JP2019216303A - Sensor node, relay node, and sensor network, and operation estimation method for relay node and operation method for relay node - Google Patents

Abstract

To provide a system for a relay node constituting a sensor network to perform power saving operation.SOLUTION: A sensor node is configured to transmit a response request frame, which requests transmission of a delivery confirmation, to a relay node that constitutes a sensor network and is configured to perform, according to predetermined operation settings, switching between an active period in which a delivery confirmation is transmitted in response to the response request frame and a sleep period in which no delivery confirmation is transmitted. The sensor node comprises: an operation state estimation unit including an estimation transmission unit configured to transmit the response request frame to the relay node according to predetermined estimation transmission operation settings and a determination unit configured to determine at least either of the active period or the sleep period of the relay node on the basis of a reception situation of the delivery confirmation; and a communication execution control unit configured to control execution of communication with a communication destination of measurement data measured by a sensor unit, on the basis of an operation setting estimation result.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a sensor network including a relay node capable of power saving operation.

  2. Description of the Related Art A sensor network for collecting measurement data sensed by a sensor by connecting the sensor to a network (wired or wireless) has been known (see Patent Documents 1 to 3 and Non-Patent Document 1). For example, in a wireless sensor network, measurement data wirelessly transmitted from a sensor node (wireless communication slave) that is a sensor having a wireless communication function is transmitted to a gateway node (eg, a boundary between the wireless sensor network and a wired network). (Base station). At this time, if it is not possible to secure sufficient communication stability between the sensor node and the gateway node due to restrictions on the installation location of the sensor node or the influence of a shield such as a metal structure, for example, in a power plant, the communication As a measure to improve stability, a relay node (router node) capable of relaying communication is arranged. As a result, the sensor node and the gateway node are connected in a multi-hop manner by one or more relay nodes, thereby enabling stable communication. Note that the relay node may be a sensor node having a relay function.

  In many cases, the sensor node is an end node located at the edge of the network. The active state operates in an active mode in which communication with other nodes is possible, and the sleep state operates in a sleep mode in which communication with other nodes is not possible. And a power saving operation in which the power saving operation is switched periodically. As a result, the sensor node driven by a battery (battery) operates in a sleep mode to put a wireless circuit or the like into a sleep state, thereby suppressing power consumption and operating for a long time without replacing the battery. Becomes possible.

  On the other hand, a relay node may asynchronously communicate with a sensor node (end node) or another relay node. For this reason, various proposals have been made as a method for causing the relay node to perform a power saving operation. For example, a method in which a relay node transmits a command specifying a transmission interval to a sensor node managed by itself and enters a sleep state during a period in which there is no communication from the sensor node (Patent Document 1), a gateway (collection) Station) transmits a command packet specifying a sleep period to a relay node and a sensor node in a sensor network, and each node receiving the command packet enters a sleep state during the specified sleep period (Patent Document 1) 2) has been proposed.

  In Patent Document 3, the relay node estimates a cycle (activation cycle) in which the sensor node is in an active state based on a reception state of measurement data transmitted from the sensor node, It is disclosed that a setting of a change of a start cycle or a start time and a processing request for various measurements are made.

JP-A-2015-216581 JP 2009-206749 A JP 2013-102263 A

Yuki Kubo and two others, "Power Saving Technology for Wireless Sensor Networks", [online], April 2009, OKI Technical Review Vol. 214, Vol. 76 No. 1, [Search April 18, 2018], Internet <URL: https: // www. oki. com / jp / otr / 2009 / n214 / pdf / 214_r09. pdf>

  The methods disclosed in Patent Literatures 1 and 2 enable a relay node and a sensor node to synchronize an active period in an active state and a sleep period in a sleep state by setting, thereby enabling a power saving operation of the relay node. . For this purpose, it is necessary to implement the function for both in the relay node and the sensor node, and the change to the existing sensor network system is increased accordingly. Since time synchronization is required between various nodes, the setup of the sensor network system becomes complicated. In Patent Literature 1, it becomes necessary for the relay node to manage the subordinate sensor nodes. In view of such a problem, the present inventors have considered a new method for the relay node to perform a power saving operation.

  In view of the above circumstances, at least one embodiment of the present invention aims to provide a method for a relay node configuring a sensor network to perform a power saving operation.

(1) The sensor node according to at least one embodiment of the present invention includes:
A relay node configuring a sensor network, wherein an active period for transmitting the acknowledgment and a sleep period for not transmitting the acknowledgment for a response request frame requesting transmission of an acknowledgment are switched according to a predetermined operation setting. A relay node configured to, the sensor node configured to transmit the response request frame,
A communication unit for connecting to the sensor network;
A sensor unit for measuring a sensing object,
The estimated transmission unit configured to transmit the response request frame to the relay node according to a predetermined estimated transmission operation setting, and at least the active period or the sleep period of the relay node based on the reception status of the delivery confirmation. A determining unit configured to determine one, an operating state estimating unit including:
A communication execution control unit configured to control execution of communication with the communication destination of the measurement data measured by the sensor unit based on the estimation result of the operation setting.

  According to the configuration (1), the sensor node is configured to communicate with the relay node that performs the power saving operation by switching between the active state and the sleep state. Then, the sensor node transmits a response request frame, which is transmission data requesting transmission of an acknowledgment to the relay node, based on the reception status of the acknowledgment transmitted from the relay node in response to the request. An active period or a sleep period is estimated, and execution of communication with a communication destination (such as a gateway) is controlled based on the estimation result.

  In this way, the sensor node estimates the operation setting (power saving operation setting) of the relay node, so that the sensor node performs communication during the active period of the relay node and does not perform communication during the sleep period. Communication with a communication destination via the communication destination can be performed at an appropriate timing. Therefore, the power saving operation of the relay node can be enabled, and power consumption of the sensor node due to communication during the sleep period of the relay node can be prevented. Further, the sensor node needs to newly store only the reception status of reception confirmation (communication record data of the past several times) necessary for estimating the power saving operation setting and the estimation result of the power saving operation setting. However, the storage area required for realizing this configuration is not large, and does not increase the cost of the sensor node.

  In addition, since precise time synchronization between the sensor node and the relay node (Patent Documents 1 and 2 and the like) is not required, the setup of the sensor network can be simplified. Since the sensor node automatically adjusts the communication frequency based on the above estimation result, there is no need for the relay node to manage the sensor node, and when one or more sensor nodes perform power saving operation, Tuning of the relay operation, such as adjusting the power saving operation of the relay node, can be eliminated.

(2) In some embodiments, in the configuration of (1) above,
The operating state estimating unit,
The two response request frames, which are the first response request frame and the second response request frame corresponding to the acknowledgment received by the sensor node, the two response request frames being transmitted when the first response request frame is transmitted. Between the time of transmission of the second response request frame and the second response request frame when a third response request frame that has not received the corresponding acknowledgment from the relay node is transmitted A transmission interval of, or a calculating unit configured to calculate a time interval of the active period based on a reception interval of the two acknowledgments received by the sensor node with respect to the two response request frames. Have further.

  The relay node alternately repeats the active period and the sleep period. Therefore, after transmitting a response request frame in the active period, the sensor node responds to the sleep period following the active period after experiencing a communication success in which a delivery confirmation for the response request frame is received. By transmitting the request frame, one experiences a communication failure when no acknowledgment for the response request frame is received, and again experiences a successful communication in the next active period.

  According to the configuration of (2), the active period of the relay node is repeated based on the transmission / reception interval of the response request frame at the time of successful communication performed in each of two adjacent active periods with the sleep period of the relay node interposed therebetween. Time interval (period) can be calculated. Further, the timing of the active period and the sleep period can be estimated.

(3) In some embodiments, in the configuration of the above (2),
The estimated transmission operation setting includes a transmission interval setting for transmitting each of the plurality of response request frames,
The operation state estimating unit further includes a transmission execution interval changing unit configured to change a transmission execution interval of the response request frame by the estimation transmission unit that transmits the response request frame according to the transmission interval setting. ,
The transmission execution interval changing unit,
The transmission execution interval of the response request frame is shortened when the acknowledgment is received, and the transmission execution interval of the response request frame is lengthened when the acknowledgment is not received.

  According to the above configuration (3), the sensor node updates the transmission execution interval of the response request frame to a longer value when communication with the relay node is successful, and increases the transmission execution interval when communication with the relay node fails. Update to a shorter value. This makes it possible to appropriately calculate the cycle in which the active period is repeated while reducing the sleep period of the relay node and the number of transmissions of the response request frames transmitted in two active periods adjacent to each other with the sleep period therebetween.

(4) In some embodiments, in the configuration of the above (3),
The transmission execution interval changing unit changes the transmission execution interval of the response request frame so that the transmission execution interval of the response request frame falls within a range of not less than a predetermined minimum value and not more than a predetermined maximum value. .
According to the configuration of the above (4), by setting the minimum value in the transmission execution interval of the response request frame, the timer time becomes too short, and the response request frame for estimation is excessively transmitted unnecessarily. Can be prevented, and an increase in power consumption at the time of estimation can be prevented. Further, by providing a maximum value for the transmission execution interval of the response request frame, it is possible to appropriately estimate the minimum time interval at which the sensor node can communicate with the relay node.

