WO2012008181A1

WO2012008181A1 - Sensor, sensor network system, method for controlling sensor, and control program

Info

Publication number: WO2012008181A1
Application number: PCT/JP2011/056269
Authority: WO
Inventors: 直正岩橋
Original assignee: オムロン株式会社
Priority date: 2010-07-16
Filing date: 2011-03-16
Publication date: 2012-01-19
Also published as: JP5187356B2; JP2012023668A

Abstract

The current consumption of a sensor which operates intermittently is reduced. Disclosed is a sensor (3a) which operates intermittently in a sensor network system containing a base station, a relay device, and the sensor (3a), and which directly transmits data to the base station or transmits data to the base station via one or more relay devices. The sensor (3a) is provided with a sleep setting unit (15) for determining a sleep period, and enters a sleep state during the abovementioned sleep period, which is between the point in which data is transmitted and the point in which a response from the base station is received. As a consequence, the time in which the sensor (3a) is active is reduced, thereby being able to reduce the current consumption.

Description

Sensor, sensor network system, sensor control method, and control program

The present invention relates to a sensor that performs intermittent operation and a sensor network system.

In recent years, sensor network systems have been realized in which sensors (sensor nodes) having a sensing function and a wireless communication function are connected by a mesh network, and data measured by each sensor is integrated in a base station that is a host system (for example, ZigBee). (Registered trademark) standard). In such a sensor network system, by arranging a plurality of relay devices having a wireless communication function, the relay device relays communication between each sensor and the base station to constitute a mesh network. The base station and the repeater are mainly supplied with power from an AC power source. On the other hand, the sensor is often driven by a battery in consideration of ease of arrangement, mobility, and downsizing. For this reason, in order to reduce maintenance work, a sensor that needs to be replaced less frequently is a practical sensor. Therefore, reducing the power consumption of the sensor is an important issue.

Conventionally, there are sensors that perform intermittent operation in order to reduce power consumption. The sensor that performs intermittent operation is activated only during the period for measuring the surrounding physical quantity, etc., and during the period for communicating to transmit the measured data to the base station, and in the sleep state where communication is not possible during the period for which measurement and communication are not performed To reduce power consumption.

FIG. 7 is a schematic diagram showing the configuration of the sensor network system 100 of the mesh network. The sensor network system 100 includes a base station 101, a plurality of relay devices 102a to 102b, and a plurality of sensors 103a to 103d. Each of the sensors 103a to 103d is activated at a predetermined timing by a built-in timer, and measures, for example, temperature. Thereafter, in order to accumulate the measured temperature data in the base station 101, each of the sensors 103a to 103d communicates with the base station 101 via one or more repeaters 102a to 102b. Here, the data transmitted from the

sensors

103a and 103b to the base station 101 reaches the base station 101 via the two

repeaters

102a and 102b. Data transmitted from the sensor 103c to the base station 101 reaches the base station 101 via a single relay 102b. The sensor 103 d communicates directly with the base station 101 and transmits data to the base station 101.

FIG. 8 is a diagram illustrating communication between the sensor 103d and the base station 101 and current consumption of the sensor 103d. The horizontal axis represents time (time) t, and the upper part of FIG. 8 shows data transmission / reception processing of the sensor 103d and the base station 101. The lower part of FIG. 8 shows the current consumption of the sensor 103d. FIG. 8 schematically shows the relationship between time and current consumption, and the scale of the graph is not accurate.

The sensor 103d in the sleep state is activated at a time t101 by an internal timer and shifts to an active state. In the active state, the sensor 103d is activated, and the current consumption is significantly larger than that in the sleep state. After the activation, the sensor 103d measures, for example, the temperature between time t101 and time t102, and transmits the measured data to the base station 101 between time t102 and time t103. The arrows in FIG. 8 indicate data transmission in communication. The base station 101 that has received data from the sensor 103d returns a reception confirmation indicating that the reception has been successful to the sensor 103d. However, the transmission of data in communication includes the reception confirmation, that is, the reception confirmation is included. Communication is performed between time t102 and time t103.

The base station 101 that has received the data checks whether or not the received data is appropriate between time t103 and time t104. When the received data is appropriate, the base station 101 transmits a response indicating that the reception of the measurement data is completed as a response to the sensor 103d between the time t104 and the time t105 to the sensor 103d. Note that the reception confirmation for this response is transmitted from the sensor 103d to the base station 101 between time t104 and time t105.

When the sensor 103d receives a response indicating that the reception of the measurement data is completed from the base station 101, the sensor 103d shifts to a sleep state with a small current consumption after time t105. As described above, the sensor 103d is in an active state at a predetermined interval, and performs an intermittent operation in which the sensor 103d enters a sleep state when communication with the base station 101 is completed.

Note that, even in the active state, the current consumption value is different between the measurement time and the communication time, but in FIG. 8, the average current consumption in the active state is depicted by omitting it.

Patent Document 1 describes a sensor network system that includes a sensor that performs intermittent operation and a base station, and reduces the power consumption of the sensor. Patent Document 1 discloses a configuration in which the time during which the sensor is activated for communication is shortened by shortening the response period of the base station to the data transmission of the sensor (the period from time t103 to time t104 in FIG. 8). Are listed.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2006-21439 (published on August 10, 2006)”

However, when the sensor transmits data to the base station via the repeater (sensors 103a to 103c in FIG. 7), the relay time by the repeater increases, and the sensor transmits data before the base station The period until receiving the response becomes longer. Therefore, as the number of repeaters through communication increases, the period during which the sensor is in an active state in order to receive a response from the base station becomes longer.

