JP6417119B2 - Wireless network system - Google Patents

Description

  The present invention relates to a wireless network system and a node device used therefor. In particular, the present invention relates to a wireless network system capable of efficiently transmitting data without securing useless data transmission pause time even if there is a restriction on data transmission time from the node device, and a node device used therefor .

Conventionally, various wireless network systems that include a plurality of nodes connected to a plurality of user devices by wires and perform wireless communication between the plurality of nodes have been proposed (see, for example, Patent Documents 1 to 3).
These wireless network systems are easy-to-install and flexible networks that can easily handle installation, movement, and increase / decrease of user devices compared to systems that are all connected by wire. It is expected to be applied to so-called smart grids that are used as quantity meters.

  For wireless communication between nodes in the wireless network systems described in Patent Documents 1 to 3, a wireless communication standard conforming to IEEE 802.15.4 using the 2.4 GHz band, which is a frequency band that can be commonly used in the world, is used. ing. However, from the viewpoints of radio wave reachability, power consumption, and coherence, it is preferable to use a wireless communication standard that conforms to IEEE 802.15.4 g / e using the 920 MHz band. In other words, the 920 MHz band has a longer radio wave reach than the 2.4 GHz band. In addition, even when there are obstacles such as buildings, it has a high characteristic that radio waves wrap around and reach. This is suitable for use in a case where a long communication distance is required or in a place where there are many obstacles. Moreover, since the reach of radio waves is long in the 920 MHz band, the transmission output can be lowered compared to the 2.4 GHz band when communicating at the same distance. For this reason, power consumption is low. Furthermore, the 920 MHz band can provide a stable system because there are few other wireless network systems that use this frequency band, such as a wireless LAN, and there is little radio wave interference from various noise sources.

However, in IEEE 802.15.4 g / e using the 920 MHz band, unlike IEEE 802.15.4 using the 2.4 GHz band, an upper limit value of data transmission time per unit time is defined. Specifically, it is specified that only a data transmission time within 6 minutes per hour can be secured (the remaining 54 minutes are set as a data transmission pause time).
In order to satisfy the constraint on the data transmission time in the 920 MHz band, for example, as shown in FIG. 1, it is conceivable to provide the data transmission time and the data transmission pause time at a constant ratio of 1: 9.

JP2012-39182A JP 2013-74355 A JP 2010-74356 A

  However, in the data transmission control method as shown in FIG. 1, since the data transmission time and the data transmission suspension time are provided at a constant ratio of 1: 9, as a result of securing a useless data transmission suspension time, data transmission is performed. Performance may be degraded. For example, since data reception from user devices is concentrated in a specific 6 minutes in one hour, even if it is desired to concentrate data transmission from a node that has received this data, data transmission as shown in FIG. In the control method, after data transmission, a data pause time that is nine times the data transmission time is ensured. For this reason, even if continuous data transmission is performed without pausing normally, the data transmission performance is reduced by ensuring useless data transmission pausing time despite satisfying the constraints in the 920 MHz band. Resulting in.

  The present invention has been made in view of the above-described conventional technology, and even if there is a restriction on the data transmission time from the node device, the data transmission can be efficiently performed without securing a wasteful data transmission pause time. It is an object of the present invention to provide a possible wireless network system and a node device used therefor.

In order to solve the above problem, the present invention provides, as a first means, a wireless network system including a plurality of nodes and performing wireless communication between the plurality of nodes, wherein at least one of the plurality of nodes In the node device that is a node, a transmission allowable size that means the size of data that can be transmitted from the node device is stored in an updatable manner, and a predetermined data transmission time and data transmission pause time per unit time are stored. The node device compares the size of the data received from the external device with the current allowable transmission size, and determines the size of the data received from the external device. When the current transmission allowable size is not larger than, the received data is transmitted, and the size of the transmitted data from the transmission allowable size Subtract, count the elapsed time from the transmission of the data to the next reception of data from the external device, convert the counted elapsed time to a data size according to the data transmission rate, The data size is added to the transmission allowable size, updated and stored, and if the size of the data received from the external device is larger than the current transmission allowable size, the elapsed time since the reception of the data is counted, The counted elapsed time is converted into a data size corresponding to the data transmission rate, and the converted data size is added to the transmission allowable size to be updated and stored, and the received data size is transmitted after the update storage. If the size is less than the allowable size, the received data is transmitted, and the size of the transmitted data is subtracted from the allowable transmission size, and the data is transmitted. The elapsed time from when the data is received to the next external device is counted, the counted elapsed time is converted into a data size corresponding to the data transmission rate, and the converted data size is set to the transmission allowable size. Provided is a wireless network system characterized in that addition is performed for update storage.

  According to the wireless network system according to the first means of the present invention, the node device stores the transmission allowable size, which means the size of data that can be transmitted from the node device, in an updatable manner, and is a predetermined unit. A data transmission rate, which means a ratio between the data transmission time per hour and the data transmission suspension time, is stored. The predetermined ratio between the data transmission time per unit time and the data transmission suspension time is, for example, a ratio of 1: 9 that satisfies the constraint condition regarding the data transmission time in the 920 MHz band.

