JP2024021986A - Communication control device, communication control method and data collection system - Google Patents

Abstract

The present invention provides a communication control device, a communication control method, and a data collection system that can shift transmission timing from transmission timing of other terminal devices. A communication control device that performs calculations using division values obtained by dividing a MAC address assigned to each device, and sets transmission timing based on the calculation results. [Selection diagram] Figure 5

Description

The present invention relates to a communication control device, a communication control method, and a data collection system.

A system is known that collects sensing data measured by a sensor included in a plurality of terminal devices from a plurality of terminal devices. Such systems are used, for example, in smart grids, building lighting management, infrastructure monitoring, crime prevention systems, elderly monitoring services, smart agriculture, etc. In particular, wireless communication using sub-gigahertz frequency bands (for example, around 920 MHz) allows radio waves to propagate farther than Wi-Fi (registered trademark) or BLE (Bluetooth Low Energy), and is less susceptible to interference from obstacles. It is expected to be used in the above-mentioned system due to its advantages such as being difficult to receive radio waves and causing little radio wave interference.

In the above-described system, it is required to avoid collisions of transmitted data by shifting the transmission timing of each terminal device when collecting sensing data. For example, Patent Document 1 listed below describes a technique in which a plurality of sensors determine a delay time until data is transmitted based on MAC (Media Access Control) addresses assigned to the sensors themselves. Further, Patent Document 1 describes that the delay time is determined using a random value Rn based on random numbers, and that an individual random value Rn is calculated using all digits of the MAC address. . Further, Patent Document 1 also describes that a random value Rn is calculated from a part of the MAC address, specifically, from the lower 8 bits of the MAC address.

JP2018-197925A

However, since MAC addresses are usually assigned as consecutive numbers, the lower 8 bits of the MAC address can also be consecutive numbers or a close value. For this reason, as described in Patent Document 1, the delay time based on all digits or a part of the lower digits of the MAC address cannot sufficiently ensure the randomness of the delay time. In other words, the transmission timing cannot be sufficiently shifted. There is a risk that the transmitted data will collide.

One of the objects of the present invention is to provide a communication control device, a communication control method, and a data collection system that can shift the transmission timing between different terminal devices to a necessary and sufficient degree.

The present invention
Perform calculations using the divided values obtained by dividing the MAC address assigned to each device, and set the transmission timing based on the calculation results.
It is a communication control device.

The present invention
Perform calculations using the divided values obtained by dividing the MAC address assigned to each device, and set the transmission timing based on the calculation results.
This is a communication control method.

The present invention
multiple terminal devices;
a communication device that receives sensing data transmitted from each of the plurality of terminal devices;
has
The terminal device includes a sensor that acquires sensing data and a communication control device,
The communication control device performs calculations using the divided values obtained by dividing the MAC address assigned to each device, sets the transmission timing based on the calculation result, and sends the sensing data to the communication device at the set transmission timing. control for sending,
It is a data collection system.

FIG. 2 is a diagram to be referred to when explaining problems to be considered in the present invention. FIG. 2 is a diagram to be referred to when explaining problems to be considered in the present invention. FIG. 2 is a diagram to be referred to when explaining problems to be considered in the present invention. FIG. 1 is a block diagram illustrating a configuration example of a communication control device according to an embodiment. 3 is a flowchart showing the flow of processing performed by a communication control device according to an embodiment. It is a figure for explaining a modification. It is a figure for explaining a modification.

Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments. The explanation will be given in the following order.
<Issues to be considered in the present invention>
<One embodiment>
<Modified example>

<Issues to be considered in the present invention>
First, in order to facilitate understanding of the present invention, problems to be considered in the present invention will be explained. FIG. 1 is a diagram showing a configuration example of a data collection system (data collection system 1). The data collection system 1 includes, for example, a plurality of terminal devices 2, an aggregator 3 (an example of a communication device) wirelessly connected to the plurality of terminal devices 2, and a cloud computer CP such as a server connected to the aggregator 3. ,have. In FIG. 1, seven terminal devices (terminal devices 2A, 2B, 2C, . . . , 2G) are shown as the plurality of terminal devices 2. Note that when there is no need to distinguish between individual terminal devices, they are collectively referred to as terminal devices 2. Of course, the number of terminal devices 2 may be other than seven. In the data collection system 1 , sensing data measured by a sensor (sensor 5 described later) included in the terminal device 2 is transmitted from the terminal device 2 to the aggregator 3 . The aggregator 3 aggregates the sensing data by receiving the sensing data transmitted from each terminal device 2, and then transmits the aggregated sensing data to the cloud computer CP.

