JP5958694B2 - Measurement information collecting system, wireless node, wireless node communication method and program - Google Patents

Description

  The present invention relates to a wireless communication system having a plurality of network topologies (tree, star type, etc.), and in particular, a measurement information collection system for a measurement device such as a smart meter using a multi-hop network, a wireless node, a wireless node communication method, and Regarding the program.

  Based on the basic policy for securing frequency for 2015/2020 issued by the Ministry of Internal Affairs and Communications, in order to promote the introduction of smart meters and the like, frequency reorganization in the 900 MHz band is being promoted promptly. Based on this, an electronic tag system using RFID (Radio Frequency Identification) such as a smart meter can use frequencies from 915 MHz to 928 MHz. In accordance with this reorganization, the mobile phone terminal uses LTE (Long Term Evolution), which is a new communication standard, and can use frequencies from 900 MHz to 915 MHz. The mobile phone base station can use a frequency of 945 MHz to 960 MHz.

  In particular, since LTE radio waves emitted by mobile phone base stations are strong, smart meters and the like close to the base stations may be susceptible to broadband radio wave interference in the same manner as other powerful radio sources. Also, radio wave interference caused by the same channel in the same frequency band is a radio wave interference. When radio interference spreads over a wide band, the route change process itself is affected, the throughput of the entire network is lowered, and it takes time to converge the route change. Patent Document 1 discloses a method for improving the throughput.

  In Patent Document 1, in a wireless network system, a plurality of frequency channels are selectively set, and an electronic device terminal and a wireless communication control station (access point) are wirelessly connected. In that case, the radio wave level for each of the plurality of frequency channels is measured at a predetermined period based on the signal received by the wireless antenna. The measured data is compared with a predetermined threshold value to determine whether the frequency channel is used or not used, and stored as usage frequency statistical data for each frequency channel. During the execution of wireless communication between the electronic device terminal and the wireless communication control station, the frequency channel is changed based on the statistical data as necessary.

  According to the above method, it is disclosed that a channel can be changed according to a substantial traffic amount without affecting normal communication by a wireless LAN, and radio wave interference can be eliminated to obtain good throughput.

JP 2005-333510 A

  However, in Patent Document 1, since the channel is changed in a state where the failure state due to the radio wave interference is not grasped, new connections such as active scan frequently occur particularly in the case of broadband radio wave interference. This state will be described with reference to an explanatory diagram schematically showing the conventional problem of FIG. When a radio wave failure occurs, the wireless node 200 is in a state where it cannot receive beacons from other wireless nodes 200 over a wide range (see FIG. 11A). When the state in which reception is not possible continues for a certain time or longer, the wireless node 200 executes channel alternative route processing. Because of the channel change, the wireless node 200 performs a channel scan, but the other wireless node 200 cannot be detected due to a broadband radio wave interference, and thus a new connection is automatically started. Therefore, in the case of radio wave interference spreading over a wide band, each adjacent wireless node 200 performs alternative route change processing almost simultaneously, so that new connection processing occurs frequently (see FIG. 11B). When new connection processing such as active scan occurs frequently, the connection destination is not easily found, and there is a problem that it takes time to converge the alternative route change processing. Further, since the active scan operation leads to power consumption of surrounding wireless nodes in addition to the implemented wireless nodes, there is a problem in power saving.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a measurement information collection system and a wireless node that can reduce the influence of broadband radio wave interference, achieve power saving and good throughput. is there.

  The first wireless node of the present invention is a first wireless node capable of communicating with a second wireless node in a measurement information collecting system configured by a network topology that collects measurement information of a measuring device from a plurality of wireless nodes. The first wireless node transmits / receives communication data to / from the second wireless node, measures at least an RSSI value, and stores at least the measured RSSI value; A control unit that determines whether broadband radio interference exists using the RSSI value, and when the control unit determines that the broadband radio interference exists, a new alternative route Before detection, the signal from the communication unit is stopped for a certain period of time, and communication with the second wireless node that is an existing communication destination is attempted.

  In the first wireless node, for example, the control unit generates a band pattern using the RSSI value, and determines whether the broadband radio wave interference exists by analyzing the band pattern, The band pattern is stored in the storage unit.

  In the first wireless node, for example, the control unit compares the stored band pattern with a newly acquired band pattern and determines whether or not a broadband radio wave interference exists. .

  In the first wireless node, for example, the control unit analyzes the band pattern to set a determination time, and determines the fixed time to stop based on the determination time.

  In the first wireless node, for example, the control unit compares and calculates the stored band pattern and the newly acquired band pattern, and changes the setting of the determination time.

  Furthermore, the first wireless node of the present invention is a first wireless node that can communicate with the second wireless node in a measurement information collection system configured by a network topology that collects measurement information of a measuring device from a plurality of wireless nodes. The first wireless node transmits / receives communication data to / from the second wireless node, detects a carrier sense at least for each frequency channel, and outputs a detection result of the carrier sense. A control unit that generates a band pattern indicating the result of the carrier sense based on the analysis and analyzes the generated band pattern to determine whether or not a broadband radio wave interference is present, the control unit, If it is determined that the broadband radio wave interference exists, the signal from the communication unit is stopped for a certain period of time before detection of a new alternative route, It is a communication destination of the presence attempts to communicate with the second wireless node.

  In the first wireless node, for example, when the alternative route cannot be detected by the passive scan for detecting the alternative route, the control unit determines whether or not a broadband radio wave interference exists.

