JP6981026B2 - Communication equipment, communication methods, communication programs and communication systems - Google Patents

Description

The present invention relates to communication devices, communication methods, communication programs and communication systems.

Conventionally, as typified by IoT (Internet of Things), it is increasing to provide communication functions to various "things". For example, by giving a communication function to a sensor device that senses water level, gas usage, electricity usage, etc., and periodically transmitting sensing data to an opposite device such as a gateway (GW), a cloud server can be used. Collective management is being carried out.

The target device to be provided with the communication function is not limited to the power supply drive in which the power is stably supplied, but may be battery-powered in which the electric power is finite or may be operated by the electric power generated by energy harvesting. In such a case, since the device operates within a limited power consumption, the power consumption of the communication function is reduced. In recent years, short-range wireless technology such as BAN (Body Area Network) that shifts a device to a sleep state during a period during which communication or processing is not performed is known.

For example, when the communication between the GW which is a hub and the device which is a node is completed, the device goes to sleep for the time set in the timer. This sleep time is set in consideration of "the time until reliable communication can be performed in consideration of the rise time of the device, the processing overhead, etc." called GuardTime (hereinafter, may be referred to as GT). Specifically, when the sensing data transmission processing is completed, the apparatus sets a timer to wake up (Wakeup) before the time when the next sensing data transmission processing occurs, and goes into a sleep state. ..

Japanese Unexamined Patent Publication No. 2010-28803 Japanese Unexamined Patent Publication No. 2011-29918

However, in the above technique, since power consumption is not consumed during the sleep period, reduction in power consumption can be expected, but it is difficult to calculate an appropriate GT for each device, and the effect of power saving is small.

Specifically, when calculating the GT set in the timer, the clock error of the MCU (Micro Control Unit) used in the communication module of the device is also taken into consideration, but there are individual differences in the width of the clock error for each communication module. Therefore, even if the communication modules used in each device are the same, not all of them operate at the same clock frequency.

Therefore, a GT that can cover the clock frequency deviation of all communication modules used in each device is set, and as a result, the sleep state time is shortened, and there is a possibility that the expected power saving effect cannot be obtained. There is. It is conceivable that the administrator or the like confirms the maximum clock error guaranteed by the communication module of each device one by one and sets the GT for each device, but it takes a lot of work time and the number of devices is large. Is not realistic if it is huge.

In one aspect, it is an object of the present invention to provide a communication device, a communication method, a communication program and a communication system capable of improving the effect of power saving.

In the first proposal, the communication device uses the time difference between the opposite device and the communication device to estimate the clock error, which is the error between the clock frequency of the opposite device and the clock frequency of the communication device. Has a part. The communication device executes communication with the opposite device from a power saving state that suppresses communication with the opposite device and a determination unit that determines a preparation time for data communication according to the estimated clock error. It has a setting unit for setting the time for returning to the normal state to be performed before the preparation period.

According to one embodiment, the effect of power saving can be improved.

FIG. 1 is a diagram showing an overall configuration example of the system according to the first embodiment. FIG. 2 is a diagram showing an example of sensing of a node. FIG. 3 is a diagram illustrating a frame configuration of BAN. FIG. 4 is a functional block diagram showing a functional configuration of each device according to the first embodiment. FIG. 5 is a diagram showing an example of information stored in the correction width DB of the node. FIG. 6 is a diagram illustrating time synchronization by BAN. FIG. 7 is a flowchart showing the flow of the GT setting process according to the first embodiment. FIG. 8 is a flowchart showing the flow of the synchronization process according to the first embodiment. FIG. 9 is a flowchart showing the flow of the data transmission process according to the first embodiment. FIG. 10 is a diagram showing preconditions at the time of effect calculation. FIG. 11 is a diagram showing radio conditions at the time of effect calculation. FIG. 12 is a diagram showing the result of the effect calculation. FIG. 13 is a diagram illustrating an analogy of the time error of the second embodiment. FIG. 14 is a functional block diagram showing a functional configuration of each device according to the second embodiment. FIG. 15 is a diagram illustrating a frame configuration of BAN. FIG. 16 is a flowchart showing the flow of the data transmission process according to the second embodiment. FIG. 17 is a flowchart showing the flow of the GT calculation process according to the second embodiment. FIG. 18 is a diagram showing a hardware configuration example of the GW device. FIG. 19 is a diagram showing an example of hardware configuration of a node.

Hereinafter, examples of the communication device, communication method, communication program, and communication system disclosed in the present application will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

[overall structure]
FIG. 1 is a diagram showing an overall configuration example of the system according to the first embodiment. As shown in FIG. 1, this system has a management server 5, a GW device 10, and a plurality of nodes 30. The GW device 10 and the plurality of nodes 30 are connected to each other so as to be communicable with each other via the network N. The network N can adopt various communication networks such as the Internet and a dedicated line regardless of whether it is wired or wireless.