The terminal device 2 has a sensor 5. For example, the terminal device 2A has a sensor 5A, and the terminal device 2B has a sensor 5B. Examples of the sensor 5 include a temperature sensor, a humidity sensor, an acceleration sensor, an environmental sensor that measures wind, temperature, and humidity, and a biological sensor that measures biological information such as body temperature and pulse.

Each terminal device 2 has a communication function to transmit sensing data obtained by the sensor 5 to the aggregator 3. The terminal device 2 transmits sensing data to the concentrator 3 by wireless communication using a sub-gigahertz frequency band, for example. Sub-gigahertz frequency band means a frequency band below 1 GHz. The terminal device 2 periodically transmits sensing data to the aggregator 3 at predetermined time intervals, for example after startup and after the initial transmission.

The aggregator 3 is, for example, a gateway or an access point, and is a communication device that transmits sensing data transmitted from the terminal device 2 to the cloud computer CP. The aggregator 3 transmits sensing data to a cloud computer CP based on communication standards such as LTE (Long Term Evolution), 4G (4th generation mobile communication system), and 5G (5th generation mobile communication system). Send to.

The cloud computer CP performs processing using the sensing data transmitted from the aggregator 3. The content of the processing differs depending on the use of the data collection system 1.

A specific example of the data collection system 1 will be explained. The data collection system 1 may be applied to, for example, a street light condition determination system. In this example, the terminal device 2 is a street light, and the sensor 5 is an acceleration sensor. Sensing data from the acceleration sensor transmitted from the street light is transmitted to the cloud computer CP via the aggregator 3. On the cloud computer CP side, by monitoring sensing data from an acceleration sensor, it is possible to detect, for example, that a street light is tilted differently from its normal installation state. By dispatching maintenance personnel to the street light in accordance with the detection result, the street light can be maintained and inspected appropriately. Of course, this example is one specific example of the data collection system 1, and the content of the present invention is not limited to this specific example.

Wireless communication is performed between the terminal device 2 and the aggregator 3 according to a communication method based on LPWA (Low Power Wide Area). Although the transmission speed of LPWA is slower than that of cellular lines such as 3G and 4G lines and wireless LAN (Local Area Network), it can transmit over a wide range, has a narrow frequency band, and consumes extremely little power. It has characteristics. Therefore, like the data collection system 1, it is suitable for a sensor network that transmits a large number of small sensing data from multiple locations.

Communication standards based on LPWA include, for example, SIGFOX (sub-GHz band (866 MHz band, 915 MHz band, 920 MHz band) (registered trademark), maximum transmission speed is about 100 bps, transmission distance is about several tens of kilometers), LoRa (sub-GHz band) (registered trademark), Wi-Fi HaLow (sub-GHz band, maximum transmission speed is approximately 150 kbps, transmission distance is approximately 1 km), Wi-SUN (sub-GHz band, maximum transmission speed is approximately 150 kbps, transmission distance is approximately 1 km) Band, maximum transmission speed is 800 kbps, transmission distance is approximately 1 km) (registered trademark), Flexnet (280 MHz band, maximum transmission speed is 10 kbps, maximum transmission distance is approximately 20 km) (registered trademark), but is limited to these. It will not be done.

Furthermore, since a plurality of terminal devices 2 are arranged in the data collection system 1, it is desired that the terminal devices 2 not only consume low power but also be small and low in cost.

By the way, the aggregator 3 receives sensing data transmitted from a plurality of terminal devices 2, but cannot receive the plurality of sensing data at the same timing. For example, as shown in FIG. 2, if the aggregator 3 is receiving sensing data transmitted from the terminal device 2A, the aggregator 3 cannot receive sensing data transmitted from other terminal devices 2B to 2G. . In order to avoid the aggregator 3 not being able to receive the sensing data transmitted from the terminal device 2B etc., the transmission timing of the sensing data of each terminal device 2 is intentionally shifted, resulting in a collision of the transmitted sensing data. It is necessary to avoid this. Although the communication time is very short, there is a high possibility that a collision of transmitted data will occur especially when the terminal device 2 is started up, such as when the power is turned on at the same time. For example, in the case where the above-mentioned terminal device 2 is a street light, a case is assumed in which the power is turned on simultaneously from a remote location after the street light is installed. Therefore, it is particularly necessary to shift the timing of the first transmission after startup.