  In the first wireless node, for example, when the control unit determines that there is no broadband radio wave interference, the control unit performs an alternative route generation process by active scanning.

  In the first wireless node, for example, the control unit generates frequency information indicating a frequency at which the wireless node is involved in broadband radio wave interference, and the communication unit transmits the generated frequency information to the second wireless node. Send to node.

  The second wireless node according to the present invention is a second wireless node that can communicate with the first wireless node in a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes. The second wireless node transmits / receives at least communication data to / from the first wireless node, and indicates a frequency at which the wireless node generated by the first wireless node is involved in broadband radio wave interference. A communication unit that receives frequency information; a storage unit that stores at least the frequency information; and a control unit that determines priority as a connection candidate of the first wireless node based on the frequency information.

  In the second radio node, for example, the communication unit measures an RSSI with the first radio node, and the control unit determines the first radio node based on the frequency information and the measured RSSI value. The priority as a connection candidate is determined.

  The measurement information collection system of the present invention is a measurement information collection system configured by a network topology that collects measurement information from a plurality of wireless nodes, and the first wireless node communicates with the second wireless node. A communication unit that transmits and receives data and measures at least RSSI, a storage unit that stores at least the measured RSSI value, and determines whether or not broadband radio wave interference exists using the RSSI value, and the broadband If it is determined that there is a radio interference, the signal from the communication unit is stopped for a certain period of time before detection of a new alternative route, and communication with the second wireless node that is an existing communication destination is attempted. And the second wireless node transmits and receives at least communication data to and from the first wireless node, and the first wireless node generates As a connection candidate for the first wireless node based on the frequency information, a communication unit that receives frequency information indicating how often the wireless node is involved in broadband radio interference, a storage unit that stores at least the frequency information, and A control unit for determining priority.

  The first wireless node communication method of the present invention is a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes. In the communication method of a wireless node, in the first wireless node, a communication unit measures at least RSSI, a storage unit stores at least the measured RSSI value, and a control unit uses the RSSI value to transmit a broadband radio wave. If it is determined whether or not a fault exists, and it is determined that the broadband radio wave interference exists, the signal from the communication unit is stopped for a certain period of time before detecting a new alternative route, and the existing communication Attempts to communicate with the second wireless node that is the destination.

  The first wireless node program of the present invention is a first wireless that can communicate with a second wireless node in a measurement information collection system configured by a network topology that collects measurement information of a measuring device from a plurality of wireless nodes. It is a program of a node, a procedure for reading out an RSSI value measured by a communication unit from a storage unit, a determination as to whether or not a broadband radio wave interference exists using the read RSSI value, and the broadband radio wave interference is If it is determined that it exists, a procedure for stopping a signal from the communication unit for a certain period of time before detecting a new alternative route and attempting communication with the second wireless node that is an existing communication destination. Let the computer run.

  The second wireless node communication method of the present invention is a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, and a second wireless node that can communicate with the first wireless node. A communication method of a wireless node, wherein a communication unit transmits / receives at least communication data to / from the first wireless node, and a frequency at which the wireless node generated by the first wireless node is involved in broadband radio wave interference is determined. The frequency information is received, the storage unit stores at least the frequency information, the control unit determines the priority as the connection candidate of the first wireless node based on the frequency information, and based on the priority Try to communicate.

  In the communication method of the second wireless node, for example, the communication unit measures an RSSI with the first wireless node, and the control unit determines the first wireless node based on the frequency information and the RSSI value. Communication is attempted based on the priority, which determines the priority as a connection candidate.

  The second wireless node program of the present invention is a second wireless that can communicate with a first wireless node in a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes. Based on a procedure for reading out frequency information from a storage unit, which is a program of a node, the frequency information indicating how often the radio node generated by the first radio node is involved in broadband radio interference, and the first frequency information The priority of the wireless node as a connection candidate is determined, and the computer is caused to execute a procedure for attempting communication based on the priority.

  According to the present invention, the state of broadband radio wave interference is detected before a new connection is made. Since it is determined whether or not a new connection is to be made based on the detected communication status data, frequent new connections can be prevented. In particular, during the occurrence of broadband radio wave interference, the wireless node substitute route processing is not performed for a certain period of time, and the normal communication is restored, so that the network topology can be quickly restored. Further, not performing the alternative route processing for a certain period of time leads to power saving, communication can be smoothly restored, and reduction in throughput can be suppressed.

  In addition, a wireless node that has detected a broadband radio wave interference communicates the failure occurrence status at the time of an alternative route connection request or a new connection request from the surroundings, thereby building a topology that avoids wireless nodes with poor communication quality, It is possible to suppress a reduction in throughput.

The conceptual diagram which shows one Embodiment of the measurement information collection system which concerns on this invention Block diagram of a wireless node according to the present invention It is a conceptual diagram which shows the alternative route method of the measurement information collection system which concerns on this invention, (a) is an alternative route change, (b) is the further alternative route change and operation | movement in a radio wave disturbance. The flowchart figure which shows 1st Embodiment of the beacon reception process of the measurement information collection system which concerns on this invention. The flowchart figure which shows 2nd Embodiment of the beacon reception process of the measurement information collection system which concerns on this invention. The flowchart figure which shows the alternative route production | generation process of FIG. Band pattern diagram for detecting broadband radio interference using radio field strength FIG. 3 is a band pattern diagram for detecting broadband radio wave interference, where (a) is an example of a band pattern, (b) is a registered band pattern, and (c) is a new band pattern. The flowchart figure which shows the connection destination selection process based on frequency information It is an example of the connection priority table which displays the priority of a wireless node, (a) is an example of a table based on frequency information, (b) is an example of a table based on frequency information and an RSSI value. It is explanatory drawing which modeled the conventional problem, (a) At the time of a radio wave disturbance, (b) is a new connection frequent occurrence state, such as active scan

  Hereinafter, a preferred embodiment of a measurement information collecting system and a wireless node used therefor according to the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a conceptual diagram showing an embodiment of a measurement information collecting system according to the present invention.

