JP6273723B2 - Wireless communication system and sensor device - Google Patents

Description

  The present invention relates to a wireless communication system and a sensor device, and more particularly to a communication system for managing a wireless communication network including a plurality of sensor devices having a function of notifying measurement data by wireless communication.

  With the shift to IT (Information Technology), the number of wireless devices has increased significantly due to its ease of use. In addition, the degree of dependence on social communication is increasing, and user demand for communication quality such as delay and connectivity is increasing.

  However, with the increase in the number of devices and communication volume, there are situations where sufficient radio resources cannot be obtained, especially in the ISM band (Industry-Science-Medical band) that allows interference from heterogeneous systems. There is an increasing situation in which these requirements cannot be satisfied only by control for ensuring quality of service (QoS) such as a transmission rate by a distributed wireless system.

  Therefore, wireless communication to provide high frequency utilization efficiency and comprehensively high application quality (Quality of Experience: QoE, satisfaction obtained by applications) by dynamically and continuously performing wireless resource allocation and network control. System research results have also been reported (for example, see Non-Patent Document 1).

  A typical communication using the ISM band is a wireless LAN, but sensor networks, smart meters, and the like have been rapidly increasing in recent years, and communication between these devices (M2M: Machine-to-Machine) As an application destination, in addition to sporadic communication such as a response to an inquiry and periodic communication, communication triggered by an event such as simultaneous reading for a large number of devices or exceeding a set threshold value is assumed.

  Applications that perform simultaneous reading and event processing expect reliable event notification with low delay, but when multiple devices perform simultaneous transmission, it is known that transmission delay increases due to congestion and packet loss occurs (for example, (Refer nonpatent literature 2).

  In such M2M communication, for example, ZigBee (registered trademark) is established as an example of a low-cost, low-power consumption short-range wireless communication standard that realizes a short-range wireless communication network (hereinafter also simply referred to as a network). (Non-Patent Document 1).

  As a wireless method for realizing a short-range wireless communication network using such an ISM band, for example, Bluetooth (registered trademark) may be assumed.

  Taking ZigBee (registered trademark) as an example, Patent Document 1 discloses a method for avoiding congestion in such a communication method.

JP 2012-195936 A

Masahiro Uno, Hitoshi Yano, Hirohiro Miyasaka, Hiroshi Oshima, Takeshi Yamamoto, Yoshizo Tanaka, Hiromi Okada, Kiyoshi Kobayashi, “Proposal of a Dynamic Multi-layer Control Autonomous Distributed Wireless System Realizing Fair QoE Satisfaction,” Shin Academic Report, SR2012-62, pp.159-164, Oct. 2012. Hiroshi Yamane, Keisuke Kawakita, Haruhisa Ichikawa, Hisaichi Haneda, Hitoshi Mitsuji, “Examination of Home Appliance Information Simultaneous Reading Using ZigBee,” IEICE Tech. Bulletin, USN2010-64, pp.143-148, Jan. 2011 . IEEE Std.802.15.4-2003, IEEE Standard for Information Technology

  Sensor networks that use ZigBee (registered trademark) are often aimed at low cost, small size, and low power, and require improved performance with simple processing. Avoiding the above congestion is an important technical issue. is there.

  However, the technique disclosed in Non-Patent Document 2 responds individually in advance to the sensor node regardless of the value of the measurement data when data is returned from a plurality of sensor devices in response to a designated call from the Coordinator. This is a technique for accelerating simultaneous reading by assigning a required time to start and additionally performing random backoff for each sensor node.

  The technique disclosed in Patent Document 1 performs communication by selectively using the first network or the second network in order to avoid congestion.

  In the technique disclosed in Non-Patent Document 2, although the influence of congestion can be reduced, the importance of the acquired measurement data is not taken into consideration, and therefore the entire measurement data group measured by the sensor network is received. It may take extra time to figure out on the side.

  In addition, the technique disclosed in Patent Document 1 requires preparation of a plurality of networks, which not only complicates the operation of the system but also increases the cost.

