JP2020025200A - Communication apparatus, communication system, and communication method - Google Patents

Abstract

To provide a communication apparatus capable of reducing the failure of receiving operation.SOLUTION: A second communication apparatus 20 includes a second communication part 22 that is configured to perform reception check of radio waves at predetermined intervals on the basis of the reception timing of a beacon signal for synchronizing communication and perform reception operation after a standby period shorter than a predetermined interval elapses when a radio wave is received during reception check.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication device, a communication system, and a communication method for performing wireless communication.

  2. Description of the Related Art Communication devices that intermittently confirm reception of radio waves to reduce power consumption are known. Patent Literature 1 discloses a wireless communication system using a wireless communication device that intermittently checks reception of radio waves.

JP 2015-119351 A

  Failure of the receiving operation in the communication system causes an increase in current consumption and a decrease in responsiveness.

  The present invention provides a communication device, a communication system, and a communication method that can suppress a failure in a reception operation.

  The communication device according to one aspect of the present invention performs radio wave reception confirmation at predetermined intervals based on the reception timing of the beacon signal for synchronizing communication, and when the radio wave is received in the reception confirmation, A communication unit that performs a reception operation after a standby period shorter than a predetermined interval has elapsed;

  A communication device according to one aspect of the present invention includes a communication unit that transmits a beacon signal for synchronizing communication to another communication device, wherein the other communication device uses a reception timing of the received beacon signal as a reference. The reception of the radio wave is performed at a predetermined interval, and when the radio wave is received in the reception confirmation, a reception operation is performed after a predetermined standby period shorter than the predetermined interval has elapsed, and the communication unit performs the reception confirmation. And transmitting a frame having a preamble length in which the period required for reception is longer than the total period of the waiting period and the waiting period to the other communication device.

  The communication method according to an aspect of the present invention performs reception confirmation of radio waves at predetermined intervals based on the reception timing of a beacon signal for synchronizing communication, and when the radio waves are received in the reception confirmation, The receiving operation is performed after a standby period shorter than a predetermined interval has elapsed.

  A program according to one embodiment of the present invention is a program for causing a computer to execute the communication method.

  A communication method according to an aspect of the present invention transmits a beacon signal for synchronizing communication to a communication device, and the communication device receives a radio wave at predetermined intervals based on a reception timing of the received beacon signal. Perform a reception, perform a reception operation after a predetermined standby period shorter than the predetermined interval has elapsed when a radio wave is received in the reception confirmation, and perform a reception operation, and a total period of a period required for the reception confirmation and a period required for the reception operation A frame having a preamble length requiring a longer period of time for reception is transmitted to the communication device.

  A program according to one embodiment of the present invention is a program for causing a computer to execute the communication method.

  According to the present invention, a communication device, a communication system, and a communication method that can suppress a failure in a reception operation are realized.

FIG. 1 is a diagram illustrating an outline of a communication system according to an embodiment. FIG. 2 is a time chart for explaining the operation of a general communication system. FIG. 3 is a time chart for explaining the operation of the communication system according to the embodiment. FIG. 4 is a diagram showing a format of a frame. FIG. 5 is a flowchart of the operation of the second communication device. FIG. 6 is a flowchart of a setting operation in which the setting examples 1 and 2 of the waiting period are integrated. FIG. 7 is a flowchart of a setting example 3 of the waiting period. FIG. 8 is a flowchart of a preamble length setting example 1. FIG. 9 is a flowchart of a preamble length setting example 2.

  Hereinafter, embodiments will be specifically described with reference to the drawings. Each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and do not limit the present invention. Further, among the components in the following embodiments, components not described in the independent claims are described as arbitrary components.

  Each drawing is a schematic diagram, and is not necessarily strictly illustrated. In each of the drawings, substantially the same components are denoted by the same reference numerals, and redundant description may be omitted or simplified.

(Embodiment)
[Constitution]
First, the configuration of the communication system according to the embodiment will be described. FIG. 1 is a diagram illustrating an outline of a communication system according to an embodiment.