FIG. 9 is a diagram illustrating communication between the sensor 103a and the base station 101 and current consumption of the sensor 103a. The horizontal axis represents time (time) t, and the upper part of FIG. 9 shows data transmission / reception processing of the sensor 103a, the

repeaters

102a and 102b, and the base station 101. The lower part of FIG. 9 shows the current consumption of the sensor 103a. FIG. 9 schematically shows the relationship between time and current consumption, and the scale of the graph is not accurate.

In the sensor network system 100, the sensor 103a communicates with the base station 101 via the two

repeaters

102a and 102b. The sensor 103a shifts from the sleep state to the active state at time t111, and measures the temperature between time t111 and time t112. The sensor 103a transmits measurement data to the repeater 102a between time t112 and time t113. In addition, between the time t112 and the time t113, the relay machine 102a receives measurement data, and transmits the reception confirmation with respect to it to the sensor 103a. Between time t113 and time t114, the relay device 102a transmits the received measurement data to the relay device 102b, and the relay device 102b transmits a reception confirmation to the relay device 102a. Between time t114 and time t115, the relay station 102b transmits the received measurement data to the base station 101, and the base station 101 transmits a reception confirmation to the relay station 102b.

The base station 101 that has received the data checks whether or not the received data is appropriate between time t115 and time t116. When the received data is appropriate, the base station 101 transmits a response indicating that the reception of the measurement data is completed as a response to the sensor 103a from the time t116 to the time t117 to the relay device 102b. Thereafter, the response from the base station 101 is received by the sensor 103a through the

repeaters

102b and 102a in order. When the sensor 103a receives a response indicating that the reception of the measurement data is completed from the base station 101, the sensor 103a shifts to a sleep state with a small current consumption after time t119.

Thus, when the number of relay stages (the number of relays that relay communication between the sensor and the base station) increases, the period during which the relay relays communication increases, and the network from the sensor to the base station increases. If the route is far, the ratio of the period during which the relay relays communication increases in the period in which the sensor is in the active state. Therefore, even if the processing of the base station is speeded up as in the technique described in Patent Document 1, the effect that the sensor receives a response from the base station is shortened, that is, the period in which the sensor is in an active state is reduced. I can't expect. Therefore, the effect of reducing the current consumption of the sensor cannot be expected so much. Further, in a mesh network (for example, ZigBee (registered trademark) Pro standard) that autonomously constructs a communication path from a sensor to a base station, the network path changes according to the surrounding wireless environment and the like. The number of relay stages with the base station changes. Therefore, the period during which the sensor is in the active state also changes. Therefore, when the number of relay stages increases, the period during which the sensor is in the active state is extended, and the battery life of the sensor is shortened.

On the other hand, a memory for buffering is installed in the repeater, and the repeater stores the transmission data from the sensor to the base station, and the transmission data (response or command, etc.) from the base station to the sensor, A technique has been proposed in which a repeater communicates with a sensor and transmits and receives these data at a predetermined time when the sensor becomes active. However, when the repeater buffers transmission data, a large-capacity memory for storing a large amount of data according to the number of surrounding sensors is required, and the power consumption of the repeater increases. Therefore, when a small memory is used for the repeater, the number of sensors that can be connected to the repeater is reduced.

The present invention has been made in view of the above problems, and an object thereof is to reduce the current consumption of a sensor that performs intermittent operation.

The sensor according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and transmits data to the base station directly or via one or more repeaters. In order to solve the above-described problem, a period determination unit that determines a sleep period is provided, and the sleep period, the sleep state, and the period from when data is transmitted until a response is received from the base station. It is characterized by becoming.

The sensor control method according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and sends data to the base station directly or via one or more repeaters. A method for controlling a sensor to transmit, in order to solve the above-described problem, a period determination step for determining a sleep period and a period from when the sensor transmits data until a response is received from the base station And a sleep step for putting the sensor in a sleep state during the sleep period.

According to the above configuration, the sensor enters a sleep state with low current consumption between the time when data is transmitted and the time when a response from the base station is received. Can be reduced. Here, the active state is a state where communication is possible, and the sleep state is a state where communication is impossible and current consumption is smaller than that of the active state. Therefore, the sensor can reduce current consumption. Therefore, for example, when the sensor operates with a battery, the battery life can be extended, and the maintenance load can be reduced.

The sensor according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and transmits data to the base station directly or via one or more repeaters. In order to solve the above-described problem, a sleep state is established for a predetermined sleep period from when data is transmitted until a response is received from the base station.

The sensor control method according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and sends data to the base station directly or via one or more repeaters. In order to solve the above-described problem, the sensor transmits a predetermined sleep period between the time when the sensor transmits data and the time when a response from the base station is received. It is characterized by including a sleep step for making a sleep state.

According to the above configuration, the sensor enters a sleep state with low current consumption between the time when data is transmitted and the time when a response from the base station is received. Can be reduced. Therefore, the sensor can reduce current consumption. Therefore, for example, when the sensor operates with a battery, the battery life can be extended, and the maintenance load can be reduced.

As described above, according to the present invention, the sensor enters a sleep state with low current consumption between the time when data is transmitted and the time when a response is received from the base station. Active time can be reduced. Therefore, the sensor can reduce current consumption. Therefore, for example, when the sensor operates with a battery, the battery life can be extended, and the maintenance load can be reduced.