The management server 5 is an example of a server device that acquires sensing data from each node 30 via the GW device 10 and collectively manages the data. For example, the management server 5 collectively manages the water level, the amount of gas used, the amount of electricity used, and the like.

The GW device 10 is an example of a network device that aggregates communication between each node 30 and the management server 5. For example, the GW device 10 receives the sensing data periodically transmitted from each node 30 and transmits it to the management server 5.

Each node 30 has a communication function such as wireless, and is an example of a sensor device that senses the water level, the amount of gas used, the amount of electricity used, and the like, and transmits the sensor device to the management server 5. Each node 30 periodically executes sensing and transmits sensing data.

Here, a sensing example of each node will be described. FIG. 2 is a diagram showing an example of sensing of a node. As shown in FIG. 2, each node 30 has a communication module A and a water level sensor B, and is installed in a manhole or the like. Then, each node 30 measures the water level data from the GW device 10 at designated intervals and transmits the water level data to the GW device 10 using the designated band.

Next, wireless communication between the GW device 10 and each node 30 will be described. BAN (Body Area Network) is used to exchange sensing data between the GW device 10 and each node 30. FIG. 3 is a diagram illustrating a frame configuration of BAN. As shown in FIG. 3, a synchronization unit called a superframe is set in the wireless frame between the GW device 10 and each node 30, and the transmission of sensing data is executed within this synchronization unit. The start timing (time) of each superframe is set as common information between the GW device 10 and each node 30.

Specifically, the superframe is composed of one Beacom, a plurality of EAPs (Exclusive Access Phases), RAPs (Random Access Phases), and MAPs (Managed Accsess Pase). Beacon is an area for transmitting a notification signal (notification packet). EAP and RAP are shared areas that can be communicated by any node, and since there is a possibility of collision, they are controlled by the CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance) method. The MAP is an area in which only the node to which the band is allocated can communicate, and the GW device 10 allocates the band (communication timing) for each node in response to a request from the node at the time of connection with the GW device 10 (Hub). .. That is, the communication band for each node is fixedly allocated in the MAP.

On the other hand, each node 30 goes into a sleep state in the superframe when data communication is not executed with the GW device 10, and returns at the timing when data communication occurs. Specifically, it returns at the start timing of Beacon in the superframe of T0, then transitions to the sleep state, then returns at the transmission timing assigned to the own node in the MAP, and goes to sleep after the completion of data transmission. , It returns again at the start timing of Beacon in the next superframe of T1.

As described above, each node 30 is in a normal state only when data transmission is performed, and is in a sleep state in which data transmission or the like is suppressed at other times, thereby suppressing power consumption. Here, each node 30 returns earlier than the start timing of the Beacon by the GT considering the time until reliable communication can be performed in consideration of the rise time of the device, the processing overhead, and the like. That is, each node 30 returns 30 seconds earlier than t when the Beacon start time t and GT are 30 seconds.

In general, this GT is set to a period that can cover the deviation of the clock frequencies (operating clocks) of all the communication modules used for each node 30, and as a result, the sleep state time is shortened, which saves time. The effect of power is small.

Therefore, in the first embodiment, each node 30 uses the time difference between the GW device 10 and its own node to estimate the clock error, which is the error between the clock frequency of the GW device 10 and the clock frequency of its own node. .. Then, each node 30 determines and sets the GT, which is the preparation time for performing data communication, according to the estimated clock error. That is, each node 30 grasps the tendency of the clock error different for each communication module and dynamically sets the optimum GT for each communication module, so that the effect of power saving can be improved.

[Functional configuration]
FIG. 4 is a functional block diagram showing a functional configuration of each device according to the first embodiment. Here, the functional configuration of the GW device 10 and the functional configuration of the node 30 will be described.

(Configuration of GW device)
As shown in FIG. 4, the GW device 10 has a communication unit 11, a storage unit 12, and a control unit 20. The storage unit 12 is an example of a storage device such as a memory or a hard disk, and the control unit 20 is an example of a processor or the like.

The communication unit 11 is a processing unit that controls communication with each node 30, and is, for example, a communication interface. For example, the communication unit 11 transmits a broadcast signal (Beacon) to each node 30 and receives sensing data from each node 30.

The storage unit 12 is a storage unit for storing programs and data, and stores the sensor value DB 13. The sensor value DB 13 is a database that stores sensor values received from each node 30 for each node. For example, the sensor value DB 13 stores an identifier that identifies a node, a sensor value measured by the node, a date and time when the sensor value was acquired, and the like in association with each other.

The control unit 20 is a processing unit that controls the entire GW device 10, and has a notification unit 21 and a data reception unit 22. The notification unit 21 and the data reception unit 22 are an example of an electronic circuit included in the processor and an example of a process executed by the processor. Further, the control unit 20 executes the allocation of the data transmission time to each node, that is, the allocation in the MAP.