  The communication system 100 shown in FIG. 1 includes a first communication device 10 functioning as a master device and a plurality of second communication devices 20 functioning as slave devices, and the first communication device 10 and the plurality of second communication devices 20 is a system for performing wireless communication using radio waves as a medium. The number of the plurality of second communication devices 20 included in the communication system 100 is not particularly limited. The communication system 100 may include at least one second communication device 20.

  Further, a relay device 30 may be interposed between the first communication device 10 and the second communication device 20. In the following embodiments, an example in which the first communication device 10 and the second communication device 20 perform communication will be mainly described. However, when the first communication device 10 and the relay device 30 perform communication, and when the relay device 30 The same applies to the case where the second communication device 20 performs communication. That is, in the following embodiments, one of the first communication device 10 and the second communication device 20 may be replaced with the relay device 30.

  The communication system 100 is used, for example, as a security system installed in a building such as a house. In this case, the first communication device 10 is, for example, a gateway device, and the second communication device 20 is, for example, an alarm (more specifically, a fire alarm). Note that the communication system 100 may be used as a system other than the security system. For example, the first communication device 10 may be a HEMS (Home Energy Management System) controller, and the second communication device 20 may be a device to be controlled by the HEMS controller. Thus, the use of the communication system 100 is not particularly limited.

  The first communication device 10 functions as a master device that manages communication synchronization in the communication system 100. Specifically, the first communication device 10 includes a power supply circuit 11, a first communication unit 12, a first control unit 13, a first storage unit 14, and a first clock unit 15.

  The power supply circuit 11 converts AC power obtained from the system power supply 40 into DC power suitable for the operation of the first communication device 10. The DC power output from the power supply circuit 11 is used for the operations of the first communication unit 12, the first control unit 13, and the first storage unit 14. The power supply circuit 11 is specifically realized by an inverter circuit, a DC-DC converter circuit, and the like.

  The first communication unit 12 is a wireless communication circuit that allows the first communication device 10 to perform wireless communication with the second communication device 20 or the relay device 30 using radio waves. The communication standard of the wireless communication performed by the first communication unit 12 is not particularly limited. The first communication unit 12 is controlled by, for example, the first control unit 13.

  The first control unit 13 performs various types of information processing related to wireless communication. The first control unit 13 is realized by, for example, a microcomputer or a processor. The first control unit 13 has a first setting unit 13a.

  The first storage unit 14 is a storage device in which a control program executed by the first control unit 13 is stored. The first storage unit 14 is realized by, for example, a semiconductor memory.

  The first clock unit 15 is a clock circuit for synchronizing communication. The first timing unit 15 may be included in the first control unit 13.

  The second communication device 20 functions as a child device in the communication system 100. Specifically, the second communication device 20 includes a battery 21, a second communication unit 22, a second control unit 23, a second storage unit 24, a clock unit 25, and a temperature sensor 26.

  The battery 21 is used as a power source of the second communication device 20. The battery 21 is a primary battery such as an alkaline dry battery or a manganese dry battery, but may be a secondary battery such as a lithium ion battery.

  The second communication unit 22 is a wireless communication circuit that allows the second communication device 20 to perform wireless communication with the first communication device 10 or the relay device 30 using radio waves. The communication standard of the wireless communication performed by the second communication unit 22 is not particularly limited. The second communication unit 22 is controlled by, for example, the second control unit 23.

  The second control unit 23 performs various information processing related to wireless communication. The second control unit 23 is realized by, for example, a microcomputer or a processor. The second control unit 23 has a second setting unit 23a.

  The second storage unit 24 is a storage device that stores a control program executed by the second control unit 23. The second storage unit 24 is realized by, for example, a semiconductor memory.

  The second timer 25 is a timer circuit that measures time. The second clock unit 25 may be included in the second control unit 23.

  The temperature sensor 26 is a sensor device that measures the temperature around the crystal oscillator included in a clock circuit (not shown) used for synchronizing communication. The temperature sensor 26 is realized by, for example, a thermistor, but may be realized by another temperature measuring element such as a thermocouple. Further, a temperature sensor built in the second control unit 23 may be used as the temperature sensor 26.

[Operation and problems of general communication system]
Next, the operation of a general communication system will be described. FIG. 2 is a time chart for explaining the operation of a general communication system. In the following description of the operation of a general communication system, the communication system 100 performs the same operation as a general communication system.