It is a mimetic diagram showing the composition of the sensor network system of one embodiment concerning the present invention. It is a block diagram which shows the structure of the sensor of one Embodiment which concerns on this invention. It is a figure which shows the communication of the sensor and base station of one Embodiment which concerns on this invention, and the consumption current of a sensor. It is a figure which shows an example of the operation | movement flow of the said sensor. It is a table | surface which shows an example of the parameter used for calculation of the consumption current of a sensor. It is a table | surface which compares and shows the active time and current consumption of the sensor of one Embodiment which concerns on this invention, and the conventional sensor for every relay stage number. It is a schematic diagram which shows the structure of the conventional sensor network system. It is a figure which shows the communication of the conventional sensor and base station, and the consumption current of a sensor. It is a figure which shows the communication of the conventional sensor and base station, and the consumption current of a sensor.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

<Configuration of sensor network system>
FIG. 1 is a schematic diagram showing a configuration of a sensor network system 10 of a mesh network. The sensor network system 10 includes a base station 1, a plurality of repeaters 2a to 2b, and a plurality of sensors (sensor nodes) 3a to 3d. For example, the base station 1 may be arranged in a server room of an office, and the sensors 3a to 3d may be arranged in each room of the office for measuring temperature and humidity, and power of each outdoor facility or You may arrange | position in each installation for measurement, such as temperature. The sensors 3a to 3d operate with the power of the built-in battery, and the relays 2a to 2b and the base station 1 operate with power supplied from an external AC power source.

Sensors 3a to 3d have a sensing (measurement) function and a wireless communication function. Each of the sensors 3a to 3d is activated at a predetermined timing by a built-in timer and measures temperature and the like. The sensors 3a to 3d may measure other quantities such as humidity or illuminance. Thereafter, in order to accumulate the measured temperature data in the base station 1, each of the sensors 3a to 3d performs wireless communication with the base station 1 via one or more repeaters 2a to 2b. . Here, data transmitted from the

sensors

3a and 3b to the base station 1 reaches the base station 1 through the two

relay devices

2a and 2b. Data transmitted from the sensor 3c to the base station 1 reaches the base station 1 through one relay device 2b. The sensor 3 d communicates directly with the base station 1 and transmits data to the base station 1. The sensor network system 10 is a mesh network that fluidly changes the communication path according to the surrounding wireless environment and the state of the

repeaters

2a and 2b. In the communication between the sensors 3a to 3d and the base station 1 or the relays 2a to 2b, the sensors 3a to 3d can communicate with each other in accordance with the signal strength of the base station 1 or the relays 2a to 2b. Data etc. are transmitted with a signal strength of a limit level.

FIG. 2 is a block diagram showing the configuration of the sensor 3a. The sensors 3a to 3d have the same configuration. The sensor 3a includes a timer unit 11, an activation unit 12, a measurement unit 13, a communication unit 14, a sleep setting unit (period determination unit) 15, and a storage unit 16.

The timer unit 11 stores the activation time (time), and outputs a signal for starting measurement to the activation unit 12 in order to shift the sensor 3a from the sleep state to the active state at a predetermined time for measurement. To do. When the timer unit 11 receives the sleep period information from the activation unit 12, the timer unit 11 causes the activation unit 12 to wait for communication in order to shift the sensor 3a from the sleep state to the active state at a time according to the sleep period. Output a signal.

When the activation unit 12 receives a signal from the timer unit 11, the activation unit 12 shifts the sensor 3a from the sleep state to the active state. When the activation unit 12 receives a measurement start signal from the timer unit 11, the activation unit 12 outputs a measurement start signal to the measurement unit 13. Further, upon receiving a communication standby signal from the timer unit 11, the activation unit 12 outputs a communication standby signal to the communication unit 14. In addition, when the activation unit 12 receives a signal for shifting to the sleep state from the sleep setting unit 15, the activation unit 12 outputs information on the sleep period to the timer unit 11 as necessary to shift the sensor 3 a from the active state to the sleep state. .

When the measurement unit 13 receives the measurement start signal, the measurement unit 13 measures the temperature and acquires the measurement value. The measurement unit 13 may be configured to acquire a measurement value from an external sensor. The measurement unit 13 outputs measurement data including the measurement value and the measurement time to the communication unit 14.

The communication unit 14 communicates with the external base station 1 or the

repeaters

2a and 2b. When the communication unit 14 receives the measurement data from the measurement unit 13, the communication unit 14 transmits the measurement data to the

communicable repeaters

2a and 2b or the communicable base station 1. In addition, when the communication unit 14 receives a communication standby signal from the activation unit 12, the communication unit 14 waits for communication from the outside in an active state in which communication is possible. Further, the communication unit 14 receives data such as a response, a command, and a reception confirmation from the

repeaters

2a and 2b or the base station 1. When receiving the reception confirmation or response, the communication unit 14 outputs the received data and the received time to the sleep setting unit 15.

When the sleep setting unit 15 receives the reception confirmation for the transmission of the measurement data and the received time from the communication unit 14, the sleep setting unit 15 stores the information of the time when the reception confirmation is received in the storage unit 16. The sleep setting unit 15 reads the past (previous communication) response waiting period (the period from when the measurement data is transmitted to the repeater until the response of the base station is returned) from the storage unit 16. The sleep period is determined according to the response waiting period, and a signal for shifting to the sleep state is output to the activation unit 12 together with the sleep period information.

When the sleep setting unit 15 receives the response of the base station 1 from the communication unit 14, the sleep setting unit 15 stores information on the time when the response of the base station 1 was received in the storage unit 16, and the sensor 3a is stored until a predetermined time for measurement. In order to enter the sleep state, a signal for shifting to the sleep state is output to the activation unit 12.

