JP7031200B2 - Communication equipment, communication system, and route cost calculation method - Google Patents

Description

The present invention relates to a communication device, a communication system, and a route cost calculation method.

As a method of constructing a communication route from a communication device of a packet source to a communication device of a destination in a multi-hop type wireless communication network, for example, the following method described in Patent Document 1 is known.

The communication network described in Patent Document 1 is composed of one master unit and a plurality of slave units, and signals are transmitted and received between the master unit and each slave unit by multi-hop communication. Each slave unit performs a process of searching for an adjacent terminal with which it can directly communicate, and the master unit receives link information about the adjacent terminal with which the slave unit can directly communicate from each slave unit. Based on the received link information, the master unit consists of a one-dimensional data table showing the terminal ID of the communication terminal on the start point side, the terminal ID of the communication terminal on the end point side, and the link cost indicating the communication quality level between both terminals. Record in the topology table. Then, the master unit performs a route search process for finding a communication route to each slave unit using a Dijkstra algorithm based on the link information recorded in the topology table.

Japanese Unexamined Patent Publication No. 2008-301269

In a mesh network in which a packet is transmitted by reselecting another communication link when the transmission of the packet on the selected communication link fails, there are multiple communication routes from the packet source device to the packet destination device. Can be. Therefore, in such a mesh network, the communication device (source device and relay device) that transmits the packet succeeds in transmitting the packet to the destination device from the adjacent devices that may have a plurality of communication routes to the destination device. It is desirable to select an appropriate destination device that is likely. The adjacent device is a communication device connected to a communication device that transmits a packet by a communication link, and refers to a communication device that the communication device that transmits a packet can directly communicate with. Further, the destination device refers to an adjacent device selected by the communication device that transmits the packet as the communication device that directly transmits the packet.

However, the Dijkstra algorithm used by Patent Document 1 as a method for constructing a communication route described above is an algorithm for searching for the shortest path, and the method described in Patent Document 1 is a straight path connecting a slave unit and a master unit. It just searches for a communication route. Therefore, the method described in Patent Document 1 cannot be used for the mesh network as described above.

An object of the present invention is to select an appropriate destination device in a mesh network for reselecting another communication link and transmitting a packet when transmission of a packet on the selected communication link fails. Is to provide a communication device for calculating the root cost of.

The communication device according to the present invention is provided with a route cost calculation unit. The route cost calculation unit calculates the root cost of the communication device for the destination device by using the route cost for each adjacent device and the link cost for each communication link. The route cost for each adjacent device is the packet loss rate at which packets do not reach the destination device from the adjacent device even if all communication routes that can be selected between the adjacent device that the communication device can directly communicate with and the packet destination device are used. Is. The link cost for each communication link is the packet loss rate at which the packet does not reach the adjacent device from the communication device in the communication link between the communication device and the adjacent device that are associated with the identifier of the communication device and transmit the packet.

According to the communication device according to one embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected to select an appropriate destination device in the mesh network for transmitting the packet. You can calculate the route cost to do so.

It is a figure which shows the configuration example of the communication system according to an embodiment. It is explanatory drawing of the link cost and the root cost according to an embodiment. It is a figure explaining an example of the calculation method of the link cost according to an embodiment. It is a figure explaining an example of the calculation method of the root cost according to an embodiment. It is a figure which shows an example of the convergence calculation of the root cost in the network configuration shown in FIG. 4C. It is a figure explaining an example of the calculation method of the root cost performed by the communication apparatus according to an embodiment. It is a figure explaining an example of the communication procedure of the communication apparatus according to an embodiment. It is a figure which shows the configuration example of the node apparatus according to an embodiment. It is a figure which shows the structural example of the aggregate according to an embodiment. It is a figure which shows the configuration example of the monitoring apparatus according to an embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings.
<Communication system configuration example>
FIG. 1 is a diagram showing a configuration example of a communication system according to an embodiment. In the configuration example shown in FIG. 1, the communication system 1 includes a monitoring device 2 and a wireless communication network 3. In the example shown in FIG. 1, the communication system 1 includes one wireless communication network 3, but the communication system 1 may include a plurality of wireless communication networks 3.

The wireless communication network 3 is, for example, a sensor network. The wireless communication network 3 includes an aggregate 4 and a plurality of node devices 5 (5-1 to 5-3). In the example shown in FIG. 1, the wireless communication network 3 includes three node devices 5-1 to 5-3, but the wireless communication network 3 may include any number of node devices 5.

The node device 5 is a device that transmits / receives data to / from the aggregate 4 using wireless communication. Further, the node device 5 can send and receive data to and from another node device 5 using wireless communication. For example, when the wireless communication network 3 is a sensor network, the node device 5 is a sensor node.

The aggregate 4 is a central node (for example, a gateway) that connects the wireless communication network 3 and the wide area network 6. The wide area network 6 is a wired or wireless communication network such as the Internet. For example, in the configuration example shown in FIG. 1, the aggregate 4 transmits the data received from the subordinate node devices 5-1 to 5-3 to the monitoring device 2 via the wide area network 6.

The monitoring device 2 is a device that monitors the state of the wireless communication network 3 through communication with the aggregate 4. In the example shown in FIG. 1, the monitoring device 2 and the aggregate 4 are connected via the wide area network 6.