  The measurement information collection system 1 includes a plurality of wireless nodes 2, a server device 3 that collects data from the wireless nodes 2 in a certain area, and a central processing device 5 that communicates with the server device 3 via the Internet line 4 or the like. It is configured. The measurement information collection system 1 described in FIG. 1 is a multistage network topology in which the network topology is a tree type and many tree types are combined. The topology may be a mesh type, a star type, or the like, and is not limited to a tree type.

  The measurement information collection system 1 mainly refers to a sensor network system that uses a smart meter, ITS (highway traffic system), medical equipment, or the like. The measurement information collection system 1 is also an electronic tag system (Ministry of Internal Affairs and Communications) that uses the 920 MHz band (frequency from 915 MHz to 930 MHz). Each element constituting the network is called a node, and the wireless node 2 of the present invention is, for example, a chip attached to a smart meter using a multi-hop network. A specific aspect is arbitrary. A smart meter as a measuring device is a meter having a bidirectional communication function. For example, it is integrated with household electric power and gas meters, exchanges data with electric power companies and gas companies, It is a device that controls. Smart meters are used not only in homes, but also in power and inventory management in factories and the like, and are also used in radioactivity measurement devices, photovoltaic power generation measurement devices, and the like.

  The server device 3 is installed in a branch office such as a specific area or a local area, and receives data from a plurality of wireless nodes 2 or transmits a control command to each wireless node 2. Further, the server device 3 becomes an upper radio node when each radio node 2 is a lower radio node. Each wireless node 2 is capable of bidirectional communication. If one is a higher-order wireless node, the other is a lower-order wireless node, which has a function as a terminal or a relay station, and both freely change the wireless node relationship. It is possible. Therefore, the server apparatus 3 can be said to be the highest radio node in the network topology. In the description of the embodiment of the present invention, the radio node 2 located on the higher radio node side is assumed to be the higher radio node 2A, and the radio node 2 located on the lower radio node side is assumed to be the lower radio node 2B. The central processing unit 5 is a host computer installed in the headquarters of an electric power company, a gas company, or the like, and is linked to the server device 3 via an infrastructure solution such as the Internet line 4.

  FIG. 2 is a block diagram illustrating an embodiment of the wireless node 2.

  The wireless node 2 mainly includes a control unit 10, a storage unit 11, a communication unit 12, and a communication circuit unit 13. The control unit 10 is a microcomputer including a CPU and the like, controls the wireless node 2, performs program execution, data analysis, and analysis, and controls the entire wireless node 2. In addition to the wireless node connected to the wireless node, the control unit 10 also transmits signals from surrounding wireless nodes, base stations such as mobile phones, other radio wave sources, and surrounding influences ( For example, the intensity of noise, radio waves, signals, etc. from fluorescent lamps (hereinafter, these are defined as RSSI “Received Signal Strength Indicator”) is analyzed and analyzed.

  The RSSI threshold (determination reference value) related to the determination may be a predetermined fixed value. Further, the threshold value may be set with reference to a normal level of thermal noise (eg, noise caused by thermal vibration in the apparatus), a noise level at the time of no signal input, or the like. A weighted average of a plurality of RSSIs may be used as a reference (ambient noise level or the like). If the received RSSI value is higher than these reference levels, it is possible to determine that a broadband radio wave interference has occurred.

  It should be noted that thermal noise (eg, noise caused by thermal vibration in the apparatus), noise at the time of no signal input, and the like can also be detected as RSSI and analyzed.

  That is, various radio waves and signals generated in a certain space where the wireless node 2 exists can be detected as RSSI and can be analyzed and analyzed.

  The storage unit 11 includes a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory), and stores various data such as measurement data, frequency information described later, and the like. In addition, a band pattern generated by the control unit 10 using RSSI and a band pattern indicating a carrier sense result generated based on a carrier sense detection result are also stored.

  The communication unit 12 performs bidirectional communication with each wireless node 2 and the server device 3 to perform communication for remote operation of home appliances and the like, and also measures the RSSI described above.

  In addition, as communication data between each node, for example, control contents to upper nodes, lower nodes or peripheral nodes, responses to control contents, commands, measurement data measured by sensors, notifications from sensors, etc. However, the present invention is not limited to this.

  The communication circuit unit 13 is configured by a UART (Universal Asynchronous Receiver Transmitter) or the like, and directly or electrically acquires measurement information of the sensor 14 that grasps a usage state of electricity or gas. The sensor 14 may be an existing gas or power meter or a measurement unit that performs measurement, and constitutes a part of a measurement device such as a smart meter. However, from the viewpoint of a function of acquiring meter information, the meter device itself. It can also be grasped.

  An alternative route change when a broadband radio wave interference occurs will be described with reference to the conceptual diagram of FIG.