In order to reliably shift the transmission timing of sensing data for each terminal device 2, it is possible to generate a random number and delay the transmission timing by an amount corresponding to the random number from the reference time. For example, if the initial transmission timing can be shifted for each terminal device 2, it is possible to avoid overlapping transmission timings even if sensing data is transmitted at regular intervals thereafter. In the case of this method, each terminal device 2 is required to have an RND (Random Number Generator) function.

FIG. 3 is a flowchart showing the process of shifting the transmission timing using random numbers. In step ST1, processing for activating each terminal device 2 is performed. For example, a command is sent from a management center or the like to each terminal device 2 at the same time, and each terminal device 2 is activated simultaneously based on the command. Each terminal device 2 may have an RTC (Real Time Clock) therein, and each terminal device 2 may be activated simultaneously when the RTC reaches a predetermined time. Note that in this example, each terminal device 2 is activated at the same time, but the terminal devices 2 may be activated at different timings. The process then proceeds to step ST2.

In step ST2, the RND function of the terminal device 2 performs a process of generating a random number (unique value). The process then proceeds to step ST3.

In step ST3, the terminal device 2 determines the delay time based on random numbers. Then, the terminal device 2 sets the timing delayed by the delay time with respect to the reference time (for example, the activation timing) as the first transmission timing of the sensing data. The process then proceeds to step ST4.

In step ST4, an initial transmission process of transmitting sensing data is performed at the transmission timing set in step ST3. The process then proceeds to step ST5.

In step ST5, sensing data is periodically transmitted at fixed time intervals starting from the transmission timing set in step ST3. The certain period of time is, for example, common to each terminal device 2, and the specific period of time differs depending on the communication method. Since the first transmission timing set in step ST3 is different for each terminal device 2, there is a low possibility that the transmission timings will overlap in the process of periodically transmitting sensing data.

According to the method described above, it is possible to avoid overlapping transmission timings. However, as described above, it is desirable that the terminal device 2 used in the data collection system 1 be as low in cost as possible. That is, if the terminal device 2 is provided with an RND function, there is a possibility that the cost of the terminal device 2 will increase. In addition, for example, in a system in which each terminal device 2 starts up at the same time and thereafter periodically transmits sensing data, it is sufficient to shift the transmission timing at startup for each terminal device 2, and use random numbers to strictly control the transmission timing. There is little need to shift it. Furthermore, there is a possibility that power consumption in the terminal device 2 will increase in order to perform the process of generating random numbers. An embodiment of the present invention will be described in detail with the above points in mind.

<One embodiment>
[Example of configuration of communication control device]
FIG. 4 is a block diagram showing a configuration example of a communication control device (communication control device 10) according to this embodiment. The communication control device 10 includes, for example, an oscillator 11, a communication circuit 12, and a control circuit 13. The communication control device 10 is, for example, an ultra-small module (for example, a rectangular parallelepiped with a width and length of about 10 mm and a thickness of about several mm) in which these components are arranged closely, and is built in each terminal device 2. has been done. The oscillator 11, the communication circuit 12, and the control circuit 13 are mounted on a printed circuit board, for example. The printed circuit board may be mounted on one side or both sides, and the number of layers does not matter.

The oscillator 11 is, for example, a TCXO (Temperature Compensated Crystal Oscillator) that incorporates a temperature sensor and a temperature compensation circuit so that changes in frequency due to changes in ambient temperature are reduced. The oscillation frequency output by the oscillator 11 is input to the communication circuit 12. The oscillator 11 may be, for example, a simple packaged crystal oscillator (SPXO) that integrates a crystal resonator (not shown) and an oscillation circuit (not shown).

The communication circuit 12 is a circuit that performs wireless communication compatible with a communication method using a sub-gigahertz frequency band. The communication circuit 12 is composed of, for example, a communication IC (Integrated Circuit) such as an RFIC (Radio Frequency Integrated Circuit). The communication circuit 12 communicates with the aggregator 3 and the like via the antenna AT. The antenna AT may be a built-in antenna housed within the casing of the communication control device 10.