  The present invention has been made to solve the above-described problems, and its purpose is to avoid congestion when receiving measurement data from a plurality of sensor device groups all at once. A wireless communication system and a sensor device are provided.

  Another object of the present invention is to provide a wireless communication system and a sensor device that make it easier to grasp the entire measurement data in a shorter time when receiving measurement data from a plurality of sensor device groups. is there.

According to one aspect of the present invention, there is provided a wireless communication system including a plurality of sensor devices arranged in a predetermined space, each sensor device including a data measuring unit for measuring a physical quantity to be measured; A storage means for storing measurement data representing the measured physical quantity, a wireless communication means for performing wireless communication in a predetermined frequency band, and controlling the wireless communication means in response to occurrence of a predetermined notification event And a control means for transmitting measurement data after a delay time determined for each sensor device, and the notification event is a steady state in which the measurement data is distributed with a specific spread for a plurality of sensor devices. than its value, is that a change above a predetermined threshold value, the control means, in accordance with a change amount of the measurement data, transmitted at an earlier timing greater measurement data amount of change So that the to determine the delay time, further comprising a receiver for receiving measurement data from a plurality of sensor devices.

Preferably, the wireless communication system further includes a resource detection unit that detects a free state of a radio resource in a predetermined frequency band, and the control unit has a large change amount according to a change amount of the measurement data and a free state. The delay time is determined so that the measurement data has a smaller delay time, and the smaller the radio resource is, the larger the delay time is transmitted.

Preferably, it further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band, and the control means is smaller in the measurement data having a larger change amount according to the change amount of the measurement data and the free state. The delay time is determined so that transmission is performed at a timing defined by the product of the first function that is the delay time and the second function that has a larger delay time as the radio resource is less free.

Preferably, the receiving device allocates a first delay time for each sensor device based on the distribution of measurement data from each sensor device in a steady state so that the appearance frequency in the distribution is not biased. The control means determines the predetermined delay time between the second delay time determined to be transmitted at a more dispersed timing and the first delay time when the measurement data having a large change amount is transmitted at an earlier timing and the available radio resources are smaller. The delay time is determined by the weighted sum of.

According to another aspect of the present invention, there is provided a sensor device for collecting measurement data of a target physical quantity that is arranged in a predetermined space, the data measuring means for measuring the physical quantity, and the measured physical quantity. Storage means for storing measurement data to be represented, wireless communication means for performing wireless communication in a predetermined frequency band, and controlling wireless communication means in response to the occurrence of a predetermined notification event, for each sensor device And a control means for transmitting measurement data after the determined delay time elapses, and the notification event is more than its own value in a steady state in which the measurement data is distributed with a specific spread for a plurality of sensor devices. is that changes more than a predetermined threshold value, the control means, in accordance with a change amount of the measurement data amount of change is to transmit at an earlier timing greater measurement data, when the delay To determine.

Preferably, it further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band, and the control means is smaller in the measurement data having a larger change amount according to the change amount of the measurement data and the free state. The delay time is determined so as to be transmitted at a timing at which the delay time becomes larger as the available radio resources are smaller.

Preferably, it further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band, and the control means is smaller in the measurement data having a larger change amount according to the change amount of the measurement data and the free state. The delay time is determined so that transmission is performed at a timing defined by the product of the first function that is the delay time and the second function that has a larger delay time as the radio resource is less free.

Preferably, a receiving device that aggregates measurement data from a plurality of sensor devices is assigned to each sensor device based on the distribution of measurement data from each sensor device in a steady state so that the frequency of occurrence in the distribution is not biased. In addition, each sensor device receives the first delay time, and in each sensor device, the control means transmits measurement data having a large change amount at an earlier timing, and at a more distributed timing as the radio resource is less free. The delay time is determined by a predetermined weighted sum of the second delay time and the first delay time determined to be.

  According to the wireless communication system and the sensor device of the present invention, it is possible to avoid congestion when receiving measurement data from a plurality of sensor device groups in a short time.

  In addition, according to the wireless communication system and the sensor device of the present invention, when measuring data from a plurality of sensor device groups is received, it is possible to grasp the entire measurement data in a shorter time.