The notification unit 21 is a processing unit that generates a notification signal including time information and transmits it to each node 30. For example, when the notification unit 21 reaches the transmission timing of the notification signal at the beginning of each superframe, the notification unit 21 generates a notification signal including the elapsed time from the beginning of the current superframe. Then, the notification unit 21 transmits a notification signal including the elapsed time as time information to each node 30.

The data receiving unit 22 is a processing unit that receives sensing data from each node 30. Specifically, when the data receiving unit 22 reaches the MAP time, it receives sensing data from each node at the time allocated to each node. Then, the data receiving unit 22 acquires the sensor value from the received sensing data and stores it in the sensor value DB 13. The data receiving unit 22 can also transmit the received sensing data to the management server 5.

(Node configuration)
As shown in FIG. 4, the node 30 has a communication unit 31, a storage unit 32, and a control unit 40. The storage unit 32 is an example of a storage device such as a memory or a hard disk, and the control unit 40 is an example of a processor or the like.

The communication unit 31 is a processing unit that controls communication with the GW device 10, and is, for example, a communication interface. For example, the communication unit 31 receives a notification signal from the GW device 10 and transmits sensing data to the GW device 10.

The storage unit 32 is a storage unit for storing programs and data, and stores the GT value DB 33 and the correction width DB 34. The GT value DB 33 is a database that stores the GT value set by the node. The information stored in the GT value DB 33 is set to an initial value at the start of data communication, and is subsequently updated by the determination unit 46 described later. For the initial value, the catalog value of the maximum error of the clock system is used. For example, the initial value of GT is calculated by "initial value = hardware startup time + (maximum clock error [ppm] x sleep setting time)". The sleep setting time is the sleep time, for example, the Beacon interval, in other words, the superframe interval.

The correction width DB 34 is a database that stores the correction history of the time error between the GW device 10 and the node 30. FIG. 5 is a diagram showing an example of information stored in the correction width DB of the node 30. As shown in FIG. 5, the correction width DB 34 stores the “number of times, time correction width (msec)”. "Number of times" indicates the number of corrections, and "time correction width" indicates the corrected time. In the case of FIG. 5, it is shown that the first time is corrected by 6.4 msec and the second time is corrected by 5.6 msec.

The control unit 40 is a processing unit that controls the entire node 30, and includes a sensing unit 41, a data processing unit 42, a state transition unit 43, a receiving unit 44, a correction unit 45, and a determination unit 46. The sensing unit 41, the data processing unit 42, the state transition unit 43, the receiving unit 44, the correction unit 45, and the determination unit 46 are examples of electronic circuits included in the processor and examples of processes executed by the processor.

The sensing unit 41 is a processing unit that acquires a sensor value using a sensor. For example, the sensing unit 41 acquires the sensor value from the sensor periodically or at the data transmission timing. Then, the sensing unit 41 outputs the acquired sensor value to the data processing unit 42.

The data processing unit 42 is a processing unit that transmits sensing data to the GW device 10. Specifically, when the transmission timing of the sensing data comes, the data processing unit 42 generates the sensing data including the sensor value acquired from the sensing unit 41 and transmits it to the GW device 10. For example, the data processing unit 42 transmits the sensing data to the GW device 10 at the transmission timing of the own node in the MAP in the superframe of the BAN.

The state transition unit 43 is a processing unit that puts the node 30 to sleep during the period when data communication does not occur and returns it at the timing when data communication occurs. Specifically, as shown in FIG. 3, the state transition unit 43 returns at the start timing of the Beacon, then transitions to the sleep state, and then returns at the transmission timing assigned to the own node in the MAP. After the data transmission is completed, the sleep state is entered and the Beacon is returned again at the start timing of the next Beacon. The GT set here is set based on the GT value stored in the GT value DB 33. That is, the initial value is set in the initial stage, and when the GT value is updated, the updated GT value is set.

The receiving unit 44 is a processing unit that receives a notification signal from the GW device 10. Specifically, the receiving unit 44 receives the notification signal transmitted by the GW device 10 at the timing of the Beacon in each superframe, and outputs the notification signal to the correction unit 45.

The correction unit 45 is a processing unit that calculates the time difference between the GW device 10 and the node 30 and executes time synchronization. Specifically, the correction unit 45 calculates the difference between the time when the notification signal is transmitted and the time when the notification signal is received as a time difference.

Further, the correction unit 45 calculates the theoretical reception time expected to receive the notification signal in consideration of the transmission rate between the GW device 10 and the node 30 and the data size of the notification signal. Then, the correction unit 45 can also calculate the difference between the theoretical reception time predicted from the notification signal and the reception time when the notification signal is actually received as a time difference.