  For example, it is assumed that for some reason, radio wave interference occurs between the wireless node 21 and the wireless node 22, resulting in failure and communication between each other. If the wireless node 21 cannot receive the beacon from the wireless node 22 for a certain period of time or has received it but the data error rate is more than a certain value (for example, a packet error or a bit error in the received data), In order to connect to the wireless node and transmit information through it, it enters alternative route detection. Here, when communication with the wireless node 23 (new wireless node) becomes possible, the switching of the alternative route is completed. Thereby, measurement data from the wireless node 21 can be transmitted from the wireless node 23 to the server device 3 via the wireless node 22 (see FIG. 3A). However, when the wireless node 21 cannot communicate with the wireless node 23 due to a stronger radio wave disturbance, it can communicate with another new wireless node 24 by active scanning or the like (see the arrow in FIG. 5B).

  However, when the alternative route cannot be detected, the occurrence of broadband radio wave interference due to broadband interference waves such as LTE around the wireless node 21 is suspected. However, since the broadband interference generated in the surrounding area may be resolved with the passage of time, when the broadband interference is detected and it is determined that the broadband interference is occurring, the wireless node 25 is connected before the new connection. Communication is suspended for a certain period of time or until broadband radio wave interference converges.

  Next, a first embodiment of a communication procedure performed by the lower radio node 2B will be described with reference to the flowchart of FIG. Although an example in which a beacon cannot be received has been described, the same applies to a case where the data error rate is a certain level (for example, a packet error or a bit error in received data).

  When a communication failure with the higher-order wireless node 2A occurs, the lower-level wireless node 2B performs a channel change process (step 30). When the corresponding channel cannot be used due to carrier sense before beacon transmission, upper wireless node 2A changes to another channel and transmits a beacon at the next beacon transmission. This change-destination channel shares information in advance between the upper radio node 2A and the lower radio node 2B. When the lower radio node 2B cannot receive the beacon of the upper radio node 2A on the latest channel, the lower radio node 2B follows the channel change of the upper radio node 2A and communicates. The control unit 10 determines whether or not the beacon transmitted from the upper radio node 2A has been received by the communication unit 12 (step 31).

  If a beacon is received (step 31 is Y), the process is terminated. When it cannot receive (step 31 is N), it is determined by the control part 10 whether the situation which cannot receive a beacon continues for a fixed time or more (step 32). If it has not continued for a certain time (N in step 32), the process is terminated. If it continues for a certain time or longer (step 32 is Y), the control unit 10 instructs the execution of an alternative route detection process by a passive scan or the like (step 33). It is determined whether or not an alternative route has been detected (step 34). When the alternative route is detected (step 34 is Y), the process is switched to the alternative route (step 35), and the process is terminated.

  On the other hand, when the alternative route cannot be detected (N in step 34), the detection process of the broadband radio wave disturbance is started (step 36). Then, the control unit 10 determines whether or not a broadband radio wave interference is occurring (step 37). The determination during the occurrence of the broadband radio wave interference, which will be described in detail later, is made by detecting and analyzing the broadband jamming wave and determining whether or not a radio wave equal to or higher than a threshold value is detected on a certain channel. If it is not determined that the broadband radio wave interference is occurring (N in step 37), the mobile station leaves the currently participating network and connects to another network (step 38). If it is determined that a broadband radio wave interference is occurring (Y in step 37), a determination time (details will be described later) predetermined for performing the alternative route process is cleared and changed (step 39).

  In the embodiment, the status of broadband radio wave interference is detected before a new connection is made. Since it is determined whether or not a new connection is to be made based on the detected communication status data, frequent new connections can be prevented. In particular, during the occurrence of wideband radio wave interference, the alternative route processing of the wireless node 2 is not performed for a certain period of time, and the normal communication is restored, so that the network topology can be quickly restored. Further, not performing the alternative route processing for a certain period of time leads to power saving, communication can be smoothly restored, and reduction in throughput can be suppressed.

  A second embodiment of the communication procedure performed by the lower radio node 2B will be described with reference to the flowchart of FIG.

  The lower radio node 2B performs a channel change process when a communication failure occurs due to radio wave interference with the upper radio node 2A (step 40). When the corresponding channel cannot be used due to carrier sense before beacon transmission, upper wireless node 2A changes to another channel and transmits a beacon at the next beacon transmission. This change-destination channel shares information in advance between the upper radio node 2A and the lower radio node 2B. When the lower radio node 2B cannot receive the beacon of the upper radio node 2A on the latest channel, the lower radio node 2B follows the channel change of the upper radio node 2A and communicates. The control unit 10 determines whether or not the beacon transmitted from the upper wireless node 2A has been received by the communication unit 12 (step 41). If a beacon has been received (step 41 is Y), the process ends. When it cannot receive (step 41 is N), it is determined by the control part 10 whether the condition where a beacon cannot be received continues more than fixed time (step 42). If it has not continued for a certain time (N in step 42), the process is terminated. If the operation continues for a certain time (step 42 is Y), the control unit 10 instructs execution of the alternative route generation process (step 43).

  Next, the alternative route generation process of step 43 will be described in detail with reference to the flowchart of FIG.

  The lower radio node 2B starts passive scan according to a command from the control unit 10 (step 50). The passive scan is a method of searching for a channel by monitoring a beacon emitted by the upper radio node 2A (or other lower radio node 2B) while the lower radio node 2B changes the channel. The control unit 10 determines whether or not the host wireless node 2A is connectable (step 51). If there is a new connectable higher-order wireless node 2A (step 51 is Y), an alternative connection process at the time of passive scan is executed according to a command from the control unit 10, and communication with the higher-order wireless node 2A is started. (Step 52). On the other hand, when there is no connectable higher-order wireless node 2A (step 51 is N), broadband radio wave interference detection processing is executed according to a command from the control unit 10 (step 53). A specific method of this detection process will be described later.

