JP2018166315A - Communication apparatus, communication method, communication program and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high power-saving effect.SOLUTION: A node estimates a clock error which is an error between a clock frequency of an opposite device and that of the node, using a time difference between the opposite device and the node. The node determines a preparation period for executing data communication. The node sets a period for returning a power-saving state for suppressing communication with the opposite device to a normal state for executing communication with the opposite device, to an advanced period by a period corresponding to the preparation period.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a communication device, a communication method, a communication program, and a communication system.

  2. Description of the Related Art Conventionally, as represented by IoT (Internet of Things), communication functions for various “things” are increasing. For example, a sensor device that senses water level, gas usage, electricity usage, etc., has a communication function, and periodically sends sensing data to a counter device such as a gateway (GW). Collective management is done.

  A device to be provided with a communication function is not limited to a power supply that is stably supplied with power, but may be operated by a battery that has a finite power or may be operated by power generated by energy harvesting. In such a case, since the device operates in a limited power, the power consumption is reduced for the communication function. In recent years, a short-range wireless technology such as BAN (Body Area Network) that changes the apparatus to a sleep state during a period when communication or processing is not performed is known.

  For example, when communication between the GW serving as the hub and the device serving as the node is completed, the device enters a sleep state for the time set in the timer. The sleep time is set in consideration of “time until communication can be reliably performed in consideration of the rise time of the apparatus, processing overhead, and the like” called GuardTime (hereinafter sometimes referred to as GT). Specifically, upon completion of the sensing data transmission process, the apparatus sets a timer to return to a time before the next sensing data transmission process occurs (Wakeup) and enters a sleep state. .

JP 2010-28503 A JP 2011-29918 A

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

  Specifically, when calculating the GT to be set in the timer, the clock error of the MCU (Micro Control Unit) used in the communication module of the apparatus is taken into consideration, but there is an individual difference in the width of the clock error for each communication module. For this reason, even if the communication module used for each device is the same, not all of them operate at the same clock frequency.

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

  An object of one aspect is to provide a communication device, a communication method, a communication program, and a communication system that can improve the power saving effect.

  In the first proposal, the communication device uses a time difference between the opposite device and the communication device to analogize a clock error that is an error between the clock frequency of the opposite device and the clock frequency of the communication device. 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 performing data communication according to the estimated clock error And a setting unit that sets the time for returning to the normal state to the preparation period.

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

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

  Embodiments of a communication device, a communication method, a communication program, and a communication system disclosed in the present application will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[overall structure]
FIG. 1 is a diagram illustrating an example of the overall configuration of a system according to the first embodiment. As shown in FIG. 1, this system includes a management server 5, a GW apparatus 10, and a plurality of nodes 30. The GW apparatus 10 and the plurality of nodes 30 are connected to each other via a network N so that they can communicate with each other. The network N can employ various communication networks such as the Internet and a dedicated line regardless of 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 sensing 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 apparatus 10 is an example of a network apparatus that aggregates communication between each node 30 and the management server 5. For example, the GW apparatus 10 receives sensing data periodically transmitted from each node 30 and transmits the sensing data to the management server 5.

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

  Here, a sensing example of each node will be described. FIG. 2 is a diagram illustrating an example of node sensing. 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 at intervals designated by the GW device 10 and transmits the water level data to the GW device 10 using the designated band.

  Next, wireless communication between the GW apparatus 10 and each node 30 will be described. Sensing data is exchanged between the GW apparatus 10 and each node 30 using a BAN (Body Area Network). FIG. 3 is a diagram for explaining the frame structure of the BAN. As shown in FIG. 3, a synchronization unit called superframe is set in the radio frame between the GW device 10 and each node 30, and transmission of sensing data is executed within this synchronization unit. Between the GW apparatus 10 and each node 30, the start timing (time) of each superframe is set as common information.