The aggregate 4 and the node device 5 are examples of communication devices according to the embodiment. Further, the monitoring device 2 is an example of a route cost calculation device according to the embodiment. Depending on the embodiment, the aggregate 4 may be an example of the route cost calculation device according to the embodiment.

The wireless communication network 3 is a multi-hop type wireless communication network. As shown in FIG. 1, the wireless communication network 3 includes not only a node device 5 that directly communicates with the aggregate 4 but also a node device 5 that communicates with the aggregate 4 via another node device 5 that relays. For example, among the plurality of node devices 5, the node device 5-1 and the node device 5-2 communicate directly with the aggregate 4. On the other hand, the node device 5-3 communicates with the aggregate 4 via the node device 5-1 or the node device 5-2.

Further, the wireless communication network 3 is a mesh network that reselects another communication link and transmits a packet when the transmission of the packet on the selected communication link fails. For example, if the node device 5-1 fails to transmit a packet to one of the adjacent devices of the aggregate 4 and the node device 5-3 capable of direct communication, the node device 5-1 transmits the packet to the other adjacent device. .. Further, for example, when the node device 5-3 fails to transmit a packet to one of the adjacent devices of the node device 5-1 and the node device 5-2 capable of direct communication, the node device 5-3 is sent to the other adjacent device. Send a packet. As described above, the adjacent device is a communication device that is connected to a communication device (packet source device or relay device) that transmits a packet by a communication link, and is a communication device that the communication device that transmits the packet can directly communicate with. Point to.

<Link cost and route cost>
In the wireless communication network 3, the communication device (packet source device and relay device) that transmits a packet has a route cost for the destination device among the route costs for each adjacent device when a plurality of adjacent devices exist. Select the adjacent device as the destination device in ascending order. The destination device refers to an adjacent device to which a communication device that transmits a packet directly transmits the packet. Further, the route cost is a packet loss rate at which the packet does not reach the destination device from the communication device even if all communication routes that can be selected between the communication device that transmits the packet and the destination device of the packet are used. Point to. For example, the root cost of an adjacent device is a packet loss rate at which packets do not reach the destination device from the adjacent device even if all communication routes selectable between the adjacent device and the destination device are used.

<Route cost and link cost>
FIG. 2 is an explanatory diagram of a link cost and a route cost according to an embodiment. In FIG. 2, the numbers shown in parentheses near each communication device (aggregator 4 and node device 5) represent the root cost of each communication device when the aggregate 4 is the destination device of the packet. In the example shown in FIG. 2, the root cost of the aggregate 4 is 0, the root cost of the node device 5-1 is 0.014, the root cost of the node device 5-2 is 0.017, and the node. The root cost of device 5-3 is 0.025.

For example, in the aggregate 4 and the node apparatus 5-3 which are adjacent devices of the node apparatus 5-1 the root cost of the aggregate 4 is smaller than the root cost of the node apparatus 5-3. Therefore, the node device 5-1 first selects the aggregate 4 as the destination device from the adjacent devices 4 and the node device 5-3, and transmits a packet from the node device 5-1 to the aggregate 4. If it fails, the node device 5-3 is selected as the destination device next. Further, in the node device 5-1 and the node device 5-2 which are adjacent devices of the node device 5-3, the root cost of the node device 5-1 is smaller than the root cost of the node device 5-2. Therefore, the node device 5-3 first selects the node device 5-1 as the destination device, and if the packet transmission from the node device 5-3 to the node device 5-1 fails, the node device 5-2 is selected. Next, select the destination device.

As will be described later, the root cost of each communication device is calculated by each communication device (aggregator 4 and node device 5) or root cost calculation device (monitoring device 2 or aggregate 4) using the link cost. The link cost refers to the packet loss rate at which a packet does not reach the adjacent device from the communication device in the communication link between the communication device that transmits the packet and the adjacent device. In FIG. 2, the numbers described in the vicinity of the communication links L1 to L4 connecting the communication devices indicate the link cost of the communication links L1 to L4. For example, the link cost 0.1 of the communication link L1 indicates that the transmission of the packet between the node device 5-1 and the aggregate 4 fails with a probability of 1 in 10 times. Although FIG. 2 shows an example in which the communication performance (transmission performance and reception performance) of each communication device is the same, the communication performance of each communication device may be different.

An example of the calculation method of the link cost and the route cost according to the embodiment will be described below.

<< Example of link cost calculation >>
The link cost of each communication link is calculated by the communication device (aggregator 4 and node device 5) connecting each communication link.

For example, as shown in FIG. 3, the communication device (aggregator 4 and node device 5) uses the number of transmitted packets transmitted by the neighboring device to the communication device and the number of received packets received by the communication device from the neighboring device. , The link cost of the communication link between the communication device and the adjacent device may be calculated. FIG. 3 is a diagram illustrating an example of a link cost calculation method according to an embodiment.

In the example shown in FIG. 3, the transmitting side communication device A determines the number of transmission packets for each receiving side communication device that receives packets from the transmitting side communication device A on the communication link connected to the transmitting side communication device A. Count. For example, the transmission side communication device A counts the number of transmission packets to the reception side communication device B, and each time a new packet is transmitted to the reception side communication device B, the number of transmission packets to the reception side communication device B is counted. Update. Then, the communication device A on the transmitting side transmits a packet including the identifier of the communication device A on the transmitting side and the updated number of transmission packets to the communication device B on the receiving side. The packet to be transmitted to the communication device B on the receiving side may be a dedicated packet for calculating the link cost or a packet for transmitting and receiving required data.

