JP2010245725A - Sensor network system and sensor network control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch a frequency to an optimal one by taking the characteristics of a sensor network system into consideration. <P>SOLUTION: Each relay router 10 transmits to a reader 20 importance related information about the importance of sensor data collection processing to be performed personally, scans a using state of each candidate frequency around self in the entire sensor data collection processing that is performed in the entire sensor network system 1, and transmits obtained scan results to the reader 20. The reader 20 calculates priorities showing the degrees for using the candidate frequency preferentially for each candidate frequency on the basis of the importance related information and the scan results received from the relay router 10, and instructs each relay router 10 to switch to the optimal frequency selected on the basis of the priorities. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sensor network technology, and more particularly to a technology for setting a frequency used for wireless communication between nodes according to the wireless environment of each node.

  In recent years, including security management, air conditioning, lighting, room temperature management, telemetering of electricity and gas meters, distribution management at production sites and warehouses, remote control of electrical products at home, heart rate, body temperature, posture, movement of limbs, The application range of wireless networks using sensors, such as monitoring of biological information in emergency situations, is expanding.

  A control network using such a wireless network is called a sensor network system, and a plurality of nodes equipped with sensors that measure physical quantities such as temperature, humidity, current, and magnet switch are networked by wireless communication. Sensor data obtained at these nodes is collected. There is also a sensor network in which actuators such as LEDs and buzzers are mounted on a node and control data for controlling these actuators is distributed.

  Wireless communication used in the sensor network system includes weak wireless, specific low-power wireless, and wireless communication such as ZigBee (registered trademark) based on IEEE 802.15.4. In particular, ZigBee is promising because it supports multi-hop radio, has features such as simplicity, high reliability, low cost, and low power consumption, and can construct a flexible network.

These wireless communications used in the sensor network are techniques for realizing a PAN (Personal Area Network), and the same radio frequency is used in the PAN. Further, in the sensor network, it is necessary to perform wireless communication using relatively small transmission power in order to realize node miniaturization and power saving.
Therefore, since it is easily affected by the surrounding wireless environment, the frequency used in common by all nodes of the sensor network is an important factor directly related to the quality performance of the sensor network.

When determining the frequency used for such wireless communication, in wireless networks such as wireless LAN and wireless tags, the access point or reader scans the frequency used in the surroundings at startup and selects the optimal frequency with less interference is doing.
At this time, there may be a case where the surrounding wireless environment changes from moment to moment. For example, when a new wireless device is installed around an arbitrary node, or when the node itself is moved around another wireless device, or when the node itself moves around another wireless device, Radio interference with the wireless device newly occurs, and normal wireless communication cannot be performed between nodes.

  Conventionally, as a technology corresponding to changes in the wireless environment, two frequencies used in the wireless network are determined, and when switching from one frequency to the other frequency, the surrounding wireless environment is scanned with an arbitrary wireless device, Determines whether or not frequency switching is possible in the wireless device, and based on the obtained scan results and switching result determination results, one wireless device selected as the master determines whether or not to switch to the other frequency in the other wireless device. The technique which performs is proposed (for example, refer patent document 1 etc.).

Special table 2008-539609 gazette

"ZigBee Specification", Document 053474r17, ZigBee Standards Organization, 2008/1/17

Such a conventional technique automates frequency switching by determining whether or not to switch frequencies based on a scan result obtained from a wireless device or a switchability determination result on the premise of a general wireless network. Yes.
However, each sensor network system has features unique to each sensor network system, such as a topology unique to multi-hop wireless communication and importance of sensor data. For this reason, simply applying the prior art to the sensor network cannot perform frequency switching in consideration of the characteristics of the sensor network system, and the sensor network system cannot obtain good performance. is there.

  That is, in the sensor network system, various sensor data are collected using multi-hop wireless from nodes arranged in a relatively wide range using relatively small transmission power. For this reason, it is necessary to assume a case where the surrounding wireless environment in each node is greatly different depending on the installation position of each node.

  FIG. 14 is an explanatory diagram showing the communication status of the sensor network (before frequency switching). Here, relay routers R1, R2, R3, and R4 are sequentially connected in a multi-hop manner to a reader L that manages the entire network, and sensor devices are arranged in the communication areas of these relay routers R1 to R4. Has been. In this sensor network, PAN is realized, and the reader L, the relay routers R1 to R4, and each node of the sensor device perform wireless communication with each other using the same frequency CH1. Thereby, the sensor data obtained by each sensor device is collected by the reader L via the relay routers R1 to R4, and is notified from the reader L to the host device.

In such a sensor network, an interference source for the frequency CH1 is generated around the relay router R4 operating at the frequency CH1, and the transmission error rate (PER) of wireless communication to the adjacent relay router R3 is increased to 30%. In this case, it is necessary to switch the frequency CH1 to, for example, the frequency CH2 with low interference.
When the reader L switches the frequency of the entire sensor network from CH1 to CH2 by confirming the deterioration of the communication status according to the report from the relay router R4 and issuing a frequency switching instruction to each node, The communication situation between the routers R4 and R3 is improved.

FIG. 15 is an explanatory diagram showing the communication status of the sensor network (after frequency switching). Here, the transmission error rate between the relay routers R4 and R3 is reduced to 0% by switching to the frequency CH2.
However, since an interference source for the frequency CH2 originally existed around the relay router R1, the communication situation between the reader L and the relay router R1 that was good at the frequency CH1 deteriorates, for example, transmission The error rate has increased to 10%.
Therefore, it is necessary to comprehensively consider not only the radio environment of some nodes but also the radio environments of all nodes in determining whether to switch frequencies.

Further, in the case of multi-hop wireless, sensor data from each sensor device is collected through wireless communication between the relay routers R1 to R4 and between the relay router R1 and the reader L. For this reason, the degree of influence on the sensor data collection efficiency in the entire sensor network differs depending on which node the wireless communication is where the communication state deteriorates.
For example, in the wireless communication between the reader L and the relay router R1, all sensor data is exchanged. Therefore, as shown in FIG. 15, the deterioration of the communication state in the wireless communication greatly affects the sensor data collection efficiency. affect. On the other hand, the wireless communication between the relay routers R4 and R3 affects only the sensor data collected by the relay router 4.
Therefore, it is necessary to consider not only the wireless environment of a node but also the amount of sensor data handled by that node in determining whether to switch frequencies.