  Specifically, the superframe includes one Beacom, a plurality of EAP (Exclusive Access Phase), RAP (Random Access Phase), and MAP (Managed Access 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 there is a possibility of collision, so they are controlled by CSMA (Carrier Sense Multiple Access) / CA (Collision Avoidance). MAP is an area where only a node to which a bandwidth is allocated can communicate, and the GW device 10 allocates a bandwidth (communication timing) for each node in response to a request from the node when connected to the GW device 10 (Hub). . That is, a communication band for each node is fixedly allocated in the MAP.

  On the other hand, in the superframe, each node 30 enters a sleep state when data communication with the GW apparatus 10 is not performed, and returns at a timing when data communication occurs. Specifically, after returning at the start timing of Beacon in the superframe of T0, and then transitioning to the sleep state, it returns at the transmission timing assigned to the own node in the MAP, and enters the sleep state after completing the data transmission. Then, it returns again at the start timing of Beacon in the next T1 superframe.

  In this way, each node 30 is in a normal state only when data transmission is performed, and is otherwise in a sleep state that suppresses data transmission and the like, thereby suppressing power consumption. Here, each node 30 returns faster than the start timing of Beacon by GT taking into consideration the time until reliable communication is possible in consideration of the rise time of the apparatus and processing overhead. That is, when the Beacon start time t and GT are 30 seconds, each node 30 returns 30 seconds earlier than t.

  Generally, since a period in which the clock frequency (operation clock) of all the communication modules used in each node 30 can be covered is set in this GT, as a result, the sleep state time is shortened and saved. The effect of electric power is small.

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

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

(Configuration of GW device)
As illustrated in FIG. 4, the GW apparatus 10 includes 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.

  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 notification signal (Beacon) to each node 30 and receives sensing data from each node 30.

  The storage unit 12 is a storage unit that stores programs and data, and stores a 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 therein an identifier for identifying a node, a sensor value measured by the node, a date and time when the sensor value is acquired, and the like.

  The control unit 20 is a processing unit that controls the GW apparatus 10 as a whole, and includes a notification unit 21 and a data reception unit 22. The notification unit 21 and the data receiving unit 22 are an example of an electronic circuit included in the processor and an example of a process executed by the processor. In addition, the control unit 20 performs allocation of data transmission time to each node, that is, allocation within the MAP.

  The notification unit 21 is a processing unit that generates a notification signal including time information and transmits the notification signal to each node 30. For example, when the notification unit 21 reaches the transmission timing of the notification signal at the head of each superframe, the notification unit 21 generates a notification signal including the elapsed time from the head of the current superframe. And the alerting | reporting part 21 transmits the alerting | reporting signal containing elapsed time as time information to each node 30. FIG.

  The data receiving unit 22 is a processing unit that receives sensing data from each node 30. Specifically, when the data reception unit 22 reaches the MAP time, the data reception unit 22 receives sensing data from each node at the time allocated to each node. And the data receiving part 22 acquires a sensor value from the received sensing data, and stores it in sensor value DB13. The data receiving unit 22 can also transmit the received sensing data to the management server 5.

(Node configuration)
As illustrated in FIG. 4, the node 30 includes 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.

  The communication unit 31 is a processing unit that controls communication with the GW apparatus 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 that stores programs and data, and stores a GT value DB 33 and a correction width DB 34. The GT value DB 33 is a database that stores GT values set by nodes. Information stored in the GT value DB 33 is set to an initial value at the start of data communication, and thereafter updated by the determination unit 46 described later. The initial value uses the catalog value of the maximum error of the clock system. For example, the initial value of GT is calculated by “initial value = hardware startup time + (maximum clock error [ppm] × sleep setting time)”. Note that the sleep setting time is a time during sleep, for example, a Beacon interval, in other words, a superframe interval.

  The correction width DB 34 is a database that stores a correction history of a time error between the GW apparatus 10 and the node 30. FIG. 5 is a diagram illustrating an example of information stored in the correction width DB of the node 30. As illustrated in FIG. 5, the correction width DB 34 stores “number of times, time correction width (msec)”. “Number of times” indicates the number of correction times, and “Time correction width” indicates the corrected time. In the case of FIG. 5, 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 reception 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 reception unit 44, the correction unit 45, and the determination unit 46 are an example of an electronic circuit included in the processor and an example of a process 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 a sensor value from the sensor periodically or at a 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 apparatus 10. Specifically, the data processing unit 42 generates sensing data including the sensor value acquired from the sensing unit 41 and transmits the sensing data to the GW device 10 at the sensing data transmission timing. For example, the data processing unit 42 transmits sensing data to the GW apparatus 10 at the transmission timing of the own node in the MAP in the BAN superframe.