  Based on the detection process, the control unit 10 determines whether or not a broadband radio wave interference is occurring (step 54). When the control unit 10 determines that the broadband radio wave interference is not occurring (step 54 is N), the lower radio node 2B executes an active scan according to a command from the control unit 10 (step 55). The active scan is a method in which the lower radio node 2B transmits a probe request by itself and searches for an upper radio node 2A that makes a probe response on an available channel. As a result of the active scan, the control unit 10 determines whether there is a connectable higher-order wireless node 2A (step 56). If the control unit determines that there is no upper wireless node 2A that can be connected (step 56 is N), the connection is made with another network away from the currently participating network (step 57). ).

  On the other hand, if there is a connectable higher-order wireless node 2A (step 56 is Y), an alternative connection process at the time of active scanning is performed (step 58), and the process is terminated. Further, when it is determined that a broadband radio wave interference is occurring (Step 54 is Y), a process of clearing or changing a determination time (details will be described later) determined in advance for performing the alternative route process is performed ( Step 59). “Clear” described here means that the determination time is set to 30 seconds, and if there is no 30-second beacon reception, it is set to 0 seconds. The change means that the determination time is changed to 60 seconds, for example.

  Compared with the situation where each wireless node 2 has previously performed active scanning all at once, in this embodiment, the state of broadband radio wave interference is detected before the start of active scanning. Based on the detected radio wave information, whether or not to perform active scan is determined, so that frequent active scans can be prevented. In particular, when a broadband radio wave failure occurs, the alternative wireless node 2B is not subjected to the alternative route processing, and returns to normal communication after the failure stops, so that the network topology can be quickly restored. Further, not performing the alternative route processing for a certain period of time leads to power saving, communication can be smoothly restored, and reduction in throughput can be suppressed.

  In the broadband radio wave interference detection process described above (steps 36 and 53), all available channels used by the lower radio node 2B (or higher radio node 2A) are passively scanned via the communication unit 12.

  By the way, RSSI can be used for detecting broadband radio wave interference. Based on the RSSI value acquired via the communication unit 12, the control unit 10 can determine that a broadband radio wave interference is occurring when an RSSI value greater than a predetermined value is detected in a frequency channel greater than a certain value. is there.

The RSSI threshold (determination reference value) related to the determination may be a predetermined fixed value. Further, the threshold value may be set with reference to a normal level of thermal noise (eg, noise caused by thermal vibration in the apparatus), a noise level at the time of no signal input, or the like. A weighted average of a plurality of RSSIs may be used as a reference (ambient noise level or the like). If the received RSSI value is higher than these reference levels, it is possible to determine that a broadband radio wave interference has occurred.

  An example of a specific method for determining whether or not broadband radio wave interference is occurring using the above-described RSSI value will be described with reference to FIG.

  Assume that RSSI = −50 dBm between the wireless node 21 and the wireless node 22, RSSI = −70 dBm between the wireless node 22 and the wireless node 23, and RSSI = −80 dBm between the wireless node 23 and the wireless node 24. From this value, it can be determined that there is radio wave interference between the radio node 21 and the radio node 22 and radio wave interference has occurred. Further, the signal strength between the wireless node 22 and the wireless node 23 and between the wireless node 23 and the wireless node 24 is a communicable signal strength.

  In the embodiment, it is determined whether or not a broadband radio wave interference is occurring by detecting a jamming wave, generating a band pattern, and analyzing the band pattern. FIG. 7 is a band pattern table in which RSSI values are detected for each channel.

  The band pattern scans in order from 1ch (channel), and shows the RSSI value for the channel in a bar graph. In FIG. 7A, RSSI is set to 1 when −60 dBm or more and 0 when −60 dBm or less. That is, −60 dBm is set as the RSSI threshold. FIG. 7B shows a value obtained by quantizing RSSI. For example, 0 is set when RSSI <= − 90 dBm, 1 is set when −90 dBm to −80 dBm, and 2 is set when −80 dBm to −70 dBm. FIG. 7C shows an actual measurement value of RSSI. The channels in the band pattern table are indicated by numbers, but are actually defined by the center frequency and the bandwidth. For example, in an active tag of 950 MHz, the bandwidth is 200 KHz, the unit channel number is [1], the center frequency is 951.0 MHz, the channel number [2] is 951.2 MHz, and so on.

  A threshold value can be determined, and the occurrence of broadband radio interference can be determined from the band pattern table. For example, (1) radio waves above a threshold value are detected by a certain number of channels, (2) radio waves above a threshold value are above a certain number and biased. For example, 5 channels out of 10 channels interfere. If it spreads over the whole like 1, 3, 5, 7 and 9, it is judged as a wideband radio wave interference. If 1, 2, 3, 4, 5 it is not spread over the whole, Judge that there is no. In addition, (3) a radio wave having a threshold value exceeding a certain number is detected for all channels that can be used by the interference avoidance function. Detection, etc. Furthermore, it is possible to grasp the period of occurrence of broadband radio wave interference from the band pattern table. By determining the generation duration time as data, it is possible to determine the determination time of the alternative route processing stop time during broadband radio wave interference.

  Next, a method for determining broadband radio interference using the result of carrier sense will be described. FIG. 8 shows a band pattern showing the result of carrier sense for each frequency channel.

