JP2019068126A - Communication device, communication system, and route cost calculation method - Google Patents

Abstract

To provide a communication device that calculates a route cost for selecting an appropriate transmission destination device in a mesh network in which if transmission of a packet on a selected communication link is failed, another communication link is re-selected and the packet is transmitted.SOLUTION: A communication device 5 includes a route cost calculation unit 5221 for calculating a route cost of the communication device 5 for a destination device by using a route cost per adjacent device which is a packet loss rate at which a packet does not reach from an adjacent device to a destination device even if all communication routes selectable between the adjacent device with which the communication device 5 can directly communicate and the destination device of a packet and a link cost per communication link which is a packet loss rate at which a packet does not reach from the communication device 5 to the adjacent device on a communication link between the communication device and adjacent device.SELECTED DRAWING: Figure 8

Description

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

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

  The communication network described in Patent Document 1 includes 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 processing for searching for an adjacent terminal capable of direct communication, and the master unit receives, from each slave unit, link information on the adjacent terminal with which the slave unit can directly communicate. Based on the received link information, the master unit is composed of a one-dimensional data table with 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. Make it recorded in the topology table. Then, based on the link information recorded in the topology table, the parent device performs route search processing for obtaining a communication route to each child device using the Dijkstra algorithm.

JP 2008-301269 A

  In a mesh network that reselects another communication link and transmits a packet when 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 It can. Therefore, in such a mesh network, the communication device (the transmission source device and the relay device) transmitting the packet succeeds in transmitting the packet to the destination device from among the adjacent devices which may have a plurality of communication routes to the destination device. It is desirable to select a likely suitable destination device. The adjacent device is a communication device connected by a communication link to a communication device that transmits a packet, and refers to a communication device with which a communication device that transmits a packet can directly communicate. Also, the transmission destination device refers to an adjacent device selected by the communication device that transmits the packet as the communication device that transmits the packet directly.

  However, the Dijkstra algorithm used in the method of establishing a communication route in Patent Document 1 described above is an algorithm for searching for the shortest path, and the method described in Patent Document 1 is a method of connecting a slave unit and a master unit. It only searches for communication routes. For this reason, the method described in Patent Document 1 can not be used for the mesh network as described above.

  An object according to one aspect of the present invention is to reselect another communication link and select an appropriate destination device in a mesh network that transmits a packet when transmission of a packet on a selected communication link fails. Providing a communication device for calculating the route cost of

  A communication apparatus according to an aspect of the present invention includes a route cost calculation unit. The route cost calculation unit calculates the route cost of the communication device with respect to the destination device using the route cost of each adjacent device and the link cost of 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 selectable between the adjacent device with which the communication device can directly communicate and the destination device of the packet are used. It is. The link cost for each communication link is a packet loss rate at which packets do not reach the adjacent device from the communication device in the communication link between the communication device and the adjacent device.

  According to the communication device according to one embodiment, if transmission of a packet on the selected communication link fails, another communication link is reselected to select an appropriate destination device in the mesh network that transmits the packet. You can calculate the root cost to

FIG. 1 is a diagram showing an example of a configuration of a communication system according to an embodiment. It is explanatory drawing of the link cost and route cost according to embodiment. It is a figure explaining an example of the calculation method of the link cost according to 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 convergence calculation of the route cost in the network configuration shown to FIG. 4C. It is a figure explaining an example of the calculation method of the root cost which the communications device according to an embodiment performs. It is a figure explaining an example of a communication procedure of a communication apparatus according to an embodiment. It is a figure which shows the structural example of the node apparatus according to embodiment. It is a figure showing an example of composition of an aggregator according to an embodiment. It is a figure which shows the structural example of the monitoring apparatus according to embodiment.