1 is a conceptual diagram showing a configuration of a wireless communication system 1000. FIG. 2 is a functional block diagram for explaining a configuration of a sensor device 100. FIG. It is a conceptual diagram which shows the system 2000 of the example of the aspect by which the radio | wireless communications system 1000 of this Embodiment is used. It is a figure for demonstrating the planar arrangement | positioning of the electric light and the sensor apparatus in the greenhouses 2000.1-2000.3. It is a figure which shows the example of the unsteady change of the light intensity generate | occur | produced in the greenhouses 2000.1-2000.3. It is a figure for demonstrating communication with the sensor apparatus 100 and the receiver 200. FIG. It is a conceptual diagram which shows the structure of experiment. In this experiment, it is a figure which shows the timing of the packet transmitted. It is a figure which shows the result of 30 cases which totaled 3 sets of PAN when changing the transfer rate of wireless LAN, and measured 10 times each as a table | surface. It is a figure for demonstrating the planar arrangement | positioning of the electric appliance and sensor apparatus in the greenhouses 2000.1-2000.3 of Embodiment 2. FIG. It is a figure which shows the frequency distribution of the sensor apparatus of the light intensity (illuminance) measured before and after generation | occurrence | production of apparatus abnormality like FIG. 6 is a diagram for explaining communication between sensor device 100 and receiving device 200 according to Embodiment 2. FIG. It is a conceptual diagram for demonstrating the procedure of allocation to the sensor apparatus 100 of initial delay time. 6 is a diagram for explaining communication between sensor device 100 and receiving device 200 of Embodiment 3. FIG.

Hereinafter, a radio communication system according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.
(Embodiment 1)
FIG. 1 is a conceptual diagram showing a configuration of a wireless communication system 1000.

  Sensor devices 100.1 to 100.6 having a communication function in wireless communication are installed in a predetermined space area. Hereinafter, the sensor devices 100.1 to 100.6 are collectively referred to as the sensor device 100.

  Each of the sensor devices 100 steadily measures a physical quantity to be measured, and appropriately transmits a measurement result to the receiving device 200 by wireless communication. Here, such wireless communication is not particularly limited, but is, for example, the ISM band, and it is assumed that contention for wireless resources necessary for communication occurs with other types of wireless communication systems.

  Hereinafter, as an example, it is assumed that the sensor device 100 and the receiving device 200 communicate with each other by using ZigBee (registered trademark), and that other types of wireless communication systems exist and compete with each other. However, the wireless communication method in which the sensor device 100 and the receiving device 200 communicate with each other is not limited to this.

  FIG. 2 is a functional block diagram for explaining the configuration of the sensor device 100.

  Referring to FIG. 2, sensor device 100 includes a wireless unit 110 that executes wireless communication processing. The wireless unit 110 includes an antenna 102 for receiving and transmitting radio waves, an RF circuit 104 that performs high-frequency processing for demodulation or modulation of wireless communication as a front end, and a digital signal obtained by decoding a signal from the RF circuit 104. A transmission / reception signal processing unit 106 for converting the signal into a signal or decoding a digital signal to be transmitted and outputting the decoded signal to the RF circuit 104, and an electric field for grasping a wireless communication state in a wireless band in which the sensor device 100 communicates And an electric field strength measuring unit 108 for measuring the strength.

  The sensor device 100 further includes a control unit 120 for executing measurement processing of the sensor device 100, transmission processing of measurement data, processing corresponding to a command from the reception device 200, a program for operating the control unit 120, , A memory 122 for storing the calculation result of the control unit 120, a power supply unit 124 for supplying power to each unit of the sensor device 100, and an event for transmitting measurement data, A timer 126 for measuring a delay time until transmission is performed, and a data measuring unit 128 for measuring a target physical quantity, for example, acceleration, light intensity, temperature, and the like. As the power supply unit 124, for example, a battery can be used. However, for example, a rechargeable battery that is automatically charged in the daytime can be used when exhausted by combining with a solar battery or the like.