(5) In some embodiments, in the above configurations (1) to (4),
The communication execution control unit,
A communication timing determination unit configured to determine a communication execution timing for executing communication with the communication destination during the active period of the relay node based on the estimation result of the operation setting,
A communication execution unit configured to execute communication with the communication destination at the communication execution timing.
According to the configuration of (5), the communication execution timing is determined so as to overlap the active period of the relay node using the estimation result of the period of the active period. According to this communication execution timing, the sensor node performs communication with the communication destination such as the gateway, so that communication can be performed during the active period of the relay node, and communication with the communication destination can be more reliably performed while suppressing power consumption. Can be done.

(6) In some embodiments, in the configuration of the above (5),
The communication timing determining unit,
An initial value setting unit configured to set an initial value of the communication execution timing,
It is configured to determine the communication execution timing by adjusting an initial value of the communication execution timing based on a reception status of the delivery confirmation with respect to the response request frame transmitted at the time of communication with the communication destination. And an adjusting unit.
According to the configuration of the above (6), the communication execution timing can be determined according to the situation, and communication with the communication destination can be performed at a more appropriate communication execution timing.

(7) In some embodiments, in the configuration of the above (6),
The adjustment unit adjusts the initial value of the communication execution timing such that the communication frequency decreases stepwise when the delivery confirmation is received.
According to the configuration of (7), by adjusting the communication execution timing stepwise, it is possible to execute communication with the communication destination at more appropriate communication execution timing.

(8) In some embodiments, in the above configurations (6) to (7),
The adjustment unit adjusts the initial value of the communication execution timing so that the communication frequency increases stepwise when the delivery confirmation is not received.
According to the configuration of (8), by adjusting the communication execution timing stepwise, it is possible to execute communication with the communication destination at more appropriate communication execution timing.

(9) In some embodiments, in the above configurations (5) to (8),
And a notifying unit configured to notify the operation state estimating unit when the acknowledgment is not received for the response request frame transmitted by the communication executing unit.
According to the configuration of the above (9), when the acknowledgment from the relay node for the response request frame transmitted based on the estimation result of the operation setting (power saving operation setting) of the relay node is not received, the relay operation estimation is performed. Department. If the acknowledgment from the relay node is not received, since the response request frame is transmitted based on the estimation result of the power saving operation setting of the relay node, for example, some change has occurred in the sensor network. It is assumed that the estimation result of the power saving operation setting of the relay node is no longer appropriate. Therefore, if such a situation is notified to the operation state estimating unit, it is possible to provide an opportunity to perform re-estimation. Can be obtained.

(10) The relay node according to at least one embodiment of the present invention includes:
A relay node configured to constitute a sensor network and configured to switch between an active period in which relay of communication performed by one or more sensor nodes is possible and a sleep period in which the communication is not relayed according to a predetermined operation setting,
A reception status monitoring unit configured to monitor a reception status of transmission data transmitted from the one or more sensor nodes; and configured to determine the operation setting based on the reception status of the transmission data. An operation setting generation unit including a setting determination unit,
An operation control unit configured to switch between the active period and the sleep period in accordance with the operation setting generated by the operation setting generation unit.

  According to the configuration of (10) above, the relay node is configured to be able to perform the power saving operation by switching between the active state and the sleep state according to the operation setting (power saving operation setting). Is generated in accordance with a reception state of transmission data or the like transmitted to a communication destination such as a gateway transmitted by the sensor node. Accordingly, the relay node can be in the sleep state during a period in which it is expected that there is no sensor node performing communication, and power consumption can be suppressed. In addition, the relay node becomes active during a period in which it is expected that at least one sensor node that executes communication exists, thereby enabling reliable relay of communication of the sensor node. Therefore, it is possible to improve the real-time property of collection of measurement data by a gateway or the like, and to suppress power consumption due to retransmission of transmission data of a sensor node.

  In addition, since precise time synchronization between the sensor node and the relay node is not required, the setup of the sensor network can be simplified. Also, compared to the case where the sensor node estimates the power saving operation setting of the relay node as described above, it is not necessary to add a function to the sensor node, and the power consumption at the time of estimation of the sensor node is reduced. This has the effect that reduction and maintenance can be concentrated on the relay node.

(11) In some embodiments, in the configuration of the above (10),
The setting determining unit determines the sleep period based on a time interval during which the transmission data is not received, based on a reception state of the transmission data, or the active period based on a time interval at which the transmission data is received. At least one of determining the period is performed.
According to the configuration (11), the relay node can appropriately determine the power saving operation setting.

(12) In some embodiments, in the above configurations (10) to (11),
A setting update unit configured to update the operation setting, further comprising:
The setting update unit,
For each active period, an expected number calculation unit configured to calculate an expected number of sensor nodes transmitting the transmission data,
For each active period, an actual number calculating unit configured to calculate an actual number of the number of the sensor nodes transmitting the transmission data,
A mismatch notification unit configured to notify the operation setting generation unit when the expected number does not match the actual number.
According to the configuration of (12), the relay node checks the expected number and the actual number of transmission data from the sensor node for each active period, and notifies when the expected number and the actual number do not match. If the expected number and the actual number do not match, it is determined that the relay node has not properly grasped the communication status of the sensor node. Therefore, by comparing the expected number and the actual number, it is possible to determine whether or not the power saving operation setting of the relay node is appropriate. If not, the power saving operation setting of the relay node is updated. Then, it is possible to maintain an appropriate power saving operation setting of the relay node that follows a change in the sensor network.

(13) The sensor network according to at least one embodiment of the present invention includes:
A sensor node according to any one of (1) to (9),
A gateway node configured to collect transmission data transmitted by the sensor node;
And a relay node configured to relay the transmission data transmitted by the sensor node to the gateway node.

  According to the configuration of the above (13), the same effects as those of the above (1) to (9) can be obtained.

(14) The sensor network according to at least one embodiment of the present invention includes:
A sensor node,
A gateway node configured to collect transmission data transmitted by the sensor node;
And the relay node according to any one of (10) to (12).

  According to the configuration of the above (14), the same effects as those of the above (10) to (12) can be obtained.

(15) The operation estimation method of the relay node according to at least one embodiment of the present invention includes:
A relay node configuring a sensor network, wherein an active period for transmitting the acknowledgment and a sleep period for not transmitting the acknowledgment for a response request frame requesting transmission of an acknowledgment are switched according to a predetermined operation setting. A relay node configured to, the relay node operation estimation method executed by the sensor node configured to transmit the response request frame,
Transmitting the response request frame to the relay node according to a predetermined estimated transmission operation setting, and determining at least one of the active period or the sleep period of the relay node based on a reception status of the acknowledgment, Steps for estimating the operating state including:
Controlling execution of communication of the measurement data measured by the sensor unit with a communication destination based on the estimation result of the operation setting.

  According to the configuration of the above (15), the same effect as in the above (1) can be obtained.

(16) The operation method of the relay node according to at least one embodiment of the present invention includes:
A relay for a relay node configured to configure a sensor network and to switch between an active period in which communication performed by one or a plurality of sensor nodes can be relayed and a sleep period in which the communication is not relayed according to a predetermined operation setting A method of operating a node,
An operation setting generation step including: a reception state monitoring step of monitoring a reception state of transmission data transmitted from the one or more sensor nodes; and a setting determining step of determining the operation setting based on the reception state of the transmission data. Steps for
Switching between the active period and the sleep period according to the operation setting generated by the operation setting generation unit.

  According to the configuration of the above (16), the same effect as the above (10) can be obtained.

  According to at least one embodiment of the present invention, a scheme is provided for a relay node constituting a sensor network to perform a power saving operation.

It is a figure showing roughly composition of a wireless sensor network concerning one embodiment of the present invention. FIG. 3 is a block diagram illustrating functions of a sensor node according to an embodiment of the present invention. It is a figure for explaining execution control of communication by a communication execution control part concerning one embodiment of the present invention. FIG. 4 is a diagram for explaining a method of estimating an active period interval by a sensor node according to an embodiment of the present invention. It is a figure showing the flow of the power saving operation setting estimation method of the relay node concerning one embodiment of the present invention. FIG. 3 is a block diagram illustrating functions of a relay node according to an embodiment of the present invention. It is a figure showing the sensor node table which the relay node concerning one embodiment of the present invention manages. FIG. 7 is a diagram illustrating an operation method of the relay node according to an embodiment of the present invention, and is a diagram for describing a situation at the time of a steady operation after learning of the relay node. It is a figure which shows the operation | movement method of the relay node which concerns on one Embodiment of this invention, and is a flowchart which shows operation | movement at the time of learning of a relay node. It is a flowchart which shows operation | movement at the time of the normal operation | movement after learning of the relay node which concerns on one Embodiment of this invention.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  FIG. 1 is a diagram schematically showing a configuration of a wireless sensor network 1 according to one embodiment of the present invention. As shown in FIG. 1, the sensor network (wireless sensor network 1) includes one or a plurality of sensor nodes 2, one or a plurality of relay nodes 5, and a gateway node (hereinafter simply referred to as a gateway 8). You. The sensor node 2 is configured to send the transmission data D to the gateway 8 by directly communicating with the gateway 8 or by communicating with the gateway 8 via the relay node 5 existing in the vicinity thereof.