The storage unit 16 stores information on the past response waiting period (for example, the length of the response waiting period, the time when the measurement data is transmitted, the time when the reception confirmation is received, and / or the time when the response of the base station 1 is received. Etc.).

<Communication processing of sensor and base station>
FIG. 3 is a diagram illustrating communication between the sensor 3a and the base station 1, and current consumption of the sensor 3a. The horizontal axis represents time (time) t, and the upper part of FIG. 3 shows data transmission / reception processing of the sensor 3a, the

repeaters

2a and 2b, and the base station 1. The lower part of FIG. 3 shows the current consumption of the sensor 3a. FIG. 3 schematically shows the relationship between time and current consumption, and the scale of the graph is not accurate.

In the sensor network system 10, the sensor 3a communicates with the base station 1 via the two

repeaters

2a and 2b (the number of relay stages is 2). The sensor 3a is activated by a built-in timer at time t1, shifts from the sleep state to the active state, and measures the temperature between time t1 and time t2.

Next, the sensor 3a transmits measurement data to the repeater 2a between time t2 and time t3. In addition, between the time t2 and the time t3, the relay machine 2a receives measurement data, and transmits the reception confirmation with respect to it to the sensor 3a.

When the communication from the sensor 3a to the repeater 2a is completed (when the sensor 3a transmits measurement data to the repeater 2a and receives a reception confirmation), the sensor 3a shifts to a sleep state (time t3). At this time, the sensor 3a determines a predetermined sleep period TS from past communication, and sets a timer so as to shift to an active state in which communication with the repeater 2a is possible after the sleep period TS elapses. Here, the period between time t3 and time t8 shown in FIG. 3 is set as the sleep period TS.

Between time t3 and time t4, the relay device 2a transmits the received measurement data to the relay device 2b, and the relay device 2b transmits a reception confirmation to the relay device 2a. Between time t4 and time t5, the relay device 2b transmits the received measurement data to the base station 1, and the base station 1 transmits a reception confirmation to the relay device 2b.

The base station 1 that has received the data checks whether or not the received data is appropriate between time t5 and time t6. When the received data is appropriate, the base station 1 transmits a response indicating that the reception of the measurement data is completed as a response to the sensor 3a to the repeater 2b between time t6 and time t7. The response may include a control command (command) for the sensor 3a. The repeater 2b receives a response between time t6 and time t7, and transmits a reception confirmation to the base station 1.

Between time t7 and time t8, the relay device 2b transmits the received response to the relay device 2a, and the relay device 2a transmits a reception confirmation to the relay device 2b.

After the sleep period TS elapses from time t3 (between time t7 and time t8), the sensor 3a is activated by the timer and shifts from the sleep state to an active state in which communication is possible.

Between time t8 and time t9, the relay device 2a transmits the received response to the sensor 3a, and the sensor 3a transmits a reception confirmation to the relay device 2a. When the sensor 3a receives the response indicating that the reception of the measurement data is completed from the base station 1, the period TA (time t3) from when the measurement data is transmitted to the repeater 2a until the response of the base station 1 is returned. From time t8). (Here, the time t3 indicates a point in time when the sensor 3a transmits measurement data to the repeater 2a and receives a reception confirmation from the repeater 2a to complete the communication, and a time t8 indicates that the sensor 3a receives the repeater. 2a refers to the time when the response of the base station 1 starts to be received.) If the number of relay stages does not change, until the response of the base station 1 is returned after transmitting measurement data to the relay 2a in the next communication Therefore, it can be predicted that a period equivalent to the period TA will be required. Therefore, the sensor 3a determines the sleep period TS in the next communication based on the calculated period TA. Specifically, in consideration of a case where a response is returned a little earlier, a period shorter than the period TA, such as a period obtained by subtracting a predetermined period from the period TA or a period obtained by multiplying the period TA by a predetermined ratio. The period is determined as the sleep period TS. Note that the period TA may be determined as the sleep period as it is.

After that (after time t9), a transition is made to a sleep state with low current consumption. The sensor 3a stands by in a sleep state until a predetermined time for measurement (for example, after 10 minutes) comes.

If the sensor 3a cannot receive a response from the base station within a predetermined period (for example, within 0.5 seconds) after shifting to the active state in order to receive a response, the sensor 3a sets the next sleep period to 0 second. Or reset the next sleep period to be shorter. Therefore, the response waiting period is reduced due to a decrease in the number of relay stages, and when the relay 2a transmits a response from the base station 1 to the sensor 3a while the sensor 3a is in the sleep state, the sensor 3a The sleep period after the next time is changed to be shorter so that a response can be received.

When data (measurement data and response from the base station 1 to the sensor 3a) is transmitted in each communication, the sensor 3a, the

repeaters

2a and 2b, and the base station 1 transmit the data within a predetermined period after transmission. If reception confirmation is not returned from the communication partner (for example, within one second), data is retransmitted to the communication partner. Therefore, when the sleep period after the sensor 3a transmits the measurement data to the relay device 2a is too long, and the sensor 3a is in the sleep state, the relay device 2a transmits a response from the base station 1 to the sensor 3a. However, since the reception confirmation cannot be obtained, the repeater 2a retransmits the response from the base station 1 to the sensor 3a after a predetermined period. Thereby, even when the sleep period is too long, the sensor 3a can receive the retransmission of the response from the base station 1 and confirm that the measurement data has arrived at the base station 1. Therefore, even if the number of relay stages (the number of relay stations via communication up to the base station 1) is reduced from the previous communication, and the response returns earlier than the previous time, the sensor 3a may receive a response retransmission. it can. Note that, when performing retransmission, the relay station 2a may add information indicating that this is not the first transmission. As a result, the sensor 3a recognizes that the first transmission from the repeater 2a has not been received, and so that the repeater 2a does not have to retransmit in the next and subsequent communications. The period can be changed short.