In the sensor network system, it is rare that sensor data obtained from each node has the same importance, and each sensor data has a different importance. Therefore, in order to preferentially collect highly important sensor data, it is necessary to switch to a frequency so that the communication status of the node is preferentially good.
Furthermore, because the sensor network system uses multi-hop radio, the node acting as a relay router itself does not sense sensor data with high importance, but relays sensor data with high importance. There is also. Accordingly, it is necessary to switch to such a frequency so that the wireless status of such a relay router is preferentially favorable.

  The present invention is for solving such a problem. In a sensor network system in which a plurality of nodes that perform wireless communication using the same frequency collects sensor data by performing multi-hop wireless communication, the sensor network system It is an object of the present invention to provide a sensor network control technique capable of switching to an optimum frequency in consideration of the above characteristics.

  In order to achieve such an object, a sensor network system according to the present invention includes a plurality of end devices, a plurality of nodes as nodes that perform wireless communication with each other using any one of a plurality of candidate frequencies in common. Relay router and one reader, the end device wirelessly transmits the sensor data measured by its own sensor, the relay router transfers the received sensor data to the reader by multi-hop wireless, and the reader passes through the relay router. The sensor network system that notifies the higher-level device of the sensor data collected in this way, and the relay router is an importance level related to the importance of the sensor data collection process performed by itself in the entire sensor data collection process performed in the entire sensor network system. Importance related information processing unit for transmitting related information to the reader; Scan processing unit that scans the usage status of each candidate frequency around you and sends the obtained scan result to the reader, and the frequency that is instructed the frequency to be used in wireless communication according to the frequency switching instruction from the reader The frequency switching processing unit for switching to the reader, the reader selects a candidate frequency that can be used by the relay router based on the scan result received from each relay router, and the important received from each relay router. Based on the degree-related information, the importance calculation unit for calculating the importance related to the sensor data collection processing performed in the relay router, the importance for each relay router, and the frequency selection result, for each candidate frequency, A priority calculation unit for calculating a priority indicating the degree to which the candidate frequency should be used with priority, and each candidate frequency Choose the best frequency based on the priority, and a frequency switching processing unit for transmitting a frequency switching instruction to switch to the optimal frequency to the relay router.

  At this time, the importance-related information processing unit transmits information indicating a child node connected to the reader to the reader as importance-related information, and the importance calculation unit transmits the relay based on the importance-related information. The number of child nodes of the router may be counted, and an index value that increases as the obtained number of child nodes increases may be calculated as the importance of the relay router.

  In addition, the importance-related information processing unit transmits information indicating the parent node to which the self is connected as importance-related information to the reader, and the importance calculation unit determines that the relay router based on the importance-related information. The number of hops from the leader to the leader may be counted, and an index value corresponding to the obtained number of hops may be calculated as the importance of the relay router.

  Also, the importance-related information processing unit sends information indicating the importance of the sensor data measured by the child nodes connected to the reader to the reader as the importance-related information. Based on the related information, the importance of all the sensor data measured at each child node of the relay router is summed, and an index value that increases as the obtained total value increases is calculated as the importance of the relay router. You may do it.

  The sensor network control method according to the present invention includes a plurality of end devices, a plurality of relay routers, and a single node that perform wireless communication with each other using any one of a plurality of candidate frequencies in common. Including the reader, the end device wirelessly transmits the sensor data measured by its own sensor, the relay router transfers the received sensor data to the reader by multi-hop wireless, and the reader sends the sensor data collected via the relay router to the host A sensor network control method used in a sensor network system for notifying a device, in which an importance-related information processing unit of a relay router performs sensor data collection performed by itself in an overall sensor data collection process performed in the entire sensor network system Import the importance related information on the importance of processing The information processing step related to the importance level to be transmitted, the scan processing unit of the relay router scans the usage status of each candidate frequency in its surroundings, the scan processing step of transmitting the obtained scan result to the reader, the relay router In response to a frequency switching instruction from the reader, the frequency switching processing unit switches the frequency used for wireless communication to the instructed frequency, and the frequency selection unit of the reader receives the scan result received from each relay router. Based on the frequency selection step for selecting candidate frequencies that can be used in the relay router based on the importance level related information received from the relay router by the importance level calculation unit of the reader, Importance calculation step for calculating the importance of data collection processing and leader priority calculation A priority calculating step for calculating a priority indicating a degree to which the candidate frequency should be used with priority for each candidate frequency from the importance for each relay router and the frequency selection result; The frequency switching processing unit includes a frequency switching processing step of selecting an optimal frequency based on the priority of each candidate frequency and transmitting a frequency switching instruction for instructing switching to the optimal frequency to the relay router.

  At this time, in the importance related information processing step, information indicating a child node connected to itself is transmitted to the reader as importance related information, and in the importance calculating step, the relay is performed based on the importance related information. The number of child nodes of the router may be counted, and an index value that increases as the obtained number of child nodes increases may be calculated as the importance of the relay router.

  Also, in the importance level information processing step, information indicating the parent node to which it is connected is transmitted to the reader as importance level related information, and in the importance level calculation step, the relay router is based on the importance level related information. The number of hops from the leader to the leader may be counted, and an index value corresponding to the obtained number of hops may be calculated as the importance of the relay router.

  Also, in the importance level information processing step, information indicating the importance level of sensor data measured by the child nodes connected to the node is transmitted to the reader as importance level related information. Based on the related information, the importance of all the sensor data measured at each child node of the relay router is summed, and an index value that increases as the obtained total value increases is calculated as the importance of the relay router. You may do it.

  According to the present invention, in the sensor network system 1 in which a plurality of nodes performing wireless communication using the same frequency collects sensor data by performing multi-hop wireless communication, the characteristics of the sensor network system, that is, the wireless environment of each node Considering the topology of the entire sensor network system or the importance of each sensor data, it is possible to appropriately determine whether to switch frequencies.

