Communication device, network system, and communication method

Abstract

To provide a communication device, a network system, and a communication method that can maintain high quality communication state by avoiding a tight state of communication.SOLUTION: When a control unit 11 of a communication device 10-2 communicatively connected to other communication devices 10-1 and 10-2 via a plurality of links 20-1 determines that a communication amount of data flowing through the links 20-1 exceeds a predetermined reference, the control unit performs a registration refusal process of refusing to set a new transmission route passing through the links 20-1 even if new route search data is newly received. The registration refusal process is performed by not obtaining route information from the new route search data or by not relaying the new route search data to the other communication devices 10-1 and 10-3.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a communication device, a network system, and a communication method that executes data relay processing. [Background technology]

[0002] In an inter-vehicle communication network that uses roadside units, the number of users participating in the network can increase due to traffic congestion, resulting in localized congestion. For example, Patent Document 1 discloses a control technique for resolving such congestion.

[0003] Patent document 1 describes a technology that compares the communication channel load of a peripheral device with the communication channel load of the device itself, identifies the peripheral device or the device itself with the highest communication channel load as the most loaded device, and changes congestion control based on the identified result. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-137656 Summary of the Invention [Problem to be solved by the invention]

[0005] In a network system using an AODV (Ad hoc On-Demand Distance Vector) type multi-hop format, a transmission route from a source communication device to a destination communication device is efficiently determined based on costs such as the number of hops. However, if a localized communication congestion state as described above occurs, the number of users using the determined transmission route will continue to increase unless the congestion is resolved, and the communication congestion state may worsen over time.

[0006] An object of the present invention is to provide a communication device, a network system, and a communication method that can avoid communication congestion and maintain high-quality communication conditions. [Means for solving the problem]

[0007] The present invention relates to a communication device communicatively connected to other communication devices via multiple links, the communication device comprising: a data relay processing unit that relays route search data received via a first link, which is one of the multiple links, and which has a destination of a specific communication device, to a next communication device connected to a link other than the first link; a storage unit that stores route information including a source and a destination obtained from the route search data; and a control unit that, if the destination of the received route search data is the communication device itself or if final route information from the communication device to the destination is stored in the storage unit, transmits route response data to the source communication device, including the route information for determining a transmission route to the destination communication device. When the control unit determines that the traffic volume of data flowing through the link exceeds a predetermined threshold, the control unit executes a registration refusal process that refuses to set up a new transmission route that passes through the link, even if the communication device receives new route search data. This configuration effectively prevents communication congestion from progressing, and also sets up a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system.

[0008] Preferably, the registration rejection process is a process of rejecting the setting of a new transmission route that passes through the first link even if the control unit receives the new route search data when the control unit determines that the communication volume of data flowing through the first link exceeds a predetermined standard. With this configuration, it is possible to avoid a situation in which the communication volume of the first link becomes congested and communication efficiency decreases.

[0009] When the control unit determines that the amount of data flowing through a second link, which is one of the plurality of links, exceeds a predetermined threshold, it is preferable that the control unit executes a registration refusal process to refuse to set a new transmission route that passes through the second link even if new route search data is received. This configuration can avoid congestion in the communication state on the second link and make the communication state of the entire network system more stable.

[0010] Preferably, the registration rejection process is a process in which, when the control unit determines that the total communication volume of data flowing through the plurality of links exceeds a predetermined threshold, the control unit rejects the establishment of a new transmission route that passes through the communication device itself, even if the new route search data is received. This configuration makes it possible to avoid a situation in which the communication device itself becomes congested and is unable to perform relay processing.

[0011] The registration rejection process is preferably performed by not acquiring the route information from the new route search data. With this configuration, a process of not registering a new transmission route that passes through a link with congested communication traffic can be realized with simple control.

[0012] The registration rejection process is preferably performed by not relaying the new route search data to other communication devices. With this configuration, a process of not registering a new transmission route that passes through a link with congested communication traffic can be realized with simple control.

[0013] Preferably, the communication device further includes a packet counter that counts packet data received via the link, and the control unit determines whether the communication volume exceeds a predetermined standard based on the detected value of the packet counter. With this configuration, the communication status of the link can be reliably detected based on the detected value of the packet counter, and whether the communication volume is congested can be accurately determined.

[0014] Preferably, the communication device further includes a wireless device that performs wireless communication with a mobile terminal, and the route search data is transmitted from the mobile terminal. With this configuration, even when the communication device is used in a roadside device or the like where the number of users participating in communication fluctuates frequently as users join and leave the communication range of the wireless device, it is possible to effectively avoid worsening of communication congestion and achieve stable communication.

[0015] Preferably, the communication device further comprises a first queue through which data originating from a specific mobile terminal passes, and a second queue through which data originating from a normal mobile terminal other than the specific mobile terminal passes, and the control unit prioritizes communication of data originating from the specific mobile terminal over communication of data originating from the normal mobile terminal, regardless of whether the amount of data communication through the first link exceeds a predetermined standard. With this configuration, data originating from a specific mobile terminal for which communication should be prioritized can be reliably transmitted to a target destination, regardless of the usage status of the network system of the normal mobile terminal.

[0016] Preferably, the communication device further includes a communication traffic prediction unit that predicts future communication traffic based on input communication traffic data, and the control unit determines whether the communication traffic of data flowing through the link exceeds a predetermined standard based on the data prediction value calculated by the communication traffic prediction unit. With this configuration, even if communication traffic is not currently congested, if there is a high probability that communication traffic will become congested in the future, communication congestion can be alleviated, thereby realizing more stable communication.