  As described above, the first communication device 10 operates with the AC power supplied from the system power supply 40, whereas the second communication device 20 operates with the battery 21. The first communication device 10 constantly performs an operation of receiving a radio wave (in other words, a signal) transmitted by the second communication device 20, whereas the second communication device 20 suppresses consumption of the battery 21. Next, the receiving operation of the radio wave transmitted by the first communication device 10 is intermittently performed.

  First, the first communication unit 12 of the first communication device 10 transmits a beacon signal for synchronizing communication (S11 in FIG. 2). The beacon signal is transmitted periodically, such as once a day. When the second communication unit 22 of the second communication device 20 receives the beacon signal transmitted by the first communication unit 12 (S12), a predetermined interval (for example, an interval of 10 seconds) based on the timing of receiving the beacon signal. To confirm the reception of the radio wave (S13). The reception confirmation of the radio wave is performed, for example, based on a comparison between a received signal strength indication (RSSI: Received Signal Strength Indication) of the radio wave and a threshold. In radio wave reception confirmation, it is determined in a short time whether only a radio wave is received or not, and substantial reception of a frame included in the radio wave is not performed.

  When it is determined in the reception confirmation that the radio wave has been received, the second communication unit 22 starts the reception operation aiming at the next radio wave transmission timing (in other words, the retransmission timing of the radio wave) (S14). The reception operation means that a frame included in a radio wave is substantially received (for example, signal processing is performed), and is different from radio wave reception confirmation.

  By the way, the first communication unit 12 of the first communication device 10 needs to perform carrier sensing before transmitting a radio wave of a specific frequency band (for example, a 920 MHz band). Carrier sensing is a process of determining whether the frequency band of the radio wave to be transmitted is being used by another system. The first communication unit 12 can transmit the radio wave only when the carrier sense is successful (that is, when the frequency band of the radio wave to be transmitted is not used by another system). Radio waves cannot be transmitted.

  Carrier sensing is performed every time radio waves are transmitted. Then, when the receiving operation of the second communication unit 22 is performed, the first communication unit 12 may fail the carrier sense (S15), and the radio wave may not be retransmitted. Then, the receiving operation of the second communication unit 22 fails, and the second communication unit 22 starts over from receiving confirmation (S16). When the reception operation fails as described above, there is a problem that current consumption (in other words, power consumption) increases. Another problem is that the responsiveness of the second communication device 20 is reduced.

[Operation of Communication System According to Embodiment]
The operation of the communication system 100 in consideration of such a problem will be described. FIG. 3 is a time chart for explaining the operation of the communication system 100.

  In the operation illustrated in FIG. 3, the transmission time of radio waves by the first communication unit 12 of the first communication device 10 (hereinafter, also referred to as a frame length) is relatively long. In addition, the second communication unit 22 of the second communication device 20 starts the receiving operation immediately after the elapse of the standby period shorter than the predetermined interval at which the reception confirmation is performed. That is, the second communication unit 22 starts the receiving operation during transmission of the radio wave (frame) whose reception has been confirmed. In other words, during transmission of one frame, both reception confirmation and reception operation are performed on the frame. The length of the waiting period is, for example, 5 ms, and is determined in advance. The length of the waiting period is equal to or longer than 0 second, but may be longer than 0 second.

  In such an operation of the communication system 100, after the reception is confirmed, the carrier sense is not performed before the reception operation is started. Therefore, the failure of the receiving operation due to the carrier sense failure of the first communication device 10 is suppressed, and the increase in the current consumption of the second communication device 20 and the decrease in the responsiveness of the second communication device 20 are suppressed.

  Here, the format of the frame will be described. FIG. 4 is a diagram showing a format of a frame. FIG. 4 also shows a period Tc required for reception confirmation and a standby period Tw when the data length of the frame is converted into time.

  The frame includes a preamble, a unique word, a destination address, a source address, data, and a check code.