Specifically, the communication circuit 12 includes a first communication circuit 12A and a second communication circuit 12B. The first communication circuit 12A performs a transmission process of transmitting data (for example, sensing data) using the oscillation frequency output from the oscillator 11. The first communication circuit 12A is composed of, for example, a filter or a modulation circuit, and modulates the oscillation frequency from the oscillator 11 according to the transmission data, outputs the modulated signal (RF signal) to the antenna AT, and performs data transmission. conduct.

The second communication circuit 12B performs reception processing. The second communication circuit 12B includes, for example, a filter, a demodulation circuit, and the like, and receives an RF signal transmitted from a base station or the like via an antenna AT, demodulates the received RF signal, and obtains received data. The received data is, for example, output to the control circuit 13 and used.

The control circuit 13 is composed of, for example, a microcontroller unit (MCU) (sometimes abbreviated as a microcomputer), and controls the components constituting the communication control device 10 such as the oscillator 11 and the communication circuit 12. control. The control circuit 13 transmits and receives data to and from an external module (for example, a host control microcomputer) via an external interface. An example of this external interface is a UART (Universal Asynchronous Receiver/Transmitter). Note that the external interface may be another interface. The upper control microcomputer is connected to a sensor 5 included in the terminal device 2 . The host control microcomputer appropriately converts the sensing data measured by the sensor 5 into digital data and supplies it to the control circuit 13. The control circuit 13 transmits sensing data supplied from the host control microcomputer to the aggregator 3 via the communication circuit 12.

Further, the control circuit 13 generates a transmission timing delayed by the delay time with respect to the reference time, and sets it in an appropriate memory. In this embodiment, the reference time will be explained as being the time of startup (specifically, when the power is turned on), but it may be other than the time of startup (for example, the time of transition from the sleep state to the active state). Then, the control circuit 13 controls the communication circuit 12 to transmit the sensing data to the aggregator 3 when the current time reaches the set transmission timing. Note that a specific example of generating the transmission timing will be described later.

[Operation example of communication control device]
Next, an example of the operation of the communication control device 10 will be described with reference to the flowchart in FIG. In step ST11, the control circuit 13 performs a process of activating each part of the communication control device 10 in response to the activation of the terminal device 2. In this example, the terminal devices 2 constituting the data collection system 1 are activated simultaneously in response to remote control of each terminal device 2. Of course, each terminal device 2 may start up simultaneously by performing autonomous control. The process then proceeds to step ST12.

In step ST12, the control circuit 13 performs processing to generate random values. The process then proceeds to step ST13.

In step ST13, the control circuit 13 determines the delay time based on the random value generated in step ST12. Then, the control circuit 13 sets the timing delayed by the delay time with respect to the reference time (for example, the activation timing) as the first transmission timing of the sensing data. The process then proceeds to step ST14.

In step ST14, the control circuit 13 controls the communication circuit 12 and transmits the sensing data to the aggregator 3 at the transmission timing set in step ST13. The transmission processing here is the first transmission processing. The process then proceeds to step ST15.

In step ST15, a process of periodically transmitting sensing data is performed at fixed time intervals starting from the transmission timing set in step ST13. The fixed time is common to each terminal device 2, and the specific time differs depending on the communication method. Since the transmission timing set in step ST13 is different for each terminal device 2, there is a low possibility that the transmission timings will overlap in the process of periodically transmitting sensing data.

[Transmission timing setting process]
Next, a specific example of the process of setting the transmission timing performed in step ST13 described above will be described. For example, the control circuit 13 performs calculations using division values obtained by dividing the MAC address assigned to each device, and sets transmission timing based on the calculation results.

In this example, an IEEE (Institute of Electrical and Electronics Engineers) address (extended 64 bits) is used as an example of the MAC address, but the MAC address is not limited to this. Of the 64-bit MAC address, the upper 24 bits are a vendor identifier called OUI (Organizationally Unique Identifier), and the lower 40 bits are a number assigned by the vendor. The MAC address is stored in an appropriate memory of the terminal device 2.

(First example)
The control circuit 13 reads the 64-bit MAC address from the memory and divides it into upper 32 bits (an example of a first division value) and lower 32 bits (an example of a second division value). Then, the control circuit 13 performs an operation by multiplying the upper 32 bits by the lower 32 bits, and sets the transmission timing based on the operation result.