Here, the time synchronization based on the notification signal transmitted by the wireless frame of BAN is calculated. FIG. 6 is a diagram illustrating time synchronization by BAN. As shown in FIG. 6, when the Beacon timing is reached, the GW device 10 transmits a notification signal in which the elapsed time from the beginning of the wireless frame (superframe) is set in the payload to the node 30. Further, the correction unit 45 of the node 30 specifies the reception time when the notification signal is received as the elapsed time from the beginning of the wireless frame. Then, the correction unit 45 compares the elapsed time (time information) in the notification signal + the transfer time of the notification signal with the reception time (elapsed time), and if there is a difference, corrects the time of the node 30. Then, the correction unit 45 stores the time correction width in the correction width DB 34.

As an example, the transmission time (time information) in the broadcast signal is 50 msec, the communication rate is 100 kbps, the data size of the broadcast signal is 50 bytes, and the elapsed time at the time of receiving the broadcast signal is 60 msec. In this case, the correction unit 45 calculates "50 + 50 bytes / 100 kbps = 50 + (50 × 8) / 100 = 54 ms" in consideration of the transmission time, and the reception is completed 54 msec after the beginning of the wireless frame on the GW device 10 side. Calculate as planned. However, since the elapsed time at the time of receiving the notification signal was 60 msec, the correction unit 45 calculates 60-54 = 6 as the time difference. Then, the correction unit 45 corrects the time of the own node 30 so as to delay it by 6 msec.

The determination unit 46 is a processing unit that calculates a clock error, which is an error between the clock frequency of the GW device 10 and the clock frequency of the node 30, using the correction width of the time correction. Further, the determination unit 46 is a processing unit that determines the BT value using the calculated clock error. Specifically, the determination unit 46 can also calculate the clock error using the time difference corrected by the correction unit 45, and the maximum stored in the correction width DB 34 after the time synchronization is executed a predetermined number of times. The clock error can also be calculated using the correction width.

For example, when the maximum error is 7 msec and the sleep setting time is 1 hour, the determination unit 46 calculates the clock error as “7.0 msec / 1 hour ≈ 2 ppm”. Then, the determination unit 46 calculates "(3600 seconds x 2 ppm) + 3 ms (hardware startup time) = 10.5 msec" as the GT by using the above GT calculation method. After that, the determination unit 46 stores the calculated GT (10.5 msec) in the GT value DB 33.

[Flow of GT setting process]
FIG. 7 is a flowchart showing the flow of the GT setting process according to the first embodiment. As shown in FIG. 7, the determination unit 46 of the node 30 sets the initial value of the GT when the node 30 is started for the first time (S101).

After that, the correction unit 45 executes the synchronization process every time the notification signal is received (S102). Then, when the time synchronization is executed more than a predetermined number of times (S103: Yes), the determination unit 46 refers to the correction width DB 34 and acquires the maximum correction width (S104).

Then, the determination unit 46 calculates the clock error using the maximum correction width, and updates the GT using the clock error (S105). After that, the node 30 goes into a sleep state and waits for a notification signal (S106). In S103, when the time synchronization is less than the specified number of times (S103: No), S106 is executed.

[Synchronization process flow]
FIG. 8 is a flowchart showing the flow of the synchronization process according to the first embodiment. The process executed here corresponds to the process executed in S102 of FIG. 7.

As shown in FIG. 8, when the receiving unit 44 of the node 30 receives the notification signal (S201), the reception unit 44 of the node 30 extracts the time information of the opposite device from the notification signal (S202). Subsequently, the correction unit 45 acquires the time information of the own device when the notification signal is received (S203), and calculates the difference using both time information (S204).

After that, the correction unit 45 corrects the time of the own device using the calculated difference (S205), and stores the calculated difference as the time correction width in the correction width DB 34 (S206).

[Flow of data transmission process]
FIG. 9 is a flowchart showing the flow of the data transmission process according to the first embodiment. The data transmission process and the GT setting process have no dependency and are executed independently.

As shown in FIG. 9, when the state transition unit 43 of the node 30 reaches the GT from the sleep state (S301: Yes), the state transition unit 43 of the node 30 wakes up the node 30 from the sleep state (S302). Subsequently, when the notification signal is received (S303: Yes), the state transition unit 43 puts the node 30 into the sleep state (S304).

After that, when the data transmission time comes (S305: Yes), the state transition unit 43 returns the node 30 from the sleep state and transitions to the normal state (S306). Then, the sensing unit 41 acquires the sensor value (S307), and the data processing unit 42 transmits the sensor value to the GW device 10 (S308). After that, the state transition unit 43 puts the node 30 into the sleep state when the transmission of the sensor value is completed (S309).

[effect]
As described above, each node 30 executes the synchronization process when the notification signal is received, and when the synchronization process is executed, the time correction width is calculated and stored. Then, after completing the synchronization processing a predetermined number of times, each node 30 selects the maximum value among the accumulated time correction widths, and estimates the clock error with the opposite device. Subsequently, each node 30 updates the GT from the initial value by using the estimated clock error.