  In FIG. 8A, a channel with carrier sense detection and a channel with no carrier sense detection (see diagonal lines) are displayed in a straight line. From this band pattern, it can be understood how many seconds (seconds) in which there is no carrier sense due to radio interference (radio interference duration). The determination time can be set based on this. FIG. 8B shows a registered bandwidth pattern. The registered band pattern is data in which radio wave information acquired from the communication unit 12 in the past is recorded, and is stored in the storage unit 11. The registered bandwidth pattern is analyzed to calculate a determination time. The determination time is a time during which a signal from the communication unit 12 is temporarily stopped when a broadband radio wave failure occurs. In other words, the time until the radio interference is calmed is grasped, and based on the time, the lower-level wireless node 2B is on standby without performing communication processing for a certain time. Further, by classifying the registered band pattern for each region, it is also possible to set a determination time corresponding to the radio disturbance duration that occurs in each region.

  The above-described determination time can be changed based on a newly acquired new band pattern. As shown in FIG. 8C, for example, the duration time of the broadband radio wave disturbance in the new band pattern is 180 s. In the registered band pattern, the duration of the broadband radio wave disturbance is registered for 60 s or less, and the determination time is set every 30 s. The control unit 10 can change the determination time every 60 s based on the new band pattern. As a method of calculating the determination time change, for example, it is possible to measure the time until a beacon can be received and use the moving average rate.

  In particular, by analyzing broadband radio interference in a region that occurs regularly and setting or updating the determination time for that region, the signal from the communication unit 12 according to the situation is kept constant while broadband radio interference occurs. The time can be stopped, and power saving and network throughput reduction of the lower wireless node 2B (or higher wireless node 2A) can be suppressed.

  Also, a topology that takes into account the state of broadband radio interference in advance by generating broadband interference information obtained from RSSI values and carrier sense results as interference status data and notifying the surrounding wireless nodes. Can be built.

  Specifically, frequency information indicating the frequency involved in radio wave interference such as the above-mentioned broadband radio wave interference is generated as interference state data and stored in the storage unit 11, and the frequency at the time of beacon transmission of the wireless node 2 or active scan response Information is notified to other wireless nodes 2. The wireless node that has received this frequency information can analyze the frequency information and lower the connection priority with the wireless node 2 where the occurrence frequency of the broadband radio wave interference is high. Accordingly, it is possible to easily construct a network topology that avoids the wireless node 2 in which the broadband radio wave interference has occurred, and it is possible to suppress a reduction in throughput even when the broadband radio wave failure occurs.

  The notification timing of interference status data (frequency information, etc.) may be set at the time of a connection request from a surrounding lower wireless node, or set at the time of beacon transmission of an upper wireless node or communication with a lower wireless node. Also good.

  In the above example, the upper wireless node 2A functions as a first wireless node that performs communication processing when itself exists in a broadband radio wave based on communication status data. Next, the lower radio node 2B serves as a second radio node that selects a connection destination based on interference status data (frequency information, etc.) received from another radio node (for example, the first radio node) described above. The operation when functioning will be described with reference to the flowchart of FIG. Note that the upper wireless node 2A and the lower wireless node 2B indicate the positions of two specific wireless nodes when viewed at a certain point in time. When viewed at different points in time, the positions of the other wireless nodes may be switched. Therefore, a specific radio node may be the first radio node, may be the second radio node, and may not be the first or second radio node.

  For example, when a certain wireless node functions as a first wireless node at a specific time, a plurality of other wireless nodes that send frequency information to the wireless node viewed from the wireless node are used as second wireless notes. Can function. Conversely, when a certain wireless node functions as a second wireless node at a specific time, a plurality of other wireless nodes that have transmitted frequency information to the wireless node can function as a first wireless note. The relationship between the first wireless node and the second wireless node is a connection relationship of 1: N, N: 1, and N: N, respectively.

  The lower radio node 2B starts a passive scan according to a command from the control unit 10 (step 60). The passive scan is a method of searching for a channel by monitoring a beacon emitted by the upper radio node 2A (or other lower radio node 2B) while the lower radio node 2B changes the channel. Next, the control unit 10 determines whether or not the host wireless node 2A is connectable (step 61). When the upper radio node 2A that can be connected by passive scan is not found (step 61 is N), the active scan by the lower radio node 2B is started (step 62).

  When a plurality of connectable wireless node candidates can be acquired by passive scan (step 60) or active scan (step 62) (step 63 is Y), according to the frequency information of each acquired connection candidate wireless node, The lower radio node 2B determines which candidate is connected (step 64).

  The lower radio node 2B compares the frequency information in each connection candidate node, selects the radio node having the least influence of the broadband interference wave as the first connection candidate, and tries priority connection (step 65).

  If the connection with the first connection candidate fails (step 65 is N), the node with the next least influence of the broadband interference wave is selected from the remaining candidates. If connection is not possible, the priority is further lowered and the same is repeated. If the connection with the connection candidate is successful, the process ends (step 65 is Y).

  The following example can be considered as a method for determining the connection priority based on the analysis result based on the frequency information. (1) Number of times substitution processing was performed within a certain time (for example, within 1 hour). For example, if the number of times of connection determination of a new node is 3 or more, it is excluded from connection candidates. (2) The number of times that broadband interference was detected by performing substitution processing within a certain time. For example, if the number of times is 3 or more in the connection determination example of the new node, it is removed from the connection candidates. (3) The total time of receiving the wideband jamming wave by detecting the wideband jamming wave by performing substitution processing within a predetermined time. For example, in the example of determining the connection of a new node, if the time is 300 seconds or more, it is removed from the connection candidates. (4) A band pattern in which substitution processing is performed within a predetermined time to detect a wideband jamming wave and receive the wideband jamming wave. For example, in FIG. 7A, 0 is determined to be no interference wave, 1 is determined to be interference wave, and so on.