  The preamble is an area located at the beginning of the frame for establishing bit synchronization. In the operation shown in FIG. 3, for example, the frame is extended by extending the preamble length. In order to achieve bit synchronization, the receiving operation needs to be started in the middle of the preamble. Therefore, the preamble length is such that the period required for receiving the preamble is longer than the total period of the period Tc (for example, 100 μs) required for the second communication device 20 to confirm reception and the waiting period Tw (for example, 5 ms). Is determined. In other words, the reception time when the preamble length is converted to the reception time is longer than the total period of the period Tc and the waiting period Tw. For example, when the preamble length is 200 bytes and the bit rate is 100 kbps, the period required for receiving the preamble (in other words, the reception time) is 200 × 8 bits / 100 k = 16 ms. The clock circuit of the second communication device 20 may advance to the plus side or return (delay) to the minus side than the clock circuit of the first communication device 10 due to factors such as the temperature characteristics of the crystal oscillator. is there.

  The unique word is an area for the second communication device 20 to determine whether the frame needs to be continuously received (whether the frame is a frame intended for the communication system 100). The unique word has a data length of, for example, 2 bytes.

  The destination address and the source address are areas for the second communication device 20 to determine whether or not the frame is addressed to itself. If the second communication device 20 determines that it is not the destination, it stops receiving. Each of the destination address and the source address has a data length of, for example, 4 bytes.

  Data is data to be transmitted in a frame. The data is, specifically, an encryption key or a command. The data has, for example, a data length of 1 to 240 bytes or less. If a common rule is applied to the first communication device 10 and the second communication device 20, the data may be encrypted or may be protected by scrambling.

  The check code is an area for a CRC (Cyclic Redundancy Check). The check code has a data length of, for example, 2 bytes.

  Note that, in addition to the above, a front part (header) and a rear part (trailer) of data may be added to the frame. Further, the data may be divided on the transmission side. The divided data is combined on the receiving side, for example.

[Details of Operation of Communication System According to Embodiment]
Next, the operation of the second communication device 20 shown in FIG. 3 will be described in detail with reference to a flowchart. FIG. 5 is a flowchart of the operation of the second communication device 20.

  First, the second communication unit 22 receives a beacon signal for synchronizing communication from the first communication device 10 (S21). The second control unit 23 determines whether it is a reception confirmation timing based on the timing at which the beacon signal is received (S22). Specifically, the second control unit 23 uses the second clock unit 25 to determine whether it is the reception confirmation timing. As described above, the reception confirmation timing comes at a predetermined interval (for example, every 10 seconds). The determination whether or not the reception confirmation timing is continued until the reception confirmation timing comes (No in S22).

  When the second control unit 23 determines that it is the reception confirmation timing (Yes in S22), the second control unit 23 causes the second communication unit 22 to perform reception confirmation (S23). If no radio wave is received in the reception confirmation by the second communication unit 22 (No in S23), it is determined whether or not it is the reception confirmation timing (S22).

  When a radio wave is received in the reception confirmation by the second communication unit 22 (Yes in S23), the second control unit 23 measures the standby period Tw (for example, 5 ms) using the second clock unit 25 (S24). Then, the second communication unit 22 starts the receiving operation immediately after the elapse of the waiting period Tw (S25). That is, the waiting period Tw is a period from the end of the reception confirmation to the start of the reception operation.

[Setting example 1 of waiting period]
The waiting period Tw is, for example, determined in advance, but may be set by the second setting unit 23a included in the second communication device 20. Hereinafter, setting example 1 of the standby period Tw by the second setting unit 23a will be described.

  The second setting unit 23a sets the waiting period Tw based on the length of the period Ts (shown in FIG. 4) from the start of the receiving operation to the end of the reception of the unique word, for example. It should be noted that the receiving operation can be determined to be successful at the timing when the unique word has been received. In other words, the period Ts is, in other words, a period from the start of the receiving operation to the time when it is determined that the receiving operation is successful.

  For example, it is assumed that the length of the period Ts from the start of the reception operation in the first reception operation to the end of the reception of the unique word is 2 ms. In this case, in the second reception operation performed after the first reception operation, the length of the period Ts in the first reception operation is used as a predicted value. That is, in the second receiving operation, the period Ts is predicted to be 2 ms. When the measured value of the period Ts is 5 ms in the second reception operation, the difference between the predicted value (Ts = 2 ms) and the measured value (Ts = 5 ms) is 3 ms, and the timing shift is increased in the direction in which the period Ts increases. It can be said that it has occurred.