The communication device B on the receiving side counts the number of received packets for each communication device on the transmitting side that has transmitted a packet to the communication device B on the receiving side on the communication link connected to the communication device B on the receiving side. For example, the receiving side communication device B counts the number of received packets for the transmitting side communication device A, and each time a new packet is received from the transmitting side communication device A, the number of received packets for the transmitting side communication device A is counted. Update. Then, the communication device B on the receiving side uses the number of received packets for the communication device A on the transmitting side and the number of transmission packets included in the packet received from the communication device A on the transmitting side to receive the communication device A on the transmitting side. The link cost of the communication link connecting to the communication device B on the side is calculated by the following equation (1).

For example, if the number of transmission packets transmitted by the transmission side communication device A to the reception side communication device B is X, and the number of reception packets received by the reception side communication device B from the transmission side communication device A is Y. Suppose. Under this assumption, the link cost of the communication link connecting the communication device A on the transmitting side and the communication device B on the receiving side is 1- (Y / X).

As shown in FIG. 3, the receiving-side communication device B stores the identifier of the transmitting-side communication device A, the number of received packets, and the link cost in association with each other in the link cost table. In this way, each communication device calculates the link cost for each communication link connected to the adjacent device, and stores the calculated link cost in the link cost table in association with the identifier of the adjacent device.

The link cost calculation method described above with reference to FIG. 3 is an example, and other methods may be used.

For example, the communication device (aggregator 4 and node device 5) may acquire the packet loss rate corresponding to the received power of the packet received from the adjacent device as the link cost for each communication link. Specifically, for example, the communication device measures the relationship between the received power and the packet loss rate in advance as the reception performance of the communication device, and stores the measurement result in the received power to packet loss rate table. Then, the communication device refers to the received power-to-packet loss rate table when receiving a packet from the adjacent device, and determines the packet loss rate corresponding to the received power of the received packet between the communication device and the adjacent device. Obtained as the link cost of the link.

Further, the communication device (aggregator 4 and node device 5) uses the bit error rate corresponding to the received power of the packet received from the adjacent device, the packet size, and the number of packet transmission retries for each communication link. You may calculate the link cost. Specifically, for example, the communication device measures the relationship between the received power and the bit error rate in advance as the reception performance of the communication device, and stores the measurement result in the received power vs. bit error rate table. When the communication device receives a packet from an adjacent device, it refers to the received power vs. bit error rate table and acquires the bit error rate corresponding to the received power of the received packet. Then, the communication device calculates the packet loss rate of the communication link with the adjacent device that transmitted the packet from the acquired bit error rate, the size of the received packet, and the number of transmission retries predetermined as the communication contract. ..

<< Calculation example of route cost >>
The root cost of each communication device (aggregator 4 and node device 5) is calculated by each communication device or root cost calculation device (monitoring device 2 or aggregate 4) using the link cost calculated by each communication device. 4 (A) to 4 (C) are diagrams illustrating an example of a route cost calculation method according to an embodiment. In the example shown in FIGS. 4A to 4C, the source device and the relay device of the packet are the node device 5, and the destination device of the packet is the aggregate 4. That is, FIGS. 4 (A) to 4 (C) show, as an example, a case where the node device 5 transmits a packet whose destination device is the aggregate 4.

First, FIG. 4A shows an example of a case in which a packet source device and a packet destination device are connected by a communication link. Specifically, the node device 5-1 and the aggregate 4 are connected by the communication link L1, and the node device 5-2 and the aggregate 4 are connected by the communication link L2. In this way, in the case where the source device and the destination device are directly connected to each other without the relay device for relaying packets between the two communication devices, the root cost of each communication device is calculated as follows.

The destination device holds the received packet and does not transmit the packet to another communication device. Therefore, the root cost of the destination device is zero. Therefore, in the example shown in FIG. 4A, the root cost of the aggregate 4 is 0.

When the source device transmits directly to the destination device via the communication link, there is no packet loss due to relay. Therefore, the root cost of the source device is the same as the link cost of the communication link connecting the source device and the destination device. Therefore, in the example shown in FIG. 4A, the root cost of the node device 5-1 is 0.1, which is the same as the link cost of the communication link L1 connecting the node device 5-1 and the aggregate 4. The root cost of the node device 5-2 is 0.15, which is the same as the link cost of the communication link L2 connecting the node device 5-2 and the aggregate 4.

Next, FIG. 4B shows an example of a case in which the source device and the destination device are connected via a relay device. Specifically, the node device 5-3 and the aggregate 4 are connected via the node device 5-1. Further, FIG. 4B shows an example of a case where one communication route connects the source device to the destination device. Specifically, the communication route connecting the node device 5-1 to the aggregate 4 is one communication route composed of the communication link L3 and the communication link L1. In this way, in the case where the source device and the destination device are connected by a one-way communication route via the relay device, the route cost of each communication device is calculated as follows.

The root cost of the destination device is 0 as described above with reference to FIG. 4 (A). Therefore, in the example shown in FIG. 4B, the root cost of the aggregate 4 is 0.

