JP2024018255A - Wireless equipment, network system, control method - Google Patents

Abstract

An object of the present invention is to perform flexible communication while suppressing memory usage. [Solution] A wireless device constituting a wireless mesh network to which message packets are transferred includes a communication control unit that performs communication control, a transmission unit that transmits message packets, a reception unit that receives message packets, and a communication control unit that performs communication control. a storage unit in which information regarding the radio field strength of another wireless device that is a transmission target is stored as a transfer table; Transfer is performed using unicast communication in descending order of strength of wireless devices. [Selection diagram] Figure 4

Description

The present invention relates to the field of ad hoc networks that communicate via multiple wireless devices.

Ad-hoc networks have been attracting attention in recent years. An ad hoc network is a network in which multiple wireless devices are scattered within an area, and when wireless devices located at a distance where direct communication cannot be performed, communicate via other wireless devices. . Such a network is called a multihop network.
Routing methods and flooding methods are typical communication methods in multi-hop networks.

When a routing method is adopted, for example, each wireless device is provided with a routing table, and communication is performed by determining a communication route according to the routing table.
However, in the routing method, since the wireless device to be relayed when transmitting a message packet is determined in advance, it is difficult to add a new wireless device or change the transfer route due to a failure of a wireless device.

Therefore, a more flexible communication method is desired.
Patent Document 1 listed below proposes a method in which broadcast communication is switched to unicast communication each time a packet is transmitted, and a transfer table is updated each time communication is performed.

JP 2017-060034 Publication

However, in the transfer table used in Patent Document 1, a record is generated for each combination of a source address (the address of the wireless device that first transmitted the information) and a destination device address (the address of the device that is the final destination). Therefore, as the number of devices and wireless devices increases, the data size increases, leading to larger memories and larger wireless devices.

On the other hand, since wireless devices are placed in various locations due to diversification of uses, there is a demand for miniaturization of wireless devices.

The present invention has been made in view of such problems, and an object of the present invention is to perform flexible communication while suppressing memory usage.

A wireless device according to the present invention is a wireless device that configures a wireless mesh network to which message packets are transferred, and includes a communication control section that performs communication control, a transmission section that transmits message packets, and a reception section that receives message packets. and a storage section in which information about the radio field strength of another wireless device to which the message packet is transmitted is stored as a transfer table, and the communication control section transfers the received message packet to the other wireless device. When transferring data to a wireless device, data is transferred using unicast communication in order from the wireless device with the highest radio field strength.
Therefore, instead of using a routing method that uses a routing table etc. to determine the transfer route in advance when transmitting a message packet, the information in the transfer table stored in the storage unit is used to send and transmit message packets according to the communication situation at the time. Transfer takes place.

A network system according to the present invention is a network system configured by a plurality of wireless devices, and each wireless device includes a communication control unit that performs communication control, a transmitter that transmits message packets, and a transmitter that receives message packets. The communication control unit includes a receiving unit and a storage unit in which information about the radio field strength of another wireless device to which the message packet is transmitted is stored as a transfer table, and the communication control unit transfers the received message packet to the other wireless device. When transferring to a device, the wireless device uses unicast communication to perform the transfer in order from the wireless device with the highest radio field strength.

The control method according to the present invention includes a communication control unit that performs communication control, a transmission unit that transmits message packets, a reception unit that receives message packets, and the radio field strength of another wireless device to which the message packets are transmitted. As a control method for a wireless device equipped with a storage unit that stores information about information as a transfer table, when forwarding a received message packet to another wireless device, unicast communication is performed in order from the wireless device with the highest radio field strength. It is used to perform the transfer.
The above-mentioned effects can also be obtained by such a network system and control method.

According to the present invention, flexible communication can be performed while suppressing memory usage.

1 is a diagram showing an overview of a wireless mesh network. FIG. 2 is a block diagram of a wireless device. FIG. 3 is a diagram for explaining main items included in a message packet. FIG. 3 is a diagram showing an example of a transfer table. FIG. 3 is a diagram showing an example of received packet history. 7 is a flowchart illustrating an example of a process executed when a wireless device is added. 3 is a flowchart illustrating an example of transfer table update processing. 3 is a flowchart illustrating an example of processing executed when a search packet is received. 3 is a flowchart illustrating an example of processing executed when generating and transmitting a message packet. 3 is a flowchart illustrating an example of a process executed when a message packet is received.

Hereinafter, embodiments will be described in the following order.
<1. Wireless device configuration>
<2. Packet structure>
<2-1. Message packet>
<2-2. Acknowledgment packet>
<2-3. Search packet>
<3. Data stored in the storage section>
<3-1. Transfer table>
<3-2. Received packet history>
<3-3. Setting data>
<4. Flowchart＞
<4-1. Adding a wireless device>
<4-2. Receiving search packet>
<4-3. Sending message packet>
<4-4. Transferring message packets>
<5. Modified example>
<6. Summary>

<1. Wireless device configuration>
A wireless device according to an embodiment will be described below with reference to the drawings.
FIG. 1 is a diagram showing the concept of a wireless mesh network.
The wireless mesh network in FIG. 1 is composed of eight wireless devices A to H. The wireless devices A to H are capable of direct communication with other wireless devices located within their respective communication ranges (hereinafter referred to as within the communication range). The communication distance of the wireless devices A to H is, for example, several tens of meters (meters) or several hundred meters.

When transmitting information from one wireless device to another wireless device located outside of communication range, the information is transmitted via several wireless devices. For example, in FIG. 1, when transmitting information from wireless device A to wireless device H, the information is transmitted via wireless devices D and F. At this time, the wireless devices D and F perform a transfer process to transfer the received data to other wireless devices.

Note that the number of wireless devices constituting the wireless mesh network is not limited to eight. Further, in the following description, an example is shown in which the wireless devices are fixed at respective positions, but some or all of the wireless devices may be mobile.