If the sensor 3a cannot receive a response from the base station 1 within a predetermined period (for example, within 3 seconds) after shifting to the active state at time t8, the measurement data is not transmitted somewhere in the communication path. Since it is considered that the measurement data has not reached the base station 1, the sensor 3a retransmits the measurement data to the repeater 2a. When the measurement data is retransmitted, the sensor 3a waits in a communicable state without shifting to the sleep state in order to reliably receive a response from the base station. That is, the sleep period is reset to zero.

<Sensor operation flow>
FIG. 4 is a diagram illustrating an example of an operation flow of the sensor.

The sensor starts at a predetermined time set in advance by a built-in timer, and shifts to an active state (S1).

After that, the sensor measures the temperature (S2).

The sensor transmits the measured measurement data to the repeater or the base station (S3). In addition, the sensor receives a reception confirmation from the repeater or the base station.

In accordance with the signal strength of the wireless communication of the relay station or the base station, the sensor updates the transmission output level so that communication is performed with the minimum signal strength (S4).

The sensor determines the sleep period based on the past response waiting period (S5). When information for resetting the sleep period is stored in the storage unit 16, the sleep period is set to 0 ms.

If the sleep period is greater than 0 ms (Yes in S6), the sensor sets a timer so as to be in the sleep state only during the determined sleep period and shifts to the sleep state (S7). Then, after the sleep period elapses, the sensor is activated by a timer and shifts to an active state in which communication is possible (S8).

The active sensor receives the response of the base station from the base station or the relay station, and receives it, and returns a confirmation of reception.

When the response of the base station is received within a predetermined period (for example, within 0.5 seconds) after shifting to the active state (Yes in S9), the sensor shifts to the sleep state (S10), and the process of S1 Return to.

When the base station response is not received within a predetermined period (for example, within 0.5 seconds) after shifting to the active state (No in S9), the sensor uses the sleep period to reset the sleep period. Is stored in the storage unit 16 (S11).

If the sleep period is 0 ms (No in S6), the mobile station stands by in a communicable active state and waits for a response from the base station (S12).

After S11, when the sensor shifts to the active state, or after S12, the sensor does not receive the base station response within a predetermined period (for example, within 3 seconds) after transmitting the measurement data. (No in S13), the process returns to S3 in order to retransmit the measurement data to the base station.

After S11, when the sensor shifts to the active state, or after S12, when the response of the base station is received within a predetermined period (for example, within 3 seconds) after the sensor transmits the measurement data (S13) Yes), the process proceeds to S10, and the sensor shifts to the sleep state.

According to this embodiment, the sensor can perform reception for a predetermined period after transmitting measurement data to the base station until receiving a response indicating that reception of the measurement data is completed from the base station. Wait in no sleep state. Therefore, current consumption can be reduced compared to a conventional sensor that waits in a communicable state until a response from the base station is received. The effect of reducing the current consumption compared with the conventional configuration becomes more prominent as the number of relay stages increases.

In addition, the sensor according to the present embodiment transmits the measurement data to the repeater based on the past response waiting period (the period from when the measurement data is transmitted to the repeater until the base station response is returned). Since the sleep period to be determined is determined, the time for the response from the base station to be returned can be predicted regardless of the number of relay stages, and when the response from the base station is returned, the communication can be shifted to the active state. it can. Therefore, the sensor can receive the response from the base station while reducing the current consumption during the response waiting period. If the response from the base station does not reach due to poor communication, the sensor can quickly measure the response. Data can be retransmitted. Therefore, the base station can receive measurement data accurately and quickly.

In addition, since the sensor predicts the time when the response from the base station is returned and shifts to the active state, when the nearest repeater capable of communicating with the sensor transmits the response from the base station to the sensor, the sensor Communication can be received appropriately. For this reason, it is difficult to cause waste that the repeater tries to communicate with the sensor many times even though the sensor is in the sleep state.

The sensor may determine the sleep period based on the response waiting period in the communication before the previous time. For example, the average of the response waiting period in the communication in the past predetermined period or the communication in the past predetermined number of times. Alternatively, the sleep period may be determined using a weighted average or the like.

In addition, when the sensor cannot receive a response from the base station within a predetermined period (for example, within 3 seconds) after transitioning to the active state, the sensor transitions to the sleep state without immediately retransmitting measurement data. Measurement data may be sent together at the time of measurement. In the next measurement, the sleep period may be reset to 0 in order to reliably receive a response from the base station.

<Comparison of sensor current consumption>
A comparison of current consumption between the sensor of this embodiment and the conventional sensor will be described below. Trial calculation of current consumption of a sensor that performs intermittent operation can be performed using a simplified formula. The average current consumption of a sensor that performs measurement at a constant interval and transmits data is expressed by the following equation.

Even in the active state, the current consumption differs during measurement, transmission, reception, or communication standby, but the average current consumption in these active states (average current consumption during active) is simply the same here. Suppose that

Figure 5 shows the value of each parameter in the above equation. The data transmission interval is 600 seconds (10 minutes). The average current consumption during active is 40 mA. The average current consumption during sleep is 0.025 mA. Since the timer is only operated during sleep, the sensor can operate with a current consumption of about 1/500 to 1/1000 compared to the average current consumption during active time. The active time (period) in one cycle includes a measurement time (t2-t1 in FIG. 3), a data transmission time (t3-t2 in FIG. 3), a response reception time (t9-t8 in FIG. 3), and a communication standby time ( This is the sum of t118-t113) in FIG. The sleep period is 600 seconds minus the active time.