  In this case, the second setting unit 23a extends the waiting period Tw immediately before the third reception operation performed next to the second reception operation. The second setting unit 23a extends, for example, the waiting period Tw by about 1 ms. The extension amount of the waiting period Tw may be within a range of 3 ms or less. If the waiting period Tw is extended, the time of the receiving operation is shortened, so that current consumption can be reduced.

  As described above, the second setting unit 23a sets the waiting period Tw of the next reception operation based on the difference between the predicted value and the actually measured value during the period Ts from the start of the reception operation to the time when the reception operation is determined to be successful. Can be set. In other words, the difference between the predicted value and the measured value is the difference between the measured values in the period Ts in the two immediately preceding reception operations (the amount of change in the period Ts).

  In the second receiving operation, if a timing shift occurs in a direction in which the period Ts decreases, the second setting unit 23a shortens the standby period, for example. In the setting example 1, the second setting unit 23a may delay the reception confirmation timing while keeping the length of the waiting period Tw. For example, the second setting unit 23a may delay the reception confirmation timing within a range of 3 ms or less.

[Setting example 2 of waiting period]
Further, a time limit (for example, 10 ms) may be provided from the start of the receiving operation to the end of the reception of the unique word. The receiving operation is determined to have failed.

  In the second receiving operation, it is assumed that the period Ts is predicted to be 2 ms, but the receiving operation has failed (that is, the unique word has not been received even after the time limit has elapsed). In this case, it is considered that a timing shift occurred in a direction in which the start of the second receiving operation was delayed by 2 ms or more from the first time, and the unique word could not be normally received (that is, the start of the receiving operation was delayed).

  In this case, the second setting unit 23a shortens the waiting period Tw immediately before the third reception operation performed next to the second reception operation. The second setting unit 23a reduces the waiting period Tw from 5 ms to 0 ms, for example. Thus, it is possible to prevent the third reception operation from failing.

  As described above, the second setting unit 23a can reduce the standby period when confirming reception of a radio wave under a predetermined condition. The predetermined condition includes that it is determined that the immediately preceding reception operation has failed. The predetermined condition may be another condition, for example, as long as the condition increases the possibility that the reception operation will fail.

  FIG. 6 is a flowchart of a setting operation in which the setting examples 1 and 2 described above are integrated. The second setting unit 23a determines whether the receiving operation is successful (S31). If the second setting unit 23a determines that the receiving operation is successful (Yes in S31), the predicted value and the measured value of the period Ts are determined. A standby period for the next reception operation is set based on the difference (S32). On the other hand, if the second setting unit 23a determines that the reception operation has been successful (No in S31), the second setting unit 23a shortens the waiting period of the next reception operation (S33). Reducing the waiting period Tw includes eliminating the waiting period Tw.

[Setting example 3 of waiting period]
As described above, in the communication system 100, communication synchronization is adjusted by the beacon signal. It is considered that the longer the period after the beacon signal is received, the greater the synchronization shift.

  For example, when the beacon signal is transmitted every 24 hours, it is considered that the synchronization deviation at the timing one hour after the reception of the beacon signal is relatively small, and the synchronization deviation at the timing 23 hours after the reception is small. As the synchronization shift increases, the possibility that the reception operation fails will increase.

  Therefore, the second setting unit 23a may set the standby period Tw based on the elapsed time from the reception of the beacon signal to the confirmation of the reception of the radio wave (that is, the reception confirmation timing). FIG. 7 is a flowchart of a setting example 3 of such a waiting period Tw. The second setting unit 23a measures the elapsed period using the second timer unit 25 (S41), and sets the standby period Tw based on the measured elapsed period (S42). The second setting unit 23a, for example, sets the standby period Tw shorter as the elapsed period becomes longer.

  For example, when the period from when a beacon signal is received to when the next beacon signal is received is divided into three periods: a first period, a middle period, and a second period, the second setting unit 23a determines that the reception confirmation timing belongs to the first period. In this case, the standby period Tw is set to 5 ms. When the reception confirmation timing belongs to the middle period, the standby period Tw is set to 3 ms. When the reception confirmation timing belongs to the latter period, the standby period Tw is set to 1 ms. Thereby, it is possible to suppress the reception operation from failing.