  In the following description, the wireless sensor network 1 as shown in FIG. 1 will be described as an example. However, the sensor network may be constructed by a wire, or may be constructed by including a wired portion and a wireless portion. The term “wireless” in the following description may be appropriately read as “wired” and applied.

  More specifically, the sensor node 2 is a device having a sensor unit 2s for measuring a sensing target and a wireless communication function for connecting to the wireless sensor network 1. In other words, the sensor node 2 is a device in which the sensor unit 2s and the wireless communication unit 2r capable of wireless communication are connected. The sensor unit 2s performs sensing (measurement) by being installed so as to be able to sense a sensing target. The wireless communication unit 2r wirelessly transmits measurement data as a result of sensing by the sensor unit 2s, and receives a delivery confirmation Fa (described later) transmitted from another node such as the relay node 5. The sensor node 2 may be configured such that one wireless communication unit 2r and one sensor unit 2s are connected (one-to-one connection), or the same or the same for one wireless communication unit 2r. A plurality of sensor units 2s for measuring different sensing targets may be connected (many-to-one connection).

  Specifically, the sensor node 2 transmits the measurement data at a predetermined transmission timing, for example, periodically (upload interval). The transmission data D such as measurement data is output from the wireless communication unit 2r after being packetized by a protocol of a network layer (layer) constituting a lower layer and framed by a protocol of a MAC layer. The transmission data D thus transmitted from the sensor node 2 is received by the gateway 8 either directly by the gateway 8 or relayed by the relay node 5.

  The sensor node 2 is normally configured to be driven by a battery (battery; the same applies hereinafter), and operates so as to repeat a sleep state (described later) and an active state (described later) periodically, for example. Power saving operation). That is, the sensor node 2 is in a sleep state (described later) when the transmission data D is not transmitted, and operates for all functions when the transmission data D is transmitted, in order to enable long-term driving without replacing the battery. It operates to be in an active state (described later) in which the sleep state has been released, such as a state in which power is supplied. However, in the present invention, the sensor node 2 may or may not perform the power saving operation. When the sensor node 2 performs the power saving operation, it is possible to reduce maintenance costs such as battery replacement for the sensor node 2.

  The gateway 8 is a device that collects measurement data transmitted from the above-described sensor nodes 2 (usually, a plurality of nodes). As shown in FIG. 1, the gateway 8 is installed at a boundary between the wireless sensor network 1 and the wired network 91 or the like. Therefore, usually, the gateway 8 does not perform a power saving operation because it is easy to secure a power source and it is necessary to cope with irregular communication from various nodes configuring the wireless sensor network 1 (always). Active state). Note that the measurement data collected by the gateway 8 may be used by the gateway 8 itself, or may be transmitted to another device such as a server installed in the wired network 91 by routing.

  The relay node 5 is a device that relays communication of the sensor node 2. That is, the relay node 5 receives the communication frame transmitted from the sensor node 2 and relays and transmits the packet (transmission data D) encapsulated in the communication frame to the gateway 8. As shown in FIG. 1, the communication frame relayed and transmitted by the relay node 5 may be directly received by the gateway 8, or may be further relayed and transmitted by one or more other relay nodes 5, and finally, In some cases, the gateway 8 receives the transmission data D. That is, the sensor node 2 and the gateway 8 are connected in a multi-hop manner via the relay node 5. Note that the relay node 5 may relay communication from the gateway 8 or another relay node 5.

  Such a relay node 5 is installed to secure stable communication between the sensor node 2 and the gateway 8. For example, when constructing the wireless sensor network 1 in a power plant, various facilities such as a boiler, a turbine, and piping are installed in the power plant, and various installations for the gateway 8 and the sensor node 2 are performed. Constraints exist. For example, regarding the installation of the gateway 8, it is possible to wire the power supply and the communication line (the wired network 91 side) for driving the gateway 8, whether the environmental conditions such as temperature and vibration are appropriate, and whether the beams and columns are installed. It is necessary to satisfy the constraints such as whether there is a structure that can be used. Regarding the installation of the sensor node 2, whether the wiring between the sensor unit 2s and the wireless communication unit 2r is possible, the above environmental conditions, and whether the wireless communication unit 2r can be installed and fixed , Etc. must be satisfied. As for the wiring of the power supply, the node may be driven by a battery, but the battery needs to be periodically replaced with the consumption of the battery.

  For this reason, the installation locations of various nodes are limited to locations that satisfy the above-described restrictions. Further, even if various nodes are installed in a place that satisfies all the restrictions on these installations, for example, a metal structure such as a dense metal pipe 93 or a shield such as a wall 94 is provided between the sensor node 2 and the gateway 8. If an object (see FIG. 1) exists, communication stability may not be sufficiently ensured due to the influence. By arranging the relay node 5 in such a case, it is possible to stabilize communication between the sensor node 2 and the gateway 8.

  In a power plant, for example, it is used to collect data regardless of real-time such that it is only necessary to be able to measure a sensing target infrequently, such as once every tens of minutes to once every several hours, or once a day. Is good. Such data irrespective of the real-time property include, for example, in a power plant, for example, statistics of temperature and vibration (average value, maximum value, minimum value, etc. of a predetermined period), oil / water leakage, auxiliary boiler, There is sensing information in auxiliary equipment such as a blower fan in which a short stoppage is not fatal to the operation of the plant.

  Further, as a wireless communication standard applied to the wireless sensor network 1, specifically, ZigBee (registered trademark) may be used. In ZigBee, the above-described sensor node 2 is an end device, the relay node 5 is a router node, and the gateway 8 is called, for example, a coordinator. However, the wireless communication standard is not limited to ZigBee and may be any one of all low-frequency and low-power consumption wireless communication standards such as Bluetooth (registered trademark) Low Energy, LoRaWAN, and SigFox, which are relayed by the relay node 5. When the number of sensor nodes 2 increases, a plurality of sensor nodes 2 may communicate with each other with the aim of activating the relay node 5 and become congested as described later. For example, a communication standard having a mechanism for avoiding communication collision is desirable.

  In the wireless sensor network 1 having the above-described configuration, the relay node 5 of the present invention can execute the above-described power saving operation. Specifically, the relay node 5 executes a power saving operation of switching between the sleep state and the active state at any predetermined timing, for example, periodically. In other words, the relay node 5 switches the operation mode between the active mode operating in the active state and the sleep mode operating in the sleep state by the power saving operation. The active state is a state in which power supply to at least some functions (circuits) such as a wireless communication circuit is stopped, and is a state in which communication (data transmission / reception) with another node is possible. The sleep state is a state in which communication with another node is not performed (or a state in which communication is not possible), and is a state other than the active state.

  More specifically, the relay node 5 is in the active state for a period (time period) such as, for example, continuing the sleep state for the time x (for example, 3 hours) and then continuing the active state for the time y (for example, 10 minutes). ) And the sleep period Ts, which is a period (time zone) in the sleep state, are alternately repeated. In the sleep period Ts, the power supply to the wireless communication function or the like is stopped, so that the relay node 5 is in the sleep state, so that the power consumption can be suppressed more than in the active state. Therefore, when the relay node 5 is configured to be driven by a battery, long-term driving can be performed without replacing the battery.

  On the other hand, when the relay node 5 performs the power saving operation, the sensor node 2 can communicate only during the active period Ta of the relay node 5. That is, when the sensor node 2 transmits the transmission data D during the active period Ta of the relay node 5, the communication is relayed because the relay node 5 receives the communication frame from the sensor node 2. However, if the relay node 5 is in the sleep state (sleep period Ts) at the transmission timing (the active period Ta of the sensor node 2) at which the sensor node 2 transmits the transmission data D, the relay node 5 transmits the communication frame from the sensor node 2. , The relay node 5 does not relay, and the sensor node 2 cannot communicate with the gateway 8. Further, when communication is not relayed by the relay node 5, the collection of measurement data by the gateway 8 causes a delay, or when the sensor node 2 that has detected communication failure performs retransmission control, the retransmission is performed. Power consumption. If the sensor node 2 does not retransmit, the measurement data collected by the gateway 8 may be missing.

(Embodiment 1)
Therefore, in some embodiments of the present invention, the sensor node 2 estimates the active period Ta and the sleep period Ts of the relay node 5 by a method described below. This allows the sensor node 2 to perform communication with the gateway 8 when the relay node 5 is estimated to be in the active state.

  This embodiment will be described with reference to FIGS. FIG. 2 is a block diagram showing functions of the sensor node 2 according to one embodiment of the present invention. FIG. 3 is a diagram for explaining communication execution control by the communication execution control unit 4 according to an embodiment of the present invention. FIG. 4 is a diagram for explaining a method of estimating the active period interval P by the sensor node according to one embodiment of the present invention. FIG. 5 is a diagram illustrating a flow of a power saving operation setting estimation method of the relay node 5 according to the embodiment of the present invention.