That is, each node 30 can obtain an error in the clock frequency of its own device and set an appropriate GT for its own device. Therefore, it is possible to set the sleep time and the wakeup time that match the performance of each node 30 without setting a uniform GT for each node 30, so that the effect of power saving can be improved.

Next, the results of trial calculation of the general power saving effect and the power saving effect according to the first embodiment will be described. FIG. 10 is a diagram showing preconditions at the time of effect calculation. As shown in FIG. 10, the clock frequency is 16 MHz, the maximum error of the clock error is 20 ppm, the power consumption during sleep is 0.005 mA, the power consumption during normal operation is 50 mA, the power consumption during data transmission is 60 mA, and the hardware is started. The margin of time and the like is 3 msec, and the data transfer rate is 100 kbps.

Next, the radio conditions at the time of effect calculation will be described. FIG. 11 is a diagram showing radio conditions at the time of effect calculation. Here, FIG. 11 shows a radio frame that is a simplification of the BAN shown in FIG. As shown in FIG. 11, the sleep setting time is set to 1 hour, and wakeup and sleep are repeated every hour. The data to be transmitted is 50 kbps, and the data transfer time is "(50 x 8) / 100 kbps = 4 ms". Further, GT is a value based on the margin (3 ms) + clock error. Here, the maximum clock error is 20 ppm, and the measured value measured in Example 1 is 2 ppm.

Under such conditions, the calculation result of GT and the calculation result of power consumption are shown in FIG. 12 for each of the conventional and the first embodiment. FIG. 12 is a diagram showing the result of the effect calculation. As shown in FIG. 12, the conventional GT is "(3600 seconds x 20 ppm) + 3 msec = 72 msec + 3 msec = 75 msec". On the other hand, in Example 1, "(3600 seconds x 2 ppm) + 3 msec = 7.2 msec + 3 msec = 10.2 msec". Therefore, the sleep time of Example 1 is 64.8 msec longer than that of the conventional one.

Further, each power consumption per hour can be calculated as power consumption during sleep time + power consumption during normal operation + power consumption during data transmission. That is, the conventional power consumption is "((3600000-75-4) x 0.005 + (75 x 50) + (4 x 60)) / 3600 = 0.006108mAh", and the power consumption of Example 1 is "((3600000-10.2-4) x 0.005 + (10.2 x 50) + (4 x 60)) / 3600≈0.005208mAh". As a result, the current consumption can be reduced by 14.7%, and the battery life can be improved by 17.2%.

In the first embodiment, an example in which each node 30 calculates and sets the GT has been described, but the present invention is not limited to this, and the GW device 10 can also calculate the GT of each node 30. Therefore, in the second embodiment, an example in which the GW device 10 calculates the GT of each node 30 and notifies each node 30 will be described. Since the overall configuration of the system is the same as that of the first embodiment, detailed description thereof will be omitted.

[Calculation method]
First, the GT calculation method in the second embodiment will be described. Specifically, the GW device 10 can be processed by using some methods. For example, each node 30 holds the time correction width when the time correction using the notification signal is performed on the node 30 side, and notifies the correction width to the GW device 10 side together with the sensoring data transmission. When the GW device 10 receives the time correction width on the node 30 side, the GW device 10 accumulates the time correction width in the same manner as in the first embodiment. Then, the GW device 10 calculates the GT by analogizing the clock error of the node 30 by using the same method as the node 30 of the first embodiment, and notifies the calculated GT to the node 30.

As another example, when the data transmission timing (bandwidth) is fixedly assigned between the GW device 10 and each node 30, the GW device 10 uses the data reception time on the GW device 10 side to set the time. You can also infer the error. Specifically, the GW device 10 calculates the scheduled data reception time on the GW device 10 side from the band allocation (data transmission start) time and the transmission data length for each node 30. Then, the GW device 10 infers the time error from the node 30 from the difference between the calculated time and the actual reception completion time, and holds it in the internal table.

FIG. 13 is a diagram illustrating an analogy of the time error of the second embodiment. As shown in FIG. 13, the data transmission time is predetermined between the GW device 10 and the node 30. In this state, the node 30 transmits the sensing data to the GW device 10 using the uplink band recognized by the node 30 at a predetermined time. The GW device 10 calculates the time difference between the GW device 10 and the node 30 by comparing the reception time when the sensing data is actually received with the scheduled reception time (theoretical value) calculated by using the transmission time and the like. do. After that, the GW device 10 calculates the clock error from the time difference, calculates the GT from the clock error, and notifies the node 30. Node 30 sets the notified GT.

[Functional configuration]
FIG. 14 is a functional block diagram showing a functional configuration of each device according to the second embodiment. Here, the method described with reference to FIG. 13 will be described.