The frequency bands used in the wireless mesh network are, for example, around frequencies such as 429 MHz (megahertz), 920 MHz, 1.2 GHz (gigahertz), 2.4 GHz, 5 GHz, and 6 GHz.

FIG. 2 is a block diagram of wireless device 100. Each of the wireless devices A to H in FIG. 1 has the configuration shown in FIG. 2.
The wireless device 100 includes a communication control section 100a, a transmission section 100b, a reception section 100c, a storage section 100d, an interface section 100e, a power supply section 100f, and an antenna section 100g.
The communication control unit 100a includes, for example, a central processing unit, and performs processing for creating message packets, processing for reading the header portion of received message packets, and processing for forwarding them depending on the situation, and processing for creating a forwarding table. Performs generation processing (or update processing), etc. That is, the communication control unit 100a performs overall control of the wireless device 100.

The transmitter 100b and the receiver 100c are configured as, for example, an IC (Integrated Circuit). Note that the transmitter 100b and the receiver 100c may be configured as one IC. In this case, the IC has a modulation section, a power amplification section, a high frequency amplification section, and a demodulation section integrated into one.
The transmitter 100b executes a process of transmitting the message packet passed from the communication controller 100a to another wireless device 100.
The receiving unit 100c receives a message packet transmitted from another wireless device 100, and performs a process of passing the message packet to the communication control unit 100a.

The storage unit 100d is configured with a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and the communication control unit 100a transfers various programs and setting data executed by the communication control unit 100a and message packets. A forwarding table for determining the destination is stored.
The storage unit 100d also stores message packets received from other wireless devices 100 as received packet history.
The forwarding table and received packet history will be described later.

The storage unit 100d also functions as a work area when the communication control unit 100a executes various processes.

The interface unit 100e receives information to be transmitted to another wireless device from an external device such as a sensor device. The interface unit 100e employs, for example, asynchronous serial communication (RS232C). Note that the interface section is not limited to wired connection and may be compatible with short-range wireless communication.

The power supply section 100f supplies power to each section of the wireless device 100 (for example, the communication control section 100a, the transmission section 100b, the reception section 100c, the storage section 100d, the interface section 100e, the antenna section 100g, etc.). The power supply unit 100f is, for example, a lithium ion battery or a dry battery.

In the embodiment described below, an example will be described in which the device 1 is connected to the wireless device A by wire. The device 1 is a device that does not have a wireless function, and is, for example, a measuring device such as a thermometer, a pressure gauge, or a flow meter, or a control device that performs some kind of output.
Similar to wireless device A, device 2 is connected by wire to wireless device B, device 3 is connected to wireless device C by wire, device 4 is connected to wireless device D by wire, and device 5 is connected to wireless device E by wire. is connected by wire. Regarding other wireless devices, some devices are also connected by wire.
Note that a wireless mesh network may be configured including a wireless device that only performs transfer without being connected to any device, or a wireless device that has two or more devices connected by wire.

<2. Packet structure>
Next, packets flowing on the wireless mesh network in this embodiment will be explained with reference to FIG. 3.
Note that the acknowledgment packet will hereinafter be referred to as an ACK (Acknowledgement) packet.

<2-1. Message packet>
The structure of the message packet is shown in FIG. Note that Figure 3 is an excerpt of only the main parts of the message packet structure, and the actual message packet includes a preamble area, synchronization code area, control data area, etc. in addition to the areas shown in Figure 3. It consists of

The message packet has each area including a message area (information that the user wants to send), and is repeatedly sent/forwarded from the source wireless device to the target device (for example, the wireless device 100 to which the measuring device is connected). etc.). In the following description, the wireless device 100 that generates a message packet and transmits it first will be referred to as the "transmission source wireless device 100." The wireless device 100 that becomes the final destination will be referred to as the "destination wireless device 100." Further, a wireless device 100 that receives a message packet and transfers it to another wireless device 100 is referred to as a "transfer source wireless device 100," and a wireless device 100 to which the message packet is transferred is referred to as a "transfer destination wireless device 100." ”.

The source address area stores a unique value (hereinafter referred to as "device address") for identifying the wireless device 100 that is the source. This value is, for example, any value from 0 to 239, and a different value is assigned to each wireless device 100.

In this embodiment, one digit in decimal notation is expressed as one byte in areas other than the message area in a message packet. For example, for "239" in decimal notation, "2" is expressed as a 1-byte binary number, "3" is expressed as a 1-byte binary number, and "9" is expressed as a 1-byte binary number. 000000100000001100001001" is stored in the source address area.

By representing each digit in decimal notation as a binary number of 1 byte in this manner, it is possible to simplify the display of message packet data using terminal software or the like.

The destination address area stores a device address for specifying the wireless device 100, which is the final destination.
Although the device address is assumed here to be assigned to the wireless device 100, the device address may be assigned not only to the wireless device 100 but also to devices connected by wire to the wireless device 100.

The transfer source address area stores a device address for identifying the transfer source wireless device 100. Note that when a wireless device transfers a received message packet to another wireless device, the device address of the wireless device is stored in the transfer source address area. Note that the transfer source address field is not essential in the message packet, and the transfer source address field may not be provided.

The transfer destination address area stores a device address for specifying the transfer destination wireless device 100. When performing unicast communication with a designated transfer destination, the device address of the transfer destination wireless device 100 is stored in the transfer destination address area. In addition, when performing broadcast communication without specifying a forwarding destination, the forwarding destination address field contains information indicating that the forwarding is not intended for a specific wireless device 100 (for example, "255" in decimal notation). Store.

The TTL (Time To Live) area is an area in which a value for determining the upper limit of the wireless devices 100 relayed when data is delivered from the source wireless device 100 to the destination wireless device 100 is stored.

The numerical value stored in the TTL area is decremented by 1 each time the transfer is repeated, and finally becomes "0". The wireless device 100 that receives a message packet in which "0" is stored in the TTL field discards the message packet without forwarding it.
This avoids or suppresses message packet congestion.