It is a block diagram which shows the structure of the sensor network system concerning this Embodiment of this invention. It is explanatory drawing which shows the topology information of a child node. It is explanatory drawing which shows the topology information of the relay router itself. It is explanatory drawing which shows sensor data importance information. It is explanatory drawing which shows a scanning result. It is a flowchart which shows the processing operation of a relay router. It is a flowchart which shows the processing operation of a reader. It is a flowchart which shows a frequency switching process. It is explanatory drawing which shows a frequency selection result. It is explanatory drawing which shows importance. It is explanatory drawing which shows a priority. It is a structural example of a sensor network system. It is a sequence diagram which shows the operation example of the sensor network system concerning this Embodiment. It is explanatory drawing which shows the communication condition (before frequency switching) of a sensor network. It is explanatory drawing which shows the communication condition (after frequency switching) of a sensor network.

Next, an embodiment of the present invention will be described with reference to the drawings.
[Sensor network system]
First, a sensor network system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a sensor network system according to the present embodiment.

  The sensor network system 1 includes a plurality of end devices ED and a plurality of relay routers 10 as nodes that perform wireless communication with each other by commonly using any one of a plurality of preset candidate frequencies (channels). , And one reader 20.

  The end device ED consists of a small terminal device equipped with sensors, wireless communication modules, control semiconductor chips, etc. that consist of various sensor devices that measure physical quantities such as temperature, humidity, current, and magnet switch. It is installed and has a function of wirelessly transmitting sensor data measured by its own sensor.

The relay router 10 is a small wireless communication terminal, and has a function of transferring sensor data received from the end device ED to the reader 20 by performing multi-hop wireless communication with other relay routers 10.
The reader 20 is composed of an information processing device having a wireless communication function, and has a function of notifying sensor data collected via the relay router 10 to the host device 30.

  In the present embodiment, each relay router 10 transmits, to the reader 20, importance-related information regarding the importance of the sensor data collection process performed by itself in the entire sensor data collection process performed in the entire sensor network system 1. The usage situation of each candidate frequency in the surroundings of itself is scanned, and the obtained scan result is transmitted to the reader 20, and the importance level related information received from the relay router 10 and the scan result are read by the reader 20 for each candidate frequency. The priority indicating the degree to which the candidate frequency should be used with priority is calculated, and each relay router 10 is instructed to switch to the optimum frequency selected based on these priorities.

[Configuration of relay router]
Next, the configuration of the relay router will be described in detail with reference to FIG.
The relay router 10 includes, as main functional units, a sensor 11, a wireless interface unit (hereinafter referred to as a wireless I / F unit) 12, an initial processing unit 13, a storage unit 14, a sensor data processing unit 15, and importance-related information processing. A unit 16, an error processing unit 17, a frequency scan processing unit 18, and a frequency switching processing unit 19 are provided.

The sensor 11 includes various sensor devices such as temperature, humidity, current, and magnet switch, and has a function of measuring a physical quantity from around the relay router 10.
The wireless I / F unit 12 includes a dedicated wireless communication circuit, and has a function of performing wireless communication with other nodes using a frequency designated by the reader 20.
The initial processing unit 13 has a function of connecting to the sensor network system 1 by performing connection processing with the reader 20 via its parent node when initializing the operation of the relay router 10.

The storage unit 14 includes a storage device such as a semiconductor memory, and has a function of storing processing information necessary for the relay router 10 to connect to the sensor network system 1 and perform wireless communication and sensor data collection processing. .
Main processing information stored in the storage unit 14 includes channel information indicating candidate frequencies used for wireless communication and current frequencies, sensor data measured by the sensor 11, sensor data received from subordinate nodes, readers 20 includes importance-related information for calculating the importance used for the frequency switching process at 20, and scan results indicating the use status of each candidate frequency in the surroundings scanned by the wireless I / F unit 12.

Among them, the importance related information includes the topology information of the child node adjacent to the relay router 10, the topology information of the relay router 10 itself, the child node adjacent to the relay router 10 and the sensor data measured by the relay router 10 itself. There is sensor data importance information indicating the importance.
Here, the child node is a node that is located in the communication area of the relay router 10 and performs direct wireless communication with the relay router 10 and is directly connected to the relay router 10 and the multi-hop wireless as well as the end device ED. A connected relay node 10 at a lower level (opposite the leader 20 in the network topology) is also included. Note that the relay node 10 at the upper level (on the leader 20 side in the network topology) that is directly connected to the relay router 10 via multi-hop radio is referred to as a parent node.

FIG. 2 is an explanatory diagram showing topology information of child nodes.
The topology information of the child node adjacent to the relay router 10 includes the neighbor information regarding the lower-level relay route directly connected to the relay router 10 by multi-hop radio, and the end device ED directly connected to the relay router 10. And neighbor information about. A neighbor generally refers to an adjacent node of the relay router 10.

  The individual neighbor information includes a PAN ID for identifying the PAN of the sensor network system 1 to which the child node belongs, a node ID for identifying the child node on the PAN, the child node includes a leader, a relay router, Various attribute information such as a node type indicating which type of the end device is included is included.

FIG. 3 is an explanatory diagram showing the topology information of the relay router itself.
The topology information of the relay router itself includes the same PANID, node ID, and node type as the neighbor information, a transmission destination node ID for identifying the reader 20 as the transmission destination of the sensor data on the PAN, and the relay router. Various attribute information such as a parent node ID for identifying a parent node directly belonging to the PAN is included.

FIG. 4 is an explanatory diagram showing sensor data importance information.
The sensor data importance level information is installed in its own sensor 11, a sensor mounted on a lower relay route directly connected to the relay router 10 by multihop radio, and an end device ED directly connected to the relay router 10. For each sensor, the importance of sensor data measured by these sensors is included.
The individual sensor data importance information includes the sensor type according to the sensor data measured by the sensor, such as temperature, humidity, current, and magnet switch, and the importance of the sensor data in the sensor data collection process in the entire sensor network system 1 Various attribute information such as importance indicating gender is included.

FIG. 5 is an explanatory diagram showing a scan result.
In the scan result, the electric field strength (noise signal level) at the candidate frequency measured by the wireless I / F unit 12 of the relay router 10 is registered for each of a plurality of preset candidate frequencies (channels).

  The sensor data processing unit 15 transmits the sensor data measured by the sensor 11 and the sensor data received from the subordinate nodes from the wireless I / F unit 12 to the parent node at a constant period or event driven, thereby to the reader 20. It has a function to notify.