[0017] The present invention also relates to a network system in which a communication device is communicatively connected to a plurality of other communication devices via a plurality of links, wherein at least one of the plurality of communication devices comprises: a data relay processing unit that relays route search data, the route search data being received via a first link among the plurality of links and having a destination set to a specific communication device, to a next communication device connected to a link other than the first link; a storage unit that stores route information including a source and a destination acquired from the route search data; and a control unit that, if the destination of the received route search data is the communication device itself or if final route information from the communication device to the destination is stored in the storage unit, transmits route response data to the source communication device, the route information including the route information for determining a transmission route to the destination communication device. When the control unit determines that the traffic volume of data flowing through the link exceeds a predetermined threshold, the control unit executes a registration refusal process that refuses to set a new transmission route that passes through the link even if new search data is received. This configuration effectively prevents communication congestion from progressing, and also sets a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system.

[0018] The present invention also relates to a communication method for a communication device communicatively connected to other communication devices via a plurality of links, the method comprising: a data relay processing step of relaying route search data, the route search data having a destination of a specific communication device received via a first link that is one of the plurality of links, to a next communication device connected to a link different from the first link; a storage step of storing route information including a source and a destination acquired from the route search data in a storage unit; a response control step of transmitting route response data, including the route information for determining a transmission route to the destination communication device, to the source communication device when the destination of the received route search data is the source communication device or when final route information from the source communication device to the destination communication device is stored in the storage unit; and a registration refusal processing step of refusing to set a new transmission route that passes through the link even when new route search data is received, when it is determined that the traffic volume of data flowing through the link exceeds a predetermined standard. This method effectively prevents communication congestion from progressing, and sets a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a communication device, a network system, and a communication method that can avoid communication congestion and maintain high-quality communication conditions. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating an example of a network system to which a communication state according to an embodiment of the present invention is applied; [Figure 2] 1 is a block diagram showing an example of the configuration of a communication device according to an embodiment of the present invention; [Figure 3] FIG. 4 is a schematic diagram illustrating control of a normal state of the communication device according to the present embodiment. [Figure 4] FIG. 10 is a schematic diagram illustrating control of a congestion state of a communication device according to the present embodiment. [Figure 5]10 is a flowchart illustrating an example of a control flow regarding relay processing of the communication device of the present embodiment. [Figure 6] 10 is a flowchart illustrating an example of a flow of control of a tight state of a communication device according to the present embodiment. [Figure 7] FIG. 10 is a schematic diagram showing a network system according to a first modified example. [Figure 8] FIG. 10 is a schematic diagram illustrating data processing for each queue in a communication device according to a first modified example. [Figure 9] 10 is a table showing an example of a route table held in a communication device of a first modified example. [Figure 10] FIG. 10 is a block diagram illustrating an example of the configuration of a communication device that determines the communication state based on a packet prediction value obtained using a trained model of a second modified example. [Figure 11] 10 is a graph showing a communication state predicted by a communication device of a second modified example. [Figure 12] FIG. 10 is a schematic diagram showing a network system according to a third modified example. [Figure 13] FIG. 11 is a block diagram showing an example of the configuration of a communication device according to a fourth modified example. [Figure 14] FIG. 13 is a block diagram showing an example of the configuration of a packet relay processing unit of a communication device according to a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] <Network System> 1 is a schematic diagram showing an example of a network system 1 to which communication devices 10-1 to 10-7 according to an embodiment of the present invention are applied. The network system 1 realizes communication between mobile terminals 101a to 101d and communication between the mobile terminals 101a to 101d and a cloud service 3 via a GW (Gateway) 2.

[0023] 1 shows an example of mobile terminals 101a to 101d as communication devices mounted on vehicles, but this is not limiting. Mobile terminals 101a to 101d may be held by a walking user carrying a smartphone or the like as a communication terminal, or by a user riding a bicycle. Alternatively, mobile terminals 101a to 101d may be mounted on a drone having autonomously moving means of travel or flying means. In other words, mobile terminals 101a to 101d can be considered communication devices that are intended to be mobile.

[0024] The network system 1 of this embodiment includes a plurality of communication devices 10-1 to 10-7 and links 20-1 to 20-7 that connect the communication devices 10-1 to 10-7.

[0025] The communication devices 10-1 to 10-7 are node devices installed in a city. Each of the communication devices 10-1 to 10-7 includes one or more RSUs (Road Side Units) 110 as wireless devices. The communication devices 10-1 to 10-7 communicate with the mobile terminals 101a to 101d via the RSUs 110a to 110c. Note that in FIG. 1, the RSUs 110 are not shown for the communication devices 10-2, 10-3, and 10-5 to 10-7. Furthermore, in this embodiment, the communication device 10-1 and the RSUs 110a to 110c, which are node devices, are illustrated as separate structures, but the communication device 10-1 and the RSUs 110a to 110c may also be configured as an integrated device.

[0026] For example, as shown in FIG. 1, three RSUs 110a to 110c are installed in the communication device 10-1, and one RSU 110d is installed in the communication device 10-4. The RSU 110a of the communication device 10-1 is communicating with the mobile terminal 101a, and the RSU 110b is communicating with the mobile terminal 101b. At the time shown in FIG. 1, the RSU 110c is not communicating with the mobile terminal 101c, but when the RSU 110c enters the communication range of the RSU 110c, the RSU 110c and the mobile terminal 101c are connected. Furthermore, the RSU 110d of the communication device 10-4 is communicating with the mobile terminal 101d.

[0027] Links 20-1 to 20-7 connect communication devices 10-1 to 10-7 so that they can communicate with each other. In the example shown in Fig. 1, multiple communication devices 10-1 to 10-7 are connected in a loop by links 20-1 to 20-7. Note that the loop connection is just an example, and multiple communication devices 10-1 to 10-7 may also be connected to each other in a mesh pattern.

[0028] The communication devices 10-1 to 10-7 connected by the links 20-1 to 20-7 have a common function for establishing communication.