This will be explained using a specific example.
For example, the MAC address of terminal device 2A is 00019003000170F1
shall be.
The control circuit 13 divides the MAC address into 32 upper bits and 32 lower bits, and calculates the following equation (1) by multiplying the two to obtain a pseudo-random value.
(0x00019003 × 0x000170F1) ...Formula (1)
Furthermore, in order to keep the calculation result (pseudo-random value) of equation (1) below a certain level (to prevent the delay from becoming too large with respect to the reference time), the control circuit 13 calculates the following equation (2) as shown below. A random value is obtained by calculating & with "0x1FFF", which is an example of a mask value.
(0x00019003 × 0x000170F1) & 0x1FFFF...Formula (2)
As the calculation result of formula (2), a random value 0x192D3 (103,123)
is obtained. (The numbers in parentheses are in decimal notation.)
Here, if the random value is converted with 100 μs as the time per unit, a delay time of 10.3 seconds is obtained.
The control circuit 13 sets the timing delayed by the obtained time (10.3 s) from the startup of the terminal device 2A as the first transmission timing of the sensing data.

Enter the MAC address of another terminal device (for example, terminal device 2B) as 00019003000170F2
shall be.
The control circuit 13 divides the MAC address into the upper 32 bits and the lower 32 bits, and calculates the following formula (3) by multiplying the two to obtain a pseudo-random value.
(0x00019003 × 0x000170F2) ... Formula (3)
Furthermore, in order to keep the calculation result of equation (3) below a certain level, the control circuit 13 performs an operation of taking & with "0x1FFF", which is an example of a mask value, and generates a random value, as shown in equation (4) below. obtain.
(0x00019003 × 0x000170F2) & 0x1FFFF...Formula (4)
As the calculation result of formula (4), random value 0x122D6 (74,454)
is obtained. (The numbers in parentheses are in decimal notation.)
Here, as in the case of the terminal device 2A, if the random value is converted with 100 μs as the time per unit, a delay time of 7.4 seconds is obtained.
The control circuit 13 sets the timing delayed by the obtained time (7.4 s) from the startup of the terminal device 2B as the first transmission timing of the sensing data.

As shown in the above-described first example, the MAC addresses assigned to each terminal device 2 making up the data collection system 1 are likely to be consecutive serial numbers. Therefore, if the entire MAC address or part of the lower bits is used as is, the delay time will be approximately the same value, making it impossible to shift the transmission timing sufficiently. However, in this example, by performing an operation of multiplying the upper 32 bits and lower 32 bits of the MAC address, the transmission timing can be sufficiently shifted even if the MAC address is a serial number.
Further, since the terminal device 2 does not need to have an RND function, even a low-spec IC can be applied as the communication control device 10.

Note that in the above example, 64 bits are halved, but the number is not limited to this. For example, the data may be divided into the upper 24 bits (for example, OUI) and the lower 40 bits (MAC address assigned by the manufacturer), and an operation may be performed in which the two are multiplied. Furthermore, it is not necessary to use all 64 bits. For example, the data may be divided into upper 8 bits and lower 20 bits, and an operation may be performed in which the two are multiplied. Alternatively, the MAC address may be divided into three or more parts instead of two, and an operation may be performed in which all or some of the divided parts are multiplied together. In addition, when multiple MAC addresses are assigned to one terminal device 2, the division value obtained by dividing one MAC address and the division value obtained by dividing the other MAC address are A multiplication operation may also be performed. The multiple (for example, two) MAC addresses assigned to one terminal device 2 include the MAC address assigned by the IC vendor to the communication control device (or control circuit) at the time of shipment, and the product using the communication control device ( For example, a MAC address is numbered and assigned by a manufacturer when a communication control device using a control circuit is shipped as a product of the manufacturer.

(Second example)
The second example is an example in which the transmission timing is set based on the calculation result obtained by multiplying the division value obtained by dividing the MAC address assigned to each device by a unique value different from the MAC address. The unique value different from the MAC address is, for example, a serial number assigned to the communication control device 10. Furthermore, in this example, the lower 32 bits obtained by dividing the MAC address are used as the division value. Of course, the division value may be other than the lower 32 bits of the MAC address.