[Setting example 4 of waiting period]
One of the causes of the communication synchronization deviation is a temperature characteristic of a crystal oscillator included in a clock circuit (not shown) used for synchronizing the communication. Therefore, the second setting unit 23a may set the waiting period Tw based on the temperature information acquired from the temperature sensor 26.

[Setting example 1 of preamble length]
The preamble length is, for example, constant (e.g., 150 Bytes (equivalent to 12 ms)), but may be set by the first setting unit 13a included in the first communication device 10. FIG. 8 is a flowchart of a preamble length setting example 1.

  For example, the preamble required for the second communication device 20 when the second communication device 20 is registered in the communication system 100 or when the second communication device 20 is activated (when the power is turned on). The information indicating the length is transmitted to the first communication device 10. That is, the preamble length is notified in advance (prior declaration) from the second communication device 20 to the first communication device 10.

  The first communication unit 12 of the first communication device 10 receives the information indicating the preamble length (S51), and the first setting unit 13a performs the operation based on the information received by the first communication unit 12 from the second communication device 20. The preamble length is set (S52).

  The preamble length required for the second communication device 20 depends on the hardware performance of the second communication device 20 and the like. Therefore, when the communication system 100 includes a plurality of second communication devices 20, the preamble length may be different for each of the plurality of second communication devices 20. Therefore, the first setting unit 13a sets the preamble length for each of the plurality of second communication devices 20 based on the information received from each of the plurality of second communication devices 20.

[Setting example 2 of preamble length]
As described above, in the communication system 100, synchronization of communication is adjusted by the beacon signal. It is considered that the longer the period after the beacon signal is received, the greater the synchronization shift.

  For example, when the beacon signal is transmitted every 24 hours, it is considered that the synchronization deviation at the timing one hour after the reception of the beacon signal is relatively small, and the synchronization deviation at the timing 23 hours after the reception is small. As the synchronization shift increases, the possibility that the reception operation fails will increase.

  Therefore, the first setting unit 13a may set the preamble length based on the elapsed time from the reception of the beacon signal to the transmission of the radio wave (frame) (that is, the transmission timing of the frame). FIG. 9 is a flowchart of such a preamble length setting example 2. The first setting unit 13a measures the elapsed period (S61), and sets the preamble length based on the measured elapsed period (S62). For example, the first setting unit 13a sets the preamble length to be longer as the elapsed period becomes longer.

  For example, if the period from when a beacon signal is received to when the next beacon signal is received is divided into three periods, a first period, a middle period, and a second period, the first setting unit 13a sets the frame transmission timing to the first period. If so, the preamble length of the frame is set to 4 ms; if the transmission timing of the frame belongs to the middle period, the preamble length of the frame is set to 7 ms; if the transmission timing of the frame belongs to the latter period, the frame Is set to 12 ms. Thereby, it is possible to suppress the reception operation from failing.

[Effects]
As described above, the second communication device 20 confirms reception of a radio wave at predetermined intervals based on the reception timing of a beacon signal for synchronizing communication, and when a radio wave is received in the reception confirmation, a predetermined And a second communication unit 22 that performs a receiving operation after a standby period shorter than the interval has elapsed.

  Such a second communication device 20 can prevent the reception operation from failing by hastening the start of the reception operation. For example, if the reception operation is started during transmission of a radio wave (frame) targeted for reception confirmation, the failure of the reception operation due to carrier sense failure is suppressed, the current consumption of the second communication device 20 increases, and A decrease in responsiveness of the second communication device 20 is suppressed.

  In addition, for example, the second communication device 20 further includes a second setting unit 23a that sets the standby period Tw.

  Such a second communication device 20 can set the waiting period Tw.

Further, for example, the second setting unit 23a sets the standby period Tw of the next reception operation based on the difference between the predicted value and the measured value from the start of the reception operation to the time when the reception operation is determined to be successful. The second communication device 20 sets the standby period Tw of the next reception operation based on the difference between the predicted value and the actually measured value from the start of the reception operation to the time when the reception operation is determined to be successful. can do.

  Further, for example, the second setting unit 23a sets the standby period Tw based on the elapsed period from the reception of the beacon signal to the confirmation of the reception of the radio wave.