The sequential number area stores a serial number (sequential number) given to each message packet generated by the transmitter wireless device 100. Specifically, "1" is stored in the sequential number field of the message packet first generated by wireless device A. "2" is stored in the sequential number field of the next message packet generated by wireless device A.

The sequential number is incremented from 1 to 256, for example, and then returns to 1 again.

The message byte number area stores a value representing the amount of data stored in the message area in number of bytes.

The message area is an area where user data is stored, such as sensor values obtained by sensor equipment.

A CRC (Cyclic Redundancy Check) area stores a redundancy code for detecting errors in data other than the CRC area. Note that a redundant code for detecting only errors in user data may be stored in the CRC area.
Furthermore, the CRC area may store an error check code other than CRC using, for example, BCC (Block Check Character). That is, the method of error checking (error correction) does not matter.

<2-2. Acknowledgment packet>
The ACK packet is a packet that the wireless device 100 that has received the transferred message packet etc. transmits to the transfer source wireless device 100, and notifies that the transferred message packet has been received.

The structure of the ACK packet is, for example, a structure in which the message area in FIG. 3 is omitted from the message packet. Illustrations are omitted.

<2-3. Search packet>
The search packet is a packet that the new wireless device 100 transmits at the installation location when the new wireless device 100 is added to the wireless mesh network. The search packet is transmitted to nearby wireless devices 100 using broadcast communication.

The structure of the search packet is similar to that of the message packet shown in FIG. Then, "255" representing broadcast communication is stored in the transfer destination address area. Further, the message area stores data in which each character of "SEARCH" indicating that the packet is a search packet is expressed as a 1-byte character code, and "6" is stored in the message byte number area.

Surrounding wireless devices 100 that have received the search packet return an ACK packet and add the wireless device 100 to a transfer table, which will be described later, as appropriate depending on the radio field strength at the time of receiving the search packet.
This makes it possible to transmit message packets via the newly added wireless device 100.

<3. Data stored in the storage section>
<3-1. Transfer table>
The transfer table stored in the storage unit 100d of the wireless device 100 will be explained with reference to FIG. 4.
The forwarding table contains the device address for identifying the nearby wireless device 100 that is the target of the forwarding, and the received signal strength indicator (RSSI) value measured when a packet is received from the nearby wireless device 100. ) are stored in association with each other.

As an example, FIG. 4 shows a transfer table stored in the storage unit 100d of the wireless device D shown in FIG. 1.

Up to five nearby wireless devices 100 are registered in the forwarding table. Further, in the transfer table, data is stored in order of increasing RSSI value, that is, in order of increasing radio field strength.

In the example shown in FIG. 4, the wireless device 100 having the highest radio field strength in communication with the wireless device D is the wireless device B (device address=002), and its RSSI value is −75 dBm.

The wireless device 100 with the second highest radio field strength is wireless device A (device address=001), and its RSSI value is −77 dBm.

Furthermore, the wireless device 100 with the third highest radio field strength is wireless device E (equipment address = 005), and its RSSI value is -82 dBm, and the wireless device 100 with the fourth highest radio field strength is wireless device F (device address = 005). Address=006), and its RSSI value is −83 dBm.The wireless device 100 with the fifth highest radio field strength is wireless device C (device address=003), and its RSSI value is −89 dBm.

Note that the maximum number of wireless devices 100 is not necessarily registered in the transfer table. For example, there may be a case where there are only three wireless devices 100 in the vicinity. Also, wireless devices 100 whose RSSI value is less than a threshold (for example, −90 dBm) are not registered in the forwarding table because there is a high possibility that they will not be able to perform good wireless communication.

When transferring a message packet, the wireless device 100 performs the transfer using unicast communication to all the wireless devices 100 stored in the transfer table. Then, the transfer process is performed in order from the wireless device 100 with the highest RSSI value.

In the example shown in FIG. 4, when the received message packet is not addressed to the wireless device D, the wireless device D first transfers the message packet to the wireless device B by unicast communication.

Next, the wireless device D transfers the message packet to the wireless device A using unicast communication, and further transfers the message packet to the wireless device E using unicast communication.

In this way, transfer processing using unicast communication is also performed for wireless device F and wireless device C.

<3-2. Received packet history>
The storage unit 100d of the wireless device 100 stores a history of message packets received to avoid or suppress congestion.

In the received packet history, the entire message packet may be stored. In this embodiment, in order to reduce the storage capacity of the storage unit 100d, only the source address and sequential number in the message packet are stored.

The number of message packets stored as the received packet history is preferably determined from the viewpoints of both the storage capacity of the storage unit 100d and the avoidance of congestion. Here, the number of message packets stored in the storage unit 100d is assumed to be ten.

An example of the received packet history stored in the storage unit 100d of the wireless device D is shown in FIG.

The table shown in FIG. 5 is a history of message packets received by the wireless device D, and the higher the data in the table, the older the message packet. The message packets stored in the received packet history are message packets that have already been transferred by the wireless device D. The wireless device D determines whether or not the newly received message packet can be transferred by comparing the newly received message packet with the information in the received packet history.

Focusing on a message packet in which wireless device A with a device address of "001" is the sender wireless device 100, four histories are stored in the received packet history shown in FIG. 5.

After receiving the message packet generated by the wireless device A with the sequential number "254", the wireless device D receives message packets with the sequential numbers "255" and "256", and then, A message packet whose sequential number is "001" is being received.

In this way, the sequential number returns to "001" after "256".

By setting the maximum value of the sequential number to a somewhat large number, it takes time for the sequential numbers to go through one round, so it is possible to reduce the possibility that different message packets will be mistakenly judged as the same and discarded. .

<3-3. Setting data>
The storage unit 100d of the wireless device 100 also stores setting data for suitably communicating using the wireless mesh network.

Here, as part of the setting data, the own station address, the number of retransmissions, the search packet transmission interval, the RSSI threshold, and the TTL value will be explained.

