node 3-1, it is possible to continue stable operation by setting the communication period ratio R1 corresponding to the communication frequency.

  The communication period ratio R is set based on, for example, a power supply method included in the node information. Each node 3 may have different power supply status depending on the power supply method. For this reason, by setting the communication period ratio R based on the power feeding method, it is possible to realize a power saving operation in each node 3.

  As the power feeding method, for example, as shown in FIG. 5, when external power feeding that is constantly fed is used as the node 3-2 and feeding by a solar cell is used as the node 3-5, the solar depending on the installation environment and the weather A battery has a large amount of change in power supply over time as compared with external power supply. For this reason, in the node 3-5, a different communication period ratio R5 is set for each fixed period. For example, the communication period ratio R5a is set in a cloudy day when power is hardly supplied, and the communication period is higher than the communication period ratio R5a in a fine day when power is easily supplied. The ratio is R5b. Thereby, the optimal communication period ratio R5 can be set for the node 3-5, and power consumption can be suppressed. Further, in the node 3-2, it is possible to continue stable operation by setting the communication period ratio R2 that is equal to every certain period.

  The communication period ratio R is set based on, for example, the battery contribution rate included in the node information. The communication period ratio R is set in proportion to the contribution rate, for example. For this reason, the power saving operation in each node 3 can be realized by setting the communication period ratio R according to the variation of the contribution rate.

  For example, as shown in FIG. 6, a device or the like that consumes a small amount of battery is used as the node 3-1, and a device or the like that consumes a large amount of battery is used as the node 3-4. In this case, when the contribution ratios of the node 3-1 and the node 3-4 are substantially equal to each other, the communication period ratio R4a of the node 3-4 is substantially equal to the communication period ratio R1 of the node 3-1. In contrast, the contribution ratio of the node 3-4 decreases with time. For this reason, the communication period ratio R4b of the node 3-4 is lower than the communication period ratio R1 of the node 3-1. Thereby, the battery consumption of the node 3-4 can be suppressed.

  Thus, by setting a higher communication period ratio R for nodes 3 with higher contribution ratios, it is possible to achieve uniform battery consumption for each node 3 and to establish fairness within the network. . Further, even when the node 3 with good power supply state and the node 3 with poor power supply state coexist, the relative battery consumption of each node 3 can be made uniform. Thereby, it is possible to improve the power saving operation effect in each node 3. Further, it is possible to avoid a situation in which the operation of the entire wireless network is difficult to continue due to battery consumption of only some of the nodes 3, and it is possible to continue stable operation.

  The radio communication system 1 of the present embodiment can be assigned to the node 3 as a control terminal or a controlled terminal based on the contribution rate, for example. For example, as illustrated in FIG. 6, the node 3-4 having a low contribution rate can be designated as a lower level of the node 3-1 having a high contribution rate. Therefore, an operation mode in which a large number of data frames are relayed preferentially to the node 3 in a good power supply state is formed in an autonomous and distributed manner. This makes it possible to continue more stable management. Further, it is possible to make the battery consumption uniform for each node 3 and to establish fairness within the network.

  Moreover, in the radio | wireless communications system 1 of this embodiment, allocation of the control terminal or controlled terminal in each node 3 can be changed based on the contribution rate acquired periodically. For this reason, even when the contribution ratio of each node 3 changes due to a change with time, the relative battery consumption of each node 3 can be made uniform. As a result, it is possible to avoid a situation where the operation of the entire wireless network becomes difficult to continue due to battery consumption of only some of the nodes 3, and it is possible to continue stable operation.

  In addition, when allocating to the node 3 as a control terminal or a controlled terminal, for example, the node 3 may be based on at least one of a device type, a power supply method, and a contribution rate. In this case, more stable operation can be continued. When assigning to the node 3 as a control terminal or a controlled terminal, setting of whether or not to give priority to any of the device type, power supply method, and contribution rate is arbitrary.

  Further, the node 3 described above may be a concept including CS2. That is, the process performed in each node 3 may be performed in CS2, and the process performed in CS2 may be performed in node 3. Further, CS2 may be replaced with a so-called node 3.

  In addition, it is needless to say that the above-described processes can be similarly applied to communication between the CS 2 and the node 3 and communication between the nodes 3.

Second Embodiment Next, a wireless communication method according to a second embodiment of the present invention will be described in detail. In addition, description is abbreviate | omitted about the main structures similar to embodiment mentioned above.