  Such a second communication device 20 can suppress the failure of the reception operation by shortening the standby period Tw when the synchronization deviation is considered to increase.

  Further, for example, the second setting unit 23a sets the standby period Tw based on the information acquired from the temperature sensor 26.

  In such a second communication device 20, for example, the standby period Tw can be set in consideration of the temperature characteristics of the crystal oscillator included in the clock circuit used for synchronizing the communication.

  Further, for example, when the second setting unit 23a confirms reception of a radio wave under predetermined conditions, the second setting unit 23a shortens the waiting period Tw.

  Such a second communication device 20 can suppress the failure of the reception operation if the predetermined condition is such that the possibility of the failure of the reception operation increases.

  Further, for example, the predetermined condition includes that it is determined that the receiving operation performed before the receiving operation is unsuccessful.

  Such a second communication device 20 can suppress the failure of the receiving operation.

  In addition, the first communication device 10 includes a first communication unit 12 that transmits a beacon signal for synchronizing communication to the second communication device 20. The first communication unit 12 transmits to the second communication device 20 a frame having a preamble length in which the period required for reception is longer than the total period of the period Tc required for reception confirmation and the standby period Tw. The second communication device 20 is an example of another communication device.

  Such a first communication device 10 can suppress a failure in the reception operation by transmitting a frame in which the preamble length is determined so as to be subjected to both the reception confirmation and the reception operation. If the failure of the receiving operation is suppressed, an increase in current consumption of the second communication device 20 and a decrease in responsiveness of the second communication device 20 are suppressed.

  Further, for example, the first communication device 10 further includes a first setting unit 13a for setting a preamble length.

  Such a first communication device 10 can set a preamble length.

  Further, for example, the first setting unit 13a sets the preamble length based on the elapsed time after transmitting the beacon signal.

  Such a first communication device 10 can suppress the failure of the receiving operation by extending the preamble length when it is considered that the synchronization shift becomes large.

  In addition, for example, the first setting unit 13a sets the preamble length based on information received by the first communication unit 12 from the second communication device 20.

  Such a first communication device 10 can set the preamble length based on the information received from the second communication device 20.

  Further, for example, the first setting unit 13a sets a preamble length for each of the plurality of second communication devices 20.

  Such a first communication device 10 can set different preamble lengths for a plurality of second communication devices 20.

  Further, the communication system 100 includes a second communication device 20 and a first communication device 10.

  Such a communication system 100 can suppress the failure of the receiving operation. If the failure of the receiving operation is suppressed, an increase in current consumption of the second communication device 20 and a decrease in responsiveness of the second communication device 20 are suppressed.

  A communication method executed by a computer such as the second communication device 20 performs reception confirmation of radio waves at predetermined intervals based on the reception timing of a beacon signal for synchronizing communications, and the radio wave is received in the reception confirmation. Then, after a standby period shorter than a predetermined interval has elapsed, the receiving operation is performed.

  With such a communication method, it is possible to prevent the reception operation from failing by hastening the start of the reception operation. For example, if the reception operation is started during transmission of a radio wave (frame) targeted for reception confirmation, the failure of the reception operation due to carrier sense failure is suppressed, the current consumption of the second communication device 20 increases, and A decrease in responsiveness of the second communication device 20 is suppressed.

  The communication method executed by the computer such as the first communication device 10 transmits a beacon signal for synchronizing communication to the second communication device 20, and a total period of a period required for reception confirmation and a period required for reception operation A frame having a preamble length that requires a longer period of time for reception is transmitted to the second communication device 20.

  Such a communication method can suppress a failure in the reception operation by transmitting a frame in which the preamble length is determined so as to be subjected to both the reception confirmation and the reception operation. If the failure of the receiving operation is suppressed, an increase in current consumption of the second communication device 20 and a decrease in responsiveness of the second communication device 20 are suppressed.

(Other embodiments)
The embodiments have been described above, but the present invention is not limited to the above embodiments.

  For example, in the above embodiment, a process performed by a specific processing unit may be performed by another processing unit. For example, a part or all of the information processing performed by the control unit (including the setting unit) in the above embodiment may be performed by the communication unit.