  Note that the connection candidate selection may be quantized, and the connection candidate may be selected from the quantized value.

  An example of a connection priority table that displays the priorities of wireless nodes that are connection candidates will be described with reference to FIG. In the connection candidate radio nodes A, B, and C, when the frequency of the broadband jamming wave detected as the frequency information of the radio node A is 10, the priority is set to 3. The priority is set to 1 when the wireless node B has not detected the broadband interference wave. When the frequency at which the wireless node C detects the broadband jamming wave is 2, the priority is 2. Therefore, connection is attempted in the order of the priority B → C → A of the wireless node.

  In the above description, an example in which the wireless node of the connection destination is determined according to the priority of the frequency information has been described. However, the connection destination may be selected by using other parameters in combination. For example, priority weighting can be performed using RSSI values in addition to frequency information.

  In evaluating the priority based on the frequency information and the RSSI value, for example, the following evaluation formula using predetermined parameters can be used.

  Evaluation formula = α × RSSI value (including quantized value) + β × (frequency of occurrence of broadband radio wave interference analyzed frequency information) (α, β: weighting values)

  As a result, a wireless node that has detected wideband radio wave interference avoids wireless nodes with poor communication quality by communicating the failure occurrence status to other wireless nodes when an alternative route connection request or a new connection request is received from the surrounding area. It is possible to perform a topology configuration, and it is possible to suppress a reduction in throughput by selecting a route with better communication status.

  As an example, even in the situation where broadband interference is occurring, if the radio field strength (RSSI value) in communication between wireless nodes is relatively strong (communication is stable), even under this influence Good throughput may be obtained.

  In addition, a wireless node that attempts to connect to a new connection or an alternative route has suffered wideband radio interference. However, if the radio field strength between the wireless node that requested the connection and the connection candidate radio node is strong, the radio node has suffered wideband radio interference. There is a possibility that better throughput can be obtained than when the radio field intensity is weak.

  Therefore, the communication quality can be reduced by lowering the criterion (weighting) based on frequency information when the signal strength is strong, and increasing the criterion (weighting) based on frequency information when the signal strength is weak (communication is unstable). It is possible to perform a topology configuration that avoids bad nodes and suppress a reduction in throughput.

  As an evaluation formula in this case, when α = 1 and β = 1 when the RSSI value is less than −50 dBm, α = 1, β = 0.5, etc. when the RSSI value is −50 dBm or more, By performing a topology configuration that avoids nodes with poor communication quality and selecting a route with better communication status, it is possible to suppress a reduction in throughput.

  The RSSI value related to the determination of the communication status is based on -50 dBm as a fixed value, but is not limited to this, and can be changed according to the status. This example will be described with reference to FIG. 10B. Even in the case where the connection candidate radio nodes A, B, and C detect the broadband jamming wave as the frequency information of the radio node A, the RSSI value is 10 times. Is -50 dBm, the priority is set to 1, and connection is attempted in the order of wireless nodes A → C → B. That is, the connection priority is different from that in FIG.

  The overall control of the measurement information collection system 1 and the wireless node 2 and the control of each wireless node 2 described above can be executed by hardware or software. Further, when executing processing by software, it is possible to install and execute a program in which a processing sequence is recorded in the memory in the control unit 10 or the storage unit 11.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  The measurement information collection system, the wireless node, the wireless node communication method, and the program according to the present invention can be applied to a use for avoiding broadband radio wave interference in a network topology. Further, the present invention can be applied to an application for constructing a network topology while avoiding an area where broadband radio wave interference occurs frequently.

1: Measurement information collection system 2, 21, 22, 23, 24, 25: Wireless node 3: Server device 4: Internet line 5: Central processing unit 10: Control unit 11: Storage unit 12: Communication unit 13: Communication circuit unit 14: Sensor

Claims (17)