This will be explained using a specific example.
For example, the serial number of terminal device 2A is G723538.
and set the MAC address to 00019003000170F1
shall be.
The control circuit 13 obtains a pseudorandom value by multiplying the serial number and the lower 32 bits by the following formula (5).
(723538 × 0x000170F1) ...Formula (5)
Furthermore, in order to keep the calculation result of equation (5) below a certain level, the control circuit 13 performs an operation of taking & with "0x1FFF", which is an example of a mask value, and generates a random value, as shown in equation (6) below. obtain.
(723538 × 0x000170F1) & 0x1FFFF...Formula (6)
As the calculation result of formula (6), the random value 0x9732 (38,706)
is obtained. (The numbers in parentheses are in decimal notation.)
Here, if the random value is converted with 100 μs as the time per unit, a delay time of 3.8 seconds is obtained.
The control circuit 13 sets the timing delayed by the obtained time (3.8 s) from the startup of the terminal device 2A as the first transmission timing of the sensing data.

Enter the serial number of another terminal device (for example, terminal device 2B) as G926040.
and set the MAC address to 00019003000170F2
shall be.
The control circuit 13 obtains a pseudorandom value by multiplying the serial number and the lower 32 bits by the following formula (7).
(92640 × 0x000170F2) ...Formula (7)
Furthermore, in order to keep the calculation result of equation (7) below a certain level, the control circuit 13 performs an operation of taking & with "0x1FFF", which is an example of a mask value, and generates a random value, as shown in equation (8) below. obtain.
(92640 × 0x000170F2) & 0x1FFFF...Formula (8)
As the calculation result of formula (8), the random value 0x530 (1,328)
is obtained. (The numbers in parentheses are in decimal notation.)
Here, if the random value is converted with 100 μs as the time per unit, a delay time of 0.1 s is obtained.
The control circuit 13 sets the timing delayed by the obtained time (0.1 s) from the startup of the terminal device 2B as the first transmission timing of the sensing data.
Even in the second example shown above, the same effects as in the first example described above can be obtained.

[About mask value]
Next, the mask value used in the above calculation will be explained. Communication in the 920MHz band depends on the purpose and protocol used.
・Communication time per transmission ・Interval for each communication (maximum delay value based on the interval (maximum delay time))
are very different. Therefore, in this embodiment, a mask value is determined based on one transmission time, time per unit, interval for each communication, and maximum delay time for the interval in the communication protocol.

(First example)
In the first example, a case will be described in which the communication protocol is SIGFOX (registered trademark). SIGFOX (registered trademark) is a low-spec, simple communication standard specialized for sensor networks. The main communication specifications of SIGFOX (registered trademark) are:
・Communication time per transmission: Approximately 6 seconds (transmitted 3 times (approximately 2 seconds) while hopping the frequency)
・Interval between each communication: Once every 10 minutes at the shortest (SIGFOX (registered trademark) has a maximum of 140 transmissions per day according to the contract)

Here, assuming that one transmission is always made within 30% of the interval for each communication,
Maximum delay time is 3 minutes (10 minutes x 0.3)
becomes.
If one communication time in one transmission is defined as time per unit,
Time per unit: 2 seconds (6 seconds ÷ 3 times)
becomes.
In this case, the setting range of the random value (value before conversion in time per unit) is:
180 seconds (maximum delay time) ÷ 2 seconds (time per unit) = 90
That is, a random value is set in the range of 0 to 90. That is, a 7-bit mask value is used to keep the random value within that range.
In the case of SIGFOX (registered trademark), since one transmission is long, one unit time is long, and the upper limit of the random value is set low. In SIGFOX (registered trademark), communication is performed three times by frequency hopping, so there is a high possibility that collision of transmitted data can be avoided even if random values overlap. Therefore, even if the random value is set low, collisions of transmitted data can be avoided.