  More specifically, in some embodiments, the sensor node 2 switches the active period Ta and the sleep period Ts according to a predetermined operation setting (hereinafter, power saving operation setting) via the relay node 5 via the gateway 8. A node that communicates with a communication destination of transmission data D (see FIG. 1). As shown in FIG. 2, the sensor node 2 includes an operation state estimating unit 3 and a communication execution control unit 4 in addition to the wireless communication unit 2r and the sensor unit 2s. The functional units of the sensor node 2 will be described.

  Note that various nodes such as the sensor node 2 and the relay node 5 may include a computer, and include a CPU (processor) (not shown) and a storage device m (2 m, 5 m) such as a memory such as a ROM or a RAM. Have. The CPU operates (calculates data, etc.) in accordance with the instructions of the program loaded into the memory (main storage device), thereby realizing functions necessary for various nodes such as the above-described functional units included in the sensor node 2. . In other words, the above-described program is software for causing a computer to realize each functional unit described below, and may be stored in a computer-readable storage medium. Alternatively, the various nodes may be configured to include a dedicated circuit (hardware) for executing at least a part of the processing of each of the functional units.

  The operation state estimating unit 3 is a functional unit configured to estimate a power saving operation setting (operation state) of the relay node 5. In other words, it is a functional unit configured to estimate the operation state of the relay node 5. More specifically, the operation state estimation unit 3 includes an estimation transmission unit 31 that transmits a response request frame Fr, which is a communication frame requesting transmission of the delivery confirmation Fa, to the relay node 5 according to a predetermined setting (estimated transmission operation setting). A determination unit that determines at least one of the active period Ta and the sleep period Ts of the relay node 5 based on the reception status of the above-described acknowledgment Fa transmitted (returned) from the relay node 5 that has received the response request frame Fr. 32.

  The acknowledgment Fa (Ack) is a communication frame having information for notifying the transmission source of the communication frame that the communication frame has been received. For example, in ZigBee (registered trademark), by specifying that an Ack request is required by an option for requesting an Ack at the MAC layer level, it is possible to request and respond to a delivery confirmation Fa between adjacent nodes. It is possible. In the present embodiment, such a sensor node 2 is configured to transmit a response request frame Fr requesting an acknowledgment Fa to an adjacent node (one hop ahead).

  However, the present invention is not limited to this embodiment. In some other embodiments, the sensor node 2 requests a delivery confirmation Fa to a communication destination such as the gateway 8 located beyond the relay node 5 (requests delivery confirmation Fa at the application layer). The frame Fr may be transmitted. In this case, since the response request frame Fr and the delivery confirmation Fa are transmitted and received via the relay node 5, the sensor node 2 determines the operation state of the relay node 5 based on whether or not the delivery confirmation Fa has been received. Becomes possible. Alternatively, for example, by executing communication with the communication destination being an adjacent node (transmitting a response request frame Fr), the request and response of the delivery confirmation Fa in the application layer may be performed between the adjacent nodes.

  In response to the response request frame Fr from the sensor node 2, the relay node 5 receives and processes a communication frame transmitted from another node such as the sensor node 2 during the active period Ta. Therefore, when the communication frame is the response request frame Fr, the relay node 5 can detect that the acknowledgment Fa has been requested, and transmits (replies) the acknowledgment Fa. Conversely, in the sleep period Ts, the relay node 5 does not transmit the reception confirmation Fa to the sensor node 2 that has transmitted the response request frame Fr because the relay node 5 does not perform the reception processing of the communication frame transmitted from another node. . In the case where the relay node 5 is configured to be able to detect the request for the delivery confirmation Fa in the sleep state depending on the function (circuit) for stopping the power supply in the sleep state, the delivery confirmation is performed. The relay node 5 may be configured not to transmit Fa.

  Therefore, when the acknowledgment Fa from the relay node 5 to the response request frame Fr transmitted by the estimation transmitting unit 31 is received, the determination unit 32 determines whether the response request frame Fr or the acknowledgment Fa At the time of transmission / reception, it can be determined that the relay node 5 is in the active state. Conversely, when the acknowledgment Fa is not received, it can be determined that the relay node 5 is in the sleep state.

  For example, if the power saving operation setting of the relay node 5 is an operation state set by time, for example, the active state or the sleep state from any time of the day to any time, the delivery confirmation Fa by the sensor node 2 is performed. It can be seen that the relay node 5 is in the active state at the reception time or the like, so that the timing of the active period Ta can be determined. Similarly, it is known that the relay node 5 enters the sleep state at a time when the acknowledgment Fa by the sensor node 2 has not been received or the like, so that the timing of the sleep period Ts can be determined (see FIG. 3).

  The case where the relay node 5 alternates between the sleep state and the active state periodically, for example, such that the sleep state continues for 3 hours (time x) and then the active state continues for 10 minutes (time y), will be described later. As described above, the determination unit 32 transmits a plurality of response request frames Fr as time elapses, and stores reception / non-reception of the delivery confirmation Fa for each response request frame Fr. The active period Ta and the sleep period Ts can be determined based on the transmission interval of the frame Fr (see FIG. 3).

  In some embodiments, whether or not the sensor node 2 has received the acknowledgment Fa may be evaluated based on whether or not the acknowledgment Fa has been received in response to the transmission of one response request frame Fr. In some other embodiments, the evaluation may be made based on the reception ratio (communication success rate) of the delivery confirmation Fa to a plurality of response request frames Fr transmitted within the specified time α. In this case, when the communication success rate is equal to or more than a predetermined value, the communication is determined to be successful, and when the communication success rate is lower than the predetermined value, the communication is determined to have failed. By evaluating the communication success rate, the response request frame between the sensor node 2 and the relay node 5 due to the communication congestion or the temporary deterioration of the wireless communication environment even though the relay node 5 is in the active state. When the transmission and reception of Fr and the delivery confirmation Fa have failed, it is possible to prevent the sensor node 2 from erroneously determining that the delivery confirmation Fa is not received due to the sleep state of the relay node 5.

  On the other hand, as illustrated in FIG. 3, the communication execution control unit 4 is measured by the sensor unit 2s based on the estimation result E of the power saving operation setting of the relay node 5 estimated by the operation state estimation unit 3 described above. This is a functional unit configured to control execution of communication of the measured data with the communication destination (the gateway 8 in the present embodiment). Specifically, the communication execution control unit 4 executes the transmission of the measurement data to the gateway 8 based on the estimation result E when the relay node 5 is estimated to be in the active state (active period Ta), When the relay node 5 is estimated to be in the sleep state (sleep period Ts), the relay node 5 is controlled not to execute the same.

  Accordingly, it is possible to prevent a communication delay or power consumption due to the communication from the sensor node 2 to the gateway 8 being executed during the sleep period Ts of the relay node 5 while enabling the power saving operation of the relay node 5. It becomes possible. Further, for example, if the sensor node 2 is operated in the sleep state together during the sleep period Ts of the relay node 5, the power consumption of the sensor node 2 can be more effectively reduced.

  In the present embodiment, the sensor node 2 is configured to operate in the sleep state during a period estimated as the sleep period Ts of the relay node 5, but in some other embodiments, the sensor node 2 operates in the sleep state. Instead, the configuration may be such that the measurement data is not simply transmitted.

  According to the above configuration, the sensor node 2 is configured to communicate with the relay node 5 that performs the power saving operation by switching between the active state and the sleep state. Then, the sensor node 2 transmits a response request frame Fr requesting transmission of the delivery confirmation Fa to the relay node 5, thereby changing the reception status of the delivery confirmation Fa transmitted from the relay node 5 in response to the request. The active period Ta or the sleep period Ts is estimated based on the estimated period, and the execution of communication with a communication destination (such as the gateway 8) is controlled based on the estimation result.

  As described above, the sensor node 2 estimates the power saving operation setting of the relay node 5, so that the sensor node 2 performs communication during the active period Ta of the relay node 5 and does not perform communication during the sleep period Ts. Communication with the communication destination via the node 5 can be performed at an appropriate timing. Therefore, the power saving operation of the relay node 5 can be enabled, and the power consumption of the sensor node 2 due to the communication during the sleep period Ts of the relay node 5 can be prevented. Further, the sensor node 2 needs to newly store the reception status (the past several communication record data) of the delivery confirmation Fa necessary for estimating the power saving operation setting of the relay node 5 and the power saving operation setting. , The storage area required for realizing this configuration is not large, and the cost of the sensor node 2 is not increased.

  In addition, since precise time synchronization between the sensor node 2 and the relay node 5 is not required, the setup of the wireless sensor network 1 can be simplified. Since the sensor node 2 automatically adjusts the communication frequency based on the estimation result E, the relay node 5 does not need to manage the sensor node 2, and one or more sensor nodes 2 perform a power saving operation. In such a case, tuning for the relay operation such as adjusting the power saving operation of the relay node 5 in accordance with the case can be unnecessary.

  In the above-described embodiment, the sensor node 2 that estimates the power saving operation setting of the relay node 5 transmits the response request frame Fr transmitted by itself, and performs estimation based on the reception status of the delivery confirmation Fa corresponding thereto. In some other embodiments, the sensor node 2 captures a communication frame (response request frame Fr, delivery confirmation Fa, and the like) transmitted and received between the relay node 5 and another sensor node 2, and captures the captured communication frame. The above estimation may be performed based on the communication frame obtained.