Then, the node device compares the size of the data received from the external device (meaning a user device such as a watt hour meter or other node) with the current allowable transmission size, and according to the result, The operation of either (1) or (2) is executed.
(1) When the size of the data received from the external device is equal to or smaller than the current allowable transmission size When the size of the data received from the external device is equal to or smaller than the current allowable transmission size, the node device immediately transmits the received data. That is, when the size of data received from the external device is equal to or smaller than the transmission allowable size, it is determined that data transmission is possible, and the received data is transmitted to another node. Further, the node device subtracts the size of the transmitted data from the allowable transmission size. That is, the transmission allowable size is reduced by the amount of the transmitted data size. In addition, the node device counts the elapsed time from data transmission until the next data reception from the external device, and converts the counted elapsed time into a data size that can be actually transmitted according to the data transmission rate. . Specifically, by multiplying the elapsed time by the data transfer rate, the data size when data is continuously transmitted within the elapsed time can be calculated. Of these, the data size that can be actually transmitted is the data transmission rate. It depends on. For example, if the data transmission ratio is 1: 9, the actually transmittable data size is 1/10 of the data size calculated by multiplying the elapsed time and the data transfer rate. In this way, the node device converts the counted elapsed time into a data size that can be actually transmitted according to the data transmission rate. Further, the node device adds the converted data size to the allowable transmission size and updates and stores it. The updated transmission allowable size is compared with the size of the data received from the external device next, and if the size of the received data is equal to or smaller than the current transmission allowable size (update stored allowable transmission size), the node The device will repeat the same procedure as above. On the other hand, when the size of the received data is larger than the current allowable transmission size, the node device executes the procedure (2) described later.

(2) When the size of the data received from the external device is larger than the current allowable transmission size When the size of the data received from the external device is larger than the current allowable transmission size, the node device immediately receives the received data. Do not send. That is, if the size of data received from the external device is larger than the current allowable transmission size, it is determined that data transmission is impossible, and the received data is paused without being immediately transmitted. Then, the node device counts the elapsed time since the data was received, and converts the counted elapsed time into a data size that can be actually transmitted according to the data transmission rate. The specific contents of the conversion procedure are the same as those described above in (1). Further, the node device adds the converted data size to the allowable transmission size and stores the updated data, and transmits the received data when the size of the received data is equal to or smaller than the allowable transmission size after the update storage. That is, if the size of the received data is equal to or smaller than the transmission allowable size after update storage, it is determined that data transmission is possible, the hibernation state is stopped, and the received data is transmitted to another node. . The subsequent operation is the same as that described in (1). That is, the node device subtracts the size of the transmitted data from the transmission allowable size (transmission allowable size after update storage), and counts the elapsed time from when the data is transmitted until the next data is received from the external device. The counted elapsed time is converted into a data size that can be actually transmitted according to the data transmission rate, and the converted data size is added to the transmission allowable size and updated and stored. The updated transmission allowable size is compared with the size of the data received from the external device next, and if the received data size is larger than the current transmission allowable size (updated and stored transmission allowable size), the node The device will repeat the same procedure as above. On the other hand, when the size of the received data is equal to or smaller than the current allowable transmission size, the node device executes the same procedure as described above in (1).

As described above, according to the wireless network system according to the first means of the present invention, the size of the data received from the external device is compared with the current allowable transmission size, and the received data is determined according to the result. Since transmission is suspended immediately (in case (1) above) or until transmission allowable size is equal to or larger than the size of received data (in case (2) above), useless data transmission suspension time is secured. It is possible to transmit data efficiently without having to do so. Also, the transmission allowable size based on the counted elapsed time converted into the data size that can be actually transmitted according to the data transmission ratio (the ratio of the data transmission time per unit time and the data transmission pause time). Therefore, even if there is a restriction on the data transmission time, it can be expected to satisfy this.

  The “size” in the first means of the present invention and the second means to be described later is not necessarily managed in a unit representing the data capacity such as bytes, but for example, the data capacity (bytes etc.) ) Can be managed in units of time obtained by dividing the data transfer rate (kbps, etc.). That is, both the size of the data received from the external device and the current allowable transmission size are managed in time units, compared with each other, and according to the magnitude relationship, (1) and (2) described above It is also possible to switch which operation is executed.

Here, the upper limit value of the data transmission time per hour is determined as in IEEE 802.15.4 g / e using the 920 MHz band, and data is not received from the external device for a while ( The elapsed time until data is received becomes longer and the allowable transmission size becomes larger), and thereafter, there is a possibility that data is continuously received from the external device. In this case, the data transmission rate is defined so as to completely correspond to the upper limit value (for example, 6 minutes) of the data transmission time per hour when the time when the allowable transmission size becomes larger is considered in one hour. (For example, 1: 9), a situation may occur in which data is transmitted from the node device exceeding the upper limit.
For this reason, as a result of earnestly examining how to transmit data in a time that is less than or equal to the upper limit value of the determined data transmission time, the present inventors set an upper limit value for the transmission allowable size. It has been found that both the upper limit value of the allowable transmission size and the data transmission rate should be defined so as to satisfy a certain relationship.

That is, in the radio network system according to the first means of the present invention, the transmission allowable size is provided with an upper limit value that is not updated and stored beyond that, and the upper limit value of the transmission allowable size is set to D [byte]. The data transmission time determined by the data transmission rate / (data transmission time + data transmission pause time) is E [no dimension], and the data transfer rate in the wireless communication between the plurality of nodes is B [bps]. When the upper limit value of the data transmission time per hour is A [min], it is preferable to satisfy the following formula (1).