The root cost of the relay device connected to the destination device via the communication link is the same as the link cost of the communication link connecting the destination device and the relay device, similar to the root cost of the source device described with reference to FIG. 4 (A). be. Therefore, in the example shown in FIG. 4B, the root cost of the node device 5-1 is 0.1, which is the same as the link cost of the communication link L1 connecting the node device 5-1 and the aggregate 4.

The root cost of the source device connected to the relay device via the communication link is that the packet is lost in either the communication link between the source device and the relay device or the communication route between the relay device and the destination device. It is a probability. The probability that a packet will be lost in the communication route between the relay device and the destination device refers to the route cost of the relay device. Therefore, in the example shown in FIG. 4B, the root cost of the node device 5-3 is the probability that the node device 5-3 cannot send a packet to the node device 5-1 and the node device from the node device 5-3. It is the sum of the probability that the packet is transmitted to 5-1 but the packet transmission to the aggregate 4 fails in the node device 5-1. That is, the root cost of the node device 5-3 is 0.12+ (1-0.12) × 0.1 = 0.208.

In the example shown in FIG. 4B, the source device and the destination device are connected via one relay device, but the source device and the destination device may be connected via a plurality of relay devices. , The root cost of each communication device can be calculated by the same calculation method as described above.

Further, FIG. 4C shows an example of a case where the source device and the destination device are connected via a relay device. Specifically, the node device 5-3 and the aggregate 4 are connected via the node device 5-1 or the node device 5-2. Further, FIG. 4C shows an example of a case where there are a plurality of communication routes connecting the source device to the destination device. Specifically, the communication route connecting the node device 5-3 to the aggregate 4 is composed of a first communication route composed of the communication link L3 and the communication link L1, and the communication link L4 and the communication link L2. There is a second communication route. Further, the communication route connecting the node device 5-3 to the aggregate 4 is a communication route when the node device 5-1 receiving the packet from the node device 5-3 returns the packet to the node device 5-3. There is also a third communication route composed of a communication link L3, a communication link L4, and a communication link L2. Further, the communication route connecting the node device 5-3 to the aggregate 4 is a communication route when the node device 5-2 receiving the packet from the node device 5-3 returns the packet to the node device 5-3. There is also a fourth communication route composed of a communication link L4, a communication link L3, and a communication link L1. In this way, in the case where the source device and the destination device are connected by a plurality of communication routes via the relay device, the route cost of each communication device is calculated as follows.

The root cost of the destination device is 0 as in FIGS. 4 (A) and 4 (B). Therefore, in the example shown in FIG. 4C, the root cost of the aggregate 4 is 0.

The root cost of the relay device connected to the destination device via the communication link is the same as the link cost of the communication link connecting the destination device and the relay device, as in FIG. 4B. Therefore, in the example shown in FIG. 4C, the root cost of the node device 5-1 is 0.1, and the root cost of the node device 5-2 is 0.15.

The root cost of the source device connected to a plurality of relay devices via a communication link is calculated as follows. As described above, in the wireless communication network 3, each communication device reselects another communication link and transmits the packet when the transmission of the packet on the selected communication link fails. Further, when a plurality of adjacent devices exist, the communication device for transmitting the packet selects the adjacent device as the destination device in ascending order of the root cost for the destination device among the route costs for each adjacent device. Therefore, in such a mesh network, the route cost of the device (source device or relay device) that transmits the packet is calculated by the sum of the probabilities A and B as in the following equation (2).

Here, the probability A is the probability that a packet will be lost on all communication links between the communication device that transmits the packet and the adjacent device. Further, the probability B is that when the transmission of the packet on the selected communication link fails, another communication link is reselected and the communication device that transmits the packet selects the adjacent device in ascending order of the route cost to the destination device. It is the sum of the probabilities that a packet will be lost on the communication route with the destination device.

In the example shown in FIG. 4C, the probability A is the probability that the node device 5-3 cannot send a packet to either the node device 5-1 or the node device 5-2, and is 0.12 × 0. It is 09. Further, the probability B includes the probability that the packet is transmitted from the node device 5-3 to the node device 5-1 but fails to be transmitted to the aggregate 4 in the node device 5-1 and the packet to the node device 5-1. The node device 5-3 sent a packet to the node device 5-2 because the transmission of the packet failed, but it is the sum of the probability that the packet transmission to the aggregate 4 in the node device 5-2 fails (1-). 0.12) × 0.1 + 0.12 × (1-0.09) × 0.15. Therefore, the root cost of the node device 5-3 is about 0.115, which is the sum of the probabilities A and the probabilities B.

In this way, the route costs of the destination device, the relay device, and the source device are first calculated as described above. However, since the source device exists in the communication route between the relay device and the destination device, the relay device packets to the destination device via the source device in addition to the communication route used in the above calculation. There is a communication route to send. Specifically, in the communication route between the node device 5-1 and the aggregate 4, in addition to the communication route that directly connects the node device 5-1 and the aggregate 4, the node device 5-3 and the node device 5- There is a communication route connecting the node 5-1 and the aggregate 4 via 2. Further, the communication route between the node device 5-2 and the aggregate 4 is via the node device 5-3 and the node device 5-1 in addition to the communication route directly connecting the node device 5-2 and the aggregate 4. There is a communication route connecting the node device 5-2 and the aggregate 4. Therefore, the route cost of the relay device is recalculated by the above equation (2) in consideration of the communication route via the source device.