Next, some embodiments of the estimation method of the power saving operation setting of the relay node 5 performed by the sensor node 2 will be described in detail with reference to FIG.
In some embodiments, the operation state estimating unit 3 uses two response request frames Fr that are the first response request frame Fr and the second response request frame Fr corresponding to the delivery confirmation Fa received by the sensor node 2. The third response request that did not receive the corresponding acknowledgment Fa from the relay node 5 between the transmission of the first response request frame Fr and the transmission of the second response request frame Fr Based on the transmission interval of the two response request frames Fr when the frame Fr is transmitted, or the reception interval of the two acknowledgments Fa received by the sensor node 2 with respect to the two response request frames Fr, A calculation unit for calculating a time interval of the period Ta may be further provided.

  As described above, the relay node 5 alternately repeats the active period Ta and the sleep period Ts. Therefore, after transmitting the response request frame Fr in the active period Ta, the sensor node experiences a communication success in which the delivery confirmation Fa for the response request frame Fr is received. To transmit a response request frame Fr during the sleep period Ts following the above, to experience a communication failure when the acknowledgment Fa for the response request frame Fr is not received, and to again experience a communication success in the next active period Ta. become.

  For example, assuming that the relay node 5 becomes active only for 10 minutes (time y) once every 3 hours (time x), as shown in FIG. 4, an active period Ta of 10 minutes and a sleep period Ts of 3 hours Thereafter, the repetition is performed such that the active period Ta for 10 minutes starts again. At this time, when the sensor node 2 transmits one response request frame Fr in, for example, a 5-minute cycle, as shown in FIG. 4, the response request frame Fr transmitted in the first active period Ta (1) is transmitted. After the last successful communication (〇 in FIG. 4), the response request frame Fr transmitted five minutes after the successful communication is performed in the first sleep period Ts (1), so that the communication is performed. It fails (x in FIG. 4). Thereafter, all the response request frames Fr transmitted at 5-minute intervals in the first sleep period Ts (1) fail in communication, but after the last communication failure, respond in the second active period Ta (2). Since the request frame Fr is transmitted, the communication is successful.

  Therefore, based on such a relationship between the communication success and the communication failure, the time at which the communication last succeeded in the first active period Ta (1) and the time when the communication succeeded first during the second active period Ta (2). By calculating the time interval between the two times and the calculated time, the time interval (active period interval P) in which the active period Ta is repeated can be obtained. Then, it can be estimated that the active period Ta is repeated at an active period interval P from a certain communication success time.

  It can also be estimated that a sleep period Ts having a period length equal to or less than the active period interval P exists between the active period intervals P. If communication succeeds two or more consecutive times in one active period Ta, it can be estimated that the time interval between the first successful communication and the last successful communication is at least a part of one active period Ta.

  According to the above configuration, the active period of the relay node 5 is determined based on the transmission / reception interval of the response request frame Fr at the time of successful communication performed in each of two adjacent active periods Ta with the sleep period Ts of the relay node 5 interposed therebetween. It is possible to calculate a time interval (cycle) in which Ta is repeated. Further, the timing of the active period Ta and the sleep period Ts can be estimated.

  In the above embodiments, in some embodiments, the above-described estimated transmission operation setting that defines the operation of the above-described estimated transmission unit 31 includes a transmission interval setting for transmitting each of the plurality of response request frames Fr. In this case, in some embodiments, the above-described operation state estimating unit 3 changes the transmission execution interval of the response request frame Fr by the estimation transmitting unit 31 that transmits the response request frame Fr according to the transmission interval setting described above. An execution interval changing unit 34 may be further provided. More specifically, the transmission execution interval changing unit 34 shortens the transmission execution interval of the response request frame Fr when the acknowledgment Fa for the response request frame Fr transmitted by the If the confirmation Fa is not received, the transmission execution interval is lengthened.

  When the transmission execution interval of the response request frame Fr is lengthened, the transmission frequency (the number of transmissions per unit time) of the response request frame Fr transmitted by the estimation transmission unit 31 decreases. Then, after the communication has succeeded once in the first active period Ta of the two active periods Ta adjacent to each other with the sleep period Ts interposed therebetween, if the transmission frequency is reduced, the other active period Ta which is the other is started. The number of response request frames Fr to be transmitted before the arrival becomes smaller. Therefore, it is possible for the sensor node 2 to suppress power consumption for estimating the power saving operation setting of the relay node 5.

  Conversely, when the transmission execution interval of the response request frame Fr is shortened, the transmission frequency of the response request frame Fr transmitted by the estimated transmission unit 31 increases. When the communication success in the first active period Ta of the two active periods Ta adjacent to each other with the sleep period Ts therebetween is repeated, the transmission execution interval of the response request frame Fr is lengthened each time. Therefore, in some cases, the transmission execution interval of the response request frame Fr becomes too long, and the response request frame Fr may not be appropriately transmitted in the sleep period Ts following the first active period Ta or the other active period Ta. obtain. In such a case, when the minimum value of the active period interval P of the relay node 5 cannot be determined, the timing at which the transmission data D can be transmitted cannot be properly determined, and the transmission data D cannot be transmitted at the upload interval or the like. Such a problem may occur. Therefore, when the communication fails, the active execution interval P can be appropriately calculated by shortening the transmission execution interval of the response request frame Fr.

  In the embodiment shown in FIG. 2, the estimation transmission unit 31 reads the estimated transmission operation setting when transmitting the response request frame Fr, and sets the transmission interval setting value to the timer time (variable). The estimating transmission unit 31 is configured to count up a counter for measuring the elapsed time up to the timer time, and to transmit the response request frame Fr every time the time is counted up to the timer time value. The counter is reset after transmitting the response request frame Fr. Then, the transmission execution interval changing unit 34 changes the timer time. That is, instead of changing the value of the estimated transmission operation setting (transmission interval setting), the value is set in the timer time as an initial value, and by changing the value of the set timer time, the value of the estimated transmission unit 31 is changed. The transmission execution interval of the response request frame Fr is changed.

  This embodiment will be described in the order of steps with reference to FIG. Note that the flow in FIG. 5 is performed after the sensor node 2 is powered on and participates (connects) in the wireless sensor network 1. The transmission interval setting value (initial value) is assumed to be sufficiently shorter than the sleep period Ts and the active period Ta of the relay node 5.

  In step S51 of FIG. 5, the sensor node 2 sets the set value of the transmission interval setting (for example, 5 minutes or the like) as an initial value in the timer time. After that, in step S52, a response request frame Fr is transmitted to estimate the power saving operation setting of the relay node 5. Then, in step S53, the sensor node 2 determines whether or not the acknowledgment Fa for the response request frame Fr transmitted in step S52 is received from the relay node 5 (whether or not the communication is successful).

  As a result of the determination in step S53, when the sensor node 2 determines that the delivery confirmation Fa has not been received (in the case of communication failure), in step S54, the sensor node 2 executes a timer time shortening process to shorten the timer time. I do. Specifically, for example, by performing an arbitrary operation on the current timer time, such as a value obtained by halving the current timer time or a value obtained by subtracting a predetermined value from the timer time, a value shorter than the current timer time is obtained. The change value is calculated, and the timer time is updated (overwritten) with the change value.

  Conversely, when the sensor node 2 determines in step S53 that the delivery confirmation Fa has been received (in the case of successful communication), in step S55, the sensor node 2 executes a timer time extension process to lengthen the timer time. Specifically, for example, a value longer than the current timer time is obtained by performing an arbitrary operation on the current timer time, such as a value obtained by doubling the current timer time or a value obtained by adding a predetermined value from the timer time. Is calculated, and the timer time is updated (overwritten) with the changed value.

  Thereafter, in step S56, it is determined whether or not the estimation of the power saving operation of the relay node 5 has been completed. If it is determined that the estimation has not been completed, after waiting for the expiration of the timer time in step S57, the process proceeds to step S57. The process returns to S52, and transmits a response request frame Fr. Conversely, if it is determined in step S56 that the estimation has been completed, the flow ends. Completion of the above estimation may be, for example, when the active period interval P has been calculated.

  Note that the communication success and the communication failure in step S53 may be evaluated based on the reception ratio (communication success rate) of the delivery confirmation Fa to one or a plurality of response request frames Fr transmitted in step S52. For example, a specified time α (α is shorter than the timer time) is subtracted from the timer time, and a plurality of response request frames Fr are periodically transmitted during the time α (timer−α). Is also good.

  In some embodiments, in the embodiment shown in FIG. 2, the transmission execution interval changing unit 34 determines that the transmission execution interval of the response request frame Fr is in a range of not less than a predetermined minimum value and not more than a predetermined maximum value. The transmission execution interval of the response request frame Fr may be changed so as to fall within the range. Specifically, in step S54 in FIG. 5 described above, the minimum value (for example, an initial value) of the timer time is compared with the above-mentioned changed value, and the larger one of the changed values is used to change the current timer time. I do. In this way, by setting the minimum value for the timer time, it is possible to prevent the response request frame Fr from being transmitted unnecessarily excessively due to the timer time becoming too short, and to increase power consumption at the time of estimation. Can be prevented.