  Further, the order of the processing described in the flowchart of the above embodiment is an example. The order of the plurality of processes may be changed, and the plurality of processes may be executed in parallel.

  Further, in the above embodiment, each component may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

  Further, each component may be realized by hardware. For example, each component may be a circuit (or an integrated circuit). These circuits may constitute one circuit as a whole, or may be separate circuits. Each of these circuits may be a general-purpose circuit or a dedicated circuit.

  Further, general or specific aspects of the present invention may be realized by a recording medium such as a system, an apparatus, a method, an integrated circuit, a computer program, or a computer-readable CD-ROM. Further, general or specific aspects of the present invention may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

  For example, the present invention may be realized as a program for causing a computer to execute a communication method. Further, the present invention may be realized as a non-transitory computer-readable recording medium on which such a program is recorded.

  Further, in the above embodiment, the communication system is realized by a plurality of devices, but may be realized as a single device. When the communication system is realized by a plurality of devices, the components included in the electric lock control system may be distributed to the plurality of devices in any manner.

  In addition, a form obtained by performing various modifications conceivable by those skilled in the art to each embodiment, or realized by arbitrarily combining components and functions in each embodiment without departing from the spirit of the present invention. Embodiments are also included in the present invention.

Reference Signs List 10 first communication device 12 first communication unit 13a first setting unit 20 second communication device 22 second communication unit 23a second setting unit 26 temperature sensor 100 communication system

Claims (17)

The reception confirmation of the radio wave is performed at a predetermined interval based on the reception timing of the beacon signal for synchronizing the communication, and when the radio wave is received in the reception confirmation, a standby period shorter than the predetermined interval has elapsed. A communication device including a communication unit that performs a receiving operation later. The communication device according to claim 1, further comprising a setting unit that sets the standby period. The setting unit sets the standby period of the next reception operation based on a difference between a predicted value and an actually measured value during a period from the start of the reception operation to the time when the reception operation is determined to be successful. The communication device according to claim 1. The communication device according to claim 2, wherein the setting unit sets the standby period based on an elapsed period from reception of the beacon signal to confirmation of reception of the radio wave. The communication device according to any one of claims 2 to 4, wherein the setting unit sets the standby period based on information acquired from a temperature sensor. The communication device according to any one of claims 2 to 5, wherein the setting unit shortens the standby period when confirming reception of the radio wave under a predetermined condition. The communication device according to claim 6, wherein the predetermined condition includes a determination that a reception operation performed before the reception operation has failed. A communication unit that transmits a beacon signal for synchronizing communication to another communication device,
The other communication device performs radio wave reception confirmation at predetermined intervals based on the reception timing of the received beacon signal, and when the radio wave is received in the reception confirmation, a predetermined standby period shorter than the predetermined interval. Performs reception operation after elapse of
The communication device, wherein the communication unit transmits, to the other communication device, a frame having a preamble length in which a period required for reception is longer than a total period of the reception confirmation period and the standby period. The communication device according to claim 8, further comprising a setting unit that sets the preamble length. The communication device according to claim 9, wherein the setting unit sets the preamble length based on an elapsed time after transmitting the beacon signal. The communication device according to claim 9, wherein the setting unit sets the preamble length based on information received by the communication unit from the another communication device. The communication device according to any one of claims 9 to 11, wherein the setting unit sets the preamble length for each of the plurality of other communication devices. A communication device according to any one of claims 1 to 7,
A communication system comprising: the communication device according to claim 8. Check the reception of radio waves at predetermined intervals based on the reception timing of the beacon signal for synchronizing communication,
A communication method for performing a receiving operation after a standby period shorter than the predetermined interval has elapsed when the radio wave is received in the reception confirmation.   A program for causing a computer to execute the communication method according to claim 14. Send a beacon signal to the communication device to synchronize communication,
The communication device performs radio wave reception confirmation at predetermined intervals based on the reception timing of the received beacon signal, and when a radio wave is received in the reception confirmation, a predetermined standby period shorter than the predetermined interval elapses. After that, perform the receiving operation,
A communication method for transmitting, to the communication device, a frame having a preamble length in which a period required for reception is longer than a total period of the period required for the reception confirmation and the period required for the reception operation.   A program for causing a computer to execute the communication method according to claim 16.

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