Hereinafter, embodiments will be described in detail based on the drawings.
<Configuration Example of Communication System>
FIG. 1 is a diagram illustrating an exemplary configuration 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 aggregator 4 and a plurality of node devices 5 (5-1 to 5-3). In the example illustrated 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 and receives data to and from the concentrator 4 using wireless communication. In addition, the node device 5 can transmit 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 concentrator 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 illustrated in FIG. 1, the aggregator 4 transmits 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 concentrator 4. In the example shown in FIG. 1, the monitoring device 2 and the concentrator 4 are connected via the wide area network 6.

  The concentrator 4 and the node device 5 are an example of the communication device according to the embodiment. The monitoring device 2 is an example of a route cost calculation device according to the embodiment. Note that, depending on the embodiment, the concentrator 4 may be an example of a route cost calculation device according to the embodiment.

  The wireless communication network 3 is a multi-hop wireless communication network. As shown in FIG. 1, the wireless communication network 3 includes not only the node device 5 that directly communicates with the concentrator 4 but also the node device 5 that communicates with the concentrator 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 directly communicate with the concentrator 4. On the other hand, the node device 5-3 communicates with the concentrator 4 via the node device 5-1 or the node device 5-2.

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

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

<Root cost and link cost>
FIG. 2 is an explanatory diagram of link cost and route cost according to the embodiment. In FIG. 2, numbers in parentheses near the respective communication devices (the aggregator 4 and the node device 5) indicate route costs of the respective communication devices when the aggregator 4 is the destination device of the packet. In the example illustrated in FIG. 2, the root cost of the aggregator 4 is 0, the root cost of the node device 5-1 is 0.014, and the root cost of the node device 5-2 is 0.017. The root cost of the device 5-3 is 0.025.

  For example, in the concentrator 4 and the node device 5-3 which are adjacent devices of the node device 5-1, the root cost of the concentrator 4 is smaller than the route cost of the node device 5-3. Therefore, the node device 5-1 first selects the aggregator 4 as the transmission destination device among the aggregator 4 and the node device 5-3 which are adjacent devices, and transmits the packet from the node device 5-1 to the aggregator 4 If the node device 5-3 fails, the node device 5-3 is next selected as the destination device. In addition, in the node device 5-1 and the node device 5-2, which are adjacent devices to 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 transmission 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 described later, the route cost of each communication device is calculated by each communication device (the concentrator 4 and the node device 5) or the route cost calculation device (the monitoring device 2 or the concentrator 4) using the link cost. The link cost refers to a packet loss rate at which a packet does not reach the adjacent apparatus from the communication apparatus in the communication link between the communication apparatus transmitting the packet and the adjacent apparatus. In FIG. 2, numerals written in the vicinity of the communication links L1 to L4 connecting the communication devices indicate link costs of the communication links L1 to L4. For example, the link cost 0.1 of the communication link L1 indicates that packet transmission between the node device 5-1 and the aggregator 4 fails with a probability of one out of ten. In addition, although the case where the communication performance (transmission performance and reception performance) of each communication apparatus is the same is shown as an example in FIG. 2, the communication performance of each communication apparatus may be different.

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

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

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

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

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

  For example, it is assumed that the number of transmission packets transmitted from the communication apparatus A on the transmitting side to the communication apparatus B on the receiving side is X and the number of received packets received from the communication apparatus A on the transmitting side is Y. Assume. Under this assumption, the link cost of the communication link that connects the communication apparatus A on the transmission side and the communication apparatus B on the reception side is 1− (Y / X).

  As shown in FIG. 3, the communication apparatus B on the receiving side stores the identifier of the communication apparatus A on the transmitting side, the number of received packets, and the link cost in the link cost table in association with each other. As described above, each communication device calculates the link cost for each communication link connecting to the adjacent device, stores the calculated link cost in the link cost table in association with the identifier of the adjacent device.

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

  For example, the communication device (the aggregator 4 and the node device 5) may obtain a 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 in advance the relationship between the received power and the packet loss rate as the reception performance of the communication device, and stores the measurement result in the received power vs. packet loss rate table. When the communication device receives a packet from the adjacent device, the communication device refers to the received power-to-packet loss rate table, and communicates the packet loss rate corresponding to the received power of the received packet between the communication device and the adjacent device. Acquire as link cost of link.