Of the active time, the measurement time, data transmission time, and response reception time are the same for the sensor of this embodiment and the conventional sensor. Here, it is assumed that it takes 11 milliseconds (ms) for the communication between the sensor, the repeater, and the base station. That is, the processing time for one arrow in FIG. 3 (periods such as t3-t2, t4-t3, t9-t8) is 11 ms. In addition, it is assumed that the active time when the sensor and the base station directly communicate with each other without using a repeater (the number of relay stages is 0) is 70 ms. That is, assume that the sum of the measurement time, data transmission time, and response reception time is 70 ms. Note that the base station confirms whether or not the received data is appropriate (t6-t5) and ignores it. When the number of relay stages is 0, the sensor sets the sleep period to 0 ms (that is, the sensor does not shift to the sleep state after receiving the response from the base station after transmitting the measurement data). The sensor may be configured to sleep for a short period even when the number of relay stages is zero.

In this case, when the number of relay stages is increased by one, the active time is extended by 22 ms (11 ms × 2 round trips). Therefore, when the number of relay stages is 1 (when there is one relay station that relays communication), it takes 92 ms to complete the process of transmitting measurement data after starting measurement at a predetermined time and receiving the response from the base station. . That is, the active time of the conventional sensor that does not perform the sleep operation is 92 ms. On the other hand, when the sensor of the present embodiment ideally performs a sleep operation (when the sensor returns from the sleep state to the active state immediately before receiving a response from the base station), the active time is 70 ms, The time does not change depending on the number of relay stages. Therefore, the active time of the sensor of this embodiment becomes shorter as compared with the conventional sensor as the number of relay stages increases. In general, in a sensor, current consumption in a sleep state is much smaller than current consumption in an active state. Therefore, the sensor of this embodiment can greatly reduce current consumption.

FIG. 6 is a table comparing the active time and current consumption of the sensor of the present embodiment and the conventional sensor for each number of relay stages. The value (%) of current consumption indicates the ratio of the current consumption of the sensor of the present embodiment to the current consumption of the conventional sensor. When the number of relay stages is 9, the sensor of this embodiment can reduce the current consumption to about 72% compared to the conventional sensor.

The sensor of the present embodiment can suppress variation in active time due to the difference in the number of relay stages. That is, since the sensor of this embodiment operates with a substantially constant active time regardless of the number of relay stages, it is possible to suppress variations in battery life of a plurality of sensors. Therefore, battery replacement of a plurality of sensors can be performed at the same timing, and a maintenance load can be reduced.

[Embodiment 2]
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2. For convenience of explanation, members / configurations having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

<Configuration of sensor network system>
The configuration of the sensor network system of the present embodiment is the same as the sensor network system 10 of the mesh network shown in FIG. In this embodiment, the base station 1 transmits information on the number of relay stages of the sensors 3a to 3d to the sensors 3a to 3d. Note that the information on the number of relay stages is included in a response to the transmission of measurement data and transmitted to the sensors 3a to 3d. Since the response waiting period mainly varies depending on the number of relay stages, each of the sensors 3a to 3d determines the sleep period after transmitting measurement data according to the number of relay stages.

When the measurement data is transmitted from the sensors 3a to 3c to the base station 1 via the relays 2a to 2b, identification information of the relayed relays 2a to 2b is transmitted to the base station 1 together with the measurement data. . For example, when the measurement data is transmitted from the sensor 3a to the base station 1 via the relay 2a and the relay 2b, the base station 1 uses the sensor 3a, the relay as information on the communication path along with the measurement data. 2a and the address (identification information) of the repeater 2b are received. Thereby, the base station 1 can recognize the number of repeaters that are relaying the communication with the sensor 3a. The base station 1 transmits a response including information on the number of relay stages to the sensor 3a.

The configuration of the sensor of this embodiment is the same as the sensor shown in FIG. The sensor 3a determines the sleep period based on the information on the number of relay stages. For example, when receiving a response from the base station 1, the communication unit 14 outputs received data to the sleep setting unit 15.

When the sleep setting unit 15 receives the reception confirmation for the transmission of the measurement data and the received time from the communication unit 14, the sleep setting unit 15 reads information on the relay stage number of the previous communication from the storage unit 16 and determines the sleep period according to the relay stage number. Then, a signal for shifting to the sleep state is output to the activation unit 12 together with information on the sleep period. The sleep setting unit 15 may set a period determined in advance according to the number of relay stages as a sleep period. The sleep setting unit 15 may determine the sleep period based on the relationship between the number of relay stages in the past communication and the response waiting period. For example, the sleep setting unit 15 can determine the sleep period based on an average response waiting period (or a minimum response waiting period or the like) when the number of relay stages is 2.

When the sleep setting unit 15 receives the response of the base station 1, the sleep setting unit 15 stores the information of the time when the response is received and the information of the number of relay stages included in the response in the storage unit 16, and the sensor 3a until a predetermined time for measurement. In order to set the sleep state to the sleep state, a signal for shifting to the sleep state is output to the activation unit 12.

The storage unit 16 stores information on the number of relay stages and information on a past response waiting period. In addition, table data indicating the number of relay stages and a predetermined sleep period corresponding thereto may be stored.