In the example shown in FIG. 4, the root costs of the node device 5-1 are 0.1 × 0.12 (probability A) and 0.1 × (1-0.12) × 0.115 (probability B). Can be recalculated as about 0.22 by the sum of. The root cost of the node device 5-2 is about 0. by the sum of 0.15 × 0.09 (probability A) and 0.15 × (1-0.09) × 0.115 (probability B). It can be recalculated as 029.

As a result of recalculating the root cost of the relay device as described above, if the root cost of the relay device changes, the root cost of the source device may also change. Therefore, the root cost of the source device is recalculated using the root cost of the relay device after the recalculation. Similarly, as a result of recalculating the root cost of the source device as described above, if the root cost of the source device changes, the root cost of the relay device may also change. Therefore, the root cost of the source device is recalculated using the root cost of the source device after the recalculation. In this way, the calculation of the route cost of the source device and the relay device is repeated. FIG. 5 is a diagram showing an example of the convergence calculation of the route cost in the network configuration shown in FIG. 4 (C). As shown in FIG. 5, as long as the link cost of each communication link does not change, the calculation result can be converged by repeating the calculation of the route cost of the source device and the relay device several times. As a result, the root cost of each communication device as shown in FIG. 2 can be obtained.

In the example shown in FIG. 4C, the source device and the destination device are connected via one relay device, but the source device and the destination device may be connected via a plurality of relay devices. , The root cost of each communication device can be calculated by the same calculation method as described above. Further, in the above description, the case of calculating until the root cost of all communication devices converges to a constant value has been described as an example, but it is not necessary to calculate until the root cost of each communication device converges to a constant value. .. This is because if each communication device possesses a root cost of an arbitrary value even if it is not an accurate value, each communication device can select the adjacent device as the destination device in ascending order of the root cost.

Further, in the above description, an example of the case where the root cost of each communication device constituting the wireless communication network 3 is calculated for the first time has been described with reference to FIG. However, even if the link cost of the communication link changes during the operation of the wireless communication network, the root cost of each communication device can be recalculated by the same method. Further, when the root cost of the node device 5 newly added to the wireless communication network 3 is calculated by using the root cost of the other communication device that has already been calculated, it can be calculated by the same method.

<Calculation method of route cost>
The communication device (aggregator 4 and node device 5) may perform the calculation of the route cost as described above with reference to FIG.

Specifically, for example, as shown in FIG. 6, each communication device holds a route cost table for recording the route cost of the communication device for each destination device, and the route cost table is exchanged with an adjacent device. The root cost of the communication device may be calculated. FIG. 6 is a diagram illustrating an example of a method of calculating a route cost performed by a communication device according to an embodiment.

In the example shown in FIG. 6, the transmitting side communication device A holds a route cost table in which the route cost of the transmitting side communication device A is recorded for each packet destination device. Similarly, the receiving-side communication device B holds a route cost table in which the route cost of the receiving-side communication device B is recorded for each packet destination device.

Further, as described above with reference to FIG. 3, each communication device calculates the link cost for each communication link connected to the adjacent device, and stores the calculated link cost in the link cost table in association with the identifier of the adjacent device. do. In the example shown in FIG. 6, the communication device B on the receiving side holds a link cost table including the link cost of the communication link connected to the communication device A on the transmitting side.

Each communication device exchanges the route cost table it holds with an adjacent device. Then, each communication device calculates the route cost for each destination device by the equation (2) using the held link cost table and the exchanged route cost table. In the example shown in FIG. 6, the communication device B on the receiving side exchanges the route cost table held by each other with the communication device A on the transmitting side. Then, the communication device B on the receiving side uses the link cost table held by the communication device B on the receiving side and the route cost table of the communication device A on the transmitting side acquired by exchange, and uses the third communication device C ( For example, the root cost of the communication device B on the receiving side whose destination device is the aggregate 4) is calculated.

As described above, according to the communication device according to the embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected and the appropriate destination in the mesh network for transmitting the packet. You can calculate the route cost to select the device.

Further, the route cost calculation described above with reference to FIG. 4 may be performed by the route cost calculation device (aggregator 4 or monitoring device 2).

Specifically, each communication device (aggregator 4 and node device 5) transmits the held link cost table to the root cost calculation device. The route cost calculation device calculates the root cost of each communication device with a specific communication device or all communication devices as the destination device by using the link cost for each communication link recorded in each received link cost table. The route cost calculation device transmits the calculation result to the corresponding communication device, and each communication device stores the route cost for each received destination device in the route cost table.

Thus, according to the route cost calculator according to the embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected and the packet is transmitted, which is appropriate for the mesh network. The route cost for selecting the destination device can be calculated.

<How to select the destination device>
As described above, when transmitting a packet to the destination device, each communication device (aggregator 4 and node device 5) transmits the adjacent device in ascending order of the route cost to the destination device among the route costs of each adjacent device. Select as the destination device. For example, each communication device may select a destination device according to a communication procedure as shown in FIG. 7. FIG. 7 is a diagram illustrating an example of a communication procedure of a communication device according to an embodiment.