  The left side of equation (1) shows the time after receiving the data of the size corresponding to the upper limit value D from the external device and transmitting it for one hour starting from the time when the allowable transmission size reaches the upper limit value D. It means the time required when data of a predetermined size is repeatedly received and transmitted. The left side of the formula (1) is the right side of the formula (1), and is equal to or less than a predetermined upper limit value A of data transmission time per hour (for example, 6 minutes in the case of IEEE 802.15.4 g / e) As long as the upper limit value D of the transmission allowable size and E (data transmission time / (data transmission time + data transmission pause time)) determined by the data transmission rate are defined, any one hour can be determined in advance. In addition, it is possible to transmit data in a time equal to or less than the upper limit value A of the data transmission time per hour.

The node device in the first means of the present invention described above compares the size of data received from the external device (actually received data size) with the allowable transmission size (data size that can actually be transmitted). Depending on the magnitude relationship, the received data is immediately transmitted or the transmission is suspended until the transmission allowable size is equal to or larger than the received data size.
However, the present invention is not limited to this, and both the size of the data received from the external device and the allowable transmission size are converted into the data size including the data transmission pause time according to the data transmission ratio. It is also possible to adopt a configuration in which operations are switched according to the magnitude relationship.

That is, in order to solve the above-described problem, the present invention provides, as a second means, a wireless network system including a plurality of nodes and performing wireless communication between the plurality of nodes, wherein at least one of the plurality of nodes A node device that is one node stores a data transmission rate that represents a ratio between a predetermined data transmission time per unit time and a data transmission pause time, and data that can be transmitted from the node device. A transmission allowable size that means a size converted into a data size including a data transmission suspension time according to the data transmission ratio is stored in an updatable manner, and the node device stores the data received from an external device. The size converted into the data size including the data transmission pause time according to the data transmission rate, and the current transmission allowable size. Comparing the figures, the case data size after conversion of the data received from the external device is currently the following transmission allowable size, and transmits the received data, in terms of the data the transmission from the transmission allowable size Subtract the subsequent data size, count the elapsed time from the transmission of the data until the next reception of data from the external device, convert the counted elapsed time to the data size, and the converted data size Is added to the allowable transmission size and updated and stored, and if the data size after conversion of the data received from the external device is larger than the current allowable transmission size, the elapsed time since the reception of the data is counted. The calculated elapsed time is converted into a data size, the converted data size is added to the transmission allowable size, updated and stored, and the external device If the data size after conversion Shin data is decreased below the transmission permissible size after the update memory, the transmits the data received from the external device, the data size after conversion of the data the transmission from the transmission allowable size Is subtracted, and the elapsed time from the transmission of the data to the next reception of data from the external device is counted, the counted elapsed time is converted into a data size, and the converted data size is converted into the transmission allowance. It is also provided as a wireless network system characterized by being updated and stored in addition to the size.

  The wireless network system according to the second means of the present invention also provides the same operational effects as the first means described above.

Also in the wireless network system according to the second means of the present invention, the transmission allowable size is provided with an upper limit value that is not updated and stored beyond that, and the upper limit value of the transmission allowable size is set to D ′ [bytes]. The data transmission time determined by the data transmission rate / (data transmission time + data transmission pause time) is E [no dimension], and the data transfer rate in the wireless communication between the plurality of nodes is B [bps]. When the upper limit value of the data transmission time per hour is A [min], it is preferable that the following expression (2) is satisfied.

  The left side of Equation (2) shows the size corresponding to the upper limit value D ′ (the data size including the data transmission pause time) for one hour starting from the time when the allowable transmission size reaches the upper limit value D ′. It means the time required when data of a predetermined size) is received from an external device and transmitted, and then data of a predetermined size is repeatedly received and transmitted. The left side of the formula (2) is the right side of the formula (2), which is equal to or less than a predetermined upper limit value A of data transmission time per hour (for example, 6 minutes in the case of IEEE802.15.4 g / e) As long as the upper limit value D ′ of the allowable transmission size and E (data transmission time / (data transmission time + data transmission pause time)) determined by the data transmission ratio are defined, any one hour can be determined in advance. It is possible to transmit data in a time equal to or less than the upper limit value A of the data transmission time per hour.

  The wireless network system according to the present invention is particularly useful when wireless communication performed between the plurality of nodes is performed in the 920 MHz band, that is, when there is a restriction on data transmission time.

  In addition, the wireless network system according to the present invention is applicable when a plurality of nodes include nodes connected to the user apparatus by wire. For example, RS485 is used as the wired communication method.

  Furthermore, the present invention is also provided as a node device used in the wireless network system, that is, a node device having a function of a node device constituting the wireless network system (a function of executing the above-described specific transmission control method). Is done.

  The node device is particularly useful when it collects data transmitted from another node connected to the user device by wire (data acquired by the user device connected to another node). When data is received from other nodes, usually the node equipment collects data sent from other nodes in order to send transmission requests from the node equipment to other nodes first. May send many send requests. That is, since such a node device may have a high data communication frequency, it is useful to apply the node device according to the present invention having a function of executing a specific transmission control method.