(Second example)
This example is an example of using a unique communication protocol that has not been standardized.
The communication protocol is
Communication speed: 100bps
Carrier sense: None/Duty within 1% (Carrier sense means detecting the carrier wave (carrier) before starting transmission, and if another terminal device is using its own channel, it will detect the carrier wave on the same frequency. It is a mechanism to avoid interference by not transmitting. Also, duty means the total amount of time that radio waves can be emitted. Usually, it means the maximum amount of time that radio waves can be emitted per hour. In other words, duty 1% means that the total transmission time is 36 seconds/hour (36 seconds per hour (3600 seconds x 0.01) or less).
Communication time per transmission: approximately 20ms Interval: approximately once every 5 minutes Maximum delay time: 30 seconds (assuming one transmission within 10% of the interval)
Time per unit: 20ms (in this example, equal to the communication time per transmission)
In this case, the random value setting range is
30000ms (maximum delay time) ÷ 20ms (time per unit) = 1500
That is, a random value is set in the range of 0 to 1500. An 11-bit mask value is used to bring the random value within the range.
Since the communication time per transmission is short, the setting range of random values is expanded to some extent in order to reliably avoid collisions of transmitted data.

(Third example)
This example is an example of using a unique communication protocol that has not been standardized. The difference from the second example is that there is a carrier sense.
Time per unit: 1 ms (In this example, while assuming that carrier sense can avoid simultaneous transmission timing collisions, the minimum shift range is set to avoid transmission timings from being exactly the same. (In other words, the time per unit is set to a value smaller than the communication time per transmission (about 20 ms).)
In this case, the setting range of the random value (value before conversion in time per unit) is:
30000ms (maximum delay time) ÷ 1ms (time per unit) = 30000
That is, a random value is set in the range of 0 to 30,000. A 15-bit mask value is used to bring the random value within the range.
By setting the time per unit even shorter than the second example described above, the range of random values can be expanded. For example, when many terminal devices 2 (sensors 5) are installed in the data collection system 1, the range of random values can be expanded by setting the time per unit, and the transmission timings may overlap. It can effectively prevent it from being put away.

The first to third examples explained above are summarized as follows.
・1 transmission time = a
・Time per unit = b
・Interval for each communication = c
- Maximum delay time = d (d = c * x%) Be sure to transmit within x% of c.
The above are the parameters.

<Condition 1; When a≦b>
Let n be the upper limit of a natural number of 2 or more that satisfies "b×n≦d".
(n: upper limit for the number of times one transmission is communicated within an interval)

<Condition 2; In the case of a system with no carrier sense where b<a>
m is a natural number of 2 or more that satisfies "a≦b×m",
(m: value to be multiplied to make the time longer than 1 transmission time the repetition unit time)
Let n be the upper limit of a natural number of 2 or more that satisfies "(b×m)×n≦d."

<Condition 3: For a system with carrier sense where b<a>
Let n be the upper limit of a natural number of 2 or more that satisfies "b×n≦d".
(n: upper limit for the number of times one transmission is communicated within an interval)
Even if the delay time deviates only within one transmission time, direct collision of transmitted data can be avoided by performing carrier sensing.

In the above conditions 1, 2 and 3,
"Pseudo-random value" is a value that is expressed as a binary number, and uses the same number of digits as the number of digits of the value expressed as a binary number, starting from the lowest bit, as a "pseudo-random value". Mask and get a random value.

[Effects obtained by this embodiment]
According to this embodiment described above, the following effects can be obtained.
It becomes possible to reliably shift the transmission timing between different terminal devices, and it is possible to avoid collisions of transmission data. Furthermore, in a system where each terminal device starts up at the same time, it is possible to reliably shift the timing of the first transmission after starting up. Therefore, when transmitting sensing data at regular intervals after the first transmission, it is possible to reliably shift not only the first transmission but also subsequent transmission timings.
Since the RND function is not required, the communication control device can be configured using an inexpensive IC, and the cost of the communication control device can be reduced. Furthermore, power consumption in the communication control device can be reduced.
In addition, the optimal mask value can be set according to the communication protocol and system configuration according to the relationship between 1 transmission time, time per unit, interval for each communication, and maximum delay time, resulting in optimal transmission. It is possible to set the timing.

<Modified example>
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the embodiments described above, and various modifications can be made based on the technical idea of the present invention.

[Modification 1]
As shown in FIG. 6, the communication control device 10 may include a higher-level control microcomputer (high-level control microcomputer 40) connected to the control circuit 13 and a sensor 41 connected to the higher-level control microcomputer 40. The sensor 41 may be one sensor or may include a plurality of sensors. The host control microcomputer 40 supplies sensing data detected by the sensor 41 to the control circuit 13. The control circuit 13 transmits sensing data received from the host control microcomputer 40 to the aggregator 3 by controlling the communication circuit 12 . Further, in the case of the configuration shown in FIG. 6, the host control microcomputer 40 may calculate the transmission timing by performing the calculation described in the embodiment, and may set the transmission timing in the control circuit 13. The control circuit 13 may transmit the sensing data received from the host control microcomputer 40 to the aggregator 3 at a set transmission timing. According to this modification, since the higher-level control microcomputer 40 performs the calculation, processing can be sped up.