[0029] The links 20-1 to 20-7 constituting the network system 1 of this embodiment are wired, such as optical fiber cables or metal cables. Note that the links 20-1 to 20-7 are not limited to a configuration in which communication between the communication devices 10-1 to 10-7 is established by wired connections, and some or all of the links 20-1 to 20-7 may be configured to establish communication between the communication devices 10-1 to 10-7 wirelessly. In the example of the network system 1 shown in Fig. 1, the shortest path is set in a format similar to the AODV (Ad hoc On-Demand Distance Vector) type multi-hop format used in the field of wireless communications.

[0030] <Communication Device> Next, common functions of the communication devices 10-1 to 10-7 will be described with reference to Fig. 2. In the following description, one of the communication devices 10-1 to 10-7 will be described as the communication device 10.

[0031] 2 is a block diagram showing an example of the configuration of communication devices 10-1 to 10-7 according to an embodiment of the present invention. As shown in FIG. 2, communication device 10 includes control unit 11, storage unit 12, packet relay processing unit 13, receiving units 14-1 to 14-n, and transmitting units 15-1 to 15-n.

[0032] The control unit 11 reads data such as programs stored in the storage unit 12 and executes various controls for functioning the communication device 10. The various controls include, for example, processing related to a route request (RREQ) and a route reply (RREP), processing for executing the functions of the packet relay processing unit 13, processing for updating data stored in the storage unit 12, and the like.

[0033] The storage unit 12 is configured by a semiconductor memory or the like. The storage unit 12 stores various types of information for functioning the communication device 10. The various types of information include, for example, programs and data for executing processes related to route search, which will be described later.

[0034] The storage unit 12 of this embodiment holds a route table 121 for managing route entries, which are information for forwarding packets. The route entries are information for establishing a route between communication devices 10 when the communication devices 10 receive a route request (RREQ) and a route reply (RREP). The contents of the route entries will be described later.

[0035] The receiving units 14-1 to 14-n receive packets via the links 20. The transmitting units 15-1 to 15-n transmit packets via the links 20. In this embodiment, a receiving unit and a transmitting unit having the same number after a hyphen are connected to the same link 20. For example, the receiving unit 14-1 and the transmitting unit 15-1 are connected to the same link 20. In the example of FIG. 1, two links 20 are connected to the communication device 10, and therefore two of the receiving units 14-1 to 14-n and the transmitting units 15-1 to 15-n are connected to the links. When two links are connected, the communication device 10 may be configured to include only the receiving units 14-1 to 14-2 and the transmitting units 15-1 to 15-2.

[0036] The packet relay processing unit 13 has a switch unit 130 that switches (exchanges) packets between each link 20. The switch unit 130 selects a corresponding transmitter 15-1 to 15-n based on information stored in the header of a packet received by the receivers 14-1 to 14-n, and executes a process of relaying the packet to the destination communication device 10.

[0037] Packet relay processing unit 13 of this embodiment includes packet counters 200-1 to 200-n corresponding to receiving units 14-1 to 14-n. Packet counters 200-1 to 200-n are communication information acquisition units that count packets received by receiving units 14-1 to 14-n. Receiving units 14-1 to 14-n and packet counters 200-1 to 200-n, each having the same number after a hyphen, correspond to one another.

[0038] The control unit 11 determines whether the communication state is congested based on the number of packets counted by the packet counters 200-1 to 200-n. More specifically, the control unit 11 monitors the flow rate (number of packets x packet size), i.e., the stream volume. The control unit 11 determines that the communication state is congested when the stream volume detected by the packet counters 200-1 to 200-n is equal to or greater than a set threshold (e.g., 90%) set for the expected stream volume. Note that the method for determining whether the communication state is congested is not limited to this. For example, the communication state may be determined based on the number of packets per unit time (throughput), or the communication state may be determined using another method.

[0039] When the communication state is congested, the control unit 11 executes control to relieve the congested state. Hereinafter, the control executed by the control unit 11 when the communication state is not congested will be referred to as control in a normal state, and the control executed by the control unit 11 when the communication state is congested will be referred to as control in a congested state.

[0040] <Normal state control> First, control in the normal state will be described with reference to Fig. 3. Fig. 3 is a schematic diagram illustrating control in the normal state of the communication device 10 of this embodiment. In the following description, it is assumed that, in the network system 1 shown in Fig. 3, communication is established between the RSU 110a of the communication device 10-1 and the mobile terminal 101a, and a route search is performed from the communication device 10-1 to the communication device 10-3.

[0041] In the example shown in Fig. 3, the path costs of links 20-1 to 20-7 are all set to 1. Although the number of hops is used as the path cost, other indices may be used to determine the priority of communications. For example, a combination of information such as bandwidth and reliability may be used, as in the case of IGRP (Interior Gateway Routing Protocol).

[0042] When a route search is initiated, the communication device 10-1, which is the sender, generates a route search packet including a route request (RREQ) message. The route search packet includes a sender ID "1.1" that identifies the communication device 10-1 itself and the RSU 110a, a destination ID "3" that identifies the destination communication device 10-3, and a route search packet ID that indicates the identity of the route search packet. The route search packet is transmitted to all nodes connected to the communication device 10-1. In the example of FIG. 1, the communication device 10-1 transmits a route search packet to each of the communication devices 10-2 and 10-7.

[0043] The flow of a route search packet in the clockwise direction (the direction of the white arrow) in FIG. 3 will be described. When the communication device 10-2 receives the route search packet, it executes a route search analysis process. In the route search analysis process, the path cost from the sender to the communication device 10-2 is calculated, and the total cost in the route search packet is updated. For example, in the case of the communication device 10-2, a process is executed to update the total cost from 0 to 1. Furthermore, the control unit 11 of the communication device 10-2 executes a process to store a route entry in the route table 121 of the storage unit 12. The route entry includes a source ID "1.1", a destination ID "3", a total cost "1", and an immediately preceding ID "1" that identifies the communication device 10-1 that relayed the route search packet to the communication device 10-2. Furthermore, the control unit 11 of the communication device 10-2 stores the route entry and executes a relay process to transmit the route search packet to the communication device 10-3.