  According to the present invention, there is provided a wireless network system capable of efficiently transmitting data without securing a useless data transmission pause time even if there is a restriction on data transmission time from the node device, and a node device used therefor Provided.

FIG. 1 is a time chart for explaining a data transmission control method of a node in a conventional wireless network system. FIG. 2 is a schematic configuration diagram of a wireless network system according to an embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of the node device constituting the wireless network system shown in FIG. FIG. 4 is a diagram for explaining the meaning of the expression (1) defined for the node devices constituting the wireless network system shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 2 is a schematic configuration diagram of a wireless network system according to an embodiment of the present invention.
FIG. 3 is a block diagram showing a schematic configuration of the node device constituting the wireless network system shown in FIG.
As illustrated in FIG. 2, the wireless network system 100 according to the present embodiment includes a plurality of node devices 20 that are respectively connected to a plurality of user devices 10 by wires 11 (in this embodiment, RS485 cables). Wireless communication (in this embodiment, communication using a wireless communication standard based on IEEE 802.15.4 g / e using the 920 MHz band) is performed between the node devices 20. The wireless network system 100 according to the present embodiment is a so-called multi-hop wireless network system in which adjacent node devices 20 autonomously construct a network and can easily cope with movement and increase / decrease of the node devices 20. .
In this embodiment, the user device 10 includes a plurality of measuring devices 10A such as watt hour meters and a personal computer 10B that collects and manages data measured by each measuring device 10A. Specifically, measurement data is wirelessly transmitted from the node device 20A connected to the measurement device 10A to the node device 20B connected to the personal computer 10B, and collected by the node device 20B. Conversely, appropriate control data such as a transmission request is wirelessly transmitted from the node device 20B to the node device 20A.
FIG. 2 shows a state in which wireless transmission is performed directly from each node device 20A to the node device 20B. However, the present invention is not limited to this, and other node devices 20A are relayed to the node device 20B. Wireless transmission is also possible. The same applies to the case where the node device 20B wirelessly transmits to the node device 20A.
FIG. 2 shows an example in which one node device 20A is connected to one measuring device 10A. However, the present invention is not limited to this, and one node device 20A is connected to a plurality of measuring devices 10A. The node device 20A can be shared by a plurality of measuring devices 10A.
FIG. 2 shows a state in which all the node devices 20 are connected to the user device 10. However, the present invention is not limited to this, and the node devices 20 that are not connected to the user device 10 (that is, other devices). It is also possible to include a node device 20) having only a relay function for transmitting data received from the other node device 20 to another node device 20. The node device 20 having only this relay function may be able to execute the transmission control method described later. However, this node device 20 does not receive data from the user device 10 and receives data only from other node devices 20.
Furthermore, in the present embodiment, all the nodes constituting the wireless network system 100 are the node devices 20 that can execute the transmission control method described later, but the present invention is not limited to this, and nodes with high communication frequency are used. Only the device 20B can be a node device capable of executing a transmission control method described later.

  As illustrated in FIG. 3, the node device 20 includes an RF unit 21 and an antenna 22. The RF unit 21 has a function of receiving data from the user device 10 and converting it into a radio signal. The converted radio signal is transmitted to another node device 20 through the antenna 22. Conversely, the radio signal received from the other node device 20 through the antenna 22 is converted into data by the RF unit 21 and transmitted to the user device 10 or another node device 20 as necessary.

  The RF unit 21 includes an interface 211, an MCU 212, a ROM 213, a RAM 214, a timer 215, and a wireless transmission / reception unit 216.

  The interface 211 converts the signal received from the user apparatus 10 into appropriate data (for example, 10-bit digital data) that can be processed by the MCU 212. Conversely, the data received from the MCU 212 is converted into a signal that can be received by the user apparatus 10. This interface 211 is an interface common to the communication standard of the user apparatus 10, and is an RS485 interface in this embodiment.

  The MCU 212 is a microprocessor used to execute various arithmetic control processes such as data transmission control, which will be described later, and realize the functions of the node device 20.

  The ROM 213 is a read-only memory that stores calculation control processing procedures in the MCU 212.

  The RAM 214 is a random access memory that executes data exchange for arithmetic control processing in the MCU 212.

  The timer 215 provides time data for arithmetic control processing in the MCU 212.

  The wireless transmission / reception unit 216 converts the data received from the MCU 212 into a wireless signal and transmits it to the antenna 22. Conversely, the radio signal received from the antenna 22 is converted into data.

  When the wireless network system 100 includes the node device 20 that is not connected to the user device 10 and has only a relay function, the interface 211 is not necessarily required for the node device 20.

  Hereinafter, a transmission control method of the node device 20 in the wireless network system 100 having the above-described configuration will be sequentially described.