  The importance-related information processing unit 16 has a function of acquiring importance-related information related to the importance of the sensor data collection process performed by itself in the entire sensor data collection process performed by the entire sensor network system 1, and a wireless A function of receiving importance level related information from a subordinate node by the I / F unit 12 and transmitting the importance level related information from the wireless I / F unit 12 to the parent node in a fixed cycle or event driven, to the reader 20 It has a function to notify.

  The error processing unit 17 counts the number of times that the acknowledgment (ACK) from the parent node with respect to the importance-related information and sensor data transmitted to the parent node has not been normally received as the number of errors, and data transmission over a certain period When the transmission error rate indicating the ratio between the number of times and the number of errors exceeds a specified value, a function for notifying the reader 20 by transmitting an error report indicating the error status from the wireless I / F unit 12 to the parent node is provided. Have.

  A known technique may be used for the error report. For example, ZigBee's Frequency Agility function defines a specification in which an error report is transmitted from a node to a coordinator managing a PAN when a certain error bit rate (25%) is exceeded (for example, And non-patent document 1).

  The frequency scan processing unit 18 controls the wireless I / F unit 12 in response to the scan request received from the reader 20 received by the wireless I / F unit 12, and determines the electric field strength of each candidate frequency around itself. It has a function of scanning as a use state of the candidate frequency and a function of notifying the reader 20 by transmitting the obtained scan result from the wireless I / F unit 12 to the parent node.

  The frequency switching processing unit 19 controls the wireless I / F unit 12 according to the frequency switching instruction from the reader 20 received by the wireless I / F unit 12 and is instructed about the frequency used for wireless communication with other nodes. It has a function to switch to a different frequency.

  The function units of the initial processing unit 13, the sensor data processing unit 15, the importance-related information processing unit 16, the error processing unit 17, the frequency scan processing unit 18, and the frequency switching processing unit 19 in the relay router 10 are a CPU or the like. And an arithmetic processing unit that implements various processing units by reading out and executing a program stored in the storage unit 14. Some or all of these functional units may be realized by an arithmetic processing circuit.

[Reader configuration]
Next, the configuration of the reader will be described in detail with reference to FIG.
The reader 20 includes, as main functions, a communication interface unit (hereinafter referred to as a communication I / F unit) 21, a wireless interface unit (hereinafter referred to as a wireless I / F unit) 22, an initial processing unit 23, a storage unit 24, a sensor. A data processing unit 25, an importance calculation unit 26, a frequency selection unit 27, a priority calculation unit 28, and a frequency switching processing unit 29 are provided.

The communication I / F unit 21 includes a dedicated data communication circuit, and has a function of performing data communication with a host device 30 such as a server via a communication line such as a LAN.
The wireless I / F unit 22 includes a dedicated wireless communication circuit, and has a function of performing wireless communication with other nodes using the optimum frequency determined by the initial processing unit 23 or the frequency switching processing unit 29.

  When initializing the operation of the reader 20, the initial processing unit 23 has a function of selecting an optimum frequency from among the candidate frequencies as a working frequency, and starts wireless communication with the child node using the selected working frequency. And a function of constructing a wireless network for the network system 1.

The storage unit 24 includes a storage device such as a semiconductor memory or a hard disk, and has a function of storing processing information necessary for the reader 20 to construct a wireless network and perform wireless communication and sensor data collection processing.
The main processing information stored in the storage unit 24 includes channel information indicating candidate frequencies used for wireless communication and current frequencies, sensor data measured by subordinate nodes, and importance levels notified from each relay router 10. There is information and scan results.

  In addition, topology information related to child nodes adjacent to the self, information related to the importance of the self such as the importance of sensor data measured by the child nodes adjacent to the self and sensors mounted on the self, wireless The scan result indicating the usage status of each candidate frequency in the vicinity of the self scanned by the I / F unit 22, the importance level related information and the scan result regarding each relay router 10 and the self, There are importance levels for sensor data collection processing, priority levels of candidate frequencies calculated from these importance levels, and the like.

  The sensor data processing unit 25 has a function of notifying the host device 30 of the sensor data received at the wireless I / F unit 22 from the relay router 10 and measured at each node. .

  The importance level calculation unit 26 stores the importance level related information received from the relay router 10 by the wireless I / F unit 22 in the storage unit 24, the relay router 10 acquired from the storage unit 24, and the importance level related to itself. Based on the information, for each node including the relay router 10 and the reader 20, the importance indicating the importance of the sensor data collection process performed by the node in the entire sensor data collection process performed by the entire sensor network system 1 is calculated. It has a function to do.

  The frequency selection unit 27 controls the wireless I / F unit 22 to scan the electric field strength of each candidate frequency around itself as the usage status of each candidate frequency and store it in the storage unit 24. The / F unit 22 refers to the scan result received from the relay router 10 and the own scan result stored in the storage unit 24, the electric field strength of the candidate frequency included in these scan results, and the radio between the nodes The relay router 10 and the reader 20 each have a function of selecting candidate frequencies that can be used based on the comparison result with the reference noise level required for communication.

  The priority calculation unit 28 calculates the importance regarding each relay router 10 and the reader 20 calculated by the importance calculation unit 26, and the candidate frequencies usable by each relay router 10 and the reader 20 selected by the frequency selection unit 27. And a function for calculating a priority indicating a degree to be preferentially used as a frequency used in all nodes for each candidate frequency.

  The frequency switching processing unit 29 instructs to select the optimum frequency to be used in all nodes based on the priority of each candidate frequency calculated by the priority calculating unit 28 and to switch to the optimum frequency. It has a function of transmitting a frequency switching instruction from the wireless I / F unit 22 to the relay router.

  Note that each functional unit of the initial processing unit 23, sensor data processing unit 25, importance calculation unit 26, frequency selection unit 27, priority calculation unit 28, and frequency switching processing unit 29 in the reader 20 is a microprocessor such as a CPU. And an arithmetic processing unit that implements various processing units by reading out and executing a program stored in the storage unit 24. Note that some or all of these functional units may be realized by an arithmetic processing circuit.

[Operation of this embodiment]
Next, the operation of the sensor network system according to this embodiment will be described. Here, the processing operation in the relay router 10 and the processing operation in the reader 20 will be described by taking as an example a case where each node of the sensor network system 1 configures a PAN by a wireless network based on ZigBee.