For example, the node device 5-3 in which the data addressed to the aggregate 4 is generated broadcasts a packet transmission request to the adjacent node device 5-1 and the node device 5-2. Upon receiving the transmission request, the node device 5-1 and the node device 5-2 return the data request to the node device 5-3. The node device 5-3 selects the node device 5-1 having the smaller root cost for the aggregate 4 from the node device 5-1 and the node device 5-2 that received the data request as the destination device, and includes the data. The packet is sent to the node device 5-1. When selecting the destination device, the node device 5-3 may use the root cost of the node device 5-1 and the node device 5-2 stored in the root cost table. Alternatively, the node device 5-3 may use the route cost notified from the node device 5-1 and the node 5-2 in addition to the data request.

When the node device 5-2 receives the data packet from the node device 5-3, the node device 5-2 returns a reception response to the node device 5-3. Then, the node device 5-2 transmits the data packet to the aggregate 4 in the same manner.

As described above, according to the communication device according to the embodiment, by referring to the route cost of the neighboring device, a packet is transmitted to the destination device from the neighboring devices in which a plurality of communication routes to the destination device may exist. You can select the appropriate destination device that is likely to succeed.

<Configuration example of each device>
<< Node device >>
The node device 5 is an example of a communication device according to an embodiment. FIG. 8 is a diagram showing a configuration example of a node device according to an embodiment. In the configuration example shown in FIG. 8, the node device 5 is a sensor node and includes a measurement unit 51 and a wireless communication unit 52.

The measuring unit 51 is, for example, various sensors such as a temperature sensor, a humidity sensor, an illuminance sensor, a rain amount sensor, a volume sensor, and / or a pressure sensor. The measurement unit 51 measures the object at a predetermined cycle or at an arbitrary timing at the position where the measurement unit 51 is installed, and outputs the measurement data to the wireless communication unit 52.

The wireless communication unit 52 transmits / receives data such as measurement data from the measurement unit 51 to / from the aggregate 4. The wireless communication unit 52 includes a storage unit 521, a control unit 522, a transmission unit 523, and a reception unit 524.

The storage unit 521 is composed of, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), or the like. The storage unit 521 stores the identifier of the node device 5, the identifier of the aggregate 4, and the like. Further, the storage unit 521 stores a link cost table (see FIG. 3) in which the link cost for each communication link connecting the node device 5 and the adjacent device is stored. Further, the storage unit 521 stores a route cost table (see FIG. 6) in which the route cost for each destination candidate device that can be selected by the node device 5 as the destination device is stored. Depending on the embodiment, the storage unit 521 may further store the received power vs. packet loss rate table and the received power vs. bit error rate table as described above.

The control unit 522 is composed of, for example, a CPU (Central Processing Unit), a multi-core CPU, or a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), or the like). The control unit 522 includes a link cost calculation unit 5221, a route cost calculation unit 5222, and a destination device selection unit 5223. The control unit 522 executes, for example, a process as described below.

The link cost calculation unit 5221 calculates the link cost by using the calculation method as described above with reference to FIG. 3 and the like. Specifically, for example, the link cost calculation unit 5221 uses the number of transmission packets transmitted by the neighboring device to the node device 5 and the number of received packets received by the node device 5 from the neighboring device to link the link cost for each communication link. May be calculated. Further, for example, the link cost calculation unit 5221 may measure the received power of the packet received from the adjacent device and acquire the packet loss rate corresponding to the measured received power as the link cost for each communication link. Further, for example, the link cost calculation unit 5221 measures the received power of the packet received from the adjacent device, and communicates using the bit error rate corresponding to the measured received power, the packet size, and the number of packet transmission retries. You may calculate the link cost for each link.

The route cost calculation unit 5222 calculates the route cost by using the calculation method as described above with reference to FIGS. 4 to 6 and the like. Specifically, for example, the route cost calculation unit 5222 calculates the route cost of the node device 5 with respect to the destination device by using the route cost for each adjacent device and the link cost for each communication link. As described above, the route cost means that the packet does not reach the destination device from the neighboring device even if all the communication routes that can be selected between the neighboring device and the destination device of the packet that the node device 5 can directly communicate with are used. Refers to the packet loss rate. Further, the link cost refers to the packet loss rate at which packets do not reach the adjacent device from the node device 5 in the communication link between the node device 5 and the adjacent device. For example, as described above with reference to FIG. 6, the route cost calculation unit 5222 uses the route cost table acquired from the adjacent device and the link cost table stored in the storage unit 521 to use the route cost for each destination candidate device. May be calculated.

As described above with reference to FIG. 7 and the like, the destination device selection unit 5223 selects the adjacent device as the destination device in ascending order of the route cost for the destination device among the route costs for each adjacent device.

The control unit 522 generates a packet containing the measurement data by the measurement unit 51. The header of the generated packet includes the identifier of the node device 5 and the identifier of the destination device (for example, the aggregate 4) of the packet. The transmission unit 523 transmits the generated packet to the destination device according to the communication procedure as shown in FIG. 7. The transmitter 523 is configured by, for example, a wireless transmitter or the like.

Further, the control unit 522 determines the destination of the packet received by the reception unit 524. The receiving unit 524 is configured by, for example, a wireless receiver or the like. When the destination of the received packet is the node device 5, the control unit 522 executes the process according to the data of the received packet. When the destination of the packet is another communication device, the transmission unit 523 transmits the received packet to the destination device according to the communication procedure as shown in FIG. 7.