In the RAM 214 of the node device 20, a transmission allowable size S0 that means the size of data that can be transmitted from the node device 20 is stored in an updatable manner, and a predetermined data transmission time and data transmission suspension time per unit time are stored. The data transmission ratio that means the ratio is stored.
As the initial allowable transmission size S0, a value given a constant initial value (for example, 2048 bytes) at the start of operation (when the power to the node device 20 is turned on) can be used. As the initial value, for example, an elapsed time until data is first received from the user device 10 or another node device 20 (hereinafter collectively referred to as “external device”) is predicted in advance. What is necessary is just to use what converted the estimated elapsed time into the data size which can be actually transmitted according to a data transmission ratio. Alternatively, the elapsed time from the start of operation to the first reception of data from the external device is actually counted by the MCU 212 using the time data given by the timer 215, and this counted elapsed time is actually measured according to the data transmission rate by the MCU 212. It is also possible to convert the converted data size to the initial transmission allowable size S0. Since the procedure for converting the elapsed time into a data size that can be actually transmitted according to the data transmission rate will be described later, detailed description thereof will be omitted here.
In addition, the data transmission ratio, that is, the ratio between the predetermined data transmission time per unit time and the data transmission pause time satisfies, for example, the constraint condition regarding the data transmission time in the 920 MHz band in this embodiment 1: The ratio is 9.

  Then, the MCU 212 of the node device 20 receives data from the user device 10 via the interface 211 and stores the received data in the RAM 214. Alternatively, the MCU 21 receives data from the other node devices 20 via the antenna 22 and the wireless transmission / reception unit 216 and stores the received data in the RAM 214. Further, the MCU 212 compares the size S1 of the received data with the current allowable transmission size S0 stored in the RAM 214, and performs the following operation (1) or (2) depending on the result. Run.

(1) When the size S1 of the data received from the external device is equal to or smaller than the current allowable transmission size S0 When the size S1 of the data received from the external device is equal to or smaller than the current allowable transmission size S0, the MCU 212 of the node device 20 The data received in the RAM 214 and stored in the RAM 214 is immediately transmitted via the wireless transmission / reception unit 216 and the antenna 22. That is, when the size S1 of the data received from the external device is equal to or smaller than the allowable transmission size S0, it is determined that the data can be transmitted, and the received data is transmitted to another node device 20. Further, the MCU 212 of the node device 20 subtracts the size S1 of the transmitted data from the transmission allowable size S0. That is, the transmission allowable size S0 is reduced by the amount of the transmitted data size S1. Further, the MCU 212 of the node device 20 counts the elapsed time from when the data is transmitted until the next data is received from the external device based on the time data given by the timer 215, and the counted elapsed time is stored in the RAM 214. It is converted to the data size that can be actually transmitted according to the data transmission rate. Hereinafter, this conversion procedure will be specifically described.

  First, the MCU 212 multiplies the elapsed time by a predetermined data transfer rate, and calculates the data size when data is continuously transmitted within the elapsed time. For example, if the data transfer rate is 100 kbps and the elapsed time is 100 msec, the data size when data is continuously transmitted within the elapsed time 100 msec is 1250 bytes (= 100 kbps × 100 msec). Of these, the data size that can be actually transmitted is determined by the data transmission rate. In the present embodiment, since the data transmission ratio is 1: 9, the actually transmittable data size is 1/10 of the data size calculated by multiplying the elapsed time and the data transfer rate. Accordingly, the MCU 212 converts the counted elapsed time of 100 msec into 125 bytes (= 1250 bytes × 1/10) which is a data size corresponding to the data transmission rate.

  The MCU 212 of the node device 20 adds the data size converted as described above to the transmission allowable size S0 and updates and stores it in the RAM 214. The updated transmission allowable size S0 is compared with the data size S1 received next from the external device, and the received data size S1 is equal to or smaller than the current allowable transmission size (updated stored allowable transmission size) S0. In this case, the MCU 212 repeats the same procedure as described above. On the other hand, when the size S1 of the received data is larger than the current allowable transmission size S0, the MCU 212 executes the procedure (2) described later.

(2) When the size S1 of the data received from the external device> the current allowable transmission size S0 When the size S1 of the data received from the external device is larger than the current allowable transmission size S0, the MCU 212 of the node device 20 receives Do not send the data immediately. That is, when the size S1 of the data received from the external device 10 is larger than the current allowable transmission size S0, it is determined that the data cannot be transmitted, and the received data is immediately stopped without being transmitted. Then, the MCU 212 of the node device 20 counts the elapsed time after receiving the data based on the time data given by the timer 215, and can actually transmit the counted elapsed time according to the data transmission rate stored in the RAM 214. Convert to the correct data size. The specific contents of the conversion procedure are the same as those described above in (1). Further, the MCU 212 of the node device 20 sequentially adds the converted data size to the allowable transmission size S0 and updates and stores it in the RAM 214. If the received data size S1 is equal to or smaller than the allowable transmission size S0 after the update storage, The data received and stored in the RAM 214 is transmitted. That is, if the size S1 of the received data is equal to or smaller than the allowable transmission size S0 after update storage, it is determined that data transmission is possible, the hibernation state is stopped, and the data received and stored in the RAM 214 is wirelessly transmitted. The data is transmitted to another node device 20 via the transmission / reception unit 216 and the antenna 22. The subsequent operation is the same as that described in (1). That is, the MCU 212 of the node device 20 subtracts the size S1 of the transmitted data from the transmission allowable size (transmission allowable size after update storage) S0, and after transmitting the data until the next data reception from the external device. The elapsed time is counted by the time data given by the timer 215, the elapsed time thus counted is converted into a data size that can be actually transmitted according to the data transmission rate stored in the RAM 214, and the converted data size is converted into the allowable transmission size S0. And updated and stored in the RAM 214. The updated transmission allowable size S0 is then compared with the data size S1 received from the external device, and the received data size S1 is greater than the current transmission allowable size (update stored allowable transmission size) S0. If larger, the MCU 212 repeats the same procedure as described above. On the other hand, when the size S1 of the received data is equal to or smaller than the current allowable transmission size S0, the MCU 212 executes the same procedure as described above in (1).