  Also, the communication device (the aggregator 4 and the 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 transmission retries of the packet, for each communication link. The link cost may be calculated. Specifically, for example, the communication apparatus measures in advance the relationship between the received power and the bit error rate as the reception performance of the communication apparatus, and stores the measurement result in the received power vs. bit error rate table. The communication apparatus refers to the received power-to-bit error rate table when receiving a packet from the adjacent apparatus, and obtains a bit error rate corresponding to the received power of the received packet. Then, the communication apparatus calculates the packet loss rate of the communication link with the adjacent apparatus that has 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 protocol. .

<< Example of calculation of root cost >>
The root cost of each communication device (aggregator 4 and node device 5) is calculated by each communication device or route cost calculator (monitoring device 2 or concentrator 4) using the link cost calculated by each communication device. FIGS. 4A to 4C are diagrams for explaining an example of a method of calculating the route cost according to the embodiment. In one example shown in FIGS. 4A to 4C, the source apparatus and the relay apparatus of the packet are the node apparatus 5, and the destination apparatus of the packet is the aggregator 4. That is, FIG. 4 (A)-FIG.4 (C) show the case where the node apparatus 5 transmits the packet which makes the aggregator 4 a destination apparatus as an example.

  First, FIG. 4A shows an example of a case where a transmission source device of a packet and a destination device of the packet are connected by a communication link. Specifically, the node device 5-1 and the concentrator 4 are connected by the communication link L1, and the node device 5-2 and the concentrator 4 are connected by the communication link L2. As described above, in the case where the transmission source device and the destination device are directly connected to each other without passing through the relay device that relays the packet between the two communication devices, the route 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 route cost of the destination device is zero. Therefore, in the example shown in FIG. 4A, the root cost of the aggregator 4 is zero.

  If the source device directly transmits to the destination device via the communication link, there is no packet loss due to relaying. For this reason, the route cost of the transmission source device is the same as the link cost of the communication link connecting the transmission source device and the destination device. Therefore, in the example illustrated 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 concentrator 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 concentrator 4.

  Next, FIG. 4B shows an example of a case where the transmission source device and the destination device are connected via the relay device. Specifically, the node device 5-3 and the concentrator 4 are linked via the node device 5-1. Further, FIG. 4B shows an example of the case where there is one communication route connecting the transmission source device to the destination device. Specifically, the communication route connecting the node device 5-1 to the concentrator 4 is a single communication route composed of the communication link L3 and the communication link L1. As described above, in the case where the transmission source device and the destination device are connected by one 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 aggregator 4 is zero.

  The route cost of the relay device linked with 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, similarly to the route cost of the transmission source device described in FIG. is there. Therefore, in the example illustrated 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 concentrator 4.

  The route cost of the transmission source device linked to the relay device via the communication link is that the packet is lost either in the communication link between the transmission source device and the relay device, or in the communication route between the relay device and the destination device It is a probability. The probability of packet loss on the communication route between the relay device and the destination device indicates 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 can not transmit a packet to the node device 5-1, and the node device from the node device 5-3 This is the sum of the probability that the node device 5-1 fails to transmit the packet to the aggregator 4 when the packet is transmitted to 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, although the transmission source device and the destination device are connected via one relay device, even in the case where the transmission source device and the destination device are connected via a plurality of relay devices. The route 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 transmission source device and the destination device are connected via the relay device. Specifically, the node device 5-3 and the concentrator 4 are linked via the node device 5-1 or the node device 5-2. Further, FIG. 4C shows an example of a case in which there are a plurality of communication routes connecting the transmission source device to the destination device. Specifically, the communication route connecting the node device 5-3 to the concentrator 4 includes a first communication route including the communication link L3 and the communication link L1, and a communication link L4 and the communication link L2. And a second communication route. In addition, in the communication route connecting the node device 5-3 to the aggregator 4, the communication route in the case where the node device 5-1 which receives 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 the communication link L3, the communication link L4, and the communication link L2. Furthermore, in the communication route connecting the node device 5-3 to the aggregator 4, the communication route in the case where the node device 5-2 which has received 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 the communication link L4, the communication link L3, and the communication link L1. Thus, in the case where the transmission 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 aggregator 4 is zero.