  Here, the memory 122 is not particularly limited. For example, a flash memory capable of storing data in a nonvolatile manner can be used. Alternatively, a volatile memory may be used on the assumption that there is a power backup from the power supply unit 124.

  The data measurement unit 128 includes an acceleration sensor that converts acceleration into an electrical signal, an optical sensor that converts light intensity into an electrical signal, a temperature sensor that converts temperature into an electrical signal, and the like depending on the application. In the following description, it is assumed that the light intensity is measured by the optical sensor.

  In the sensor device 100, the data measurement unit 128 measures the illuminance value to be sensed. The control unit 120 stores the measurement value in the memory 122. As will be described in detail later, the control unit 120 determines the timer according to the measured value (variation amount from the steady state) in the memory 122 and the amount of wireless free resources measured by the electric field strength measuring unit 108 in the wireless unit 110. 126 timer values are set.

  When the timer set time elapses, the control unit 120 promptly processes the measurement value stored in the memory 122 by the radio unit 110 and transmits it as transmission data from the antenna in the form of a radio wave.

  FIG. 3 is a conceptual diagram showing an example system 2000 in which the wireless communication system 1000 according to the present embodiment is used.

  As shown in FIG. 3, there are three greenhouses 2000.1 to 2000.3 installed, and in this greenhouse, illumination by electric lamps is performed in a predetermined time zone in order to keep warm and adjust sunshine hours. Shall be made.

  FIG. 4 is a diagram for explaining a planar arrangement of the electric light and the sensor device in the greenhouses 2000.1 to 2000.3.

  As shown in FIG. 4, electric lamps 300.1 to 300. n is installed, and the sensor devices 100.1 to 100. m is installed.

  FIG. 5 is a diagram illustrating an example of an unsteady change in light intensity generated in the greenhouses 2000.1 to 2000.3.

  That is, consider a situation in which all the lights are extinguished due to a power failure during the above-described illumination period.

In this case, as shown in FIG. 5, in a steady state, the distribution of illuminance (light intensity) in the greenhouse is, for example, a normal distribution centered on the intensity I ₁ .

  In each of the sensor devices 100, a change amount of a measurement value that is a trigger for transmitting measurement data to the reception device 200 is set in advance in the memory 122 as a notification threshold value ΔI.

  Such a notification threshold value ΔI may be registered at the time of installation of the sensor device 100, or may be configured by a command from the receiving device 200.

  When all the lights have disappeared due to a power failure (in the case of a total power failure), the change in the light intensity measured in all the sensor devices 100 exceeds the notification threshold value ΔI.

  Therefore, at this time, if notification of measurement data is simultaneously performed from all the sensor devices 100 to the receiving device 200, a problem of congestion occurs.

  In the sensor device 100 of the present embodiment, each sensor device 100 autonomously sets a delay time until notification according to the amount of change in measurement data.

  FIG. 6 is a diagram for explaining communication between the sensor device 100 and the receiving device 200.

  Referring to FIG. 6, for example, in a steady state, receiving device 200 sequentially detects sensor devices 100.1 to 100. n and the called sensor device 100. It is assumed that measurement data is collected by receiving a response of measurement data from i by the receiving apparatus 200.

  At this time, all blackouts occur, and in all sensor devices 100, measurement data changes that exceed the notification threshold ΔI (the amount of change in measurement data within a predetermined time exceeds the notification threshold). Shall be.

  At this time, each sensor device 100 determines a delay time D until notification is performed according to the following equation.

Here, Dmax is the maximum value of the delay time, and ΔI is the amount of change in the measurement data from the steady state. α is a coefficient that determines the degree of dispersion of the delay amount. Preferably, it is a coefficient that can be varied to correct the degree of dispersion according to the radio resource usage status of other systems, and β is the amount of change in the measurement data. Is a coefficient for converting to a time.