As described above, according to the wireless network system 100 according to the present embodiment, the data size S1 received from the external device is compared with the current allowable transmission size S0, and the received data is immediately determined according to the result. Since transmission is suspended (in the case of (1) above) or until the transmission allowable size S0 becomes equal to or larger than the received data size S1 (in the case of (2) above), useless data transmission suspension time is set. Data can be transmitted efficiently without securing. Also, the transmission allowable size based on the counted elapsed time converted into the data size that can be actually transmitted according to the data transmission ratio (the ratio of the data transmission time per unit time and the data transmission pause time). Since S0 is updated, data transmission is performed in order to perform communication using a wireless communication standard conforming to IEEE 802.15.4 g / e using the 920 MHz band between a plurality of node devices 20 as in the present embodiment. Even if there are time constraints, it can be expected to satisfy this.

However, as in this embodiment, when performing communication using a wireless communication standard based on IEEE 802.15.4 g / e using the 920 MHz band, the upper limit (6 minutes) of the data transmission time per hour is It has been established. Then, the node device 20 does not receive data from the external device for a while (therefore, the elapsed time until the data is received becomes long and the transmission allowable size S0 becomes large), and thereafter, the data is continuously received from the external device. There is also a possibility that it will be a situation to receive. In this case, when considering 1 hour starting from the time when the allowable transmission size S0 becomes larger, the data transmission rate is defined to completely correspond to the upper limit (6 minutes) of the data transmission time per hour ( In the above-described example, 1: 9) may occur, and data may be transmitted from the node device 20 exceeding the above upper limit value.
For this reason, as a result of earnestly examining how to transmit data in a time equal to or less than the upper limit value of the determined data transmission time, whichever time is taken, the present inventors have determined an upper limit value for the transmission allowable size S0. And the upper limit value of the allowable transmission size S0 and the data transmission rate should be defined so as to satisfy a certain relationship.

In other words, in the wireless network system 100 according to the present embodiment, the transmission allowable size S0 is provided with an upper limit value that is not updated and stored, and the upper limit value of the transmission allowable size S0 is D [bytes]. The data transmission time determined by the ratio / (data transmission time + data transmission suspension time) is E [dimensionless], the data transfer rate in wireless communication between a plurality of nodes is B [bps], and the data per hour determined in advance When the upper limit value of the transmission time is A [min], it is preferable that the following expression (1) is satisfied.

Hereinafter, the meaning of the formula (1) will be described in detail with reference to FIG.
FIG. 4 is a diagram for explaining the meaning of the expression (1) defined for the node devices 20 constituting the wireless network system 100.
As shown in FIG. 4, the upper limit value of the data transmission time per hour predetermined by the wireless communication standard or the like is A [min] (for example, 6 minutes), and the data transfer rate in wireless communication is B [bps]. If (for example, 100 kbps), the upper limit value C [byte] of the data transmission size per hour is represented by C = (B / 8) · A · 60.

  Next, E is data transmission time / (data transmission time + data transmission pause time) determined by the data transmission rate. For example, if the data transmission ratio is changed from 1: 9 to 1:10, E = 1 / 11≈0.0909. If the elapsed time from the transmission of data to the next reception of data from the external device is 1 second, the elapsed time of 1 second is converted to the actually transmittable data size (added to the transmission allowable size S0). Data size) F [bytes] is expressed by F = (B / 8) · E.

Here, after the node device 20 receives data of a size corresponding to the upper limit value D from the external device and transmits it for one hour starting from the time when the allowable transmission size S0 reaches the upper limit value D. , X [byte] data is repeatedly received and transmitted. That is, the following situations (a) to (d) are assumed.
(A) When the allowable transmission size S0 reaches the upper limit value D, the node device 20 receives data of a size corresponding to the upper limit value D from the external device, and immediately transmits the received data. As a result, the transmission allowable size S0 becomes 0 bytes.
(B) After transmitting data having a size corresponding to the upper limit value D, when the transmission allowable size S0 becomes X [bytes] as time elapses, the node device 20 transmits X [bytes] received from the external device. ] Data immediately. As a result, the transmission allowable size S0 becomes 0 bytes.
(C) After transmitting the data of X [bytes], when the transmission allowable size S0 becomes X [bytes] again with the passage of time, the node device 20 transmits the data of X [bytes] received from the external device. Send immediately. As a result, the transmission allowable size S0 becomes 0 bytes again.
(D) The operation of (c) is repeated for one hour starting from the time when the allowable transmission size S0 reaches the upper limit value D.

  If the time required for the allowable transmission size S0 to increase from 0 bytes to X [bytes] is G [sec], G = X / F. Further, if the time required to transmit the data of X [byte] is H [sec], it is expressed by H = X / (B / 8). Therefore, if the sum of the time required for the allowable transmission size S0 to increase from 0 bytes to X [bytes] and the time required to transmit the data of X [bytes] is I, it is expressed as I = G + H. .