[Operation of relay router]
First, the processing operation of the relay router according to the present embodiment will be described in detail with reference to FIG. FIG. 6 is a flowchart showing the processing operation of the relay router.
The relay router 10 starts the processing operation of FIG. 6 in response to its activation.
First, the initial processing unit 13 executes various initial processes based on the ZigBee specification, thereby starting wireless communication with the parent node and connecting to the wireless network for the sensor network system 1 (step 100).

Here, the self connection process to the wireless network, the connection process to the wireless network of the child node located within the communication area of the self, the acquisition and storage unit of the topology information about the self and the child node obtained by the connection process result 14, various initial processes such as acquisition of importance of sensor data obtained by itself and child nodes and storage in the storage unit 14 are executed.
In addition, about the importance of sensor data, what is registered in advance in each node may be used. The importance corresponding to the sensor type may be acquired.

  Thereafter, the relay router 10 measures the transmission timing of various data at regular intervals using the timer function of the CPU (step 101), and according to the arrival of the transmission timing (step 101: YES) The information processing unit 16 acquires importance related information from the storage unit 14 and transmits it to the parent node from the wireless I / F unit 12 to notify the reader 20 (step 102).

Further, when new sensor data measured by the sensor 11 or the child node is stored in the storage unit 14, the sensor data processing unit 15 acquires the sensor data from the storage unit 14, and the wireless I / O The reader 20 is notified by transmitting it from the F unit 12 to the parent node (step 103).
The importance-related information and sensor data are notified to the reader 20 by transmitting from the wireless I / F unit 12 to the parent node in an event-driven manner according to the timing at which an event of updating or acquiring these data occurs. May be.

  Thereafter, the relay router 10 normally receives an acknowledgment (ACK) for the importance level related information and sensor data transmitted from the wireless I / F unit 12 by the error processing unit 17 from the parent node by the wireless I / F unit 12. It is checked whether or not it has been completed (step 104), and if data can be normally received within a specified time after data transmission (step 104: YES), the process returns to step 101.

  On the other hand, when the acknowledgment has not been received normally (step 104: NO), the error processing unit 17 determines that a transmission data error has occurred, counts the number of errors (step 105), and counts the number of data transmissions in a certain period. The transmission error rate indicating the ratio between the error number and the error count is calculated and compared with a specified value (step 106).

If the transmission error rate is equal to or less than the specified value (step 106: YES), the process returns to step 101.
If the transmission error rate exceeds the specified value (step 106: NO), an error report indicating the status of the transmission data error such as the network ID and error rate of the self and the parent node is sent to the wireless I / F unit. By transmitting from 12 to the parent node, the reader 20 is notified (step 107), and the process returns to step 101.

In step 101, if the transmission timing has not arrived (step 101: NO), the relay router 10 confirms whether the scan request from the reader 20 is received by the wireless I / F unit 12 (step 110). ).
Here, when a scan request is received (step 110: YES), the frequency scan processing unit 18 controls the wireless I / F unit 12 to determine the electric field strength of each candidate frequency around itself as each candidate. Scanning is performed as a frequency usage state (step 111), and the obtained scan result is transmitted from the wireless I / F unit 12 to the parent node, thereby notifying the reader 20 (step 112) and returning to step 101.

If the scan request is not received in step 110 (step 110: NO), the relay router 10 confirms whether the frequency switching instruction from the reader 20 is received by the wireless I / F unit 12 (step 110). 120).
Here, when the frequency switching instruction is received (step 120: YES), the frequency switching processing unit 19 controls the wireless I / F unit 12 to instruct the frequency used for wireless communication with other nodes. Switch to frequency (step 121) and return to step 101. If no frequency switching instruction has been received (step 120: NO), the process returns to step 101.

[Reader operation]
Next, the processing operation of the reader according to the present embodiment will be described in detail with reference to FIG. FIG. 7 is a flowchart showing the processing operation of the reader.
The reader 20 starts the processing operation of FIG. 7 in response to its activation.
First, the initial processing unit 23 executes various initial processes based on the ZigBee specification, thereby starting wireless communication with the child node to construct a wireless network for the sensor network system 1 (step 130).

  Here, the wireless I / F unit 22 scans the electric field strength (noise signal level) of each candidate frequency around itself, and determines the candidate frequency having the lowest electric field strength as the working frequency of the wireless network, Various initial processes such as connection processing of a child node located in the own communication area to the wireless network, acquisition of topology information regarding the child node obtained as a result of the connection processing, and storage in the storage unit 24 are executed.

  Thereafter, the reader 20 confirms whether the importance level related information from the relay router 10 is received by the wireless I / F unit 22 (step 131). Here, when importance level related information is received (step 131: YES), the importance level calculation unit 26 stores the received importance level related information in the storage unit 24 (step 132), and returns to step 131.

  If the importance level related information is not received in step 131 (step 131: NO), the reader 20 confirms whether the wireless I / F unit 22 has received sensor data from the relay router 10 (step 131). Step 133). If sensor data is received (step 133: YES), the sensor data processing unit 25 notifies the host device 30 from the communication I / F unit 21 (step 134), and returns to step 131.

If the sensor data is not received at step 133 (step 133: NO), the reader 20 confirms whether the error report is received from the relay router 10 by the wireless I / F unit 22 (step 135). . If no error report has been received (step 135: NO), the process returns to step 131.
On the other hand, if an error report has been received (step 135: YES), a frequency switching process for switching the active frequency being used in the wireless network to a new frequency is executed (step 136), and the process returns to step 131.

FIG. 8 is a flowchart showing the frequency switching process.
The reader 20 executes the frequency switching process shown in FIG. 8 in step 136 of FIG.
First, the reader 20 transmits a scan request for each relay router 10 from the wireless I / F unit 22 (step 150), and in response to this, the scan result returned from the wireless I / F unit 22 is displayed as a wireless I / F. The data is received via the unit 22 and stored in the storage unit 24 (step 151). Further, the frequency selection unit 27 controls the wireless I / F unit 22 to scan the electric field strength of each candidate frequency around itself as the usage status of each candidate frequency and store it in the storage unit 24 (step 152). ).