  Similarly, in step S55, a predetermined maximum value is compared with the above-mentioned changed value, and the timer value having the smaller value is changed to the current timer time. As described above, by setting the maximum value for the timer time, it is possible to appropriately estimate the minimum time interval at which the sensor node 2 can communicate with the relay node 5.

According to the above configuration, the sensor node 2 updates the transmission execution interval of the response request frame Fr to a longer value when communication with the relay node 5 is successful, and updates the transmission execution interval when communication with the relay node 5 fails. Update to a shorter value. This reduces the number of transmissions of the sleep period Ts of the relay node 5 and the number of response request frames Fr transmitted in the two active periods Ta adjacent to each other with the sleep period Ts interposed therebetween, and at the same time, the cycle in which the active period Ta is repeated (active period The interval P) can be appropriately calculated.
Note that the present invention is not limited to this embodiment, and in some other embodiments, the current timer time may be unconditionally changed with the changed value in steps S54 and S55 in FIG.

  In some other embodiments, for example, the relay node 5 is set to the active state for 10 minutes (time y) every 3 hours (time x) of the sleep period Ts, and the power saving operation setting of the relay node 5 is set. May be configured to register information on the sensor node 2 in advance. In such an embodiment, if the delivery confirmation Fa for the response request frame Fr transmitted one or more times by the sensor node 2 can be received once, since the sleep period Ts is known, the cycle in which the active period Ta is repeated is x + y time Can be calculated.

Next, some embodiments relating to the above-described communication execution control unit 4 will be described.
In some embodiments, as illustrated in FIG. 2, the communication execution control unit 4 executes communication with the communication destination during the active period Ta of the relay node 5 based on the estimation result E by the operation state estimation unit 3. A communication timing determining unit 41 that determines a communication execution timing and a communication execution unit 44 that performs communication with a communication destination at the communication execution timing may be provided.

  Specifically, the communication timing determination unit 41 determines the interval or an interval such as a common multiple of the interval based on, for example, the active period interval P estimated by the operation state estimation unit 3 (determination unit 32). The communication execution timing may be determined such that communication with the communication destination is performed at the active period interval P starting from the transmission / reception time of the response request frame Fr or the delivery confirmation Fa. Alternatively, as described later, the communication timing determining unit 41 may set an initial value of the communication execution timing, and determine the communication execution timing while adjusting the initial value.

  According to the above configuration, the communication execution timing is determined to overlap the active period Ta of the relay node 5 using the estimation result E of the period of the active period Ta (active period interval P). The sensor node 2 performs communication with a communication destination such as the gateway 8 in accordance with the communication execution timing, so that communication can be performed during the active period Ta of the relay node 5 and power consumption is suppressed while the communication with the communication destination is suppressed. Communication can be performed more reliably.

  In some of the above-described embodiments, as shown in FIG. 2, the communication timing determination unit 41 sets the above-described initial value of the communication execution timing (hereinafter, communication timing initial value Ps). The communication timing is adjusted by adjusting the communication timing initial value Ps based on the reception status of the acknowledgment Fa for the response request frame Fr transmitted at the time of communication with the communication destination (such as the gateway 8). And an adjusting unit 41b that determines the execution timing. The sensor node 2 normally transmits measurement data (transmission data D) to a communication destination at a predetermined transmission timing such as a predetermined upload interval (frequency), and transmits the transmission data in accordance with the predetermined transmission timing. Adjustment for transmitting D is performed.

  That is, when the active period interval P obtained by the estimation is not the minimum interval (period) of the active period of the relay node 5, the active period interval is a prescribed upload interval and an interval obtained by a common multiple of the active period interval P. The difference from the interval closest to the specified upload interval may be unacceptably large. In such a case, since the active period interval P is not the minimum value, there is a possibility that the communication execution timing can be set closer to the specified upload interval and the above difference can be tolerated. Therefore, the sensor node 2 searches for a more appropriate communication execution timing through the adjustment by the adjustment unit 41b.

  Specifically, the adjustment unit 41b may adjust the communication timing initial value Ps when the acknowledgment Fa for the response request frame Fr is received. For example, the communication timing initial value Ps may be adjusted so that the communication frequency decreases stepwise. The value Ps may be adjusted. Conversely, the adjusting unit 41b may adjust the communication timing initial value Ps when the acknowledgment Fa for the response request frame Fr is not received. For example, the adjusting unit 41b may adjust the communication timing initial value Ps so that the communication frequency increases stepwise. It may be adjusted.

  More specifically, the adjusting unit 41b sets the communication timing initial value Ps as a variable to the active period interval P, and changes the variable value according to the reception status of the delivery confirmation Fa. The communication timing initial value Ps may be, for example, a common multiple (P × n, where n is an integer of 1 or more) of the active period interval P. Further, the width of the step-by-step increase and decrease of the communication frequency by the adjustment unit 41b is an interval smaller than the communication timing initial value Ps or the active period interval P.

  For example, the adjustment unit 41b sets the active period interval P equal to or greater than 2 by setting the interval that is smaller than the specified upload interval and is closest to the upload interval calculated based on the active period interval P as the communication timing initial value Ps. The transmission of the response request frame Fr and the reception confirmation of the delivery confirmation Fa may be performed from the communication timing initial value Ps to the communication period initial value Ps to the active period interval P (Ps + P) in a cycle divided by the number. Through such processing, the communication timing determination unit 41 determines, as the communication execution timing, an interval closest to the specified upload interval found between the communication timing initial value Ps and the active period interval P.

According to the above configuration, the communication execution timing can be determined according to the situation, and communication with the communication destination can be performed at more appropriate communication execution timing.
Note that the operation estimation method of the relay node may include a step for executing the same processing as that of the communication timing determination unit 41 described above.

  In addition, in some embodiments, the communication execution control unit 4 notifies the operation state estimation unit 3 when the delivery confirmation Fa is not received for the response request frame Fr transmitted by the communication execution unit 44. The unit 45 may be further provided. If the acknowledgment Fa from the relay node 5 is not received, the response request frame Fr is transmitted based on the estimation result E of the power saving operation setting of the relay node 5, so that, for example, some change in the wireless sensor network 1 It is assumed that the estimation result E of the power saving operation setting of the relay node 5 is no longer appropriate due to the occurrence or the like.

Therefore, if such a situation is notified to the operation state estimating unit 3, it is possible to give an opportunity to perform re-estimation. Can be obtained.
Note that the operation estimation method of the relay node may include a step for executing the same processing as that of the notification unit 45 described above.

(Embodiment 2)
Next, some other embodiments of the present invention will be described with reference to FIGS.
FIG. 6 is a block diagram showing functions of the relay node according to one embodiment of the present invention. FIG. 7 is a diagram illustrating a sensor node table managed by a relay node according to an embodiment of the present invention. FIG. 8 is a diagram illustrating an operation method of the relay node according to the embodiment of the present invention, and is a diagram for describing a situation at the time of a steady operation after learning of the relay node. FIG. 9 is a diagram illustrating an operation method of the relay node according to an embodiment of the present invention, and is a flowchart illustrating an operation of the relay node at the time of learning. FIG. 10 is a flowchart showing an operation of the relay node according to the embodiment of the present invention at the time of a steady operation after learning.

  In the present embodiment, the relay node 5 that performs the above-described power saving operation monitors the transmission status of the transmission data D from the sensor node 2 in an initial state after power-on or the like, and based on the monitoring result, the own node Is determined when the active period Ta and the sleep period Ts are set. That is, the relay node 5 grasps the communication status of the sensor node and determines the operation setting (power saving operation setting) of its own node. As a result, the relay node 5 sets the active period Ta when it is estimated that the sensor node 2 communicates (transmits the transmission data D) (time zone), and sets the sleep period when it is estimated that the sensor node 2 does not communicate. It is possible to generate a power saving operation setting so as to be Ts, and an appropriate power saving operation of the relay node 5 according to the operation of the sensor node 2 can be achieved.

  More specifically, in some embodiments, as described above, the relay node 5 includes an active period Ta in which one or a plurality of sensor nodes 2 can relay a communication performed, and a sleep period Ts in which the communication is not relayed. Is a device that switches according to a predetermined operation setting (hereinafter, power saving operation setting). As illustrated in FIG. 6, the relay node 5 includes an operation setting generation unit 6 related to a power saving operation and an operation control unit 7.

The operation setting generation unit 6 is a functional unit configured to generate a power saving operation setting. Usually, the sensor node 2 is configured to transmit measurement data to the gateway 8 at a preset upload interval or the like. Therefore, the relay node 5 operates in the active state without entering the sleep state at the time of initialization in which the power saving operation setting has been initialized and the content setting has not yet been performed. To monitor. Then, the relay node 5 grasps (learns) the active period Ta and the sleep period Ts of each sensor node 2 based on the monitoring result, and stores it as the power saving operation setting of its own node.
More specifically, the operation setting generation unit 6 includes a reception status monitoring unit 61 and a setting determination unit 62.