  On the other hand, when the time required to transmit data having a size corresponding to the upper limit value D of the allowable transmission size S0 is M [sec], M = D / (B / 8). Then, during one hour starting from the time when the allowable transmission size S0 reaches the upper limit value D, the operation of (b) to (d) (when the allowable transmission size S0 becomes X [bytes], the external device The time during which the received X [byte] data is transmitted) is represented by 60 · 60-M [sec]. Therefore, when the data of X [bytes] is repeatedly transmitted for one hour starting from the time when the transmission allowable size S0 reaches the upper limit value D, the total of the repeated transmission data sizes is J [bytes]. J = {(60 · 60−M) / I} · X.

Accordingly, in the above-described situations (a) to (d), the total data size transmitted from the node device 20 during one hour starting from the time when the allowable transmission size S0 reaches the upper limit value D is represented by K [ Byte], K is represented by K = D + J because it corresponds to the sum of the upper limit value D of the allowable transmission size S0 and the total J of the repeated transmission data sizes. When K is converted into time and L [min], L = (K / C) · A.
If L ≦ A is satisfied, it is possible to transmit data in a time L that is not more than the upper limit value A [min] of the determined data transmission time even in the above-described situations (a) to (d). In other words, it is possible to transmit data in a time equal to or less than the upper limit value A [min] of the determined data transmission time, regardless of which one hour is taken.

  When the above L is expressed by other variables B, D, and E, it becomes equal to the left side of the above-described equation (1). For example, when A = 6 min, B = 100 kbps, D = 750 kbytes, and E = 1/11, L≈5.9, which is equal to the left side of Expression (1), satisfies Expression (1). In other words, when A = 6 min and B = 100 kbps are determined by the wireless communication standard or the like, if one sets D = 750 kbytes and E = 11/11 so as to satisfy Equation (1), which one hour The data can be transmitted in a time equal to or less than the upper limit value A (6 min) of the determined data transmission time.

In the present embodiment, an example in which both the transmission allowable size S0 and the received data size S1 are managed in units of data (bytes) is described. However, the present invention is not limited to this, and time It is also possible to manage by the unit. In this case, both the allowable transmission size S0 and the received data size S1 are managed by a value obtained by dividing the data capacity (in bytes) by the data transfer rate (100 kbps in the above example). Further, the above-described conversion procedure executed by the MCU 212 (the elapsed time from when the data is transmitted until the next data is received by the external device is counted by the time data given by the timer 215, and the counted elapsed time is stored in the RAM 214. The procedure for converting to a data size that can be actually transmitted according to the data transmission ratio is as follows.
That is, first, the MCU 212 calculates a data size when data is continuously transmitted within the elapsed time. For example, if the elapsed time is 100 msec, the data size when data is continuously transmitted within the elapsed time 100 msec is 100 msec itself. Of these, the data size that can be actually transmitted is determined by the data transmission rate. If the data transmission ratio is 1: 9, the actually transmittable data size is 1/10 of 100 msec. Accordingly, the MCU 212 converts the counted elapsed time of 100 msec into 10 msec (= 100 msec × 1/10) which is a data size corresponding to the data transmission rate.
The MCU 212 of the node device 20 adds the data size converted as described above to the transmission allowable size S0 (time unit) and updates and stores it in the RAM 214.
In the case where the transmission allowable size S0 is managed in units of time as described above, in order to transmit data in a time equal to or less than the upper limit value A (6 min) of the determined data transmission time, no matter which one hour is taken, After determining the upper limit value D of the allowable transmission size S0 that satisfies the above-described equation (1) in units of bytes, this may be divided by the data transfer rate B and set as a unit of time.

In the present embodiment, the size of data received from an external device (actually received data size) S1 is compared with the allowable transmission size (data size that can be actually transmitted) S0, and the size is determined according to the size relationship. In the above description, the received data is transmitted immediately or the transmission is paused until the transmission allowable size S0 is equal to or larger than the received data size S1, but the data size S1 received from the external device is described. The transmission allowable size S0 is converted into a data size including the data transmission suspension time according to the data transmission ratio stored in the RAM 214, and the operation is switched according to the magnitude relationship. It is also possible. Specifically, when the data transmission ratio is 1: 9, the size S1 of the data received from the external device is converted to S1 × 10, which is the data size including the data transmission suspension time when compared. . On the other hand, the allowable transmission size S0 is converted to S0 × 10 which is the data size including the data transmission suspension time, and this converted value is updated and stored as the allowable transmission size and compared with S1 × 10. .
In this case, the elapsed time from the transmission of data to the next reception of data from the external device is counted by the time data given by the timer 215, and stored in the RAM 214 when the counted elapsed time is converted into the data size. The transmitted data transmission rate is not used. This is because the transmission allowable size is updated and stored as the data size including the data transmission suspension time as described above. Specifically, for example, if the data transfer rate is 100 kbps and the elapsed time is 100 msec, the data size (byte unit) when data is continuously transmitted within the elapsed time 100 msec is 1250 bytes (= 100 kbps). × 100 msec). The data size in the case of continuous data transmission corresponds to the data size including the data transmission pause time, and the elapsed time counted by this is converted into the data size.