  The route cost of the relay apparatus linked with the destination apparatus via the communication link is the same as the link cost of the communication link connecting the destination apparatus and the relay apparatus, as in FIG. 4 (B). Therefore, in the example illustrated 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 route cost of the transmission source device linked to the plurality of relay devices via the communication link is calculated as follows. As described above, in the wireless communication network 3, each communication device reselects another communication link and transmits a packet when transmission of a packet on the selected communication link fails. In addition, when there are a plurality of adjacent devices, the communication device that transmits the packet selects the adjacent device as the transmission destination device in ascending order of the route cost for the destination device among the route costs of the adjacent devices. Therefore, in such a mesh network, the route cost of an apparatus (transmission source apparatus or relay apparatus) transmitting a packet is calculated by the sum of the probability A and the probability 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. Also, probability B indicates that, when transmission of a packet on the selected communication link fails, another communication link is reselected and the communication device that transmits the packet selects an adjacent device selected in order of small route cost to the destination device This is the sum of the probability of packet loss on the communication route to the destination device.

  In the example illustrated in FIG. 4C, the probability A is a probability that the node device 5-3 can not transmit a packet to any of the node device 5-1 and the node device 5-2, and 0.12 × 0. It is 09. Also, the probability B is a probability that the node device 5-3 transmits a packet to the node device 5-1 but fails to transmit the packet to the aggregator 4 in the node device 5-1, and a packet to the node device 5-1 The node device 5-3 transmits a packet to the node device 5-2, but the node device 5-2 has a probability of failing to transmit the packet to the aggregator 4 in the node device 5-2. 0.12) x 0.1 + 0.12 x (1-0.09) x 0.15. Therefore, the root cost of the node device 5-3 is approximately 0.115 which is the sum of the probability A and the probability B.

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

  In the example shown in FIG. 4, the root cost of the node device 5-1 is 0.1 × 0.12 (probability A) and 0.1 × (1−0.12) × 0.115 (probability B). It can be recalculated to about 0.22 by the sum of. Further, the root cost of the node device 5-2 is approximately 0. 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 route cost of the relay device as described above, if the route cost of the relay device changes, the route cost of the transmission source device may also change. Therefore, the route cost of the transmission source device is recalculated using the route cost of the relay device after the recalculation. Similarly, as a result of recalculation of the route cost of the source device as described above, if the route cost of the source device changes, the route cost of the relay device may also change. Therefore, the route cost of the transmission source device is recalculated using the route cost of the transmission source device after the recalculation. Thus, the calculation of the route cost of the transmission source device and the relay device is repeated. FIG. 5 is a diagram showing an example of calculation of convergence of 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 root cost of the transmission source device and the relay device several times. As a result, the route cost of each communication device as shown in FIG. 2 can be obtained.

  In the example shown in FIG. 4C, although the transmission source device and the destination device are connected via one relay device, even in the case where the transmission source device and the destination device are connected via a plurality of relay devices. The route cost of each communication device can be calculated by the same calculation method as described above. In the above description, although the case where calculation is performed until the route costs of all the communication devices converge to a constant value is described as an example, the route costs of each communication device may not be calculated to converge to a constant value. . This is because each communication device can select an adjacent device as a destination device in ascending order of the route cost if each communication device possesses an arbitrary value of the route cost even if it is not an accurate value.

  Further, in the above, an example in the case of calculating the route cost of each communication device configuring the wireless communication network 3 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 route cost of each communication device can be recalculated by the same method. Also, in the case of calculating the route cost of the node device 5 newly added to the wireless communication network 3 using the calculated route costs of other communication devices, the same method can be used.