  Note that the coefficient α can be configured such that its function form is set in advance so that the smaller the amount of available wireless resources measured by the electric field strength measurement unit 108, the larger the value. Such a function form of the coefficient α and the value of the coefficient β can be experimentally determined in advance. Here, the “wireless free resource amount” is a wireless resource that can be used to perform a target communication, that is, a free time or a free frequency. For example, in a wireless system where a fixed frequency is secured, this is the amount of time available at that frequency, and the frequency (channel) that is shared and used by multiple wireless systems, such as the ISM band. If it can be changed as appropriate within the frequency band, it also includes the frequency vacancy.

  In this case, since the value of the coefficient α increases as the amount of free wireless resources decreases, the timing of notification from each sensor device 100 to the receiving device 200 is slower and distributed, and packets are transmitted. become. As a result, congestion can be avoided.

  Note that the smaller the amount of free wireless resources, the slower the timing of notification to the receiving apparatus 200 and the more dispersed the packet is to be transmitted. It may not be a linear function.

  In addition, since the measurement data from the sensor device whose measurement data has changed greatly is notified to the reception device 200 earlier, the measurement data from a plurality of sensor device groups is received in a shorter time. This makes it possible to grasp the entire measurement data. When the average value from multiple sensor devices is important, it is possible to set a delay time using a periodic function or a random function so as not to cause a bias while giving a difference in priority to each data. It is.

  That is, the “importance” of the measurement data from the sensor device 100 is set in advance depending on the statistics grasped on the receiving device 200 side, and in the embodiment shown by the equation (1), The measurement data with the higher importance is configured to be notified with a shorter delay time. For example, if the maximum amount of change is a statistic that the receiver wants to grasp, the measurement data that has the largest change in the measured value is highly important. It becomes possible to grasp the whole picture. However, when the average value of measurement data from a plurality of sensor devices is a statistic that the receiving side wants to grasp, this delay is not simply determined by the magnitude of the amount of change determined by Equation (1). For example, a configuration may be used in which a periodic function whose size changes depending on the sensor number or a “modified delay time” obtained by multiplying a random function value as a weight is used for the time.

Further, in the above example, it has been described that the amount of available wireless resources is measured by the electric field strength measurement unit 108. However, for example, the reception device 200 itself that is the reception destination detects in advance, or the reception device 200 It may be configured to notify the sensor device 100 by referring to external information.
(Experimental result)
In the following, the result of experimentally creating a situation corresponding to the situation described in FIG. 6 will be described.

  In this experiment, it is defined that the excess amount from the threshold corresponds to the importance level, and the transmission delay time of the largest measured value of multiple sensor devices is used as the QoE index. To do.

  The transmitter sensor and receiver used in the experiment are equipped with a wireless module and a microprocessor with a 10-bit A / D converter. A cadmium sulfide (CdS) cell connected to the A / D converter Is measured as an integer value from 0 (dark) to 1023 (bright).

  The transmitting sensor device transmits a value only when the measured value increases by 200 or more in 0.015 seconds.

  FIG. 7 is a conceptual diagram showing the configuration of such an experiment.

  As shown in FIG. 7, PAN (Personal Area Network) of a ZigBee (registered trademark) star network in which measured values from 30 sensor devices 100 are a set of one receiving device and ten transmitting-side sensor devices. ) Collect by 3 groups. The data transmission delay time D was set by the following equation in consideration of the maximum value being transmitted in the shortest since the distribution of the measurement value x was almost uniform.

D [ms] = 1024-x
This corresponds to α = β = 1 and Dmax = 1024 in the equation (1).

  In the experiment, three coordinators of PAN were eliminated, and the radio resources were fixed at the same frequency and the usable radio resources were restricted assuming a situation where there were many PANs. By using UDP (User Datagram Protocol) to transfer at a constant rate, free wireless resources were reduced over time.

  In addition, a situation was simulated in which all sensor devices transmit measurement values simultaneously using strobe light emission as a trigger.

  The receiving device receives the measured value from each sensor device (88 Bytes per sensor device) through ZigBee (registered trademark), serially transmits it to the personal computer PC at 57600Baud with a time stamp added, and at the same time emits light by itself. The triggered time is also serially transmitted to the PC.

  Then, the transmission delay time is calculated from the time stamp in the receiving device recorded in the transmitted data.