  The reception status monitoring unit 61 monitors the reception status of the transmission data D transmitted from one or more sensor nodes 2. Specifically, when receiving the transmission data D transmitted by the sensor node 2, the relay node 5 extracts information used to determine the power saving operation setting from the communication frame of the transmission data D. Specifically, for example, the transmission source (address of the sensor node 2) is extracted from the header information of the communication frame, and stored as the history data H together with the communication time such as the reception time of the communication frame. By executing this operation over a predetermined learning period (monitoring period), a plurality of pieces of history data H are stored in the storage device 5m. Note that the destination of the transmission data D (the destination of the network layer) may be further extracted from the communication frame. If the destination is the gateway 8, it can be confirmed that the transmission data D is for communication of the measurement data from the sensor node 2 to the gateway 8.

  The setting determining unit 62 determines the power saving operation setting of the own node based on the reception status of the transmission data D transmitted from the sensor node 2. That is, a plurality of pieces of history data H obtained during the learning period described above are analyzed to determine a power saving operation. More specifically, the setting determination unit 62 may determine the sleep period Ts based on a reception interval of the transmission data D based on a time interval during which the transmission data D transmitted by one or more sensor nodes 2 is not received. good. Alternatively, the active period Ta may be determined based on a time interval at which the transmission data D transmitted by one or more sensor nodes 2 is received. Both of these may be performed. If the period in which the sleep period Ts or the active period Ta is to be set is known, the other period may be set as the other period, and the power saving operation setting can be generated.

  That is, the sensor node 2 to which the relay node 5 relays can be grasped from the transmission sources of the plurality of pieces of history data H accumulated during the learning period. In addition, by confirming a plurality of pieces of history data H for each transmission source, it is possible to know the communication time of each sensor node 2 with a communication destination such as the gateway 8. Therefore, by confirming the communication time of the plurality of pieces of history data H for each sensor node 2, it is possible to estimate the communication interval of each sensor node 2 based on the plurality of communication times.

  Further, by using the estimated value of the communication interval of each sensor node 2 (estimated communication interval G), as illustrated in FIG. From the source of the transmission data D, the communication time of each sensor node 2 with the subsequent communication destination can be estimated. Therefore, the setting determination unit 62 operates in the active state in a predetermined time zone including the estimated time, for example, by adding a predetermined time before and after the estimated time of communication of each sensor node 2. In the time period, a power saving operation setting that operates in the sleep state is generated.

  In the embodiment shown in FIG. 6, the relay node 5 manages one or a plurality of sensor nodes 2 which the own node needs to relay in a sensor node table 5T as shown in FIG. The sensor node table 5T includes, for each sensor node 2, an estimated communication interval G, a reception time of the latest transmission data D, and a reception time of the latest transmission data D, followed by transmission from the same sensor node 2. An assumed reception time at which the data D is received is stored.

  The operation setting generation unit 6 may operate according to the flow shown in FIG. 8 in some embodiments. Referring to FIG. 8 in the order of steps, when the power is turned on, the relay node 5 shifts to the learning mode. That is, after participating in the wireless sensor network 1 and initializing (clearing) the sensor node table 5T in step S81, in step S82, the device waits for transmission data D transmitted from the sensor node 2. In step S83, when the transmission data D to be relayed is received, the transmission source is extracted from the communication frame of the transmission data D, and is registered in the sensor node table 5T, for example, when the transmission source transmits the transmission data D for the first time. If there is no such information, it is registered in the sensor node table 5T. In step S84, the history data H is stored in the storage device 5m or the like.

  Then, in step S85, it is determined whether or not to complete the learning mode. If it is determined that the learning mode is to be continued, the process returns to step S82, and the above steps S82 to S85 are repeated. The completion of the learning mode may be determined to be completed when a predetermined period of time set as being capable of completing the learning mode has elapsed. Alternatively, the completion may be determined when a new sensor node 2 has not been added even after a predetermined time has elapsed since the last registration of the sensor node 2 registered in the sensor node table 5T. When at least one of the plurality of conditions is satisfied, it may be determined to be completed.

  Conversely, if it is determined in step S85 that the learning mode is to be completed, the estimation communication interval G (described above) is calculated for each sensor node 2 using the plurality of pieces of history data H accumulated by executing step S84. The registration is performed in the sensor node table 5T. At this time, the latest reception time of the communication frame is extracted from the history data H for each sensor node 2, and registered at the latest reception time. After that, the operation shifts to the steady operation mode by the operation control unit 7 described below.

  On the other hand, the operation control unit 7 switches between the active period Ta and the sleep period Ts of the own node according to the power saving operation setting generated by the operation setting generation unit 6. Referring to the above-described sensor node table 5T, the estimated reception time of the transmission data D from the sensor node 2 to be relayed next becomes the estimated reception time closest to the current time among the estimated reception times of the sensor nodes 2. can get. Therefore, the operation control unit 7 performs a control (power saving operation) so as to be in a sleep state from the current time to an estimated reception time closest to the time, and to be in an active state near the assumed reception time. After entering the active state, the operation control unit 7 determines the timing to enter the next sleep state and the timing to enter the active state by performing, for example, the same processing as described above, and performs the power saving operation according to the determination. May be executed. Alternatively, the respective timings of the sleep state and the active state may be determined based on the sensor node table 5T, and the power saving operation may be executed at a cycle based on the timing. As a result, the relay node 5 alternately repeats the active period Ta and the sleep period Ts over time (see FIG. 10).

  More specifically, the operation control unit 7 may operate according to the flow shown in FIG. 9 will be described in the order of steps. In step S91 after the shift to the steady operation mode, the relay node 5 determines that the next estimated reception time for each sensor node 2 registered in the sensor node table 5T is the closest to the current time. Find the reception time. In step S92, the sleep state is established until the estimated reception time found in step S91. In step S93, after returning from the sleep state (after switching to the active state), of the times registered at the next assumed reception time in the sensor node table 5T, within an arbitrary time (β) from the current time (currently). The sensor node 2 whose time is within (time + β) is extracted. Thereafter, in step S94, the transmission data D from the extracted one or more sensor nodes 2 is awaited.

  Then, in step S95, if a communication frame for communicating the transmission data D can be received from all of the sensor nodes 2 extracted in step 53 within the current time + β, the sensor node table 5T is stored in step S96. It is determined whether or not there is a change. For example, when a communication frame from another sensor node 2 not registered in the sensor node table 5T is received, it is determined that there is a change.

  For example, in Zigbee, when participating in the wireless sensor network 1, the sensor node 2 broadcasts an isolation notification (Beacon request) by means of CSMA / CA carrier sense so as to interrupt the time during which other communication exists, The presence of the own node is notified to the neighboring relay node 5 (neighboring node). The sensor node 2 transmits an isolation notification until the relay node 5 responds (Beacon response) to the isolation notification transmitted by the own node. 2 is detected. Therefore, the relay node 5 may be configured to determine that there is a change in the sensor node table 5T in response to receiving the isolation notification from the sensor node 2. Alternatively, the gateway 8 registers the new sensor node 2 with the gateway 8 before the new sensor node 2 joins the wireless sensor network 1. By notifying the relay node 5, the relay node 5 may be configured to determine that there is a change in the sensor node table 5T. A physical switch or a software switch is provided in the relay node 5, and a person switches the mode of the relay node 5 when the sensor node 2 is installed, so that the relay node 5 determines that there is a change in the sensor node table 5T. You may comprise so that it may be.

  If there is no change in step S96, the process returns to step S91 and repeats the above-described steps. Conversely, in step S96, if there is a change, the mode transits to the learning mode (see FIG. 8).

  On the other hand, if the communication frames cannot be received from all the sensor nodes 2 in step S95 described above, the mode transits to the learning mode. In this embodiment, in order to prevent a transition to the learning mode when a communication frame cannot be received with a slight timing shift, reception is further waited for a predetermined time in step S97. For example, reception may be further waited for β, or reception may be waited for β × m (m is an integer of 1 or more). Thereafter, in step S98, it is determined whether or not the communication frames from all the extracted sensor nodes 2 have been received. If the communication frames have been received, the process proceeds to step S96 described above. Transition.

  According to the above configuration, the relay node 5 is configured to be able to perform the power saving operation by switching between the active state and the sleep state according to the power saving operation setting. It is generated according to the reception status of transmission data D or the like directed to a communication destination such as the gateway 8 that transmits. Thereby, the relay node 5 can be in a sleep state during a period in which it is expected that the sensor node 2 executing communication does not exist, and power consumption can be suppressed. In addition, the relay node 5 is in an active state during a period in which it is expected that at least one sensor node 2 that performs communication is present, so that the communication of the sensor node 2 can be reliably relayed. Therefore, it is possible to improve the real-time property of measurement data collection by the gateway 8 and the like, and to suppress power consumption accompanying retransmission of the transmission data D of the sensor node 2.