<How to calculate root cost>
The calculation of the route cost as described above with reference to FIG. 4 may be performed by the communication device (the aggregator 4 and the node device 5).

  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 exchanges the route cost table with an adjacent device. The root cost of the communication device may be calculated. FIG. 6 is a diagram for explaining an example of a method of calculating a route cost performed by the communication device according to the embodiment.

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

  Also, as described above with reference to FIG. 3, each communication device calculates the link cost for each communication link connecting to the adjacent device, 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 apparatus B on the receiving side holds a link cost table including the link cost of the communication link connected to the communication apparatus A on the transmitting side.

  Each communication device exchanges the held route cost table with the adjacent device. Then, each communication device calculates the route cost for each destination device using equation (2), using the link cost table held and the exchanged route cost table. In the example illustrated in FIG. 6, the communication devices B on the receiving side exchange the route cost tables held by each other with the communication device A on the transmitting side. Then, the communication apparatus B on the reception side uses the link cost table held by the communication apparatus B on the reception side and the route cost table of the communication apparatus A on the transmission side acquired by the exchange to use the third communication apparatus C ( For example, the route cost of the communication apparatus B on the receiving side with the aggregator 4) as the destination apparatus is calculated.

  Thus, according to the communication device according to the embodiment, when transmission of a packet on the selected communication link fails, an appropriate destination in the mesh network that reselects another communication link and transmits the packet The root cost for selecting a device can be calculated.

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

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

  Thus, according to the route cost calculation device according to the embodiment, when transmission of a packet on the selected communication link fails, it is appropriate in a mesh network that reselects another communication link and transmits the packet. The root cost for selecting the destination device can be calculated.

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

  For example, the node device 5-3 that has generated data addressed to the aggregator 4 broadcasts a packet transmission request to the adjacent node device 5-1 and the node device 5-2. The node device 5-1 and the node device 5-2 having received the transmission request return the data request to the node device 5-3. The node device 5-3 selects, as a transmission destination device, the node device 5-1 having a small root cost for the aggregator 4 among the node devices 5-1 and 5-2 that have received the data request, and includes data. The packet is transmitted to the node device 5-1. When selecting the transmission destination device, the node device 5-3 may use the route cost of the node device 5-1 and the node device 5-2 stored in the route 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 receiving 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 aggregator 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 adjacent device, transmission of a packet from the adjacent device to the destination device among the adjacent devices in which there may be a plurality of communication routes to the destination device It is possible to select an appropriate destination device that is likely to succeed.

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

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

  The wireless communication unit 52 transmits and receives data such as measurement data by the measurement unit 51 with the aggregator 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 configured by, for example, a random access memory (RAM), a read only memory (ROM), or the like. The storage unit 521 stores the identifier of the node device 5, the identifier of the aggregator 4, and the like. The storage unit 521 also stores a link cost table (see FIG. 3) in which the link cost for each communication link that connects the node device 5 and the adjacent device is stored. Furthermore, the storage unit 521 stores a route cost table (see FIG. 6) in which a route cost for each destination candidate device that can be selected by the node device 5 as a destination device is stored. Note that, depending on the embodiment, the storage unit 521 may further store the received power-to-packet loss rate table and the received power-to-bit error rate table as described above.

  The control unit 522 is configured by, for example, a central processing unit (CPU), a multi-core CPU, or a programmable device (such as a field programmable gate array (FPGA) or a programmable logic device (PLD)). The control unit 522 includes a link cost calculation unit 5221, a route cost calculation unit 5222, and a transmission destination device selection unit 5223. The control unit 522 executes, for example, processing as described below.