[0044] The communication device 10-3 is the destination identified by the destination ID. When the communication device 10-3 receives the route search packet, it updates the total cost from 1 to 2 and generates a route reply packet including the total cost and a route reply (RREP) message. The route reply packet is transmitted in the direction opposite to the direction from which the route search packet was transmitted based on the route entry generated when the route search packet was relayed. In the example of FIG. 3, the route reply packet transmitted from the communication device 10-3 reaches the communication device 10-1 via the communication device 10-2. As a result, the communication device 10-1 learns that the total cost in the clockwise direction is 2 based on the received route reply packet.

[0045] Next, we will explain the flow of route search packets in the counterclockwise direction (the direction of the black arrow) in Figure 3. Similar to communication device 10-2, when communication device 10-7 receives a route search packet from communication device 10-2, it updates the total cost in the route search packet from 0 to 1 and performs relay processing, and also performs processing to store the route entry in route table 121 of storage unit 12.

[0046] When the communication device 10-6 receives the route search packet from the communication device 10-7, it updates the total cost in the route search packet from 1 to 2 and executes relay processing, and also executes processing to store the route entry in the route table 121 of the storage unit 12. Similar processing is executed for the communication device 10-5 and the communication device 10-4, and the value of the path cost set to the total cost is added each time relay processing is executed. When the route search packet reaches the communication device 10-3, the communication device 10-3 transmits a route response packet, just as in the case of the clockwise direction. The route response packet reaches the communication device 10-1 via the communication device 10-4, the communication device 10-5, the communication device 10-6, and the communication device 10-7. As a result, the communication device 10-1 learns that the total cost in the counterclockwise direction is 5.

[0047] The communication device 10-1 sets the route with the lowest total cost from the received route response packets as the transmission route for transmitting packets from the communication device 10-1 to the communication device 10-3. In the example of FIG. 3, the total cost of the clockwise route is "2" and the total cost of the counterclockwise route is "5", so the clockwise route with the lowest total cost is set as the transmission route. The set transmission route is maintained until a preset expiration date expires. After the expiration date has passed, the same process is executed, and a search is made for a route with a low total cost (hereinafter, sometimes referred to as an appropriate route).

[0048] <Controlling the Stress State> Next, control of the congestion state will be described with reference to Fig. 4. Fig. 4 is a schematic diagram illustrating control of the congestion state of the communication device 10 of this embodiment. In this description, it is assumed that in the network system 1 shown in Fig. 4, communication is established between the RSU 110a of the communication device 10-1 and the mobile terminal 101a, and communication is established between the RSU 110b and the mobile terminal 101b, and an appropriate route is set. Furthermore, it is assumed that before communication is established between the RSU 110c and the mobile terminal 101c, the communication state of the link 20-1 of the communication device 10-2 is congested, and the communication state of the communication device 10-7 is not congested.

[0049] After determining that the communication state is congested, the control unit 11 of the communication device 10-2 sets a new registration denial to the route table 121. As a result, even if the communication device 10-2 receives a route search packet including a route request (RREQ) message, a route entry based on the route search packet will not be generated. Furthermore, the control unit 11 executes processing to stop the packet relay processing unit 13 from relaying the route search packet to other communication devices 10.

[0050] In this state, even if communication is established between the RSU 110c and the mobile terminal 101c and the communication device 10-1 transmits a route search packet to the communication device 10-2, the communication device 10-2 does not generate a route entry, and the route search packet is not forwarded to the communication device 10-3 either. Therefore, the communication device 10-3 does not transmit a route response packet to the communication device 10-1.

[0051] On the other hand, the communication state of communication device 10-7 is not tight, so the normal control described above is performed. The route discovery packet is relayed counterclockwise through communication device 10-7, communication device 10-6, communication device 10-5, communication device 10-4, and communication device 10-3 in that order, and route entries are stored in each of communication devices 10-4 to 10-7. As shown in the route table of communication device 10-3 in FIG. 4, the total cost of the counterclockwise route is "5." Having received the route discovery packet counterclockwise, communication device 10-3 transmits a route response packet clockwise (in the reverse direction). The route response packet reaches communication device 10-1 via communication device 10-4, communication device 10-5, communication device 10-6, and communication device 10-7.

[0052] Since communication device 10-1 does not receive a route response packet for the clockwise route, it sets a transmission route based on the route response packet received on the counterclockwise route. As communication device 10-2 rejects the new registration, the counterclockwise route with a total path cost of "5" is set as the transmission route for transmitting packets from communication device 10-1 to communication device 10-3. Since the communication condition is not congested on the counterclockwise route, stable communication is performed, and it is possible to avoid a situation in which the communication condition becomes even more congested on the clockwise route.

[0053] For communication from the mobile terminal 101a (communication device 10-1) to the communication device 10-3 and communication from the mobile terminal 101b (communication device 10-1) to the communication device 10-3, the clockwise route with a total cost of "2" is continued even during the congestion control. In this example, even in the congestion state, the already established transmission route is maintained until its expiration date.

[0054] <Control flow of communication device> Next, an example of the control flow of the communication device 10 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of the control flow regarding the relay process of the communication devices 10-1 to 10-7 of this embodiment.

[0055] When the control unit 11 receives a route search packet, it determines whether the destination in the route search packet is itself (step S1). If the control unit 11 determines that the destination in the route search packet does not indicate itself, it shifts the process to step S2, where it causes the packet relay processing unit 13 to execute relay processing (step S1: No).