  FIG. 8 is a diagram illustrating the timing of packets communicated in this experiment.

  A method in which all devices simultaneously start communication upon occurrence of a trigger event is referred to herein as “conventional communication”.

  In conventional communication, all devices start transmission at the same time by a trigger (broken line in FIG. 8), so that although control in a lower layer such as transmission backoff is performed, congestion may occur. In an environment where other systems are operated in the same place and the radio resources are reduced, the possibility of congestion is higher.

  On the other hand, the proposed method controls the transmission timing as described above, and can realize QoE improvement and congestion avoidance as shown by the solid line in FIG.

  FIG. 9 is a diagram illustrating the results of 30 cases in which three sets of PANs are totaled when the wireless LAN transfer rate is changed and measured 10 times each.

  In the transmission delay time comparison of the maximum measured value that is the QoE index, the average delay time and the maximum time are both shorter than the conventional method in which no data transmission delay is added regardless of the amount of free resources due to wireless LAN transfer. In other words, high QoE has been achieved.

  In addition, the proposed scheme is advantageous as far as the average time is concerned even with the transmission delay of all received measurements. When the wireless LAN transfer rate was 30 Mbps, a temporary decrease in the wireless LAN transfer rate was observed due to the influence of ZigBee (registered trademark).

  However, by adopting the configuration of the sensor device 100 of the present embodiment, it is possible to avoid congestion of measurement data transmitted from a plurality of sensor devices when a predetermined event occurs, compared to the conventional method. It is.

  In addition, since the transmission data with higher importance is notified to the reception device 200 earlier, when measuring data from a plurality of sensor device groups is received, the entire measurement data can be viewed in a shorter time. It becomes possible to grasp.

In the above description, the “trigger for transmitting measurement data to the receiving device 200” has been described as the change amount of the measurement data within a predetermined time exceeding the notification threshold. Such a trigger may be a call command for simultaneous transmission from the receiving apparatus 200.
(Embodiment 2)
In the first embodiment, a case has been described where events for notifying measurement data occur almost simultaneously in all of the plurality of sensor devices, such as a total power failure.

  However, the communication configured by the sensor device 100 and the receiving device 200 described in the first embodiment is not necessarily performed in almost all of the plurality of sensor devices at the same time even when an event for notifying measurement data occurs. The system 1000 has an advantageous effect. Therefore, also in the second embodiment, the configurations of the sensor device 100 and the receiving device 200 are the same as those of the first embodiment.

  Hereinafter, such a case will be described as a second embodiment.

  FIG. 10 is a diagram for explaining a planar arrangement of the electric light and the sensor device in the greenhouse 2000.1 to 2000.3 of the second embodiment.

  In FIG. 10, power supply systems PSL11, PSL12 to PSL31, PSL32 are provided for each row of electric lamps arranged in the longitudinal direction of the greenhouse.

  Accordingly, it is assumed that these power systems can be individually powered off due to some device abnormality.

  In FIG. 10, as an example, it is assumed that the power supply system PSL12 in the greenhouse 2000.1 and the power supply system PSL22 in the greenhouse 2000.2 are turned off.

  FIG. 11 is a diagram showing the frequency distribution of the sensor device of the measured light intensity (illuminance) before and after the occurrence of the device abnormality as shown in FIG.

Referring to FIGS. 10 and 11, when only a part of the power supply system is cut off, the light intensity measured by the sensor device in the greenhouse 2000.3 having little influence is obtained from the distribution in the steady state. Does not change greatly and has a distribution centered on the intensity I ₂₂ . On the other hand, the light intensity measured by the sensor device in the greenhouse 2000.1 or 2000.2 in which the power supply system is cut off has a distribution centered on the intensity I ₂₁ .

  In this case, the sensor device in which the data to be measured is greatly reduced notifies the measurement value having a more important significance. This is because these sensor devices just notify the measured value of the place where the abnormality of the device has occurred.

  Accordingly, in this case as well, similarly to the first embodiment, the delay time is determined by the equation (1), and the measurement data is notified from each sensor device 100 according to this.