The setting data for the local station address is assigned a different value for each wireless device 100, and has the same meaning as the device address described above.

The setting data for the number of retransmissions specifies the number of times a message packet is retransmitted when an ACK packet transmitted from the destination wireless device 100 cannot be confirmed when the message packet is transmitted using unicast communication. This is what I did. The number of retransmissions is used not only when retransmitting message packets, but also when transferring received message packets.

By setting a value of 1 or more as the number of retransmissions, it is possible to increase the possibility that the message packet will reach the destination wireless device 100. Note that the configuration may be such that retransmission is performed one more time than the value set as the setting data for the number of retransmissions. Thereby, even if "0" is set, retransmission is performed at least once, so it is possible to improve the possibility that the message packet will reach the target wireless device 100.

The search packet transmission interval setting data is a setting for periodic transmission of search packets. For example, the unit of the setting data is "time", and if "1" is set, a search packet is transmitted by broadcast communication to surrounding wireless devices 100 every hour.

Note that when "0" is set as the search packet transmission interval, it is treated as a setting in which search packets are not periodically transmitted. That is, the search packet transmission interval setting data is also used to set whether or not to periodically transmit search packets.

In the RSSI threshold setting data, a threshold value for determining whether or not to register surrounding wireless devices 100 in the transfer table is set.

In the TTL value setting data, a numerical value to be stored in the TTL area of the message packet is set. The TTL value can be set to any value each time a message packet is generated, but by using this setting data, the user can save the trouble of setting the TTL value each time a message packet is generated. can.

The range of values that can be set as the TTL value is, for example, a maximum of 15 in consideration of congestion control. Of course, if the size of the wireless mesh network is large and the physical range in which the wireless device 100 is installed is wide, the upper limit of the value that can be set as the TTL value may be set to 16 or more.

As the setting data stored in the storage unit 100d, various other items such as setting values for channels used in wireless communication are stored.

<4. Flowchart>
<4-1. Adding a wireless device>
Processing executed in the wireless device 100 newly added to the wireless mesh network or the wireless device 100 that has been restarted will be described with reference to FIG. 6. That is, the process shown in FIG. 6 is a process executed in the wireless device 100 after startup.

After the power is turned on, the communication control unit 100a of the wireless device 100 transmits a search packet using broadcast communication in step S101.

This search packet is received by other wireless devices 100 located within a predetermined distance, and ACK packets are returned as appropriate. The details will be described later.

In step S102, the communication control unit 100a determines whether an ACK packet has been received. If it is determined that an ACK packet has been received, the communication control unit 100a performs a transfer table update process in step S103. This transfer table update process is a process that is executed upon reception of an ACK packet, and the content of the process differs depending on the radio field strength at the time of receiving the ACK packet.
Note that the wireless device 100 that is the transmission source of the ACK packet and that is the target of determination as to whether or not to be registered in the transfer table will be referred to as the “processing target wireless device 100.”

This will be specifically explained with reference to FIG.

In the transfer table update process, the communication control unit 100a determines in step S201 whether the RSSI value at the time of packet reception is equal to or greater than a threshold value (-90 dBm in the above example).

If it is determined that the RSSI value is greater than or equal to the threshold value, the communication control unit 100a compares the RSSI values with each other in step S202, and determines that the RSSI value for the wireless device 100 to be processed is within the top five RSSI values stored in the transfer table. Determine whether or not it fits.

If it is determined that the wireless device 100 is in the top five in the transfer table, the communication control unit 100a decides to register the wireless device 100 to be processed in the transfer table.

When determining to register the wireless device 100 to be processed in the transfer table, the communication control unit 100a determines in step S203 whether the wireless device 100 to be processed has already been registered in the transfer table.

If it is determined that the wireless device 100 is registered, the communication control unit 100a updates the record for the wireless device 100 to be processed by updating the RSSI value in step S204, and ends the transfer table update process.

On the other hand, if it is determined in step S203 that the wireless device 100 to be processed is not registered in the forwarding table, the communication control unit 100a registers the wireless device 100 to be processed in the forwarding table and performs the forwarding table update process in step S205. finish.

In addition, in the registration process of step S205, if the number of records registered in the transfer table is 4 or less, a process of newly adding the wireless device 100 to be processed to the transfer table is performed, and the number of registered records is increased. If the upper limit is five, the record of the wireless device 100 with the lowest RSSI value is deleted and the wireless device 100 to be processed is registered. At this time, the five records including the wireless device 100 to be processed are appropriately sorted in descending order of RSSI value.

If it is determined in step S202 that the RSSI value is not within the top five of the forwarding table, the communication control unit 100a determines whether the wireless device 100 to be processed is already registered in the forwarding table in step S206. do.

If it is determined that the wireless device 100 is registered, the communication control unit 100a performs a process of deleting the record of the wireless device 100 to be processed from the transfer table in step S207, and ends the transfer table update process.
By performing this deletion process, only wireless devices 100 that can always guarantee constant communication quality are registered in the transfer table.

If it is determined in step S206 that the wireless device 100 to be processed is not registered in the transfer table, the communication control unit 100a ends the transfer table update process shown in FIG. 7.

Further, even when it is determined in step S201 that the RSSI value at the time of packet reception is less than the threshold value, the determination process in step S206 is executed, and the deletion process in step S207 is executed as appropriate depending on the determination result.

Returning to the explanation of FIG. 6.
After completing the transfer table update process, the communication control unit 100a returns to step S102 and determines whether an ACK packet from another wireless device 100 has been received.

The processes in step S102 and step S103 can be repeatedly executed as many times as the number of wireless devices 100 within the reachable range (within the above-mentioned communication range) of the search packet transmitted from the wireless device 100. Finally, the top five devices with the highest RSSI values among the surrounding wireless devices 100 are registered in the transfer table.

Of course, if the number of wireless devices 100 located within the communication range is small, the number of wireless devices registered in the transfer table will be small.