In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, the first wireless node capable of communicating with a second wireless node,
The first wireless node is
Communication that transmits / receives communication data to / from the second wireless node and measures an RSSI value corresponding to the intensity of a radio wave or a signal emitted from a radio wave source existing in the vicinity of the second radio node. And
A storage unit for storing at least the measured RSSI value;
And compared with a predetermined reference level the RSSI value, when the RSSI value is higher value and a control unit for judging that interference is present,
With
If the control unit determines that the radio wave interference exists, the control unit stops the signal from the communication unit for a certain period of time before detecting a new alternative route, and the second wireless node that is an existing communication destination A first wireless node attempting to communicate with the first wireless node. A first wireless node according to claim 1, comprising:
The control unit generates a band pattern using the RSSI value, determines whether or not the radio wave interference exists by analyzing the band pattern,
The bandwidth pattern is a first wireless node stored in the storage unit. A first wireless node according to claim 2, comprising:
The control unit compares the stored band pattern with a newly acquired band pattern, and determines whether or not the radio wave interference exists, a first wireless node. A first wireless node according to claim 3, comprising:
The control unit is a first wireless node that analyzes the band pattern, sets a determination time, and determines the fixed time to stop based on the determination time. A first wireless node according to claim 4, comprising:
The control unit is a first wireless node that compares the stored band pattern with a newly acquired band pattern and changes the setting of the determination time. In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, the first wireless node capable of communicating with a second wireless node,
The first wireless node is
A communication unit that transmits / receives communication data to / from the second wireless node and detects carrier sense at least for each frequency channel;
The communication unit generates a band pattern indicating the carrier sense result based on the carrier sense detection result, and compares the generated band pattern with a registered band pattern which is data in which radio wave information acquired in the past is recorded. A control unit for determining whether or not there is a radio interference that should stop the signal from
With
If the control unit determines that the radio wave interference exists, the control unit stops the signal from the communication unit for a certain period of time before detecting a new alternative route, and the second wireless node that is an existing communication destination A first wireless node attempting to communicate with the first wireless node. The first wireless node according to claim 1 or 6, comprising:
The control unit is a first wireless node that determines whether or not the radio wave interference exists when an alternative route cannot be detected by a passive scan that detects an alternative route. The first wireless node according to any one of claims 1, 6 and 7,
If the control unit determines that the radio wave interference does not exist, the control unit performs a substitute route generation process by active scan. The first wireless node according to any one of claims 1 to 8, comprising:
The control unit generates frequency information indicating how often the wireless node is involved in the radio interference ,
A first wireless node, wherein the communication unit sends the generated frequency information to the second wireless node. In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, the second wireless node capable of communicating with the first wireless node,
The second wireless node is
At least communication data is transmitted / received to / from the first radio node, and the radio node generated by the first radio node has a radio wave or signal intensity emitted from a radio wave source that exists in the vicinity. A communication unit that measures a corresponding RSSI value and receives frequency information indicating a frequency at which the RSSI value is higher than a predetermined reference level .
A storage unit for storing at least the frequency information;
A control unit that determines priority as a connection candidate of the first wireless node based on the frequency information;
A second wireless node comprising: A second wireless node according to claim 10, comprising:
The communication unit measures an RSSI value with the first wireless node,
The control unit is a second radio node that determines a priority as a connection candidate of the first radio node based on the frequency information and the measured RSSI value. A measurement information collection system configured by a network topology that collects measurement information from a plurality of wireless nodes,
The first wireless node is
A communication unit that transmits / receives communication data to / from the second wireless node and measures an RSSI value corresponding to the intensity of a radio wave or a signal emitted from a radio wave source existing around the second radio node. When,
A storage unit for storing at least the measured RSSI value;
The RSSI value is compared with a predetermined reference level, and when the RSSI value is high, it is determined that broadband radio interference exists, and it is determined that the broadband radio interference exists. A control unit that attempts to communicate with the second wireless node that is an existing communication destination by stopping a signal from the communication unit for a certain period of time before detection of a new alternative route,
The second wireless node is
A communication unit that transmits and receives at least communication data to and from the first wireless node, and receives frequency information indicating a frequency at which the wireless node generated by the first wireless node is involved in broadband radio wave interference;
A storage unit for storing at least the frequency information;
A control unit that determines priority as a connection candidate of the first wireless node based on the frequency information;
Measurement information collection system with In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, a communication method of a first wireless node capable of communicating with a second wireless node,
The first wireless node is
The communication unit measures an RSSI value corresponding to the intensity of a radio wave or signal emitted from a radio wave source existing around the second radio node ,
A storage unit stores at least the measured RSSI value,
The control unit is compared with a predetermined reference level the RSSI value, when the RSSI value is higher values a determination is that the wideband interference is present,
If it is determined that the broadband radio wave interference exists, the signal from the communication unit is stopped for a certain period of time before detection of a new alternative route, and communication with the second wireless node that is an existing communication destination is performed. A communication method of the first wireless node to be attempted. In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, a first wireless node program capable of communicating with a second wireless node,
A procedure of reading out an RSSI value corresponding to the intensity of a radio wave or signal emitted from a radio wave source existing in the vicinity of the second radio node measured by the communication unit from the storage unit;
The read RSSI value is compared with a predetermined reference level, and when the RSSI value is a high value, it is determined that broadband radio interference exists, and the broadband radio interference exists. If determined, a procedure for stopping a signal from the communication unit for a certain period of time before detection of a new alternative route, and attempting communication with the second wireless node that is an existing communication destination;
A program that causes a computer to execute. In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, a communication method of a second wireless node capable of communicating with the first wireless node,
The communication unit transmits / receives at least communication data to / from the first wireless node, and for the wireless node generated by the first wireless node , a radio wave or signal emitted from a radio wave source that exists in the vicinity Measuring the RSSI value corresponding to the intensity of the received frequency information indicating the frequency at which the RSSI value is involved in radio interference indicating a value higher than a predetermined reference level ,
A storage unit stores at least the frequency information,
A communication method of a second wireless node, in which a control unit determines priority as a connection candidate of the first wireless node based on the frequency information, and attempts communication based on the priority. The communication method of the second wireless node according to claim 15,
The communication unit measures an RSSI value with the first wireless node;
A communication method of a second wireless node that attempts communication based on the priority, wherein the control unit determines a priority as a connection candidate of the first wireless node based on the frequency information and an RSSI value. In a measurement information collection system configured by a network topology that collects measurement information of a measurement device from a plurality of wireless nodes, a program for a second wireless node capable of communicating with the first wireless node,
For the wireless node generated by the first wireless node, an RSSI value corresponding to the intensity of a radio wave or a signal emitted from a radio wave source existing around is measured, and the RSSI value is determined in advance. A procedure for reading out frequency information indicating the frequency of being involved in radio interference indicating a value higher than the level from the storage unit;
Based on the read frequency information, determining a priority as a connection candidate of the first wireless node, and attempting communication based on the priority,
A program that causes a computer to execute.

Images