  The link cost calculation unit 5221 calculates the link cost 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 adjacent device to the node device 5 and the number of received packets received by the node device 5 from the adjacent device for the link cost for each communication link. You may calculate Also, for example, the link cost calculation unit 5221 may measure the reception power of the packet received from the adjacent device, and acquire the packet loss rate corresponding to the measured reception power as the link cost for each communication link. Furthermore, 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 transmission retries of the packet. The link cost per link may be calculated.

  The route cost calculation unit 5222 calculates a route cost 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 using the route cost of each adjacent device and the link cost of 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 communication routes selectable between the neighboring device with which the node device 5 can directly communicate and the destination device of the packet are selected. Point to packet loss rate. Also, the link cost indicates a 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 be the route cost for each destination candidate device. You may calculate

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

  The control unit 522 generates a packet including 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 aggregator 4) of the packet. The transmitting unit 523 transmits the generated packet to the transmission destination device in accordance with the communication procedure as shown in FIG. The transmission unit 523 is configured of, for example, a wireless transmitter or the like.

  Also, the control unit 522 determines the destination of the packet received by the receiving unit 524. The receiving unit 524 is configured of, 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 processing in accordance with the data of the received packet. If 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.

  Thus, according to the communication device according to the embodiment, when transmission of a packet on the selected communication link fails, an appropriate destination in the mesh network that reselects another communication link and transmits the packet The root cost for selecting a device can be calculated.

  Also, according to the communication device according to the embodiment, by referring to the route cost of the adjacent device, it is possible to successfully transmit the packet to the destination device from among the adjacent devices which may have a plurality of communication routes to the destination device. It is possible to select an appropriate destination device that is likely to be.

<Consolidator>
The aggregator 4 is an example of the communication device according to the embodiment. Moreover, the aggregator 4 may be an example of a route cost calculation device depending on the embodiment. FIG. 9 is a diagram illustrating an exemplary configuration of a concentrator according to the embodiment. In the configuration example shown in FIG. 9, the concentrator 4 includes a wireless communication unit 41 and an information processing unit 42.

  The wireless communication unit 41 transmits and receives data to and 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 configured of, for example, a RAM, a ROM, and the like. The storage unit 411 stores the identifier of the aggregator 4 and the like. Further, the storage unit 411 stores a link cost table (see FIG. 3) in which link costs for each communication link connecting the concentrator 4 and the adjacent device are stored. Furthermore, the storage unit 411 stores a route cost table (see FIG. 6) in which a route cost for each destination candidate device that can be selected by the aggregator 4 as a destination device is stored. Note that, depending on the embodiment, the storage unit 411 may further store the reception power-to-packet loss rate table and the reception power-to-bit error rate table as described above.

  The control unit 412 is configured of, for example, a CPU, a multi-core CPU, or a programmable device (such as an FPGA or a PLD). The control unit 412 includes a link cost calculation unit 4121, a route cost calculation unit 4122, and a transmission destination device selection unit 4123.

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

  The control unit 411 generates a packet to be transmitted to the node device 5, and transmits the generated packet to the transmission destination device via the transmission unit 412. The transmission unit 412 is configured 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 receiving unit 413, and processes the received packet. The receiving unit 413 is configured of, for example, a wireless receiver or the like. For example, when the data of the received packet is 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 and receives data to and from the monitoring device 2 via the wide area network 6, for example. The information processing unit 42 is configured by, 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 configured of, for example, a CPU, a multi-core CPU, or a programmable device (such as an FPGA or a PLD). The storage unit 422 is configured by, for example, a RAM, a ROM, or the like. The communication unit 423 is configured by, for example, a wired and / or wireless communication interface device.

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

  When the aggregator 4 functions as a route cost calculation device according to the embodiment, the processing unit 421 aggregates link cost tables stored in the respective communication devices 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 apparatus for each communication apparatus using the link cost stored in the aggregated link cost table. The route cost for each destination candidate device means that the packet reaches the destination candidate device from the communication device even if all selectable communication routes between the communication device and the destination candidate device for packets transmitted by the communication device are used. Not refers 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 calculation device according to the embodiment, when transmission of a packet on the selected communication link fails, it is appropriate in a mesh network that reselects another communication link and transmits the packet. The root 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 the 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 the 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 read / write unit 26.