Furthermore, in the configuration shown in FIG. 6, part of the series of calculations may be performed by the host control microcomputer 40, and the remaining calculations may be performed by the control circuit 13. For example, the host control microcomputer 40 may perform calculations up to multiplication by a mask value, and the control circuit 13 may calculate the delay time by converting the calculation result in terms of time per unit. Alternatively, the host control microcomputer 40 may perform calculations to obtain mask values, the control circuit 13 may perform calculations using the mask values, and obtain the delay time based on the calculation results.

[Modification 2]
As shown in FIG. 7, the control circuit 13 may be connected to the sensor (sensor 42) without the host control microcomputer. The sensor 42 may be one sensor or may include a plurality of sensors. In the configuration shown in FIG. 7, the control circuit 13 directly controls the sensor 42. That is, the control circuit 13 transmits the sensing data received from the sensor 42 to the aggregator 3 at the transmission timing set by itself. According to this modification, since there is no host control microcomputer, the communication control device 10 can be made smaller and the cost can be reduced.

[Other variations]
In the embodiment described above, each terminal device performs the calculation, but rather than all terminal devices, a specific one or more terminal devices 2 perform the calculation after acquiring the division value and serial number. You may also do this. Then, the transmission timing based on the calculation result may be set for the corresponding terminal device.

The configuration, method, process, shape, material, numerical value, etc. of the embodiment described above can be combined or replaced with each other without departing from the gist of the present invention. Furthermore, it is also possible to divide one item into two or more items, and it is also possible to combine two or more items into one item. Furthermore, it is also possible to omit some of them.

Further, the communication control device according to the embodiment or the modified example is, for example, a configuration of an electronic device such as a computer, an imaging device, a clock, a display device, a medical device, a mobile object such as a vehicle, an aircraft, a ship, a base station, etc. It may also be used as a component.

1... Data collection system 2... Terminal device 5, 41, 42... Sensor 10... Communication control device 12... Communication circuit 13... Control circuit 40... Upper control microcomputer

Claims (12)

Perform calculations using the divided values obtained by dividing the MAC address assigned to each device, and set the transmission timing based on the calculation results.
Communication control device. setting the transmission timing based on a calculation result obtained by multiplying a first division value and a second division value obtained by dividing the MAC address;
The communication control device according to claim 1. setting the transmission timing based on a calculation result obtained by multiplying the division value by a unique value different from the MAC address;
The communication control device according to claim 1. The unique value is a serial number assigned to each device,
The communication control device according to claim 3. setting the transmission timing based on a calculation result obtained by multiplying the calculation result by a predetermined mask value that makes the calculation result below a certain level;
The communication control device according to claim 1. Determining a delay time by converting the calculation result multiplied by the mask value in terms of time per unit, and setting the timing delayed by the delay time with respect to the reference time as the transmission timing.
The communication control device according to claim 5. The mask value is determined based on one transmission time, one unit of time, an interval for each communication, and a maximum delay time for the interval.
The communication control device according to claim 5. performing control for transmitting predetermined sensing data at the set transmission timing;
A communication control device according to any one of claims 1 to 7. transmitting the predetermined sensing data by wireless communication using a sub-gigahertz frequency band;
The communication control device according to claim 8. Perform calculations using the divided values obtained by dividing the MAC address assigned to each device, and set the transmission timing based on the calculation results.
Communication control method. multiple terminal devices;
a communication device that receives sensing data transmitted from each of the plurality of terminal devices;
has
The terminal device includes a sensor that acquires the sensing data and a communication control device,
The communication control device performs calculation using division values obtained by dividing the MAC address assigned to each device, sets transmission timing based on the calculation result, and transmits the sensing data to the transmission timing at the set transmission timing. Performs control for sending to a communication device,
Data collection system. The plurality of terminal devices are activated simultaneously in response to remote control for each terminal device,
The data collection system according to claim 11.

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