  The state transition unit 43 is a processing unit that causes the node 30 to sleep during a period in which data communication does not occur and to return at a timing at which data communication occurs. Specifically, as shown in FIG. 3, the state transition unit 43 returns at the start timing of the Beacon, and then returns to the sleep state and then returns at the transmission timing assigned to the own node in the MAP. Then, after the data transmission is completed, the state transits to the sleep state and is resumed at the next Beacon start timing. Note that the GT set here is set based on the GT value stored in the GT value DB 33. That is, in the initial stage, when the initial value is set and 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 apparatus 10. Specifically, the receiving unit 44 receives the notification signal transmitted by the GW apparatus 10 at the timing of Beacon in each superframe, and outputs the notification signal to the correction unit 45.

  The correction unit 45 is a processing unit that calculates a time difference between the GW apparatus 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 the time difference.

  Furthermore, the correction unit 45 calculates the theoretical reception time that is expected to receive the notification signal, in consideration of the transmission rate between the GW apparatus 10 and the node 30 and the data size of the notification signal. And the correction | amendment part 45 can also calculate the difference of the theoretical reception time estimated from the alerting | reporting signal, and the reception time which actually received the alerting | reporting signal as a time difference.

  Here, time synchronization based on a broadcast signal transmitted in a BAN radio frame is calculated. FIG. 6 is a diagram for explaining time synchronization by BAN. As illustrated in FIG. 6, the GW apparatus 10 transmits to the node 30 a notification signal in which the elapsed time from the top of the radio frame (superframe) is set in the payload at the Beacon timing. 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 head of the radio 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 corrects the time of the node 30 if there is a difference. Then, the correction unit 45 stores the time correction width in the correction width DB 34.

  As an example, description will be made assuming that 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 when the broadcast signal is received 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 after 54 msec from the head of the radio frame on the GW apparatus 10 side. Calculate to be scheduled. However, the correction unit 45 calculates 60−54 = 6 as the time difference because the elapsed time when the notification signal is received is 60 msec. Then, the correction unit 45 corrects the time of the own node 30 so as to be delayed by 6 msec.

  The determination unit 46 is a processing unit that calculates a clock error that is an error between the clock frequency of the GW apparatus 10 and the clock frequency of the node 30 using the correction width of the time correction. The determination unit 46 is a processing unit that determines a 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 after the time synchronization is executed a predetermined number of times, the maximum value stored in the correction width DB 34 is obtained. 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 × 2 ppm) +3 ms (hardware activation time) = 10.5 msec” as the GT using the above-described GT calculation method. Thereafter, the determination unit 46 stores the calculated GT (10.5 msec) in the GT value DB 33.

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

  Thereafter, the correction unit 45 executes a synchronization process every time a notification signal is received (S102). Then, when the time synchronization of the specified number of times or more is executed (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). Thereafter, the node 30 enters 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.

[Flow of synchronization processing]
FIG. 8 is a flowchart of the synchronization process according to the first embodiment. Note that the processing executed here corresponds to the processing executed in S102 of FIG.

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

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

[Data transmission processing flow]
FIG. 9 is a flowchart of a data transmission process according to the first embodiment. Note that the data transmission process and the GT setting process are executed independently with no dependency.

  As illustrated in FIG. 9, when the state transition unit 43 of the node 30 reaches GT from the sleep state (S301: Yes), the node 30 returns the node 30 from the sleep state (S302). Subsequently, when the notification signal is received (S303: Yes), the state transition unit 43 sets the node 30 to 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 makes a transition to the normal state (S306). And the sensing part 41 acquires a sensor value (S307), and the data processing part 42 transmits a sensor value to the GW apparatus 10 (S308). Thereafter, when the transmission of the sensor value is completed, the state transition unit 43 sets the node 30 to the sleep state (S309).