  In addition, since precise time synchronization between the sensor node 2 and the relay node 5 is not required, the setup of the wireless sensor network 1 can be simplified. Further, as compared with the case where the sensor node 2 estimates the power saving operation setting of the relay node 5 as described above, it is not necessary to add a function to the sensor node 2, and when the sensor node 2 is estimated. This has the effect of reducing power consumption and consolidating maintenance in the relay node 5.

  In some embodiments, the relay node 5 may further include a setting updating unit 64 that updates the power saving operation setting described above. The setting update unit 64 includes an expected number calculation unit 64a that calculates an expected number of sensor nodes 2 that transmit the transmission data D for each active period Ta, and a sensor node that transmits the transmission data D for each active period Ta. It has a number-of-actuals calculation unit 64b that calculates the number of actual results of 2, and a notifying unit 64c that notifies the operation setting generation unit 6 when the expected number does not match the actual number.

  This embodiment will be described with reference to FIG. In FIG. 10, the relay node 5 repeats the active period Ta six times as time passes. In the first to fourth and sixth active periods Ta, the relay node 5 is expected to receive the transmission data D transmitted by only one of the sensor nodes 2 among the sensor nodes 2a to 2c. , The expected number is 1. On the other hand, in the fifth active period Ta, the expected number is 2 since the relay node 5 is expected to receive the transmission data D transmitted by the two sensor nodes 2 of the sensor nodes 2a and 2c.

  It is assumed that all of the actual numbers of transmission data D actually received are 1 with respect to the expected number of each active period Ta set as described above. In this case, since the expected number in each fifth active period Ta is 2, the expected number and the actual number in each fifth active period Ta do not match. Therefore, the above-described notification is made by the notification unit 64c. In the embodiment shown in FIG. 10, the case where the actual number is smaller than the expected number is shown. However, when the actual number is larger than the expected number in the active period Ta of any of the relay nodes 5, the notification unit is also provided. 64c is notified.

  According to the above configuration, the relay node checks the expected number and the actual number of transmission data D from the sensor node 2 for each active period Ta, and notifies when the expected number and the actual number do not match. If the expected number and the actual number do not match, it is determined that the relay node 5 has not properly grasped the communication status of the sensor node 2. Therefore, it is possible to determine whether the power saving operation setting of the relay node 5 is appropriate by comparing the expected number and the actual number, and if not, the power saving operation setting of the relay node 5 is updated. By doing so, it is possible to maintain an appropriate power saving operation setting of the relay node 5 that follows a change in the sensor network.

  The present invention is not limited to the above-described embodiment, and includes a form in which the above-described embodiment is modified and a form in which these forms are appropriately combined.

REFERENCE SIGNS LIST 1 wireless sensor network 2 sensor node 2 r wireless communication unit 2 s sensor unit 3 operation state estimation unit 31 estimation transmission unit 32 determination unit 34 transmission execution interval change unit 4 communication execution control unit 41 communication timing determination unit 41 a initial value setting unit 41 b adjustment unit 44 Communication execution unit 45 Notification unit 5 Relay node 5T Sensor node table 6 Operation setting generation unit 61 Reception status monitoring unit 62 Setting determination unit 64 Setting update unit 64a Expected number calculation unit 64b Actual number calculation unit 64c Notification unit 7 Operation control unit 8 Gateway 91 Wired network 93 Metal pipe 94 Wall Fr Response request frame Fa Delivery confirmation Ta Active period Ts Sleep period D Transmission data E Estimation result P of power saving operation setting of relay node E Active period interval G Estimated communication interval

Claims (16)

A relay node configuring a sensor network, wherein an active period for transmitting the acknowledgment and a sleep period for not transmitting the acknowledgment for a response request frame requesting transmission of an acknowledgment are switched according to a predetermined operation setting. A relay node configured to, the sensor node configured to transmit the response request frame,
A communication unit for connecting to the sensor network;
A sensor unit for measuring a sensing object,
The estimated transmission unit configured to transmit the response request frame to the relay node according to a predetermined estimated transmission operation setting, and at least the active period or the sleep period of the relay node based on the reception status of the delivery confirmation. A determining unit configured to determine one, an operating state estimating unit including:
A communication execution control unit configured to control execution of communication with a communication destination of the measurement data measured by the sensor unit based on the estimation result of the operation setting. . The operating state estimating unit,
The two response request frames, which are the first response request frame and the second response request frame corresponding to the acknowledgment received by the sensor node, the two response request frames being transmitted when the first response request frame is transmitted. Between the time of transmission of the second response request frame and the second response request frame when a third response request frame that has not received the corresponding acknowledgment from the relay node is transmitted A transmission interval of, or a calculating unit configured to calculate a time interval of the active period based on a reception interval of the two acknowledgments received by the sensor node with respect to the two response request frames. The sensor node according to claim 1, further comprising: The estimated transmission operation setting includes a transmission interval setting for transmitting each of the plurality of response request frames,
The operation state estimating unit further includes a transmission execution interval changing unit configured to change a transmission execution interval of the response request frame by the estimation transmission unit that transmits the response request frame according to the transmission interval setting. ,
The transmission execution interval changing unit,
The transmission execution interval of the response request frame is shortened when the acknowledgment is received, and the transmission execution interval of the response request frame is lengthened when the acknowledgment is not received. 3. The sensor node according to 2.   The transmission execution interval changing unit changes the transmission execution interval of the response request frame so that the transmission execution interval of the response request frame falls within a range of not less than a predetermined minimum value and not more than a predetermined maximum value. The sensor node according to claim 3, wherein: The communication execution control unit,
A communication timing determination unit configured to determine a communication execution timing for executing communication with the communication destination during the active period of the relay node based on the estimation result of the operation setting,
The sensor node according to claim 1, further comprising: a communication execution unit configured to execute communication with the communication destination at the communication execution timing. The communication timing determining unit,
An initial value setting unit configured to set an initial value of the communication execution timing,
It is configured to determine the communication execution timing by adjusting an initial value of the communication execution timing based on a reception status of the delivery confirmation with respect to the response request frame transmitted at the time of communication with the communication destination. The sensor node according to claim 5, further comprising: an adjusting unit.   The sensor node according to claim 6, wherein the adjustment unit adjusts an initial value of the communication execution timing so that a communication frequency decreases stepwise when the delivery confirmation is received. .   The sensor according to claim 6, wherein the adjustment unit adjusts an initial value of the communication execution timing so that a communication frequency increases stepwise when the delivery confirmation is not received. node.   The system according to claim 1, further comprising: a notifying unit configured to notify the operation state estimating unit when the acknowledgment is not received for the response request frame transmitted by the communication executing unit. Item 9. The sensor node according to any one of Items 5 to 8. A relay node configured to constitute a sensor network and configured to switch between an active period in which relay of communication performed by one or more sensor nodes is possible and a sleep period in which the communication is not relayed according to a predetermined operation setting,
A reception status monitoring unit configured to monitor a reception status of transmission data transmitted from the one or more sensor nodes; and configured to determine the operation setting based on the reception status of the transmission data. An operation setting generation unit including a setting determination unit;
A relay node, comprising: an operation control unit configured to switch between the active period and the sleep period according to the operation setting generated by the operation setting generation unit.   The setting determining unit determines the sleep period based on a time interval during which the transmission data is not received, based on a reception state of the transmission data, or the active period based on a time interval at which the transmission data is received. The relay node according to claim 10, wherein at least one of determining a period is performed. A setting update unit configured to update the operation setting, further comprising:
The setting update unit,
For each active period, an expected number calculation unit configured to calculate an expected number of sensor nodes transmitting the transmission data,
For each active period, an actual number calculating unit configured to calculate an actual number of the number of the sensor nodes transmitting the transmission data,
12. The relay node according to claim 10, further comprising: a mismatch notification unit configured to notify the operation setting generation unit when the expected number does not match the actual number. 13. A sensor node according to any one of claims 1 to 9,
A gateway node configured to collect transmission data transmitted by the sensor node;
A relay node configured to relay the transmission data transmitted by the sensor node to the gateway node. A sensor node,
A gateway node configured to collect transmission data transmitted by the sensor node;
A sensor network comprising: the relay node according to claim 10. A relay node configuring a sensor network, wherein an active period for transmitting the acknowledgment and a sleep period for not transmitting the acknowledgment for a response request frame requesting transmission of an acknowledgment are switched according to a predetermined operation setting. A relay node configured to, the relay node operation estimation method executed by the sensor node configured to transmit the response request frame,
Transmitting the response request frame to the relay node according to a predetermined estimated transmission operation setting, and determining at least one of the active period or the sleep period of the relay node based on a reception status of the acknowledgment, Steps for estimating the operating state including:
Controlling the execution of communication with the communication destination of the measurement data measured by the sensor unit based on the estimation result of the operation setting. A relay for a relay node configured to configure a sensor network and to switch between an active period in which communication performed by one or a plurality of sensor nodes can be relayed and a sleep period in which the communication is not relayed according to a predetermined operation setting A method of operating a node,
An operation setting generation step including: a reception state monitoring step of monitoring a reception state of transmission data transmitted from the one or more sensor nodes; and a setting determining step of determining the operation setting based on the reception state of the transmission data. Steps for
Switching between the active period and the sleep period in accordance with the operation setting generated by the operation setting generation unit.

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