[0056] In step S2, the packet relay processing unit 13 executes packet relay processing to reflect the path cost in the total cost in the route search packet and then relay the route search packet to the next communication device 10 (for example, communication device 10-3) as described above (step S2). At the same time, the control unit 11 executes storage processing to store route information including the source, destination, and total cost (cost information) in the route table 121 of the storage unit 12 based on the information acquired from the route search packet (step S3).

[0057] In step S1, if the control unit 11 determines that the destination in the route search packet is itself, it shifts the process to step S4 (step S1: Yes). In step S4, the control unit 11 executes a response control process to transmit a route reply packet to the source communication device 10 (step S4).

[0058] After the process of step S3 or step S4, the control unit 11 determines whether the communication volume is equal to or greater than a set threshold in order to determine whether the communication is in a normal state or a tight state (step S5). For example, the control unit 11 monitors the detection values ​​of the packet counters 200-1 to 200-n, and determines whether the detected stream volume per unit time exceeds the set threshold. In this embodiment, the set threshold is set as a predetermined percentage (for example, 90%) of the expected stream volume. Note that the set threshold is not limited to this method. For example, the set threshold may take into account abnormalities in transmission and reception power, momentary interruptions in wired links, route congestion, and the frequency of communication failures using the route in question.

[0059] In step S5, if the control unit 11 determines that the communication volume is less than the set value (step S5: No), the process returns to step S1. In step S5, if the control unit 11 determines that the communication volume is equal to or greater than the set value threshold (step S5: Yes), the process proceeds to control of the tightness state in step S6.

[0060] Next, the flow of control of the congested state in step S6 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing an example of the flow of control of the congested state in the communication device 10 of this embodiment. When control of the congested state is started, the control unit 11 executes a registration refusal process to refuse to register a new route entry in the route table 121 of the storage unit 12 (step S11). Then, the control unit 11 executes a relay stop process to not forward a route search packet to other communication devices 10 even if the route search packet is received (step S12). Based on a command from the control unit 11, the packet relay processing unit 13 stops relaying the route search packet to other communication devices 10. Note that in this embodiment, relaying of new route search packets is stopped, but relaying of packets using already established transmission routes continues.

[0061] After the relay stop process of step S12, the control unit 11 determines whether the communication volume is less than a set threshold (step S13). Here, it determines whether the congestion in the communication state has been alleviated. The process of step S13 may be performed a predetermined time after the processes of steps S11 and S12 have been executed. The set threshold used as the criterion for determination in step S13 may be the same value (e.g., 90%) as the set threshold of step S5 in FIG. 5, but may also be a set threshold lower than the set threshold of step S5 (e.g., 80%) from the viewpoint of determining whether the congestion state has been reliably alleviated.

[0062] In step S13, if the control unit 11 determines that the communication volume is not less than the set value (step S13: No), it continues to monitor the communication volume. Also, in step S13, if the control unit 11 determines that the communication volume is less than the set threshold (step S13: Yes), it proceeds to the process of step S14.

[0063] When the process proceeds to step S14, the control unit 11 executes a process to cancel the registration refusal that refuses the registration of a new route entry in the route table 121 of the storage unit 12 (step S14). Then, the control unit 11 executes a process to cancel the relay stop that does not forward the route search packet to other communication devices 10 even if the route search packet is received (step S15). After the process of step S15, the control unit 11 ends the control of the congested state.

[0064] In the above embodiment, the destination communication device 10-3 transmits the route response packet, but the communication device 10 having the final route information regarding the route to the destination communication device may transmit the route response packet. In that case, the route response packet may be transmitted to all communication devices 10 connected to the communication device 10.

[0065] As described above, the communication device 10 of the above embodiment is configured as follows. The communication device 10-2 is communicatively connected to other communication devices 10-1 and 10-2 via a plurality of links 20-1, and includes a packet relay processing unit (data relay processing unit) 15 that executes processing to relay a route search packet (route search data) having a specific communication device 10-3 as its destination, received via a link (first link) 20-1 that is one of the plurality of links 20-1 to 20-7, to a next communication device 10-3 that is connected to a link 20-3 different from link 20-1; a memory unit 12 that stores route information including a source and a destination obtained from the route search packet; and a control unit 11 that executes processing to transmit to the source communication device 10 (e.g., communication device 10-3) a route response packet (route response data) including route information for determining a transmission route to the destination communication device 10 (e.g., communication device 10-3) if the destination of the received route search packet is itself or if final route information from itself to the destination is held in the memory unit 12. When the control unit 11 determines that the amount of data flowing through the links 20-1 to 20-7 exceeds a predetermined standard, it executes a registration refusal process to refuse to set a new transmission route that passes through the congested link 20-1 even if new route search data is received.

[0066] The communication method of the communication device 10 of this embodiment includes the following steps. That is, the communication method includes a packet relay processing step (data relay processing step) that executes a process of relaying a route search packet (route search data) having a specific communication device 10-3 as its destination, received via link (first link) 20-1, which is one of a plurality of links 20-1 to 20-7, to the next communication device 10-3 connected to link 20-3 different from link 20-1; a storage step that stores route information including the source and destination obtained from the route search packet in a memory unit 12; a response control step that executes a process of transmitting a route response packet (route response data) to the source communication device 10-1, including route information for determining a transmission route to the destination communication device 10-3, when it is determined that the communication volume of data flowing through links 20-1 to 20-7 exceeds a predetermined standard, even if new route search data is received.

[0067] With this configuration and method, even if a new route search is requested when the communication status of any of the links 20-1 to 20-7 is congested, a new transmission route that passes through links other than the congested link 20-1 is registered. This prevents the communication status of the link 20-1 from becoming even more congested. Furthermore, the new transmission route from the source to the destination also avoids the congested link 20-1, thereby realizing a stable communication status.

[0068] Furthermore, the registration rejection process of this embodiment is executed by not acquiring route information from a new route search packet.