The sensor response wait period mainly varies depending on the number of relay stages. According to the present embodiment, each sensor determines the sleep period according to the number of relay stages of the communication path, so that the response waiting period can be appropriately predicted. Therefore, it is possible to reduce the active time while waiting for a response and reduce the current consumption.

It should be noted that the sensor that has received the response from the base station may determine the number of relaying relay devices from the communication path information (address of each relaying device) added to the response.

In addition, the base station may transmit information indicating the sleep period to each sensor instead of information on the number of relay stages. For example, the base station determines the number of relay stages from information on the communication path with a certain sensor, determines a predetermined sleep period according to the past or the latest number of relay stages, and transmits information indicating the determined sleep period to the sensor. May be. The sleep setting unit of the sensor can determine the sleep period in the next communication based on the received information indicating the sleep period.

Also, the base station may transmit information indicating a level that changes according to the number of relay stages to each sensor, and the sensor may determine the sleep period according to the level indicated by the received information. For example, if the number of relay stages is 0 to 1, level 1 is assumed, when the number of relay stages is 2 to 4, level 2 is assumed, and when the number of relay stages is 5 or more, level 3 is expected to change the response waiting period according to the level. it can. Therefore, the sensor can predict the response waiting period according to the received level and determine the sleep period. Note that the base station may determine the sleep period and transmit information indicating the sleep period as the level to the sensor.

Further, the sensor may be configured to be in a sleep state for a certain period of time from transmission of measurement data to the base station to reception of a response from the base station regardless of the number of relay stages.

[Other variations]
A first sensor according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and transmits data to the base station directly or via one or more of the repeaters. A sensor for transmitting, comprising a period determining unit for determining a sleep period, wherein the sleep period is in a sleep state from when data is transmitted until a response is received from the base station. Yes.

According to a first sensor control method of the present invention, in a sensor network system including a base station, a repeater, and a sensor, the base station performs an intermittent operation and directly or via one or more of the repeaters. A method of controlling a sensor for transmitting data to a period determining step for determining a sleep period, and between the time when the sensor transmits data and the time when a response is received from the base station, A sleep step, and a sleep step for setting a sleep state.

In addition, the period determining unit predicts a response waiting period from when the sensor transmits data until receiving a response from the base station, and before the response from the base station returns, The sleep period may be determined so as to shift to a communicable active state.

According to the above configuration, the period determination unit predicts the response waiting period and determines the sleep period, so that the sensor can shift to a communicable active state before the response from the base station is returned. . Therefore, it is possible to more reliably receive a response from the base station, reduce the active time, and reduce current consumption.

Further, the period determination unit may determine the sleep period based on a response waiting period from when the sensor transmits data until a response is received from the base station in past communication.

According to the above configuration, the period determining unit can determine the sleep period based on the response waiting time in the past communication, and therefore can predict the response waiting period. Therefore, it is possible to determine a sleep period as long as possible so that a response from the base station can be received. Therefore, the active time can be reduced more efficiently. In addition, since the active time of a plurality of sensors can be made more uniform regardless of the number of repeaters that relay communication, for example, when the sensors operate on batteries, the battery life of the plurality of sensors is made more uniform. be able to. Therefore, the maintenance load can be reduced.

In addition, the period determination unit may determine the sleep period according to the number of repeaters that relay communication with the base station.

The response waiting period mainly varies depending on the number of repeaters that relay communication with the base station. According to said structure, since a sleep period is determined according to the number of the relay machines which relay communication with a base station, a response waiting period can be estimated. Therefore, it is possible to determine a sleep period as long as possible so that a response from the base station can be received. Therefore, the active time can be reduced more efficiently. In addition, since the active time of a plurality of sensors can be made more uniform regardless of the number of repeaters that relay communication, for example, when the sensors operate on batteries, the battery life of the plurality of sensors is made more uniform. be able to. Therefore, the maintenance load can be reduced.

In addition, the base station transmits information indicating a level corresponding to the number of relays that relay communication with the sensor to the sensor, and the period determination unit determines the sleep period according to the level. It may be a configuration.

According to the above configuration, the base station transmits information indicating a level corresponding to the number of relays that relay communication with the sensor to the sensor. Since the number of repeaters that relay communication is related to the response waiting time, the period determination unit of the sensor receives the response from the base station by determining the sleep period according to the level indicated by the above information. As long as possible, the longest possible sleep period can be determined. Therefore, the active time can be reduced more efficiently. In addition, since the active time of a plurality of sensors can be made more uniform regardless of the number of repeaters that relay communication, for example, when the sensors operate on batteries, the battery life of the plurality of sensors is made more uniform. be able to. Therefore, the maintenance load can be reduced.

In addition, when the sensor shifts from the sleep state to the active state after the sleep period elapses after transmitting data, and cannot receive a response from the base station within a predetermined period after the transition to the active state The period determination unit may change the sleep period in the next communication to be short.

For example, when the relay communication path changes and the number of relays that relay communication changes, the response waiting time may change accordingly. When the response waiting time is shortened, it is conceivable that a response from the base station is returned while the sensor is in the sleep state.

According to the above configuration, when the response from the base station cannot be received within a predetermined period after the transition to the active state, the period determining unit changes the sleep period in the next communication to be short. Therefore, the number of repeaters that relay communication is reduced, the response waiting time is shortened, and even if a response is returned from the base station while the sensor is in the sleep state, this will be handled in the next communication. And the sensor can properly receive a response from the base station.

The second sensor according to the present invention performs intermittent operation in a sensor network system including a base station, a repeater, and a sensor, and sends data to the base station directly or via one or more repeaters. The transmitting sensor is in a sleep state for a predetermined sleep period from when data is transmitted to when a response from the base station is received.