If it is determined in step S102 that an ACK packet has not been received, the communication control unit 100a proceeds to step S104 and waits until a predetermined period of time has elapsed. The predetermined waiting time here is a time based on the value of the above-mentioned search packet transmission interval, which is one of the setting data stored in the storage unit 100d. Specifically, it is set to 1 hour, 24 hours, etc.

If it is determined that the predetermined time has elapsed, the communication control unit 100a returns to step S101 and transmits the search packet again. Note that the transfer table may be cleared when transmitting the search packet. This can prevent information about a wireless device 100 that is inappropriate as a transfer destination from remaining in the transfer table.

If it is determined that the predetermined time has not elapsed, the communication control unit 100a repeats the process of step S104.
Note that when the value of the search packet transmission interval is set to "0", the determination result in step S104 is always "No".

<4-2. Receiving search packet>
FIG. 8 shows an example of processing executed by the communication control unit 100a when the wireless device 100 receives a search packet. Note that processes similar to those in FIGS. 6 and 7 are given the same step numbers, and description thereof will be omitted as appropriate.

In step S301, the communication control unit 100a of the wireless device 100 determines whether a search packet has been received. If it is determined that the wireless device 100 has not received the message, the wireless device 100 executes the process of step S301 again.

On the other hand, if it is determined that a search packet has been received, the communication control unit 100a executes substantially the same process as the transfer table update process shown in FIG. 7 in the process after step S201. The difference from the transfer table update process is that an ACK packet is returned according to conditions.

Specifically, in step S201, the communication control unit 100a determines whether the RSSI value at the time of receiving the search packet is greater than or equal to a threshold value.

If it is determined that the RSSI value is equal to or greater than the threshold value, the communication control unit 100a returns an ACK packet in step S302. The wireless device 100 that has transmitted the search packet in response to this executes the processing from step S102 onward in FIG.

Subsequently, in step S202, the communication control unit 100a determines whether the RSSI value is within the top five of the transfer table, and if it is determined that the RSSI value is within the top five, the communication control unit 100a performs each process from step S203 to step S205. is executed, and if it is determined that it is not in the top five, each process from step S206 to step S207 is executed.
As a result, the transfer table is updated.

Furthermore, if it is determined in step S201 that the RSSI value is less than the threshold value, the processes in step S206 and step S207 are executed, thereby appropriately deleting the corresponding record from the transfer table.

After executing each process, the communication control unit 100a returns to the process of step S301 again.

As understood from FIG. 8, the wireless device 100 that has received the search packet does not transmit the ACK packet if the RSSI value is less than the threshold. By not transmitting an ACK packet, it is not registered in the transfer table of the wireless device 100 that is the source of the search packet.
If a wireless device 100 that cannot perform good wireless communication is registered in the transfer table, the number of times message packets will be retransmitted will increase, resulting in wasted communication bandwidth. This can be prevented by not returning an ACK packet when the RSSI value is less than the threshold.

<4-3. Sending message packet>
FIG. 9 shows an example of processing executed by the communication control unit 100a when the wireless device 100 transmits a message packet. Note that processes similar to those in FIGS. 6 and 7 are given the same step numbers, and description thereof will be omitted as appropriate.

In step S401, the communication control unit 100a of the wireless device 100 determines whether an opportunity to transmit a message packet has arrived. For example, it is determined that a transmission opportunity has arrived when the user performs an operation to transmit a message packet, or when a predetermined time for acquiring and transmitting a sensor value of a sensor device has arrived. If it is determined that the transmission opportunity has not arrived, the communication control unit 100a repeats the process of step S401.

On the other hand, if it is determined that the transmission opportunity has arrived, the communication control unit 100a performs processing to generate and transmit a message packet in step S402. In the transmission process at this time, unicast communication is used that targets the wireless device 100 with the highest RSSI value in the transfer table.

Subsequently, in step S102, the communication control unit 100a determines whether an ACK packet has been received.

If it is determined that an ACK packet has been received, the communication control unit 100a performs a transfer table update process in step S103.

On the other hand, if it is determined that the ACK packet has not been received, the communication control unit 100a determines in step S404 whether the number of retransmissions is less than the threshold value. If it is determined that the number of retransmissions has not reached the threshold, the communication control unit 100a returns to step S402 and retransmits the message packet.

If it is determined that the number of retransmissions has reached the threshold, there is a high possibility that the message packet did not reach the destination wireless device 100 even if it was transmitted a predetermined number of times. If such a wireless device 100 is registered in the transfer table, useless wireless communication will occur thereafter.
Therefore, the communication control unit 100a performs processing to delete the record of the wireless device 100 from the transfer table in step S207.

After the process in step S207 or after the transfer table update process in step S103, the communication control unit 100a, in step S403, selects an unselected transmission target, that is, a record that is not selected as the destination of the message packet in the transfer table. Check if there is one.

If it is determined that there is an unselected transmission target, the communication control unit 100a returns to step S402 and transmits a message packet to the wireless device 100 as the next transmission destination.

On the other hand, if it is determined that there are no unselected transmission targets, that is, if it is determined that message packets have been transmitted to all wireless devices 100 stored in the transfer table, the communication control unit 100a returns to step S401. , waits until the next message packet transmission opportunity arrives.

In the example shown in FIG. 9, message packets are first transmitted to the wireless device 100 with the highest RSSI value in the transfer table until it can receive an ACK packet or the number of retransmissions reaches a threshold. Then, the wireless device 100 with the next highest RSSI value is selected as a new transmission target, and message packets are transmitted until an ACK packet can be received or the number of reproductions reaches a threshold value.

That is, the process is completed for each wireless device 100 that is a transmission target, but other methods may be used.

For example, a message packet is transmitted once to each of the plurality of wireless devices 100 stored in the transfer table. Then, the second message packet is transmitted only to the wireless device 100 that has not been able to receive the ACK packet.