(Configuration of GW device)
As shown in FIG. 14, the GW device 10 has a communication unit 11, a storage unit 12, and a control unit 20. Since the communication unit 11 and the storage unit 12 are the same as those in the first embodiment, detailed description thereof will be omitted. The control unit 20 is a processing unit that controls the entire GW device 10, and has a data receiving unit 23, an analogy unit 24, and a notification unit 25.

The data receiving unit 23 is a processing unit that receives sensing data from the node 30. Specifically, the data receiving unit 23 receives the sensing data transmitted when the node 30 reaches a predetermined time.

The analogy unit 24 is a processing unit that estimates the time difference from the node 30 and the clock error from the node 30. For example, a band for transmitting sensing data from the node 30 to the GW device 10 is allocated with a time of 100 msec from the beginning of the wireless frame, and the band is used by the node 30 to the GW device 10 at a communication rate of 100 kbps. It is assumed that 50 bytes of data are transmitted.

In this case, the analogy unit 24 calculates by "100 + 50 bytes / 100 kbps" that the reception is scheduled to be completed 104 msec after the beginning of the wireless frame on the GW device 10 side. However, the analogy unit 24 estimates that 109-104 = 5 msec is the time error between the GW device 10 and the node 30 when the actual data reception completion time is 109 msec from the beginning of the wireless frame.

Further, the analogy unit 24 calculates “time difference / sleep setting time = 5.0 msec / 1 hour ≈ 1 ppm” as a clock error. As a result, the analogy unit 24 uses "GT initial value = hardware startup time + (maximum clock error [ppm] x sleep setting time)" to "3ms (hardware startup time) + (3600 seconds x 1ppm)". ) = 6.6 msec ”is calculated as GT. Then, the analogy unit 24 outputs the calculation result “GT = 6.6 msec” to the notification unit 25.

The notification unit 25 is a processing unit that transmits the GT value determined by the analogy unit 24 to the corresponding node 30. For example, the notification unit 25 transmits the calculation result “GT = 6.6 msec” to the node 30 and instructs the node 30 to update the GT.

(Node configuration)
As shown in FIG. 14, the node 30 has a communication unit 31, a storage unit 32, and a control unit 40. Since the communication unit 31 and the storage unit 32 are the same as those in the first embodiment, detailed description thereof will be omitted. The control unit 40 is a processing unit that controls the entire node 30, and includes a sensing unit 41, a data processing unit 42, a state transition unit 43, and a GT correction unit 47. Of these, here, the data processing unit 42 and the GT correction unit 47 that execute processing different from that of the first embodiment will be described.

The data processing unit 42 is a processing unit that generates sensing data including time information and transmits it to the GW device 10 at a predetermined time. For example, when the transmission timing is reached in each superframe, the data processing unit 42 generates sensing data including the elapsed time from the beginning of the current superframe and the sensor value. Then, the data processing unit 42 transmits the sensing data to the GW device 10.

The GT correction unit 47 is a processing unit that executes initial setting and updating of the GT. For example, the GT correction unit 47 sets an initial value in the GT value DB 33 when the node 30 is started for the first time. The initial value can be calculated by the same method as in Example 1. Then, when the GT correction unit 47 receives the GT value from the GW device 10, the GT correction unit 47 updates the value stored in the GT value DB 33 with the received GT value.

[Frame structure]
FIG. 15 is a diagram illustrating a frame configuration of BAN in the second embodiment. By the method described above, since each node 30 recognizes the data transmission timing of its own device without using the broadcast signal, it can return immediately before the data transmission assigned by the MAP. At this time, as shown in FIG. 15, the node 30 returns before the start time of data transmission by the GT time notified from the GW device 10. As a result, the sleep state can be made longer.

[Data transmission process]
FIG. 16 is a flowchart showing the flow of the data transmission process according to the second embodiment. As shown in FIG. 16, when the state transition unit 43 of the node 30 reaches the GT from the sleep state (S401: Yes), the state transition unit 43 of the node 30 wakes up the node 30 from the sleep state (S402).

Subsequently, the sensing unit 41 acquires the sensor value (S403), and the data processing unit 42 transmits the sensing data including the time information and the sensor value to the GW device 10 (S404). After that, the state transition unit 43 puts the node 30 into the sleep state when the transmission of the sensing data is completed (S405).

[GT calculation process]
FIG. 17 is a flowchart showing the flow of the GT calculation process according to the second embodiment. As shown in FIG. 17, when the analogy unit 24 of the GW device 10 receives the sensing data by the data receiving unit 23 (S501: Yes), the analogy unit 24 specifies the reception time (S502).

Subsequently, the analogy unit 24 calculates the scheduled reception time (theoretical value) using the time information and the like included in the sensing data (S503), and estimates the clock error using the difference between the reception time and the theoretical value. (S504), GT is calculated using the analogy result (S505). Then, the notification unit 25 notifies the node 30 of the calculated GT value (S506).