[0069] As a result, no route information is acquired, so the data in the route search packet to be sent to the next communication device 10-3 is not updated, and even if a route response packet is received, data cannot be sent to the sender, and a new route response packet will not be sent to the sender. A process that prevents a new transmission route that passes through link 20-1 from being registered can be achieved with simple control.

[0070] Furthermore, the registration refusal process of this embodiment is executed by not relaying the new route search data to the next communication device 10-3 (another communication device) connected to the link 20-2 different from the link 20-1.

[0071] As a result, the new route search packet will no longer be relayed from communication device 10-2 to the next communication device 10-3, so the new route search packet will no longer reach the destination and a new route response packet will no longer be sent to the source. A process that prevents the new transmission route that passes through link 20-1 from being registered can be achieved with simple control.

[0072] The communication device 10 of this embodiment further includes a packet counter 200 that counts packet data received via the link 20, and the control unit 11 determines whether the communication volume exceeds a predetermined standard based on the detected value of the packet counter 200.

[0073] This makes it possible to reliably detect the communication state of the link 20 based on the detected value of the packet counter 200, and to accurately determine whether or not the communication state is congested.

[0074] Next, a modified example of the above embodiment will be described. In the following description, the same reference numerals will be used to designate components that are common to or similar to the above embodiment, and the description thereof may be omitted.

[0075] <First Modification> FIG. 7 is a schematic diagram showing a network system 1a of a first modified example. Mobile terminals 101a to 101c in FIG. 7 are communication devices mounted on normal vehicles. Priority mobile terminal 201a is a communication device mounted on a vehicle in which communication with network system 1a is given priority over mobile terminals 101a to 101c mounted on normal vehicles. A vehicle in which priority mobile terminal 201a is mounted is assumed to be, for example, an ambulance that provides high public benefit and should be given priority. Communication device 10 or RSUs 110a to 110c distinguish between mobile terminals 101a to 101c mounted on normal vehicles and priority mobile terminal 201 mounted on a vehicle in which communication is given priority, based on an ID or the like indicating the type of vehicle included in a signal output by priority mobile terminal 201.

[0076] In the example of Figure 7, the mobile terminal 101a has established communication with the RSU 110a of the communication device 10-1, and a transmission route to the destination communication device 10-3 has already been determined. Similarly, the mobile terminal 101b has established communication with the RSU 110b of the communication device 10-1, and a transmission route to the destination communication device 10-3 has already been determined. Note that the mobile terminal 101c has not established communication with any of the RSUs 110a to 110c. Furthermore, the priority mobile terminal 201a has established communication with the RSU 110c of the communication device 10-1.

[0077] Fig. 8 is a schematic diagram illustrating data processing for the first queue 250a and the second queue 250b of the communication device 10-2 of the first modified example. Note that Fig. 8 does not illustrate the mobile terminal 101c with which communication has not been established.

[0078] In the first modified example, in order to prioritize communication with the priority mobile terminal 201a, the route table 121 is managed based on a source ID that can identify each of the mobile terminals 101a to 101c and the priority mobile terminal 201a. The source ID of the mobile terminal 101a is set to "1.1.1b", the source ID of the mobile terminal 101b is set to "1.2.1b", and the source ID of the priority mobile terminal 201a is set to "1.3.1a".

[0079] As shown in FIG. 8, the communication device 10 includes a plurality of first queues 250a and second queues 250b through which packets pass before passing through the link 20. The second queue 250b is a queue for the mobile terminals 101a to 101b mounted on normal vehicles. Note that even for the mobile terminal 101c with which communication has not been established, packets will be transmitted through the second queue 250b when communication is established. In contrast, the first queue 250a is a queue for the priority mobile terminal 201a mounted on a vehicle with priority communication. Packets originating from the priority mobile terminal 201a pass through the first queue 250a and are transmitted to their destination in preference to packets passing through the second queue 250b.

[0080] In the first modification, packets passing through the first queue 250a are always given priority, and a transmission route is selected based on the communication status for packets passing through the second queue 250b. That is, the congestion state control in the above embodiment is performed only for route search packets passing through the second queue 250b, and is not performed for route search packets passing through the first queue 250a.

[0081] Fig. 9 is a table showing examples of route tables 121a to 121b held in the communication device 10 of the first modified example. As shown in Fig. 9, the communication device 10 of the first modified example has a plurality of route tables 121a to 121b corresponding to a first queue 250a and a second queue 250b.

[0082] The control unit 11 determines whether the communication state is congested based on the overall stream amount without distinguishing between the plurality of first queues 250a and second queues 250b. In the example of Fig. 7, whether the communication state is congested is determined based on the total number of packets whose source is the mobile terminals 101a to 101b and the number of packets whose source is the priority mobile terminal 201a. When the control unit 11 determines that the communication state is congested, the above-mentioned control of the congested state is executed.

[0083] 7, if control unit 11 of communication device 10-2 determines that the communication conditions are congested, a counterclockwise transmission route will be set instead of a clockwise one even if mobile terminal 101c is connected to any of RSUs 110a to 110c. Note that the clockwise transmission route will continue for priority mobile terminal 201a and mobile terminals 101a to 101b.

[0084] In this way, the communication device 10 of the first modified example further includes RSUs (wireless units) 110a to 110c that perform wireless communication with the mobile terminals 101a to 101c and the priority mobile terminal 201a, and the route search packets are sent from the mobile terminals 101a to 101c and the priority mobile terminal 201a.

[0085] This makes it possible to effectively avoid communication congestion and achieve stable communication even when used in a case where the number of users joining and leaving the communication range of RSUs 110a to 110c (for example, the number of mobile terminals 101a to 101c and priority mobile terminal 201a) fluctuates frequently.