  The storage unit 21 includes, for example, a RAM, a ROM, and the like. The processing unit 22 is configured by, for example, a CPU, a multi-core CPU, or a programmable device (such as an FPGA or a PLD). The input unit 23 includes, for example, a keyboard, a mouse, and a touch pad. The output unit 24 is configured of, for example, a liquid crystal display or a CRT (Cathode Ray Tube). The communication unit 25 includes, for example, a wired and / or wireless communication interface device. The storage medium read / write unit 26 is constituted by, for example, 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 cause the output unit 24 to display the received measurement data.

  The processing unit 22 also calculates the link cost of each communication device (the concentrator 4 and the node device 5). Specifically, for example, the processing unit 22 aggregates link cost tables stored in the respective communication devices 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 means that the packet reaches the destination candidate device from the communication device even if all selectable communication routes between the communication device and the destination candidate device for packets transmitted by the communication device are used. Not refers 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 calculation device according to the embodiment, when transmission of a packet on the selected communication link fails, it is appropriate in a mesh network that reselects another communication link and transmits the packet. The root cost for selecting the destination device can be calculated.

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

DESCRIPTION OF SYMBOLS 1 communication system 2 monitoring apparatus 3 wireless communication network 4 aggregating unit 5, 5-5 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 Section 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 Root cost calculation unit 4123 Transmission destination device selection unit 5221 Link cost calculation unit 5222 Root cost calculation unit 5223 Transmission destination device selection unit A, B Communication devices L1 to L4 Communication link

Claims (9)

  Even when using all communication routes selectable between an adjacent device with which a communication device can directly communicate and a destination device of a packet, each adjacent device has a packet loss rate at which the packet does not reach the destination device from the adjacent device And the link cost for each communication link, which is a 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 communication apparatus, comprising: a route cost calculator configured to calculate the route cost of the communication apparatus with respect to a destination apparatus.   The apparatus further includes a transmission destination device selection unit that selects the adjacent device as the transmission destination device to which the communication device directly transmits the packet, in the order of the route cost for the destination device being smaller among the route costs for each adjacent device. The device according to claim 1.   The apparatus further comprises a link cost calculation unit that calculates the link cost for each communication link using the number of transmission packets transmitted by the adjacent apparatus to the communication apparatus and the number of received packets received by the communication apparatus from the adjacent apparatus. The communication device according to claim 1 or 2.   The communication apparatus according to claim 1, further comprising a link cost calculation unit configured to acquire, as the link cost for each communication link, a packet loss rate corresponding to received power of a packet received from the adjacent apparatus by the communication apparatus. .   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 from the adjacent device by the communication device, the packet size, and the number of transmission retries of the packet The communication device according to claim 1, further comprising: A storage unit storing a link cost table storing the link cost for each communication link, and a route cost table storing the route cost for each destination candidate apparatus that can be selected by the communication apparatus as the destination apparatus In addition,
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. A link cost for storing the link cost for each communication link, which is a 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 capable of direct communication with the communication device A communication device for storing a table;
All selectable communication routes between the communication device and destination candidate devices of packets transmitted by the communication device using the link cost stored in the link cost table aggregated from the plurality of communication devices And a route cost calculation device for calculating, for each of the communication devices, a route cost for each of the destination candidate devices, which is a packet loss rate at which the packet does not reach the destination candidate device from the communication device. The communication device uses the route 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 use the route of the communication device. Calculate the cost,
The communication system according to claim 7. Even when using all communication routes selectable between an adjacent device with which a communication device can directly communicate and a destination device of a packet, each adjacent device has a packet loss rate at which the packet does not reach the destination device from the adjacent device And the link cost for each communication link, which is a 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 method of calculating a root cost, wherein a computer executes calculating the root cost of the communication device relative to a destination device.

Images