[effect]
As described above, each node 30 executes the synchronization process when receiving the notification signal, and calculates and accumulates the time correction width when executing the synchronization process. Each node 30 then completes the synchronization process a specified number of times, then selects the maximum value among the accumulated time correction widths, and analogizes the clock error with the opposing device. Subsequently, each node 30 uses the estimated clock error to update the GT from the initial value.

  That is, each node 30 can determine an error in the clock frequency of the own device and set an appropriate GT for the own device. For this reason, since the sleep time and the return time that match the performance of each node 30 can be set without setting a uniform GT for each node 30, the power saving effect can be improved.

  Next, the result 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 the preconditions for the trial calculation of the effect. 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 activated A margin such as time is 3 msec, and a data transfer rate is 100 kbps.

  Next, the radio conditions at the time of effect trial calculation will be described. FIG. 11 is a diagram illustrating radio conditions at the time of effect trial calculation. Here, FIG. 11 shows a radio frame obtained by simplifying the BAN shown in FIG. As shown in FIG. 11, the sleep set time is set to 1 hour, and the return and sleep are repeated every hour. The data to be transmitted is 50 kbps, and the data transfer time is “(50 × 8) / 100 kbps” = 4 ms. GT is a value based on a margin (3 ms) + clock error. Here, the clock error is 20 ppm at the maximum, and the actual measurement value measured in Example 1 is 2 ppm.

  Under such conditions, the results of the trial calculation of GT and the trial calculation result of power consumption are shown in FIG. FIG. 12 is a diagram showing the results of the trial calculation. As shown in FIG. 12, the conventional GT is “(3600 seconds × 20 ppm) +3 msec = 72 msec + 3 msec = 75 msec”. On the other hand, in Example 1, “(3600 seconds × 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 prior art.

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

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

[Calculation method]
First, a GT calculation method according to the second embodiment will be described. Specifically, the GW apparatus 10 can perform processing using several 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 apparatus 10 side together with the sensing data transmission. When receiving the time correction width on the node 30 side, the GW apparatus 10 accumulates the time correction width in the same manner as in the first embodiment. Then, the GW apparatus 10 calculates the GT by analogy with the clock error of the node 30 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 allocated 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 An error can be analogized. Specifically, the GW device 10 calculates the data reception scheduled time on the GW device 10 side from the band allocation (data transmission start) time for each node 30 and the transmission data length. Then, the GW apparatus 10 estimates the time error with the node 30 from the difference between the calculated time and the actual reception completion time, and holds it in an internal table.

  FIG. 13 is a diagram illustrating an analogy of time error according to the second embodiment. As illustrated in FIG. 13, the data transmission time is determined in advance between the GW apparatus 10 and the node 30. In this state, the node 30 transmits sensing data to the GW apparatus 10 using an 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 using the transmission time or the like. To do. Thereafter, the GW apparatus 10 calculates a clock error from the time difference, calculates a GT from the clock error, and notifies the node 30 of it. The node 30 sets the notified GT.

[Function configuration]
FIG. 14 is a functional block diagram of a functional configuration of each apparatus according to the second embodiment. Here, the method described in FIG. 13 will be described.

(Configuration of GW device)
As illustrated in FIG. 14, the GW apparatus 10 includes a communication unit 11, a storage unit 12, and a control unit 20. In addition, since the communication part 11 and the memory | storage part 12 are the same as that of Example 1, detailed description is abbreviate | omitted. The control unit 20 is a processing unit that controls the entire GW apparatus 10, and includes a data reception 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 has reached a predetermined time.

  The analogy unit 24 is a processing unit that analogizes the time difference with the node 30 and the clock error with the node 30. For example, a band for sensing data transmission from the node 30 to the GW apparatus 10 is assigned as a time of 100 msec from the head of the radio frame, and the node 30 uses the band to the GW apparatus 10 at a communication rate of 100 kbps. Assume that 50 bytes of data are transmitted.