By adopting such a processing order, the first message packet can be quickly transmitted to each wireless device 100, thereby speeding up the timing at which the message packet reaches the wireless device 100, which is the final destination. I can do it.

<4-4. Transferring message packets>
FIG. 10 shows an example of processing executed by the communication control unit 100a when the wireless device 100 receives a message packet. Note that processes similar to those in FIGS. 6, 7, 8, and 9 are given the same step numbers, and descriptions thereof will be omitted as appropriate.

In step S501, the communication control unit 100a of the wireless device 100 determines whether a message packet has been received. If it is determined that no message packet has been received, the communication control unit 100a repeats the process of step S501.

On the other hand, if it is determined that a message packet has been received, the communication control unit 100a first returns an ACK packet to the wireless device 100 to which the message packet was transmitted in step S302.

Subsequently, the communication control unit 100a performs a transfer table update process in step S103, and determines whether the destination of the received message packet is the own station in the subsequent step S502.

If the destination of the message packet is the own station, the communication control unit 100a takes in the received message packet in step S503 and performs appropriate processing.

On the other hand, if the destination of the message packet is not the local station, that is, if the final destination address is not the local station address, the communication control unit 100a processes the received message packet Check for duplicates.

The duplication check is, for example, a process of checking whether the same message packet as the currently received message packet has already been received. For example, wireless device D shown in FIG. 1 may receive the same message packet not only from wireless device A, but also from wireless device B, wireless device C, and so on.

If the same message packet is transferred every time it is received, unnecessary communication will increase and congestion will occur. Therefore, a duplicate check is performed to check whether the received message packet has already been received.

In the duplication check, first, in step S504, it is determined whether there is a history of received packets with matching source addresses. For example, about 10 histories are stored in the received packet history, and it is checked whether each history matches the source address of the currently received message packet (for example, the wireless device 100 that generated the message packet). judge.

If it is determined that there is a history of received packets with matching source addresses, the communication control unit 100a proceeds to step S505, and further determines whether there is a history of received packets with matching sequential numbers. That is, it is determined whether there is a history of received packets in which both the source address and sequential number match.

If there is a history in which both match, the message packet received this time has already been transferred, so the communication control unit 100a performs a process of discarding the message packet received this time in step S506, and returns to the process of step S501.

If it is determined in step S504 that there is no history of received packets with matching source addresses, or if it is determined in step S505 that there is no history of received packets with matching sequential numbers, the communication control unit 100a determines in step S507 that there is no history of received packets with matching source addresses. It is determined whether the TTL value in the received message packet is 0 or not.

If it is determined that the TTL value is 0, the message packet is discarded in step S506.

On the other hand, if it is determined that the TTL value is 1 or more, the communication control unit 100a subtracts the TTL value in step S508, and in the subsequent step S509, the transmission source address and sequential number of the message packet received this time are calculated from the received packet. Performs processing to store as history.

Note that if it is determined in step S507 that the TTL value is 0, the received packet history is not stored. This is because the message packet received this time has not been transferred. That is, if the same message packet is subsequently received and the TTL value of the message packet is 1 or more, the transfer process is performed normally.

In addition, in the duplication check from step S504 to step S509, a process was performed to check whether a message packet with matching two items, the source address and sequential number, was received in the past, but in addition, the destination address also matched. It may be determined whether or not to do so. This can reduce the possibility of erroneously determining that different message packets are the same.
Note that when determining whether or not the destination addresses match, the item of the destination address is also stored in addition to the source address and sequential number shown in FIG. 5 as the received packet history.

After finishing the process of registering the received packet in the history in step S509, the communication control unit 100a transfers the message packet in step S510. The wireless device 100 selected as the transfer destination here is the wireless device 100 with the highest RSSI value in the transfer table. However, the wireless device 100 that is the transmission source (transfer source) when receiving the current message packet is excluded from the selection of the transfer destination. That is, there is no point in sending back the sent message packet as it is.

Subsequently, in step S102, the communication control unit 100a determines whether an ACK packet has been received. Since the subsequent processing is substantially the same as the example shown in FIG. 9, the explanation will be simplified.

If it is determined that an ACK packet has been received, the communication control unit 100a performs a transfer table update process in step S103.

On the other hand, if it is determined that the ACK packet has not been received, the communication control unit 100a determines in step S404 whether the number of retransmissions is less than the threshold, and if the number of retransmissions has not reached the threshold, The process returns to step S510 and transfers the message packet again.

If it is determined that the number of retransmissions has reached the threshold, the communication control unit 100a performs processing to delete the record of the wireless device 100 that is the transfer destination from the transfer table in step S207.

After the process of step S207 or after the process of step S103, the communication control unit 100a checks in step S511 whether there is an unselected transfer target, and if there is, returns to step S510, The wireless device 100 is selected as the next transfer destination and the message packet is transferred. However, in the process of step S511 as well, the wireless device 100 that is the transmission source (transfer source) when receiving the current message packet is excluded from the selection of the transfer destination.

If it is determined in step S511 that there is no unselected transfer target, that is, if it is determined that the message packet has been transferred to all wireless devices 100 stored in the transfer table, the communication control unit 100a proceeds to step S501. Return and wait until receiving the next message packet.

Note that in FIG. 10 as well, the message packet may be configured to be transferred to each wireless device 100 for the first time, and then transferred to each wireless device 100 again as appropriate.

<5. Modified example>
In the message packet transfer process shown in FIG. 10, the wireless communication channel used may be changed each time the message packet is retransferred to the same wireless device 100.
For example, when there are three channels used in a wireless mesh network, the channel that can be received by the transfer destination wireless device 100 may be unknown. In preparation for such a case, by changing the channel used each time retransfer is performed, it is possible to increase the possibility that the transferred message packet will be received by the transfer destination wireless device 100.

Similarly, in the transmission of the message packet shown in FIG. 9, the channel may be changed every time it is retransmitted.