  In the wireless communication system 1 of this embodiment, a communication period T1 in which data reception is started and a sleep period T2 in which data reception is not started are allocated within the basic interval T that is periodically set in the node 3 (allocation means). ), The first data D1 and the second data D2 are sequentially transmitted to the node 3 within the communication period T1 of the node 3 (transmission means). Thereafter, the timing for starting the sleep period T2 is controlled according to the determination of whether or not to receive the second data D2 (control means).

  In the assigning means, for example, CS2 or the upper node 3 assigns the communication period T1 to the lower node 3. In the transmission means, for example, CS2 transmits each data D1, D2 to the node 3. In the control means, for example, the node 3 determines whether or not to receive based on the header information stored in the first half of the second data D2, and controls the timing of starting the sleep period T2.

  The first data D1 includes control data of a device attached to the node 3, and includes, for example, control data that requires urgency, data related to assignment change in the communication period T1, and the like. Transmission of the first data D1 is started and ended within the period of the communication period T1.

  The second data D2 includes data necessary for only some of the nodes 3, and includes data necessary for communication, for example. After the transmission of the first data D1, the transmission of the second data D2 is started within the period of the communication period T1, and the transmission is ended outside the period of the communication period T1.

  In the wireless communication system 1 of the present embodiment, the node 3 controls the timing for starting the sleep period T2 in accordance with the determination as to whether or not the second data D2 is received. Therefore, the sleep period T2 of each node 3 can be controlled according to the necessity of the second data D2. Thereby, it is possible to realize a power saving operation in each node 3.

  An example of receiving the second data D2 based on the determination described above will be described using the node 3-1 in FIG. In this case, the node 3-1 starts the sleep period T <b> 21 after receiving the second data D <b> 2. That is, the node 3-1 adds the extension period T1h to the communication period T11 in order to receive the second data D2. For this reason, the communication period T1 can be extended only to the node 3-1 that requires the second data D2. Thereby, it becomes possible to improve the power saving effect in each node 3.

  An example of the case where the second data D2 is not received by the determination described above will be described using the node 3-2 in FIG. In this case, the node 3-2 determines that the second data D2 is not received based on the header information stored in the first half of the second data D2, for example. Thereafter, simultaneously with the end of the communication period T12, the sleep period T22 is started. For this reason, the node 3-2 does not need to extend the communication period T1 and can shorten the communication period T12, compared with the node 3-1 that receives the second data D2. Thereby, it becomes possible to improve the power saving effect in each node 3.

  In the control means, the determination as to whether or not each node 3 receives the second data D2 may be made by transmitting information relating to the determination from CS2 to each node 3, for example. In this case, the CS 2 generates information related to the determination for each node 3 based on the synchronization signal B acquired from each node 3 and transmits the information to each node 3.

  As an example of the case where the above-described determination is performed, a description will be given using the node 3-3 in FIG. In this case, the communication period T1 in the node 3-3 includes a first communication period T13 in which the first data D1 is transmitted and a second communication period T14 in which the second data D2 is transmitted. The second communication period T14 is allocated after the first communication period T13, and may be allocated separately from the first communication period T13, for example. The length of the second communication period T14 is shorter than the length of the first communication period T13, for example.

  At this time, when the second data D2 is received by the determination, the node 3-3 starts the sleep period T23 after receiving the second data D2, similarly to the node 3-1 in FIG. To do. On the other hand, when the second data D2 is not received by the determination, the node 3-3 starts the sleep period T24 instead of starting the second communication period T14 after the end of the first communication period T13. For this reason, when the second data D2 is not received, the communication period T1 can be significantly shortened. Thereby, it becomes possible to greatly improve the power saving effect in each node 3.

  Note that the wireless communication system 1 of the present embodiment may be combined with the above-described embodiment, for example. That is, the node 3 higher than the CS 2 or each node 3 acquires the node information of each node 3, generates information related to the determination as to whether or not to receive the second data D 2, and transmits the information to each node 3. Each node 3 determines whether or not to receive the second data D2 based on the node information or the received CS2 or the information related to the determination generated by the upper node 3. For this reason, the communication period T1 suitable for each node 3 can be set in detail based on the node information acquired by the CS2. As a result, the power saving effect in each node 3 can be further improved.

Third Embodiment Next, a wireless communication method as a third embodiment of the present invention will be described in detail. In addition, description is abbreviate | omitted about the main structures similar to embodiment mentioned above.

  In the wireless communication system 1 of the present embodiment, at least one node 3 among a plurality of nodes 3 is assigned as a controlled terminal. The controlled terminal is a node 3 that is embodied as an actuator or the like including a control system among the nodes 3 and that is likely to receive urgent control data from the CS 2. The urgent control data here is control data for urgently stopping the valve or control data for urgently stopping the gas pipe. In the present embodiment, the communication method differs between the wireless communication between the control support terminals and the wireless communication between other routes.