As described above, according to the communication device according to the embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected and the appropriate destination in the mesh network for transmitting the packet. You can calculate the route cost to select the device.

Further, according to the communication device according to the embodiment, by referring to the route cost of the adjacent device, the packet can be successfully transmitted to the destination device from the adjacent devices in which a plurality of communication routes to the destination device can exist. You can select the appropriate destination device that is likely to be.

<Aggregator>
The aggregate 4 is an example of a communication device according to an embodiment. Further, the aggregate 4 may be an example of a route cost calculation device depending on the embodiment. FIG. 9 is a diagram showing a configuration example of an aggregate according to an embodiment. In the configuration example shown in FIG. 9, the aggregate 4 includes a wireless communication unit 41 and an information processing unit 42.

The wireless communication unit 41 transmits / receives data to / from the node device 5 using wireless communication. The wireless communication unit 41 includes a storage unit 411, a control unit 412, a transmission unit 413, and a reception unit 414.

The storage unit 411 is composed of, for example, a RAM, a ROM, or the like. The storage unit 411 stores the identifier of the aggregate 4 and the like. Further, the storage unit 411 stores a link cost table (see FIG. 3) in which the link cost for each communication link connecting the aggregate 4 and the adjacent device is stored. Further, the storage unit 411 stores a route cost table (see FIG. 6) in which the route cost for each destination candidate device that can be selected by the aggregate 4 as the destination device is stored. Depending on the embodiment, the storage unit 411 may further store the received power vs. packet loss rate table and the received power vs. bit error rate table as described above.

The control unit 412 is composed of, for example, a CPU, a multi-core CPU, a programmable device (FPGA, PLD, etc.) or the like. The control unit 412 includes a link cost calculation unit 4121, a route cost calculation unit 4122, and a destination device selection unit 4123.

The link cost calculation unit 4121 can perform the same processing as the link cost calculation unit 5221 described above. The route cost calculation unit 4122 can perform the same processing as the route cost calculation unit 5222 described above. The destination device selection unit 4123 can perform the same processing as the above-mentioned destination device selection unit 5223.

The control unit 411 generates a packet to be transmitted to the node device 5, and transmits the generated packet to the destination device via the transmission unit 412. The transmitter 412 is composed of, for example, a wireless transmitter or the like. Further, the control unit 411 receives the packet transmitted from the node device 5 via the reception unit 413, and processes the received packet. The receiving unit 413 is composed of, for example, a wireless receiver or the like. For example, when the data of the received packet is the measurement data by the node device 5, the control unit 411 outputs the data of the received packet to the information processing unit 42.

The information processing unit 42 transmits / receives data to / from the monitoring device 2 via, for example, the wide area network 6. The information processing unit 42 is composed of, for example, a board computer or the like. The information processing unit 42 includes a processing unit 421, a storage unit 422, and a communication unit 423.

The processing unit 421 is composed of, for example, a CPU, a multi-core CPU, a programmable device (FPGA, PLD, etc.) or the like. The storage unit 422 is composed of, for example, a RAM, a ROM, or the like. The communication unit 423 is composed of, for example, a wired and / or wireless communication interface device or the like.

The processing unit 421 processes data transmitted / received to / from the node device 5 via the wireless communication unit 41 and data transmitted / received to / from the monitoring device 2 via the communication unit 423. For example, the processing unit 421 receives the measurement data from the node device 5 via the control unit 412, and transmits the received measurement data to the monitoring device 2 via the communication unit 423.

Further, when the aggregate 4 functions as a route cost calculation device according to the embodiment, the processing unit 421 aggregates the link cost table stored in each communication device via the wireless communication unit 41. That is, the processing unit 421 receives the phosphorus cost table stored in each node device 5 from each node device 5 via the wireless communication unit 41, and receives the phosphorus cost table stored in the storage unit 411 via the control unit 411. do. The processing unit 421 calculates the route cost for each destination candidate device for each communication device using the link cost stored in the aggregated link cost table. The route cost for each destination candidate device is that the packet arrives from the communication device to the destination candidate device even if all selectable communication routes between the communication device and the destination candidate device of the packet transmitted by the communication device are used. Does not refer to the packet loss rate. The processing unit 421 transmits the calculated route cost to the corresponding communication device via the wireless communication unit 41.

Thus, according to the route cost calculator according to the embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected and the packet is transmitted, which is appropriate for the mesh network. The route cost for selecting the destination device can be calculated.

<Monitoring device>
The monitoring device 2 is an example of a route cost calculation device according to an embodiment. The monitoring device 2 is, for example, a computer. FIG. 10 is a diagram showing a configuration example of a monitoring device according to an embodiment. In the configuration example shown in FIG. 10, the monitoring device 2 includes a storage unit 21, a processing unit 22, an input unit 23, an output unit 24, a communication unit 25, and a storage medium reading / writing unit 26.

The storage unit 21 is composed of, for example, a RAM, a ROM, or the like. The processing unit 22 is composed of, for example, a CPU, a multi-core CPU, a programmable device (FPGA, PLD, etc.) or the like. The input unit 23 is composed of, for example, a keyboard, a mouse, a touch pad, and the like. The output unit 24 is composed of, for example, a liquid crystal display, a CRT (Cathode Ray Tube), or the like. The communication unit 25 is composed of, for example, a wired and / or wireless communication interface device or the like. The storage medium reading / writing unit 26 includes a device that reads data from a portable storage medium such as a magnetic disk, an optical disk, a magneto-optical disk, or a flash memory, and writes the data to the portable storage medium.