Each record stored in the received packet history may be configured to be deleted from the received packet history after a predetermined period of time (for example, several days or one week) has elapsed since it was stored. This can reduce the possibility of erroneously determining that different message packets are the same message packet. Alternatively, the maximum number of records stored in the received packet history may be set to a larger value (for example, 100). Thereby, even if many message packets are received in a short period of time, it is possible to appropriately check for duplication.

<6. Summary>
As explained in each of the above examples, the wireless devices 100 (A, B, C, D, E, F, G, H) constitute a wireless mesh network to which message packets are transferred. , information about the radio field strength of the communication control unit 100a that performs communication control, the transmission unit 100b that transmits message packets, the reception unit 100c that receives message packets, and other wireless devices 100 to which message packets are transmitted. and a storage unit 100d in which the received message packet is stored as a transfer table, and the communication control unit 100a selects the units in order from the wireless device 100 with the highest radio field strength (RSSI value) when forwarding the received message packet to the other wireless device 100. Transfer is performed using cast communication.
That is, instead of using a routing method in which a transfer route is determined in advance using a routing table or the like when transmitting a message packet, the message packet is sent in accordance with the communication situation at the time using information in the transfer table stored in the storage unit 100d. and transfer is performed.
Therefore, even if a radio wave interference occurs in a part of the wireless mesh network, the forwarding table is rewritten to take into account the radio wave interference as message packets are sent and received, so that the transmission can be routed through the appropriate route. can send message packets. That is, good fault tolerance can be achieved.
Such a configuration is suitable for, for example, a system that collects data at a frequency of about once a day or every few hours.
Further, since the transfer is performed in order from the wireless device 100 with the highest radio field strength, good wireless communication is performed preferentially, so that it is possible to quickly deliver the information to the target wireless device 100.
Furthermore, since the user does not have to create the routing table himself/herself, convenience can be improved.
The data stored in the storage unit 100d for performing such transfer processing is a transfer table shown in FIG. 4. The transfer table is approximately 30 bytes at most for five wireless devices 100. Therefore, appropriate transfer processing can be performed while suppressing the storage capacity of the storage unit 100d.

Further, the transfer table stored in the storage unit 100d may store information about the wireless devices 100 whose radio wave intensity (RSSI value) is equal to or higher than a threshold value.
By appropriately setting the threshold, only information about wireless devices 100 that can be transferred is stored in the transfer table. Therefore, unnecessary transfer processing for message packets can be reduced, and bandwidth compression in the communication environment can be avoided. Further, by suppressing unnecessary transfer of message packets, power consumption of the wireless device 100 can be reduced. This is effective when the wireless device 100 is battery-powered.

Furthermore, information regarding a predetermined number of wireless devices 100 may be stored in the transfer table stored in the storage unit 100d.
By limiting the number of pieces of information stored in the transfer table, it is possible to reduce the number of times transfer is performed to all wireless devices 100 stored in the transfer table. Therefore, it is possible to avoid bandwidth compression in the communication environment.

When the communication control unit 100a of the wireless device 100 obtains information on the radio field strength (RSSI value) of another wireless device 100 that is not stored in the transfer table, the communication control unit 100a of the wireless device 100 transmits the information of the other wireless device 100 that is already stored in the transfer table. The transfer table may be managed such that a process of comparing the radio field strength is performed and another wireless device 100 with the lowest radio field strength as a result of the comparison process is not stored in the transfer table.
For example, each time a message packet is transferred, it is possible to obtain information on the radio field strength of other wireless devices 100 that are not stored in the transfer table. Then, the transfer table can be managed (replaced records) so that information about the wireless device 100 that is more suitable as a transfer destination is stored in the transfer table. Thereby, the message packet can be transmitted to the appropriate wireless device 100, and the possibility of packet loss in which the message packet does not reach the intended wireless device 100 can be reduced.

If the communication control unit 100a of the wireless device 100 cannot receive an acknowledgment packet (ACK packet) from another wireless device 100 targeted for unicast communication, the communication control unit 100a transfers information about the other wireless device 100. May be deleted from the table.
This makes it possible to prevent the wireless device 100 or the like that is unable to send or receive message packets due to a failure or the like from being deleted from the transfer table, thereby preventing unnecessary transfer processing from being executed.

The storage unit 100d of the wireless device 100 stores message packets received by the reception unit 100c as a reception packet history, and the communication control unit 100a determines whether or not the received message packet can be transferred when the reception unit 100c receives the message packet. In determining whether transfer is possible, if the received packet history includes information in which the sequential number of the received message packet matches the information identifying another wireless device 100 that is the source of the received message packet. However, it may be determined that the transfer is not possible.
The sequential number is, for example, a serial number given to message packets generated in the wireless device 100, and is given independently for each wireless device 100. Since it takes a fairly long time for sequential numbers to cycle through one cycle, in a situation where the received packet history is updated appropriately, it is necessary for both the wireless device 100 that is the transmission source (generation source) and the sequential number to match. If the received message packet is stored in the received packet history, there is a high possibility that the message packet has already been transferred. Therefore, by canceling the transfer process for the currently received message packet, it is possible to reduce unnecessary transfer processes and avoid bandwidth pressure on the communication environment.
Furthermore, if the method records only the source address and sequential number as the received packet history, the amount of data of the received packet history stored in the storage unit 100d would be about 60 Bytes at most even if 10 message packets are recorded. be done. Thereby, wasteful transfer processing can be effectively suppressed while suppressing the usage amount of the storage unit 100d.

The communication control unit 100a of the wireless device 100 transmits a search packet using broadcast communication at startup, and updates the forwarding table based on an acknowledgment packet (ACK packet) received from another wireless device 100 in response to the search packet. You can.
Thereby, the wireless device 100 newly added to the wireless mesh network is appropriately registered in the transfer table of other nearby wireless devices 100 by transmitting a search packet after activation. Therefore, the newly added wireless device 100 can transmit and transfer subsequent message packets without any problem.
In other words, a new wireless device 100 can be easily incorporated into a wireless mesh network without performing complicated initial setting processing.