As described above, both the size S1 of the data received from the external device and the allowable transmission size S0 are converted into the data size including the data transmission pause time according to the data transmission ratio, and compared. Even in the case where the operation is switched according to the relationship, it is preferable to perform the following in order to transmit data in a time equal to or less than the upper limit value of the determined data transmission time, regardless of which one hour is taken. In other words, the transmission allowable size (translated transmission allowable size) S0 is provided with an upper limit value that is not updated and stored. The upper limit value of the transmission allowable size S0 is set to D ′ [bytes], depending on the data transmission ratio. Data transmission time determined / (data transmission time + data transmission pause time) is E [dimensionless], data transfer speed in wireless communication between a plurality of nodes is B [bps], data transmission time per predetermined time When the upper limit value of A is defined as A [min], it is preferable that the following expression (2) is satisfied.

  The above formula (2) differs from the formula (1) only in that D in the numerator on the left side of the above formula (1) is replaced with D ′ · E. This is because the relationship of D = D ′ · E is established between the transmission allowable size D ′ after conversion to the data size including the data transmission pause time and the transmission allowable size D before conversion, while others This is because the variables A, B, and E are not affected by the presence or absence of conversion.

10, 10A, 10B ... User device 11 ... Wired 20, 20A, 20B ... Node device 100 ... Wireless network system

Claims (8)

A wireless network system comprising a plurality of nodes and performing wireless communication between the plurality of nodes,
In the node device that is at least one of the plurality of nodes, a transmission allowable size that means the size of data that can be transmitted from the node device is stored in an updatable manner, and per predetermined unit time. The data transmission rate, which means the ratio of the data transmission time and the data transmission pause time, is stored,
The node device is
Compare the size of the data received from the external device and the current allowable transmission size,
When the size of data received from the external device is less than or equal to the current allowable transmission size, the received data is transmitted, and the size of the transmitted data is subtracted from the allowable transmission size, and the data is transmitted. The elapsed time until the next data reception from the external device is counted, the counted elapsed time is converted into a data size that can be actually transmitted according to the data transmission rate, and the converted data size is Add to the transmission allowance size and store the update,
When the size of the data received from the external device is larger than the current transmission allowable size, the elapsed time since the reception of the data is counted, and the counted elapsed time is actually determined according to the data transmission rate. Converted to a transmittable data size, added to the transmission allowable size and updated and stored the converted data size, if the size of the data received from the external device is less than or equal to the transmission allowable size after the update storage, Transmits the data received from the external device, subtracts the size of the transmitted data from the allowable transmission size, and counts the elapsed time from when the data is transmitted until the next data is received from the external device Then, the counted elapsed time is converted into a data size that can be actually transmitted according to the data transmission rate, and the converted data size is converted into the transmission permission. Wireless network system and updates stored by adding the size. The transmission allowable size is provided with an upper limit value that is not updated and stored beyond that,
The upper limit value of the allowable transmission size is D [bytes], the data transmission time determined by the data transmission ratio / (data transmission time + data transmission pause time) is E [dimensionless], and data in wireless communication between the plurality of nodes The following equation (1) is satisfied, where B is the transfer rate and B is the predetermined upper limit value of the data transmission time per hour: A [min] The wireless network system described.

A wireless network system comprising a plurality of nodes and performing wireless communication between the plurality of nodes,
The node device that is at least one of the plurality of nodes stores a data transmission rate that represents a ratio between a predetermined data transmission time and a data transmission pause time per unit time, and A transmission allowable size that means a data size that can be transmitted from the node device is converted into a data size including a data transmission suspension time according to the data transmission ratio is stored in an updatable manner,
The node device is
Compare the data size received from an external device to the data size including the data transmission pause time according to the data transmission rate, and the current allowable transmission size,
When the converted data size of the data received from the external device is equal to or smaller than the current allowable transmission size, the received data is transmitted and the converted data size of the transmitted data is subtracted from the allowable transmission size. And counting the elapsed time from the transmission of the data to the next reception of data from the external device, converting the counted elapsed time to a data size, and converting the converted data size to the allowable transmission size. Add and store updates,
When the data size after conversion of the data received from the external device is larger than the current allowable transmission size, the elapsed time since the data was received is counted, and the counted elapsed time is converted into the data size. The converted data size is added to the transmission allowable size and updated and stored, and if the converted data size of the data received from the external device is equal to or smaller than the transmission allowable size after the update storage, the external device Transmit the received data, subtract the converted data size of the transmitted data from the transmission allowable size, and count the elapsed time from the transmission of the data to the next reception of the data from the external device The calculated elapsed time is converted into a data size, and the converted data size is added to the transmission allowable size and updated and stored. Wireless network system that. The transmission allowable size is provided with an upper limit value that is not updated and stored beyond that,
In the wireless communication between the plurality of nodes, the upper limit value of the allowable transmission size is D ′ [bytes], the data transmission time determined by the data transmission ratio / (data transmission time + data transmission pause time) is E [dimensionless]. 4. The following expression (2) is satisfied, where a data transfer rate is B [bps] and a predetermined upper limit value of data transmission time per hour is A [min]. The wireless network system described in 1.

  The wireless network system according to any one of claims 1 to 4, wherein the wireless communication performed between the plurality of nodes is performed in a 920 MHz band.   6. The wireless network system according to claim 1, wherein the plurality of nodes include nodes connected to user devices by wire.   A node device used in the wireless network system according to claim 1.   The node device according to claim 7, wherein the node device collects data acquired by the user device transmitted from another node connected to the user device by wire.

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