  FIG. 12 is a diagram for explaining communication between the sensor device 100 and the receiving device 200 according to the second embodiment.

  In the second embodiment as well, with the above configuration, it is possible to avoid congestion of measurement data transmitted from a plurality of sensor devices when a predetermined event occurs.

In addition, since the transmission data with higher importance is notified to the reception device 200 earlier, when measuring data from a plurality of sensor device groups is received, the entire measurement data can be viewed in a shorter time. It becomes possible to grasp.
(Embodiment 3)
In the third embodiment, similarly to the first embodiment, the delay time is set by the equation (1), and the measurement data is received when a predetermined event occurs from each sensor device 100 to the receiving device 200. The device 200 is notified.

  However, for example, when the number of sensor devices 100 is increased and the measurement data measured in the steady state is concentrated on a relatively uniform value, in order to avoid more congestion, It is desirable that the delay time can be set in a distributed manner.

  In the third embodiment, a method for setting such a delay time will be described.

  Therefore, also in the second embodiment, the configurations of the sensor device 100 and the receiving device 200 are the same as those of the first embodiment except for the points described below.

First, in the third embodiment, the initial delay time τ ₀ (i) is assigned to each sensor device 100 in a steady state so that the delay times assigned thereto are evenly distributed. τ ₀ (i) means the initial delay time of the sensor device 100 with sensor number i.

  FIG. 13 is a conceptual diagram for explaining the procedure for assigning the initial delay time to the sensor device 100.

  As shown in FIG. 13, it is assumed that a distribution of light intensity (illuminance) measured by the sensor device group is obtained in a steady state. One sensor device is sequentially selected from the group of sensor devices 100 with a probability inversely proportional to the steady distribution. For the sensor devices 100 that are sequentially selected, initial delay times that are uniformly distributed from a predetermined minimum value to a maximum value are sequentially assigned in order from the smallest.

  By doing in this way, the initial delay time can be assigned to each sensor device 100 without being biased to the appearance frequency in the steady distribution.

  FIG. 14 is a diagram for explaining communication between the sensor device 100 and the receiving device 200 according to the third embodiment.

  As illustrated in FIG. 14, in the steady state, it is assumed that collection of measurement data from all the sensor devices 100 is executed by the receiving device 200 every certain period.

At the end of the steady state data collection, the initial delay time τ ₀ (i) assigned as shown in FIG. 13 is notified from the receiving device 200 to each sensor device 100.

  In FIG. 14, when a notification event occurs, for example, when an abnormality such as a partial power failure occurs and the state becomes an unsteady state, measurement is performed from each sensor device 100 with a delay time D determined as follows. The data is notified to the receiving device 200.

Here, Dmax is the maximum value of the delay time, ΔI is the amount of change in measurement data from the steady state, α is a coefficient that determines the degree of dispersion of the delay amount, and preferably other systems Is a coefficient that can be varied in order to correct the degree of dispersion according to the radio resource usage status, and β is a coefficient for converting the amount of change in measurement data into time. The meaning of these coefficients is the same as in the first embodiment.

  For example, α is measured at an appropriate time interval by the radio field intensity measuring unit 108 and α is determined to be an appropriate value according to the radio resource usage status nearest to transmission.

  More specifically, the transfer time per packet when sufficient free resources are obtained to notify the measurement value is calculated in advance, and the amount of free resources within a certain time obtained by measurement is calculated. On the other hand, when the delay amount is dispersed by α, α is determined so that the total transfer time of packets that are considered to be stochastically transmitted within the predetermined time is equal to or less.

Further, the coefficient γ (0 <γ <1) is a parameter for adjusting the weight of the initial delay time τ ₀ (i) and the importance of the measurement data with respect to the delay time, and this is also experimentally determined in advance. It shall be decided.

  Even with such a configuration, it is possible to avoid congestion of measurement data transmitted from a plurality of sensor devices when a predetermined event occurs.

  In addition, since the transmission data with higher importance is notified to the reception device 200 earlier, when measuring data from a plurality of sensor device groups is received, the entire measurement data can be viewed in a shorter time. It becomes possible to grasp.