Subsequently, the reader 20 reads the relay router 10 and its own scan result from the storage unit 24 by the frequency selection unit 27, and is necessary for the electric field strength of the candidate frequency included in these scan results and wireless communication between nodes. Candidate frequencies that can be used in the reader 20 and each relay router 10 are selected based on the comparison result with the reference noise level (step 153).
FIG. 9 is an explanatory diagram showing the frequency selection result. Here, for each node comprising the reader 20 and each relay router 10, the availability of each candidate frequency (channel) is indicated by ○ (usable) and x (unusable).

  Next, the reader 20 reads the importance level related information of itself and each relay router 10 from the storage unit 24 by the importance level calculation unit 26, and consists of the reader 20 and each relay router 10 based on the importance level related information. For each node, the importance indicating the importance of the sensor data collection process performed at the node in the entire sensor data collection process performed by the entire sensor network system 1 is calculated (step 154).

  FIG. 10 is an explanatory diagram showing importance. Here, as the importance of the node composed of the reader 20 and each relay router 10, three types of importance including the number of child nodes, the number of hops, and the importance of sensor data are shown.

The importance of the number of child nodes is an index value that increases as the number of child nodes adjacent to the node increases. For example, the number of child nodes adjacent to the node is counted based on the importance related information. The number of child nodes may be used.
Thereby, when selecting the optimum frequency, a node having a larger number of child nodes, that is, a node collecting sensor data from many sensors can be considered as an important node.

The hop count importance is an index value that decreases as the hop count from the node to the leader 20 increases. For example, the hop count of the node counted based on the importance related information is the maximum of the multihop radio. A value obtained by subtracting from the specified number of hops equal to or greater than the number of hops may be used.
As a result, when selecting the optimum frequency, a node with a smaller number of hops, that is, a node that transfers more sensor data can be considered as an important node.
Note that an index value obtained by weighting the number of hops according to the number of all nodes connected to the lower level of the node may be used as the pop number importance.

The sensor data importance is an index value that increases as the total importance of all the sensor data measured at the child nodes adjacent to the node increases. For example, the sensor data importance is based on the importance related information. A value obtained by summing the importance of all sensor data measured at the child nodes adjacent to each other may be used.
As a result, when selecting an optimum frequency, the more important the node that collects sensor data that is more important, that is, the node that collects sensor data that is important in the sensor data collection process in the sensor network system is more important. Can be considered as a node.

After that, the leader 20 sums up three kinds of importance levels including the child node number importance level, the hop number importance level, and the sensor data importance level for each node including the reader 20 and each relay router 10. Thus, the importance level for each node is calculated. At this time, the three importance levels may be simply summed up equally, or the node-by-node importance levels may be calculated by performing a product-sum calculation using individual weighting factors set in advance. Further, any one or two weighting factors may be set to zero.
Thereby, the importance according to node according to the characteristic calculated | required by the sensor network system 1 is computable.

  Subsequently, the leader 20 uses the priority calculator 28 to calculate the importance of each relay router 10 and the node 20 related to the reader 20 calculated by the importance calculator 26, the relay router 10 selected by the frequency selector 27, and Based on the candidate frequencies that can be used by the reader 20, a priority indicating a degree to be preferentially used as a frequency that is commonly used by all nodes is calculated for each candidate frequency (step 155).

  FIG. 11 is an explanatory diagram showing priorities. Here, the node-by-node importance of the node is arranged in the intersection column of the candidate frequency and the node composed of the reader 20 and each relay router 10. Of these, the node-by-node importance of candidate frequencies determined to be unusable at an arbitrary node is replaced with “0”. That is, in FIG. 9, in the column in which a circle indicating availability is described, the importance level for each node of the node is described, and “0” is described in a column in which an x mark indicating unusable is described. Has been.

The priority calculation unit 28 calculates the priority by frequency by summing the importance by node for each candidate frequency.
As a result, in the priority by frequency, the importance by node regarding the candidate frequency determined to be unusable at any node is not evaluated, and only the importance by node regarding the candidate frequency determined to be usable at any node is determined. Can be evaluated.

  Therefore, not only the frequency that can be used in many nodes, but also a node that is highly important in the entire sensor data collection process in which the sensor data collection process in the entire node is performed as the node. Candidate frequencies that are to be included are selected as optimal frequencies.

  Thereafter, the reader 20 uses the frequency switching processing unit 29 to select the candidate frequency indicating the highest frequency priority among the frequency priorities calculated by the priority calculation unit 28 as the optimum frequency to be used in all nodes. Is selected (step 156), and a frequency switching instruction for instructing switching from the working frequency to the optimum frequency is transmitted from the wireless I / F unit 22 to the relay router (step 157).

  Thereby, the working frequency is switched to the optimum frequency at each node, and wireless communication is resumed between the nodes. The reader 20 reconstructs the wireless network of the sensor network system 1 by the initial processing unit 23 (step 158), a series of frequency switching processing is terminated.

[Operation example of this embodiment]
Next, an operation example of the sensor network system according to the present embodiment will be described with reference to FIGS. FIG. 12 is a configuration example of a sensor network system. FIG. 13 is a sequence diagram illustrating an operation example of the sensor network system according to the present embodiment.
Here, in the sensor network system 1 having the configuration shown in FIG. 12, a case where the reader 20 performs frequency switching processing according to an error report from the relay router R1 will be described as an example.

As shown in FIG. 12, the sensor network system 1 is provided with 1, a reader L (20), and four relay routers R1 to R4 (10). Relay routers R1 to R4 are connected in the order of R2, R3, and R4.
Further, four end devices are connected to the reader L, and similarly, two, two, two, and three end devices are connected to the relay routers R1, R2, R3, and R4, respectively. Yes.

In such a sensor network system 1, importance level related information is transmitted from each relay router R1 to R4 to the reader L (step 200). The reader L receives the importance related information and stores it in the storage unit (step 201).
Further, the sensor data measured by the child node and itself is transmitted from each relay router R1 to R4 to the reader L (step 202). The reader L receives these sensor data and notifies the host device 30 (step 203).
The transmission timing of the importance related information and sensor data may be different for each of the relay routers R1 to R4.

Thereafter, when the transmission error rate exceeds the specified value at the relay router R1, an error report is transmitted from the relay router R1 to the reader L (step 210).
In response to this, a scan request is transmitted from the reader L to each of the relay routers R1 to R4 (step 211), and a scan result is transmitted from each of the relay routers R1 to R4 to the reader L (step 212).