The communication control unit 100a of the wireless device 100 may periodically transmit search packets.
The radio wave intensity between the wireless devices 100 may change from moment to moment due to changes in the communication environment, failures or maintenance of the wireless devices 100, and the like. Therefore, by having the communication control unit 100a transmit search packets periodically (every hour, every few hours, every day, etc.), the transfer table can be periodically updated to the latest state. Therefore, message packets can be transferred appropriately even if the communication environment or the like changes.

Wireless device 100 may be configured to not periodically transmit search packets.
In situations where changes in the communication environment are unlikely to occur, transmission of search packets may cause bandwidth compression in the communication environment. According to this configuration, it is possible to set whether or not to periodically transmit search packets, so by making appropriate settings according to the environment, unnecessary transmission of packets can be suppressed.
For example, if the operation is such that the wireless device 100 does not transmit or receive data at night, it is possible to switch the setting to not transmit search packets in the evening before, and then switch again to transmit the search packets the next morning. , transmission and reception of search packets can be suppressed, and power consumption of the wireless device 100 can be reduced.

In a network system configured with a plurality of wireless devices 100, each wireless device 100 includes a communication control section 100a that performs communication control, a transmitting section 100b that transmits message packets, a receiving section 100c that receives message packets, and a communication control section 100a that performs communication control. A storage unit 100d is provided in which information about the radio field strength of another wireless device 100 to which a packet is transmitted is stored as a transfer table. Then, when transferring the received message packet to another wireless device 100, the communication control unit 100a of each wireless device 100 performs the transfer in order from the wireless device 100 with the highest radio field strength (RSSI value) using unicast communication. It is something.

Information about the radio field strength of the communication control unit 100a that performs communication control, the transmission unit 100b that transmits message packets, the reception unit 100c that receives message packets, and other wireless devices 100 to which message packets are transmitted is provided. A control method executed by a wireless device 100 including a storage unit 100d stored as a transfer table is based on a wireless device 100 having a high radio field strength (RSSI value) when forwarding a received message packet to another wireless device 100. This is a control method in which transfer is performed sequentially using unicast communication.
A program for realizing such a control method in the wireless device 100 is stored in an HDD (Hard Disk Drive) as a recording medium built in equipment such as a computer device, or in a microcomputer having a CPU (Central Processing Unit). The information can be recorded in advance in a ROM or the like. Alternatively, the program may be a flexible disk, CD-ROM (Compact Disk Read Only Memory), MO (Magneto Optical) disk, DVD (Digital Versatile Disc), Blu-ray Disc (registered trademark), magnetic disk, semiconductor It can be stored (recorded) temporarily or permanently in a removable recording medium such as a memory or a memory card. Such a removable recording medium can be provided as so-called package software.
In addition to installing such a program into a personal computer or the like from a removable recording medium, it can also be downloaded from a download site via a network such as a LAN (Local Area Network) or the Internet.

The various effects described above can also be obtained by such a network system, control method, and program.

Note that the above-mentioned examples can be combined in any way, and even when various combinations are used, it is possible to obtain the various effects described above.

100 Wireless devices A to H Wireless device 100a Communication control section 100b Transmission section 100c Receiving section 100d Storage section

Claims (11)

A wireless device configuring a wireless mesh network in which message packets are transferred, the wireless device comprising:
a communication control unit that performs communication control;
a transmitter that transmits a message packet;
a receiving unit that receives message packets;
a storage unit in which information about the radio field strength of another wireless device to which the message packet is to be transmitted is stored as a transfer table;
The communication control unit transfers the received message packet to another wireless device using unicast communication in order from the wireless device with the highest radio field intensity. The wireless device according to claim 1, wherein the transfer table stores information about wireless devices whose radio field intensity is equal to or higher than a threshold value. The wireless device according to claim 2, wherein the transfer table stores information about a predetermined number of wireless devices. The communication control unit includes:
When information on the radio field strength of another wireless device not stored in the transfer table is obtained, performing a process of comparing it with the radio field strength of the other wireless device already stored in the transfer table;
The wireless device according to claim 3, wherein the transfer table is managed so that another wireless device with the lowest radio field intensity as a result of the comparison process is not stored in the transfer table. According to claim 1, when the communication control unit fails to receive an acknowledgment packet from another wireless device targeted for the unicast communication, the information about the other wireless device is deleted from the transfer table. Wireless device described. The storage unit stores message packets received by the reception unit as a reception packet history,
The communication control unit determines whether the received message packet can be transferred when the reception unit receives the message packet,
In determining whether the transfer is possible, if the received packet history includes information in which the sequential number of the received message packet matches the information identifying another wireless device that is the source of the received message packet, The wireless device according to claim 1, wherein the wireless device is determined to be unable to be transferred. The communication control unit transmits a search packet using broadcast communication at startup,
The wireless device according to claim 1, wherein the forwarding table is updated based on an acknowledgment packet received from another wireless device in response to the search packet. The wireless device according to claim 7, wherein the communication control unit periodically transmits the search packet. The wireless device according to claim 8, wherein the wireless device can be set not to periodically transmit the search packet. A network system composed of a plurality of wireless devices,
Each wireless device is
a communication control unit that performs communication control;
a transmitter that transmits a message packet;
a receiving unit that receives message packets;
a storage unit in which information about the radio field strength of another wireless device to which the message packet is to be transmitted is stored as a transfer table;
In the network system, the communication control unit transfers received message packets to other wireless devices using unicast communication in descending order of radio field strength. a communication control unit that performs communication control;
a transmitter that transmits a message packet;
a receiving unit that receives message packets;
A method for controlling a wireless device includes: a storage unit storing information about the radio field strength of another wireless device to which a message packet is transmitted as a transfer table;
A control method in which received message packets are transferred to other wireless devices using unicast communication in order of radio field strength.

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