  In this case, the analogy unit 24 calculates “100 + 50 bytes / 100 kbps” that the reception is scheduled to be completed 104 msec after the start of the radio frame on the GW apparatus 10 side. However, when the actual data reception completion time is 109 msec from the beginning of the radio frame, the analogy unit 24 analogizes that 109−104 = 5 msec is a time error between the GW apparatus 10 and the node 30.

  Further, the analogizing unit 24 calculates “time difference / sleep setting time = 5.0 msec / 1 hour≈1 ppm” as the clock error. As a result, the analogy unit 24 uses “GT initial value = hardware start-up time + (maximum clock error [ppm] × sleep setting time)” to “3 ms (hardware start-up time) + (3600 seconds × 1 ppm). ) = 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 illustrated in FIG. 14, the node 30 includes a communication unit 31, a storage unit 32, and a control unit 40. In addition, since the communication part 31 and the memory | storage part 32 are the same as that of Example 1, detailed description is abbreviate | 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. Among these, here, the data processing unit 42 and the GT correction unit 47 that execute processing different from the first embodiment will be described.

  The data processing unit 42 is a processing unit that generates sensing data including time information and transmits the sensing data to the GW device 10 at a time specified in advance. 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 top 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 update of GT. For example, the GT correction unit 47 sets an initial value in the GT value DB 33 when the node 30 is activated for the first time. The initial value can be calculated by the same method as in the first embodiment. And the GT correction | amendment part 47 will update the value memorize | stored in GT value DB33 with the received GT value, if GT value is received from GW apparatus 10. FIG.

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

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

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

[GT calculation processing]
FIG. 17 is a flowchart of a GT calculation process according to the second embodiment. As illustrated in FIG. 17, when the analog receiving unit 24 of the GW apparatus 10 receives the sensing data by the data receiving unit 23 (S501: Yes), the receiving time is specified (S502).

  Subsequently, the analogy unit 24 calculates the scheduled reception time (theoretical value) using the time information included in the sensing data (S503), and analogizes 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 calculated value of GT to the node 30 (S506).

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

  Although the embodiments of the present invention have been described so far, the present invention may be implemented in various different forms other than the embodiments described above. Therefore, different embodiments will be described below.

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

[Node unit]
The process described in Example 1-2 above can be executed in units of nodes. Further, by executing periodically, the GT can be updated following the aging deterioration of the built-in electronic circuit. Further, Examples 1 and 2 can be appropriately combined within a consistent range.

[system]
The processing procedure, control procedure, specific name, information including various data and parameters shown in the written document and drawings can be arbitrarily changed unless otherwise specified.

  Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution / integration of each device is not limited to that shown in the figure. That is, all or a part of them can be configured to be functionally or physically distributed / integrated in arbitrary units according to various loads or usage conditions. Further, all or any part of each processing function performed in 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 apparatus 10]
FIG. 18 is a diagram illustrating a hardware configuration example of the GW apparatus 10. As illustrated in FIG. 18, the GW apparatus 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 or a wireless interface that controls communication of other devices. The HDD 10b is an example of a storage device that stores programs, data, and the like.

  Examples of the memory 10c include a RAM (Random Access Memory) such as an SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), a flash memory, and the like. Examples of the processor 10d include a central processing unit (CPU), a digital signal processor (DSP), a field programmable gate array (FPGA), and a programmable logic device (PLD).

  The GW apparatus 10 operates as an information processing apparatus that executes a communication method by reading and executing a program. That is, the GW apparatus 10 executes a program that executes the same function as the notification unit 21 and the data receiving unit 22 and a program that executes the same function as the data receiving unit 23, the analogy unit 24, and the notification unit 25. As a result, the GW apparatus 10 can execute a process for executing functions similar to those of 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 embodiments is not limited to being executed by the GW apparatus 10. For example, the present invention can be similarly applied to a case where another computer or server executes the program or a case where these programs cooperate to execute the program.

  This program can be distributed via a network such as the Internet. The program is recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO (Magneto-Optical disk), DVD (Digital Versatile Disc), and the like. It can be executed by being read.