[0086] Furthermore, the communication device 10 of the first modification further includes a first queue 250a through which data having a specific priority mobile terminal 201a as its source passes, and a second queue 250b through which data having a normal mobile terminal 101a-101c as its source passes, other than the specific priority mobile terminal 201a. Regardless of whether the amount of data traffic flowing through the link 20 exceeds a predetermined standard, data communication having a specific priority mobile terminal 201a as its source is prioritized over data communication having a normal mobile terminal 101a-101c as its source.

[0087] As a result, data originating from priority mobile terminal 201a, which is in a situation where communication should be prioritized, can be reliably transmitted to the intended destination regardless of the usage status of network system 1a of other mobile terminals 101a to 101c.

[0088] <Second Modification> FIG. 10 is a block diagram showing an example of the configuration of a communication device 10 that determines the communication state based on a packet prediction value acquired using a trained model of the second modified example.

[0089] 10, in the second modification, the number of packets detected by the packet counter 200 of the packet relay processing unit 13 is input to an LSTM (Long Short-Term Memory) unit 300. The LSTM unit 300 calculates a packet prediction value at a certain time in the future using a trained model 310 that has trained several years' worth of packet data in chronological order. Note that the trained model 310 may be trained on time series data of communication volume calculated based on congestion information in addition to the time series data of packet data.

[0090] Fig. 11 is a graph showing the communication state predicted by the communication device 10 of the second modified example. As shown in Fig. 11, the future communication volume can be accurately predicted by the LSTM unit 300, which is suitable for predicting time-series data. In the second modified example, when the control unit 11 determines that congestion will occur in the future, the above-described control of the congestion state is executed.

[0091] As described above, the communication device 10 of the second modified example further includes the LSTM unit 300 as a communication traffic prediction unit that predicts future communication traffic based on time-series data of input communication traffic. The control unit 11 determines whether the communication traffic of data flowing through the link 20 exceeds a predetermined standard based on the packet prediction value (data prediction value) calculated by the LSTM unit 300.

[0092] As a result, even if communication is not currently congested, if there is a high probability that communication will become congested in the future, communication congestion will be alleviated, thereby realizing more stable communication.

[0093] In the second modification, an example of supervised learning using LSTM (Long Short-Term Memory) has been described, but the present invention is not limited to this. For example, a configuration may be adopted in which future communication volume is predicted using other machine learning such as real-time reinforcement learning.

[0094] <Third Modification> 12 is a schematic diagram showing a network system 1b of a third modified example, which differs from the first modified example in that the communication device 10-2 is connected to the communication device 10-6 via a link 20-8, and the communication device 10-3 is connected to the communication device 10-5 via a link 20-9.

[0095] 12, the communication device 10-1 is connected to three links 20-1, 20-2, and 20-8. Here, as in the above embodiment, if the communication of the transmission route passing through link 20-1 is congested, the above-mentioned control of the congested state (registration refusal processing) is executed. In the third modification, if the communication of the transmission route passing through link 20-8 is also congested in this state, registration distance processing is executed so that the transmission route passing through link 20-8 is not newly registered.

[0096] In this way, in the communication device 10 of the third variant, when it is determined that the amount of data flowing through link (second link) 20-8, which is one of the multiple links 20-1, 20-2, 20-8, exceeds a predetermined standard, even if second new route search data is received from link 20-8, a process is executed to control the packet relay processing unit 13 so that a new transmission route passing through link 20-8 is not registered in the communication device 10-1, which is the source that transmitted the second new route search data.

[0097] This makes it possible to avoid a communication state in the different link 20-8 becoming congested, and to make the communication state of the entire network system 1b more stable.

[0098] <Fourth Modification> Next, a communication device 10a configured to switch between normal state control and tight state control based on whether or not all data (packet counter total) passing through the packet relay processing unit 13 exceeds a predetermined standard will be described.

[0099] Fig. 13 is a block diagram showing an example of the configuration of a communication device 10a according to a fourth modified example. The communication device 10a shown in Fig. 13 is a node device connected to four links 20-1 to 20-4. The communication device 10a includes a receiver 14-1 and a transmitter 15-1 corresponding to link 20-1, a receiver 14-2 and a transmitter 15-2 corresponding to link 20-2, a receiver 14-3 and a transmitter 15-3 corresponding to link 20-3, and a receiver 14-4 and a transmitter 15-4 corresponding to link 20-4. The receivers 14-1 to 14-4 and the transmitters 15-1 to 15-4 are all interfaces supporting data communication at 100 Mbps.

[0100] The packet relay processing unit 13 also has a packet counter 200-1 corresponding to the receiving unit 14-1, a packet counter 200-2 corresponding to the receiving unit 14-2, a packet counter 200-3 corresponding to the receiving unit 14-3, and a packet counter 200-4 corresponding to the receiving unit 14-4.

[0101] In the example shown in Figure 13, packet data input from receiving unit 14-1 is output from transmitting unit 15-4 through packet relay processing unit 13, packet data input from receiving unit 14-2 is output from transmitting unit 15-3 through packet relay processing unit 13, packet data input from receiving unit 14-3 is output from transmitting unit 15-2 through packet relay processing unit 13, and packet data input from receiving unit 14-4 is output from transmitting unit 15-1 through packet relay processing unit 13.

[0102] A backplane capacity (e.g., 300 Mbps) is set as a performance value in the switch unit 130 of the communication device 10a. The backplane capacity is set as a limit value for the amount of streams passing through the packet relay processing unit 13. In the fourth modification, the control unit 11 executes a process of switching between control in a normal state and control in a tight state so as not to reach this backplane capacity. The predetermined standard is a value set based on the backplane capacity. For example, 90% of the backplane capacity is set as the predetermined standard (e.g., 270 Mbps). The control unit 11 monitors whether the amount of streams exceeds the predetermined standard via the packet relay processing unit 13.