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  DESCRIPTION OF SYMBOLS 100 Sensor apparatus, 102 Antenna, 104 RF circuit, 106 Transmission / reception signal processing part, 108 Electric field strength measurement part, 120 Control part, 122 Memory, 124 Power supply part, 126 Timer, 128 Data measurement part, 200 Reception apparatus.

Claims (8)

A wireless communication system,
A plurality of sensor devices arranged in a predetermined space, each of the sensor devices,
Data measuring means for measuring the physical quantity to be measured;
Storage means for storing measurement data representing the measured physical quantity;
Wireless communication means for performing wireless communication in a predetermined frequency band;
Control means for controlling the wireless communication means in response to the occurrence of a predetermined notification event and transmitting the measurement data after a lapse of a delay time determined for each sensor device;
The notification event is that the measurement data has changed by a predetermined threshold or more than its own value in a steady state distributed with a specific spread for the plurality of sensor devices,
The control means determines the delay time according to the amount of change in the measurement data so as to transmit measurement data having a larger amount of change at an earlier timing,
A wireless communication system further comprising a receiving device that receives measurement data from the plurality of sensor devices. It further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band,
The control means, in response to said idle state and the change amount of the measurement data, the amount of change becomes smaller delay time larger the measured data, as free of the radio resources is small, a larger delay time The wireless communication system according to claim 1, wherein the delay time is determined so as to transmit at a timing. It further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band,
  The control means, according to the amount of change of the measurement data and the free state, a first function that makes the measurement data with a large amount of change a smaller delay time, and the less free of the radio resource, The wireless communication system according to claim 1, wherein the delay time is determined so as to be transmitted at a timing defined by a product of a second function having a larger delay time. The receiving device assigns a first delay time for each sensor device based on the distribution of the measurement data from each sensor device in a steady state so that the appearance frequency in the distribution is not biased,
  In each of the sensor devices, the control means includes a second delay time determined to transmit the measurement data having a large change amount at an earlier timing, and at a more dispersed timing as the radio resource is less free. The wireless communication system according to claim 2, wherein the delay time is determined by a predetermined weighted sum with the first delay time. A sensor device arranged in a predetermined space for collecting measurement data of a target physical quantity,
Data measuring means for measuring the physical quantity;
Storage means for storing measurement data representing the measured physical quantity;
Wireless communication means for performing wireless communication in a predetermined frequency band;
Control means for controlling the wireless communication means in response to the occurrence of a predetermined notification event and transmitting the measurement data after a lapse of a delay time determined for each sensor device;
The notification event is that the measurement data has changed by a predetermined threshold or more than its own value in a steady state distributed with a specific spread for the plurality of sensor devices,
The control unit determines the delay time so as to transmit measurement data having a larger change amount at an earlier timing in accordance with the change amount of the measurement data. It further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band,
The control means, in response to said idle state and the change amount of the measurement data, the amount of change becomes smaller delay time larger the measured data, as free of the radio resources is small, a larger delay time The sensor device according to claim 5 , wherein the delay time is determined so as to transmit at a timing. It further comprises resource detection means for detecting a free state of radio resources in a predetermined frequency band,
  The control means, according to the amount of change of the measurement data and the free state, a first function that makes the measurement data with a large amount of change a smaller delay time, and the less free of the radio resource, The sensor device according to claim 5, wherein the delay time is determined so that transmission is performed at a timing defined by a product of a second function having a larger delay time. For each sensor device, a receiving device that aggregates measurement data from the plurality of sensor devices is based on the distribution of the measurement data from the sensor devices in a steady state so that the frequency of occurrence in the distribution is not biased. Each of the sensor devices receives a first delay time assigned to
  In each of the sensor devices, the control means determines a second delay time determined to transmit the measurement data having a large change amount at an earlier timing, and at a more dispersed timing as the radio resource is less free. The sensor device according to claim 6, wherein the delay time is determined by a predetermined weighted sum of the first delay time and the first delay time.