[Hardware configuration of node 30]
FIG. 19 is a diagram illustrating a hardware configuration example of the node 30. As illustrated in FIG. 19, the node 30 includes a wireless unit 30a, a sensor 30c, an HDD 30d, a memory 30e, and a processor 30f.

  The wireless unit 30a is a wireless interface that controls communication of another device via the antenna 30b. The sensor 30c is a sensor device that measures a water level and the like. The HDD 30d is an example of a storage device that stores 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 and a CPU.

  The node 30 operates as an information processing apparatus 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 reception 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 for executing functions similar to those of the data processing unit 42, the state transition unit 43, the reception unit 44, the correction unit 45, the determination unit 46, and the GT correction unit 47. It should be noted that the program referred to in the other embodiments is not limited to being executed by the node 30. For example, the present invention can be similarly applied to a case where another computer or server executes the program or a case where these programs cooperate to execute the program.

  This program can be distributed via a network such as the Internet. The program can be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, and a DVD, and being 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 for analogizing a clock error that is an error between the clock frequency of the counter device and the clock frequency of the communication device using a time difference between the counter device and the communication device;
A determination unit that determines a preparation time for performing data communication according to the estimated clock error;
A setting unit configured to set a time for returning from a power saving state for suppressing communication with the opposite device to a normal state for executing communication with the opposite device before the preparation period. apparatus. Based on the reception time of the packet received from the opposite device and the transmission time of the packet, a calculation unit that calculates a time difference between the opposite device and the communication device;
It further has a state transition unit that transitions to the power saving state after data communication with the opposite device is completed, and returns from the power saving state to the normal state before the preparation time from the start time of the next data communication. The communication apparatus according to claim 1. The calculation unit acquires the transmission time from a notification packet in which the opposite device notifies the transmission time, the acquired transmission time, the size of the notification packet, and the communication speed between the opposite device and the communication device And calculating the reception theoretical time for receiving the broadcast packet, calculating the time difference from the reception theoretical time and the reception time,
The communication device according to claim 2, wherein the analogizing unit estimates the value obtained by dividing the time difference by time information indicating an execution interval of the data communication as the clock error.   The analogizing unit specifies a maximum time difference among the time differences based on each notification packet when the notification packet is received a plurality of times, and analogizes the clock error using the maximum time difference. The communication apparatus according to claim 3, wherein: A calculation unit that calculates the time difference between the opposite device and the communication device from a reception time of the packet received from the opposite device and a preset scheduled reception time of the packet;
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 period with the start of the data communication to the opposing device. Item 4. The communication device according to Item 1. The communication device
Using the time difference between the opposite device and the communication device, analogizing the clock error that is the error between the clock frequency of the opposite device and the clock frequency of the communication device,
According to the analogized clock error, determine a preparation time for data communication,
A communication method, comprising: setting a time for returning from a power saving state for suppressing communication with the opposite device to a normal state for executing communication with the opposite device before the preparation period. . In the communication device,
Using the time difference between the opposite device and the communication device, analogizing the clock error that is the error between the clock frequency of the opposite device and the clock frequency of the communication device,
According to the analogized clock error, determine a preparation time for data communication,
A communication program for executing a process of setting, before the preparation period, a time for returning from a power saving state for suppressing communication with the opposite device to a normal state for executing communication with the opposite device . In a communication system including a management device and a communication device,
The management device
When a transmission opportunity is made in advance, a transmission unit that transmits a notification packet including a transmission time to the communication device,
The communication device
When the notification packet is received, the notification packet is received using the transmission time included in the notification packet, the size of the notification packet, and the communication speed between the management device and the communication device. A calculation unit for calculating the reception theoretical time;
An analogy unit for calculating a time difference from the reception theoretical time and the reception time, and using the time difference to estimate a clock error that is an error between the clock frequency of the management device and the clock frequency of the communication device;
A determination unit that determines a preparation time for performing data communication according to the estimated clock error;
After data communication with the management device is completed, the state transits to a power saving state for suppressing the data communication, and returns from the power saving state to the normal state before the preparation time from the start time of the next data communication. A communication system comprising: a transition unit.

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