  This allocation of controlled terminals may be performed manually by an administrator or user of the wireless communication system 1 in advance, or as a controlled terminal on the CS 2 side based on information sent from each node 3. You may make it identify automatically. In such a case, the case requiring urgency is classified in advance, and if the information sent from the node 3 is included in the case requiring urgency, this is specified as the controlled terminal. Also good. Other than this, it may be determined whether or not the terminal is a controlled terminal based on information sent from the node 3. For example, when CS2 identifies that a signal received from a certain node 3 is a unique signal sent from a robot, it identifies that there is a possibility of sending urgent control data, and You may make it allocate as a controlled terminal.

  For the control support terminals (CS2, node 3-1, node 3-4), as shown in FIG. 8, the time ratio of the communication period T1 is increased within the basic interval T, and the sleep period T2 is shortened accordingly. . The amount of increase in the communication period T1 may be any value, but as shown in FIG. 8, all the basic intervals T may be assigned to the communication period T1 and the sleep period T2 may be set to zero. Further, as shown in FIG. 8, the communication period T1 may be set to the end points Ts1 to Ts3 or the like so as to be shorter than the basic interval T. In such a case, the end points Ts1 to Ts3 are the start points of the sleep period T2.

  Here, when transmitting control data from the CS 2 to the node 3-4, the control data is transmitted from the control support terminal CS2 to the node 3-4 via the node 3-1. For the control support terminals (CS2, node 3-1, node 3-4), as shown in the time chart of FIG. 9, the basic interval T is allotted to the communication period T1 and the sleep period T2 is set to 0 as an example. Explain. With the time ratio of the active communication period T1 thus increased, the downlink data communication is performed from the CS2 to the control data D22 to the node 3-4.

  CS2 generates this data D22 at timing t14 and transmits it to the node 3-1. Since all basic intervals are assigned to the communication period T1, the node 3-1 can receive the data D22 at the timing t14, and can transmit the data D22 to the node 3-4 at the same timing t14. Since all the basic intervals of the node 3-4 are also allocated to the communication period T1, the data D22 can be received at this timing t14.

  For this reason, according to this embodiment, it becomes possible to perform downlink data communication of data D22 from CS2 to node 3-4 more quickly. Even if the data D22 requires urgency, the data D22 can be transmitted to the node 3-4 as the controlled terminal without waiting until the sleep period T2 elapses. Various controls in the node 3-4 performed based on this are quickly executed. As a result, it is possible to prevent a serious control delay caused by a delay in transmission of data D22 from CS2 to node 3-4 as a controlled terminal.

  By the way, when performing upstream data communication of data D23 from these control support terminals (CS2, node 3-1, node 3-4) from node 3-4 to CS2, this time ratio was increased. You may make it carry out using communication period T1. Further, as shown in FIG. 9, it is assumed that CS2, node 3-1, and node 3-4 are not specified as control support terminals and the time ratio of communication period T1 is not increased, and is designated by the master side. The data D23 may be transmitted in accordance with the communication period T1. In such a case, as shown in FIG. 9, the data D23 generated by the node 3-4 at the timing t15 is subjected to uplink data communication to the node 3-1 in the communication period T1 starting at the timing t16. Then, the node 3-1 transmits the data D23 in the communication period T1 that starts at the timing t17 specified by CS2.

  In particular, there are only a few nodes 3 that need to send control data requiring urgency in the total number of nodes. Therefore, the ratio of the control support terminal to the total number of nodes is very small. Only such a control support terminal increases the time ratio of the communication period T1 as described above, and for the other nodes 3, the sleep period T2 is set longer without increasing the time ratio of the communication period T1 as in the conventional case. As a result, the power consumption of the entire wireless communication system 1 does not increase so much, and the power saving performance can be continuously maintained.

  Therefore, according to the present embodiment, it is possible to perform downlink data communication more promptly for data requiring urgency from the CS 2 to the node 3 while maintaining the power saving performance of the entire system.

  Note that the present embodiment is not limited to the above-described embodiment. For example, the increase amount of the communication period T1 shown in FIG. 8 may be determined based on the allowable delay time until transmission from CS2 to the node 3 of the controlled terminal. The allowable delay time referred to here is a delay time allowed for sending control data requiring urgency from the CS 2 to the node 3 of the controlled terminal. This allowable delay time may be defined as, for example, within seconds from the time when the control data is generated in the CS 2 as a start time. The wireless communication system 1 identifies the allowable delay time based on information transmitted from the controlled terminal when the control support terminal is actually specified, and determines the increase amount of the communication period T1 based on the allowable delay time. It may be. In particular, when there are a plurality of controlled terminals, the information transmitted from each of the controlled terminals may be grasped, and the amount of increase may be different between the controlled terminals.