The reader L selects each of the relay routers R1 to R4 and a candidate frequency that can be used by itself based on these scan results (step 213), and also determines the importance for each node based on the stored importance related information. The degree is calculated (step 214).
Then, the priority for each frequency is calculated based on the frequency selection result and the importance for each note (step 215), and the optimum frequency is selected based on the priority for each frequency (step 216).

Here, in the case of the topology of the sensor network system 1 as shown in FIG. 12, the numbers of child nodes of the reader L and the relay routers R1 to R4 are “5”, “3”, “3”, “3”, “ 3 ", and the importance of the number of child nodes as shown in FIG. 10 is calculated.
In addition, since the hop numbers of the leader L and the relay routers R1 to R4 are “0”, “1”, “2”, “3”, and “4”, respectively, the specified hop number is “10”. The hop count importance obtained from the difference between the specified hop count and the actual hop count is “10”, “9”, “8”, “7”, and “6”, respectively, as shown in FIG.

Further, as shown in FIG. 12, the importance levels of the sensor data measured by the relay routers R1 to R4 are “2”, “5”, “3”, and “1”, respectively, and are measured by the end device of the reader L. Assume that the importance of each sensor data is “2”.
Similarly, the importance of the sensor data measured by the end device of the relay router R1 is “5”, and the importance of the sensor data measured by the end device of the relay router R2 is “1”. Assume that the importance of the sensor data measured by the R3 end device is “1”, and the importance of the sensor data measured by the end device of the relay router R4 is “1”.

In such a case, the sensor data importance obtained by summing up the importance for each of the reader L and the relay routers R1 to R4 is “10”, “15”, “3”, respectively, as shown in FIG. “3” and “3”.
Therefore, as shown in FIG. 10, the importance by node obtained by summing the importance of the number of child nodes, the importance of the number of hops, and the importance of sensor data for each of the reader L and the relay routers R1 to R4 is “ 25 ”,“ 27 ”,“ 14 ”,“ 13 ”,“ 12 ”.

Thereafter, in FIG. 9, the node-by-node importance corresponding to the column in which “O” indicating availability is described is totaled for each candidate frequency. As a result, the frequency priorities of the candidate frequencies CH1 to CH5 are “12”, “52”, “64”, “66”, and “40”, respectively, as shown in FIG.
As a result, the CH4 having the highest frequency priority “66” among the candidate frequencies is selected as the optimum frequency.

  When switching the working frequency according to an error report from the relay router R1 as in the prior art, for example, CH3 that can be used by the most relay routers is selected as the optimum frequency. However, in CH3, radio wave interference is likely to occur in the relay router R1 that collects a lot of highly important sensor data, and sensor data collection processing corresponding to the purpose required of the sensor network system 1 cannot be realized.

  According to the present embodiment, since CH4 is selected as the optimum frequency, radio wave interference is likely to occur in the relay routers R3 and R4, but the amount of sensor data collected by these relay routers R3 and R4 is small, and Since the importance of the sensor data is low, it is possible to realize sensor data collection processing corresponding to the purpose required for the sensor network system 1.

In this way, the optimum frequency is selected by the reader L, a frequency switching instruction is transmitted from the reader L to each of the relay routers R1 to R4 (step 217), and each subordinate end is subordinate from each of the relay routers R1 to R4. A frequency switching instruction is transmitted to the device (step 218).
As a result, the working frequency is switched to the optimum frequency in all nodes belonging to the sensor network system 1 (step 219).

[Effects of the present embodiment]
As described above, in the present embodiment, each relay router 10 reads the importance-related information related to the importance of the sensor data collection process performed by itself in the entire sensor data collection process performed by the entire sensor network system 1. And the usage status of each candidate frequency in its surroundings is scanned, the obtained scan result is transmitted to the reader 20, and the reader 20 uses the importance related information received from the relay router 10 and the scan result. For each candidate frequency, a priority indicating the degree to which the candidate frequency should be used with priority is calculated, and switching to the optimum frequency selected based on the priority is instructed to each relay router 10. ing.

  Accordingly, in the sensor network system 1 in which a plurality of nodes performing wireless communication using the same frequency collects sensor data by performing multi-hop wireless communication, the characteristics of the sensor network system, that is, the wireless environment of each node, the sensor network Considering the topology of the entire system or the importance of each sensor data, it is possible to appropriately determine whether to switch frequencies.

  In this embodiment, the relay router 10 transmits information indicating the child node connected to itself (topology information of the child node) to the reader 20 as importance related information. The number of child nodes adjacent to the relay router 10 is counted based on the degree related information, and an index value that increases as the number of obtained child nodes increases is calculated as the importance of the relay router 10. Therefore, when selecting the optimum frequency, a node having a larger number of child nodes, that is, a node collecting sensor data from many sensors can be considered as an important node.

  In the present embodiment, the relay router 10 transmits information indicating the parent node to which the relay router 10 is connected (topology information of the relay router itself) to the reader 20 as importance related information. Since the number of hops from the relay router 10 to the leader 20 is counted based on the importance level related information, and an index value that decreases as the obtained number of hops increases, the importance level of the relay router 10 is calculated. When selecting the optimum frequency, a node with a smaller number of hops, that is, a node that transfers more sensor data can be considered as an important node.

  Further, in the present embodiment, information indicating the importance of sensor data (sensor data importance information) measured by the child node connected to the reader 20 as importance related information from the relay router 10 to the reader 20. The reader 20 sums the importance of all the sensor data measured at the child nodes of the relay router based on the importance related information, and the index value that increases as the total value obtained increases. Since it is calculated as the importance of the relay router, when selecting the optimum frequency, the more important sensor data is collected in the node, that is, the sensor data that is more important in the sensor data collection process in the sensor network system Can be considered as an important node.

  In this embodiment, the information indicating the child node connected to itself, the information indicating the parent node to which the self is connected, and the importance of the sensor data measured by the child node connected to the self As an example, the case where all three types of information indicating “” are transmitted from the relay router 10 to the reader 20 as importance related information has been described. However, the present invention is not limited to this. Any one or more of the three types described above may be transmitted from the relay router 10 to the reader 20 as importance related information according to the characteristics of the sensor network system.