[effect]
As shown in FIG. 15, each node 30 can return to the sleep state by the GT time notified from the GW device 10 before the start time of the data transmission assigned by the MAP. It can be made longer and the power consumption can be further reduced.

By the way, although the examples of the present invention have been described so far, the present invention may be carried out in various different forms other than the above-mentioned examples. Therefore, different embodiments will be described below.

[Communication method]
In the above-mentioned Example 1-2, wireless communication has been described as an example, but the present invention is not limited to this, and various wired communications can be similarly processed. Further, in the first embodiment, an example in which the transition to the normal state is performed by the superframe and then the transition to the sleep state is performed again until the time of data transmission has been described, but the present invention is not limited to this. For example, the node 30 can be controlled to maintain the normal state until the time of data transmission after transitioning to the normal state by the superframe, and to sleep until the next superframe after the completion of data transmission.

[Node unit]
The process described in Example 1-2 can be executed for each node. Further, by executing the test periodically, the GT can be updated according to the aging deterioration of the built-in electronic circuit. Further, Examples 1 and 2 can be appropriately combined within a consistent range.

[system]
Information including processing procedures, control procedures, specific names, various data and parameters shown in documents and drawings can be arbitrarily changed unless otherwise specified.

Further, each component of each of the illustrated devices is a functional concept, and does not necessarily have to be physically configured as shown in the figure. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure. That is, all or a part thereof can be functionally or physically distributed / integrated in any unit according to various loads, usage conditions, and the like. Further, each processing function performed by each device may be realized by a CPU and a program analyzed and executed by the CPU, or may be realized as hardware by wired logic.

[Hardware configuration of GW device 10]
FIG. 18 is a diagram showing a hardware configuration example of the GW device 10. As shown in FIG. 18, the GW device 10 includes a communication interface 10a, an HDD (Hard Disk Drive) 10b, a memory 10c, and a processor 10d.

The communication interface 10a is a network interface card, a wireless interface, or the like that controls communication of other devices. The HDD 10b is an example of a storage device for storing programs, data, and the like.

Examples of the memory 10c include RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), ROM (Read Only Memory), flash memory and the like. Examples of the processor 10d include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), a PLD (Programmable Logic Device), and the like.

Further, the GW device 10 operates as an information processing device that executes a communication method by reading and executing a program. That is, the GW device 10 executes a program that executes the same functions as the notification unit 21 and the data reception unit 22, and a program that executes the same functions as the data reception unit 23, the analogy unit 24, and the notification unit 25. As a result, the GW device 10 can execute a process of executing the same functions as the notification unit 21, the data reception unit 22, the data reception unit 23, the analogy unit 24, and the notification unit 25. The program referred to in the other examples is not limited to being executed by the GW device 10. For example, the present invention can be similarly applied when other computers or servers execute programs, or when they execute programs in cooperation with each other.

This program can be distributed over networks such as the Internet. In addition, this program is recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO (Magneto-Optical disk), or DVD (Digital Versatile Disc), and is recorded from the recording medium by the computer. It can be executed by being read.

[Hardware configuration of node 30]
FIG. 19 is a diagram showing a hardware configuration example of the node 30. As shown in FIG. 19, the node 30 has a radio unit 30a, a sensor 30c, an HDD 30d, a memory 30e, and a processor 30f.

The wireless unit 30a is a wireless interface or the like that controls communication of other devices via the antenna 30b. The sensor 30c is a sensor device that measures the water level and the like. The HDD 30d is an example of a storage device for storing programs, data, and the like.

Examples of the memory 30e include RAM such as SDRAM, ROM, flash memory, and the like. Examples of the processor 30f include an MCU, a CPU, and the like.

Further, the node 30 operates as an information processing device that executes a communication method by reading and executing a program. That is, the node 30 executes a program that executes the same functions as the sensing unit 41, the data processing unit 42, the state transition unit 43, the receiving unit 44, the correction unit 45, the determination unit 46, and the GT correction unit 47. As a result, the node 30 can execute a process of executing the same functions as the data processing unit 42, the state transition unit 43, the receiving unit 44, the correction unit 45, the determination unit 46, and the GT correction unit 47. The program referred to in the other embodiment is not limited to being executed by the node 30. For example, the present invention can be similarly applied when other computers or servers execute programs, or when they execute programs in cooperation with each other.

This program can be distributed over networks such as the Internet. Further, this program can be executed by being recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and read from the recording medium by the computer.