  Incidentally, the allowable delay time in the controlled terminal may be set based on information acquired from the controlled terminal, but may be input in advance to the CS2 side via a user or a system administrator. Good. Further, after the wireless communication system 1 is in operation, the CS 2 may make an inquiry to each node 3 each time, and the allowable delay time may be calculated by identifying the data included in the response. In such a case, it is first determined whether the data sent from the node 3 is data specific to the actuator having the control system, and if it is data specific to the actuator, the details are analyzed. For example, if the node 3 is an actuator and is responsible for closing the valve, the time until the valve is closed, the flow rate of the fluid flowing through the pipe provided with the valve, and the size of the pipe Or the like, and an allowable delay time may be set based on the acquired data. In such a case, it is desirable to set the increase amount of the time ratio of the communication period T1 to be shorter as the allowable delay time is longer.

  Further, the radio communication system 1 may further determine the amount of increase in the time ratio of the communication period T1 according to the number of nodes between the controlled terminals from CS2. For example, in the example of FIG. 2, the number of nodes between CS 2 and the node 3-4 as the controlled terminal is 1. As the number of nodes between the CS2 and the controlled terminal increases, the urgent data reaches the node 3 of the controlled terminal from the CS2. Conversely, as the number of nodes between the controlled terminals from CS2 increases, the arrival time of control data requiring urgency to the controlled terminal is increased by increasing the amount of increase in the time ratio of the communication period T1. Is possible.

  Furthermore, according to the present embodiment, as shown in FIG. 10, when a highly urgent uplink data communication is performed from the node 3 of the controlled terminal to the CS 2, the communication period T1 with an increased time ratio is given priority. May be used. For example, in the case where the node 3-4 as a controlled terminal has a control function as an actuator and a sensing function for detecting various data, an emergency that leads to a failure such as a plosive sound, noise, loose screws, etc. Data may be detected. When such emergency data is detected at t18, the node 3-4 generates data D24 based on the detected data and transmits it to the node 3-1. The node 3-1 performs uplink data communication of the data D24 to CS2.

  Since the time ratio of the communication period T1 has been increased in advance, the control support terminal temporarily increases the communication period T1 to the basic interval T, so that the emergency data D24 generated at t18 is the sleep period. It is possible to immediately send to CS2 without waiting at T2.

  Note that the wireless communication system 1 of the present embodiment may be combined with the above-described embodiment, for example. Thereby, it is possible to further improve the power saving effect in the entire system.

1 Wireless communication system 2, 71 CS
3, 71 Node 72 Node B Communication D for synchronization Data R Communication period ratio T Basic interval T1 Communication period T2 Sleep period

Claims (6)

In a wireless communication method in a tree-type network that transmits and receives data between two or more nodes arranged with a collection control station as a root,
Obtain node information of the above nodes periodically,
A wireless communication method, wherein a communication period ratio indicating a ratio of a communication period to a basic interval in the node is set based on the node information acquired in each cycle. Obtain a synchronization signal periodically transmitted from the node,
The frequency of transmitting the synchronization signal of the node and the communication period ratio are set based on the node information included in the synchronization signal acquired in each cycle. Wireless communication method. The node information has a contribution ratio indicating a ratio of a remaining battery value when the node information is acquired with respect to a maximum value of the battery,
The wireless communication method according to claim 1, wherein the communication period ratio is set higher as the contribution ratio increases. The wireless communication method according to claim 3, wherein the first node having the first contribution rate is designated as a lower level of the second node having the second contribution rate higher than the first contribution rate. The node information includes at least one of a device type used for the node, a power supply method, and a contribution indicating a ratio of a remaining battery value when the node information is acquired with respect to a maximum value of the battery,
Based on the node information or information related to the determination generated by the collection control station or a node higher than the node, the determination whether the node receives the data is set,
The wireless communication method according to claim 1, wherein the timing for starting a sleep period in which the data is not received is controlled according to the determination. In a wireless communication system in a tree-type network that transmits and receives data between two or more nodes arranged with a collection control station as a root,
Obtaining means for periodically obtaining node information of the node;
A wireless communication system comprising: setting means for setting a communication period ratio indicating a ratio of a communication period to a basic interval in the node based on the node information acquired in each cycle.

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