The processing unit 22 receives the measurement data of each node device 5 via the communication unit 25. The processing unit 22 may display the received measurement data on the output unit 24.

Further, the processing unit 22 calculates the link cost of each communication device (aggregator 4 and node device 5). Specifically, for example, the processing unit 22 aggregates the link cost table stored in each communication device via the communication unit 25. The processing unit 22 calculates the route cost for each destination candidate device for each communication device using the link cost stored in the aggregated link cost table. The route cost for each destination candidate device is that the packet arrives from the communication device to the destination candidate device even if all selectable communication routes between the communication device and the destination candidate device of the packet transmitted by the communication device are used. Does not refer to the packet loss rate. The processing unit 22 transmits the calculated route cost to the corresponding communication device via the communication unit 25.

Thus, according to the route cost calculator according to the embodiment, if the transmission of the packet on the selected communication link fails, another communication link is reselected and the packet is transmitted, which is appropriate for the mesh network. The route cost for selecting the destination device can be calculated.

The present invention is not limited to the above embodiments, and various improvements and changes can be made without departing from the gist of the present invention.

1 Communication system 2 Monitoring device 3 Wireless communication network 4 Aggregator 5, 5-1 to 5-3 Node device 6 Wide area network 21 Storage unit 22 Processing unit 23 Input unit 24 Output unit 25 Communication unit 26 Storage medium read / write unit 41 Wireless communication Unit 42 Information processing unit 51 Measurement unit 52 Wireless communication unit 411 Storage unit 412 Control unit 413 Transmission unit 414 Reception unit 421 Processing unit 422 Storage unit 423 Communication unit 521 Storage unit 522 Control unit 523 Transmission unit 524 Reception unit 4121 Link cost calculation unit 4122 Route cost calculation unit 4123 Destination device selection unit 5221 Link cost calculation unit 5222 Route cost calculation unit 5223 Destination device selection unit A, B Communication devices L1 to L4 Communication links

Claims (9)

For each of the adjacent devices, which is the packet loss rate at which the packet does not reach the destination device from the adjacent device even if all the communication routes that can be selected between the adjacent device that the communication device can directly communicate with and the destination device of the packet are used. At the packet loss rate at which the packet does not reach the adjacent device from the communication device at the communication link between the communication device and the adjacent device that transmits the packet by associating the root cost of the communication device with the identifier of the communication device. A communication device including a route cost calculation unit that calculates the route cost of the communication device with respect to the destination device by using the link cost for each communication link. Further, a destination device selection unit for selecting the adjacent device as the destination device to which the communication device directly transmits the packet is provided in ascending order of the route cost to the destination device among the route costs for each adjacent device. , The communication device according to claim 1. Further provided is a link cost calculation unit that calculates the link cost for each communication link using the number of transmitted packets transmitted by the adjacent device to the communication device and the number of received packets received by the communication device from the adjacent device. , The communication device according to claim 1 or 2. The communication device according to claim 1 or 2, further comprising a link cost calculation unit in which the communication device acquires a packet loss rate corresponding to the received power of a packet received from the adjacent device as the link cost for each communication link. .. A link cost calculation unit that calculates the link cost for each communication link using the bit error rate corresponding to the received power of the packet received by the communication device from the adjacent device, the packet size, and the number of packet transmission retries. The communication device according to claim 1 or 2, further comprising. A storage unit that stores a link cost table in which the link cost for each communication link is stored and a route cost table in which the route cost for each destination candidate device that the communication device can select for the destination device is stored. Further preparation
The route cost calculation unit calculates the route cost for each destination candidate device using the route cost table acquired from the adjacent device and the link cost table stored in the storage unit.
The communication device according to any one of claims 1 to 5. The communication link, which is the packet loss rate at which the packet does not reach the adjacent device from the communication device in the communication link between the communication device to which the identifier is associated and transmits the packet and the adjacent device capable of directly communicating with the communication device. A communication device that stores a link cost table that stores each link cost,
All selectable communication routes between the communication device and the destination candidate device for packets transmitted by the communication device using the link cost stored in the link cost table aggregated from the plurality of communication devices. A communication system including a route cost calculation device for calculating a route cost for each destination candidate device, which is a packet loss rate at which the packet does not reach the destination candidate device even if the communication device is used. The communication device uses the root cost of each adjacent device capable of directly communicating with the communication device and the link cost of each communication link between the communication device and the adjacent device to provide the route of the communication device. Calculate the cost,
The communication system according to claim 7. The packet arrives at the destination device from the neighboring device even if all communication routes that can be selected between the neighboring device that is associated with the identifier and the communication device that transmits the packet can directly communicate with the destination device of the packet are used. The root cost for each adjacent device, which is the packet loss rate that does not occur, and the communication link, which is the packet loss rate at which the packet does not reach the adjacent device from the communication device in the communication link between the communication device and the adjacent device. A route cost calculation method in which a computer executes to calculate the root cost of the communication device with respect to the destination device by using the link cost for each.

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