According to the second sensor control method of the present invention, in a sensor network system including a base station, a repeater, and a sensor, the base station performs intermittent operation and directly or via one or more of the repeaters. A method of controlling a sensor for transmitting data to a sleep step of setting the sensor to a sleep state for a predetermined sleep period from when the sensor transmits data to when a response from the base station is received including.

The sensor network system according to the present invention includes a base station, a repeater, and the sensor.

(Program and recording medium)
Note that a part of the sensor may be realized by a computer. In this case, a control program that causes the computer to operate as each unit and a computer-readable recording medium that records the control program are also included in the present invention. Enter the category.

Each block of the sensors 3a to 3d, particularly the sleep setting unit 15, may be configured by hardware logic, or may be realized by software using a CPU (central processing unit) as follows.

That is, the sensors 3a to 3d include a CPU that executes instructions of a control program that realizes each function, a ROM (read memory) that stores the program, a RAM (random access memory) that develops the program, the program, and various A storage device (recording medium) such as a memory for storing data is provided. An object of the present invention is to provide a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program for the sensors 3a to 3d, which is software that realizes the above-described functions, is recorded in a computer-readable manner This can also be achieved by supplying to the sensors 3a to 3d and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU (microprocessor unit)).

Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, a CD-ROM (compact disk-read-only memory) / MO (magneto-optical) / Disc system including optical disc such as MD (Mini Disc) / DVD (digital versatile disc) / CD-R (CD Recordable), card system such as IC card (including memory card) / optical card, or mask ROM / EPROM ( A semiconductor memory system such as erasable, programmable, read-only memory, EEPROM (electrically erasable, programmable, read-only memory) / flash ROM, or the like can be used.

Alternatively, the sensors 3a to 3d may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, an intranet, an extranet, a LAN (local area network), an ISDN (integrated services network, digital network), a VAN (value-added network), and a CATV (community antenna) television communication. A network, a virtual private network, a telephone line network, a mobile communication network, a satellite communication network, etc. can be used. Further, the transmission medium constituting the communication network is not particularly limited. For example, IEEE (institute of electrical and electronic engineering) (1394), USB, power line carrier, cable TV line, telephone line, ADSL (asynchronous digital subscriber loop) loop Wireless such as IrDA (infrared data association) or remote control, Bluetooth (registered trademark), 802.11 wireless, HDR (high data rate), mobile phone network, satellite line, terrestrial digital network, etc. But it is available.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

The present invention can be used for a sensor that performs intermittent operation.

1

Base station

2a, 2b Repeater 3a-3d Sensor (sensor node)
11 Timer unit 12 Start unit 13 Measuring unit 14 Communication unit 15 Sleep setting unit (period determination unit)
16 Memory unit

Claims

In a sensor network system including a base station, a relay device, and a sensor, a sensor that performs intermittent operation and transmits data to the base station directly or through one or more relay devices,
A period determining unit for determining a sleep period;
A sensor which is in a sleep state during the sleep period during a response waiting period from when the sensor transmits data to when a response from the base station is received.
The period determining unit predicts the response waiting period, and determines the sleep period so that the sensor transitions to an active state in which communication is possible before a response from the base station is returned. The sensor according to claim 1.
The sensor according to claim 1, wherein the period determining unit determines the sleep period based on the response waiting period in past communication.
2. The sensor according to claim 1, wherein the period determining unit determines the sleep period according to the number of repeaters that relay communication with the base station.
The base station transmits information indicating a level corresponding to the number of relays that relay communication with the sensor to the sensor,
The sensor according to claim 1, wherein the period determining unit determines the sleep period according to the level.
When the sensor transitions from the sleep state to the active state after the elapse of the sleep period after transmitting data, and cannot receive a response from the base station within a predetermined period after the transition to the active state, The sensor according to claim 1, wherein the period determining unit changes the sleep period in the next communication to be shorter.
In a sensor network system including a base station, a relay device, and a sensor, a sensor that performs intermittent operation and transmits data to the base station directly or through one or more relay devices,
A sensor that is in a sleep state for a predetermined sleep period from when data is transmitted to when a response from the base station is received.
A sensor network system comprising a base station, a relay station, and the sensor according to claim 1.
In a sensor network system including a base station, a repeater, and a sensor, a sensor control method that performs intermittent operation and transmits data to the base station directly or through one or more of the repeaters,
A period determining step for determining a sleep period;
A sensor control method comprising: a sleep step for setting the sensor to a sleep state during the sleep period from when the sensor transmits data to when a response from the base station is received.
In a sensor network system including a base station, a repeater, and a sensor, a sensor control method that performs intermittent operation and transmits data to the base station directly or through one or more of the repeaters,
A sensor control method comprising a sleep step of setting the sensor to a sleep state for a predetermined sleep period from when the sensor transmits data to when a response from the base station is received.
In a sensor network system including a base station, a relay station, and a sensor, a sensor control program that performs intermittent operation and transmits data to the base station directly or via one or more relay stations,
A period determining step for determining a sleep period;
The computer having the sensor executes a sleep step of putting the sensor in a sleep state during the sleep period from when the sensor transmits data until receiving a response from the base station. Control program.
In a sensor network system including a base station, a relay station, and a sensor, a sensor control program that performs intermittent operation and transmits data to the base station directly or via one or more relay stations,
A computer having the sensor execute a sleep step for setting the sensor to a sleep state for a predetermined sleep period from when the sensor transmits data to when a response from the base station is received. Control program.