  Further, in the present embodiment, the case where the sensor 11 is mounted on each relay node 10 and the sensor data measured by the relay node 10 is transmitted to the reader together with the sensor data from the child node has been described as an example. However, the present invention is not limited to this. Even when the sensor 11 is not mounted on the relay node 10, the present embodiment can be applied in the same manner as described above, and the same operational effects can be obtained.

  In the present embodiment, an end device ED is included as a child node of the reader 20, and sensor data from these end devices ED is transmitted to the reader together with sensor data from the relay router 10. However, the present invention is not limited to this. Even when the end device ED is not included as a child node of the reader 20, the present embodiment can be applied in the same manner as described above, and the same operational effects can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Sensor network system, 10 ... Relay router, 11 ... Sensor, 12 ... Wireless I / F part, 13 ... Initial processing part, 14 ... Memory | storage part, 15 ... Sensor data processing part, 16 ... Importance related information processing part, DESCRIPTION OF SYMBOLS 17 ... Error processing part, 18 ... Frequency scan processing part, 19 ... Frequency switching processing part, 20 ... Reader, 21 ... Communication I / F part, 22 ... Wireless I / F part, 23 ... Initial processing part, 24 ... Memory | storage part , 25 ... sensor data processing unit, 26 ... importance calculation unit, 27 ... frequency selection unit, 28 ... priority calculation unit, 29 ... frequency switching processing unit, 30 ... host device, ED ... end device.

Claims (8)

A node that performs wireless communication with each other using any one of a plurality of candidate frequencies in common includes a plurality of end devices, a plurality of relay routers, and a reader. Sensor that wirelessly transmits measured sensor data, the relay router transfers the received sensor data to the reader by multi-hop wireless, and the reader notifies the host device of the sensor data collected via the relay router A network system,
The relay router is
Importance-related information processing unit for transmitting importance-related information related to the importance of sensor data collection processing performed by itself in the entire sensor data collection processing performed in the entire sensor network system;
A scan processing unit that scans the usage status of each candidate frequency in its surroundings, and transmits the obtained scan result to the reader;
A frequency switching processing unit that switches the frequency used in the wireless communication to the instructed frequency in response to a frequency switching instruction from the reader,
The reader is
Based on the scan result received from each relay router, a frequency selection unit that selects candidate frequencies that can be used by the relay router, and
Based on importance-related information received from each relay router, an importance calculation unit that calculates importance related to sensor data collection processing performed in the relay router, and
A priority calculation unit for calculating a priority indicating the degree to which the candidate frequency should be used with priority for each candidate frequency from the importance and the frequency selection result for each relay router;
A frequency switching processing unit that selects an optimal frequency based on the priority of each candidate frequency and transmits the frequency switching instruction for instructing switching to the optimal frequency to the relay router. . The sensor network system according to claim 1,
The importance related information processing unit transmits information indicating a child node connected to the reader as the importance related information to the reader,
The importance calculating unit counts the number of child nodes of the relay router based on the importance related information, and calculates an index value that increases as the number of obtained child nodes increases as the importance of the relay router. A sensor network system characterized by The sensor network system according to claim 1,
The importance related information processing unit transmits information indicating a parent node to which the self is connected as the importance related information to the reader.
The importance calculation unit counts the number of hops from the relay router to the leader based on the importance related information, and calculates an index value according to the obtained number of hops as the importance of the relay router A sensor network system characterized by The sensor network system according to claim 1,
The importance-related information processing unit transmits, as the importance-related information, information indicating the importance of sensor data measured by a child node connected to the reader to the reader,
The importance calculation unit, based on the importance related information, sums the importance of all sensor data measured at each child node of the relay router, and the index value that increases as the obtained total value increases Is calculated as the importance of the relay router. A sensor network system, wherein: A node that performs wireless communication with each other using any one of a plurality of candidate frequencies in common includes a plurality of end devices, a plurality of relay routers, and a reader. Sensor that wirelessly transmits measured sensor data, the relay router transfers the received sensor data to the reader by multi-hop wireless, and the reader notifies the host device of the sensor data collected via the relay router A sensor network control method used in a network system,
The importance-related information processing unit of the relay router transmits importance-related information related to the importance of the sensor data collection process performed by itself in the entire sensor data collection process performed in the entire sensor network system to the reader. Degree related information processing step,
A scan processing step in which the scan processing unit of the relay router scans the usage status of each candidate frequency in its surroundings, and transmits the obtained scan result to the reader;
A frequency switching step in which the frequency switching processing unit of the relay router switches the frequency used in the wireless communication to the instructed frequency in response to a frequency switching instruction from the reader; Based on the scan result received from the router, a frequency selection step of selecting candidate frequencies that can be used in the relay router,
Importance calculation step in which the importance calculation unit of the reader calculates importance related to sensor data collection processing performed in the relay router based on importance related information received from each relay router;
The priority calculation unit of the leader calculates, for each of the candidate frequencies, a priority indicating the degree to which the candidate frequency should be used with priority from the importance for each relay router and the frequency selection result. A priority calculation step;
A frequency switching processing step in which the frequency switching processing unit of the reader selects an optimal frequency based on the priority of each candidate frequency and transmits the frequency switching instruction to instruct switching to the optimal frequency to the relay router; A sensor network control method comprising: The sensor network control method according to claim 5,
The importance-related information processing step transmits information indicating a child node connected to the reader to the reader as the importance-related information.
The importance level calculating step counts the number of child nodes of the relay router based on the importance level related information, and calculates an index value that increases as the number of obtained child nodes increases as the importance level of the relay router. A sensor network control method characterized by: The sensor network control method according to claim 5,
The importance related information processing step transmits information indicating a parent node to which the self is connected as the importance related information to the reader,
The importance calculating step counts the number of hops from the relay router to the leader based on the importance related information, and calculates an index value according to the obtained number of hops as the importance of the relay router A sensor network control method characterized by: The sensor network control method according to claim 5,
The importance-related information processing step transmits, as the importance-related information, information indicating the importance of sensor data measured by a child node connected to the reader to the reader.
In the importance calculation step, based on the importance related information, the importance of all sensor data measured at each child node of the relay router is totaled, and an index value that increases as the obtained total value increases. Is calculated as the importance of the relay router. A sensor network control method, comprising:

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