10 GW device 11 Communication unit 12 Storage unit 13 Sensor value DB
20 Control unit 21 Notification unit 22, 23 Data reception unit 24 Analogy unit 25 Notification unit 30 Node 31 Communication unit 32 Storage unit 33 GT value DB
40 Control unit 41 Sensing unit 42 Data processing unit 43 State transition unit 44 Reception unit 45 Correction unit 46 Determination unit 47 GT correction unit

Claims (8)

In communication equipment
An analogy unit that estimates a clock error, which is an error between the clock frequency of the opposite device and the clock frequency of the communication device, by using the time difference between the opposite device and the communication device.
A determination unit that determines the preparation time for data communication using a wireless frame according to the estimated clock error, and a determination unit.
From the power saving state that suppresses communication with the opposite device with respect to the communication timing for receiving the broadcast signal among the plurality of communication timings specified in the synchronization unit in the wireless frame with the opposite device. The return time for returning to the normal state for executing communication with the opposite device is set before the preparation time to correct the return time, and the communication for receiving the notification signal among the plurality of communication timings. A communication device having a setting unit for suppressing correction of the return time based on the preparation time, except for the timing. A calculation unit that calculates the time difference between the opposite device and the communication device based on the reception time of the notification signal received from the opposite device and the transmission time of the notification signal.
After the data communication with the opposite device is completed, the state transitions to the power saving state, and the power saving state returns to the normal state before the preparation time from the start time of the communication timing for receiving the next notification signal. The communication device according to claim 1, further comprising a state transition unit. The calculation unit acquires the transmission time from the notification signal for which the opposite device notifies the transmission time, the acquired transmission time, the size of the notification signal, and communication between the opposite device and the communication device. Using the speed, the theoretical reception time for receiving the notification signal is calculated, and the time difference is calculated from the theoretical reception time and the reception time of the notification signal.
The communication device according to claim 2, wherein the analogy unit estimates a value obtained by dividing the time difference by time information indicating an interval of the broadcast signal to the clock error. When the notification signal is received a plurality of times, the analogy unit identifies the maximum time difference among the time differences based on each notification signal, and estimates the clock error using the maximum time difference. The communication device according to claim 3, which is characterized. Further, it has a calculation unit for calculating the time difference between the opposite device and the communication device from the reception time of the notification signal received from the opposite device and the scheduled reception time of the notification signal set in advance.
The claim is characterized in that the setting unit transmits an instruction to advance the time for starting the return from the power saving state to the normal state by the preparation time with the start of the data communication to the opposite device. Item 1. The communication device according to item 1. The communication device
Using the time difference between the opposite device and the communication device, the clock error, which is the error between the clock frequency of the opposite device and the clock frequency of the communication device, is estimated.
According to the estimated clock error, the preparation time for performing data communication using the wireless frame is determined.
From the power saving state that suppresses communication with the opposite device with respect to the communication timing for receiving the broadcast signal among the plurality of communication timings specified in the synchronization unit in the wireless frame with the opposite device. The return time for returning to the normal state for executing communication with the opposite device is set before the preparation time to correct the return time, and the communication for receiving the notification signal among the plurality of communication timings. A communication method characterized by executing a process of suppressing the correction of the return time based on the preparation time, except for the timing. For communication equipment
Using the time difference between the opposite device and the communication device, the clock error, which is the error between the clock frequency of the opposite device and the clock frequency of the communication device, is estimated.
According to the estimated clock error, the preparation time for performing data communication using the wireless frame is determined.
From the power saving state that suppresses communication with the opposite device with respect to the communication timing for receiving the broadcast signal among the plurality of communication timings specified in the synchronization unit in the wireless frame with the opposite device. The return time for returning to the normal state for executing communication with the opposite device is set before the preparation time to correct the return time, and the communication for receiving the notification signal among the plurality of communication timings. A communication program characterized in that a process of suppressing correction of the return time based on the preparation time is executed except for the timing. In a communication system including a management device and a communication device,
The management device is
It has a transmission unit that transmits a notification signal including a transmission time to the communication device when a predetermined transmission trigger is reached.
The communication device is
When the notification signal is received, the notification signal is received using the transmission time included in the notification signal, the size of the notification signal, and the communication speed between the management device and the communication device. A calculation unit that calculates the theoretical reception time, and
The time difference is calculated from the reception theoretical time and the reception time of the notification signal, and the time difference is used to estimate the clock error, which is the error between the clock frequency of the management device and the clock frequency of the communication device. Department and
A determination unit that determines the preparation time for data communication using a wireless frame according to the estimated clock error, and a determination unit.
Among a plurality of communication timings specified in synchronization units within a wireless frame with the management device, the communication timing for transmitting the notification signal is managed from a power saving state that suppresses communication with the management device. The return time for returning to the normal state for executing communication with the device is set before the preparation time to correct the return time, and among the plurality of communication timings, other than the communication timing for receiving the notification signal. With respect to the setting unit that suppresses the correction of the return time based on the preparation time,
After the data communication with the management device is completed, the state transitions to the power saving state for suppressing the data communication, and the power saving state is set before the preparation time from the start time of the communication timing for receiving the next notification signal. A communication system characterized by having a state transition unit that returns from the normal state to the normal state.

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