[0103] If the detection values ​​of packet counters 200-1 to 200-4 can be obtained, it is possible to detect the amount of streams passing through packet relay processing unit 13 (switch unit 130). In some cases, a packet counter may also be provided in each of transmitting units 15-1 to 15-4, and the amount of packet data on both the input side and the output side may be directly monitored to obtain the amount of streams.

[0104] If the amount of streams passing through the packet relay processing unit 13 (switch unit 130) per unit time exceeds a predetermined standard, the control unit 11 can determine that the communication device 10a is in a congested state, and therefore shifts from normal state control to congested state control. For example, if the amount of streams passing through the packet relay processing unit 13 per unit time acquired based on the detection values ​​of the packet counters 200-1 to 200-4 is 260 Mbps, which does not exceed the predetermined standard of 270 Mbps, the control unit 11 continues normal state control, but if it is 280 Mbps, which exceeds the predetermined standard of 270 Mbps, the control unit 11 shifts to congested state control.

[0105] The control of the congested state performed by the communication device 10a in the fourth modified example differs from that of the above embodiment and modified examples 1 to 3. In the fourth modified example, when the control unit 11 of the communication device 10a determines that the total communication volume of data flowing through the multiple links 20-1 to 20-4 exceeds a predetermined standard, the communication device 10a performs a registration refusal process to refuse to set a new transmission route that passes through the communication device 10a itself, even if new route search data is received, until the congested state is released.

[0106] The registration rejection process is executed by not acquiring route information from a new route search packet and not relaying packet data to other communication devices 10, in order to prevent the new setting of a transmission route that passes through all links 20-1 to 20-4. That is, even if a route search packet is received from all links 20-1 to 20-4 connected to the communication device 10a, route information is not registered and relay processing of the route search packet is not performed. Because a transmission route that passes through the communication device 10a is not set, it is possible to effectively prevent the occurrence of a situation in which relay processing in the communication device 10a is not performed due to the backplane capacity being reached.

[0107] <Fifth Modification> Next, referring to a communication device 10a-2 different from the fourth modified example, an example will be described in which control is switched between the normal state and the congested state based on whether all data passing through the packet relay processing unit 13 exceeds a predetermined standard. Fig. 14 is a block diagram showing an example of the configuration of the packet relay processing unit 13 of the communication device 10a-2 of the fifth modified example. Note that the communication device 10a-2 of the fifth modified example corresponds to the communication device 10-2 of Fig. 12 described in the third modified example, and is a node device to which three links 20-1, 20-2, and 20-8 are connected.

[0108] The backplane capacity as a performance specification value of the switch unit 130 shown in Fig. 14 is assumed to be 100 Mbps. The predetermined standard set based on the backplane capacity is assumed to be 90 Mbps, which is 90% of the backplane capacity. Packet data on the transmission route flowing from link 20-1 to link 20-2 via communication device 10a-2 is assumed to be packet data 1, indicated by a dashed line in Fig. 14. Packet data on the transmission route flowing from link 20-2 to link 20-1 via communication device 10a-2 is assumed to be packet data 2, indicated by a dashed line in Fig. 14.

[0109] In the communication device 10a-2 of this fifth variant, if the stream volume of packet data 1 input from link 20-1 is 40 Mbps and the stream volume of packet data 2 input from link 20-2 is 40 Mbps, the total stream volume will be 80 Mbps, which exceeds the predetermined standard of 90 Mbps, so the control unit 11 will not determine that the state is congested, and normal state control will be executed.

[0110] On the other hand, if the stream volume of packet data 1 is 46 Mbps and the stream volume of packet data 2 is 46 Mbps, the total packet stream volume will be 96 Mbps, which exceeds the predetermined standard of 90 Mbps, and tightness control will be executed so that a transmission route passing through communication device 10a-2 is not set.

[0111] In the communication device 10a-2 of the fifth modification, new route registration is not performed for the transmission route passing through the links 20-1, 20-2, and 20-8, and the forwarding of route search packets is also stopped until the congestion state is resolved. This makes it possible to prevent the traffic flowing through the switch unit 130 of the communication device 10a-2 from reaching the backplane capacity (100 Mbps), and also sets a new transmission route that does not pass through the communication device 10a-2, thereby stabilizing the communication state in the entire network system.

[0112] Note that the fourth and fifth modified examples can also be applied to a configuration including the first queue 250a and the second queue 250b described in the first modified example, or a configuration including a communication volume prediction unit such as the LSTM unit 300 described in the second modified example. In these cases, as in the fourth and fifth modified examples, the determination of whether the state is normal or congested is made based on all data passing through the packet relay processing unit 13.

[0113] Although the embodiments and modifications of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate. Furthermore, the series of processes in the above-described embodiments and modifications can be executed by hardware or software. When the series of processes are executed by software, the programs constituting the software are installed into a computer or the like from a network or a recording medium. The computer may be a computer incorporated into dedicated hardware. Furthermore, the computer may be a computer capable of executing various functions by installing various programs, such as a general-purpose personal computer. [Explanation of symbols]

[0114] 1,1a,1b network system 10-1~10-7 Communication equipment 11 Control section 12 Storage section 15 Packet relay processing unit (data relay processing unit) 20-1~20-9 Link 101a~101c, 201a Mobile terminal 110a~110c RSU (Radio Equipment) 200 Packet Counter 250a 1st queue 250b 2nd queue 300 LSTM units (communication volume prediction section)

Claims

1. A network system in which a plurality of communication devices are connected to each other via a plurality of links so as to be able to communicate with each other, At least one communication device among the plurality of communication devices, a data relay processing unit that executes a process of relaying route search data having a specific communication device as a destination, the route search data being received via a first link that is one of the plurality of links, to a next communication device connected to a link different from the first link; a storage unit that stores route information including a source and a destination obtained from the route search data; a control unit that executes a process of transmitting route response data including the route information for determining a transmission route to a destination communication device to a source communication device when the destination of the received route search data is the device itself or when final route information from the device itself to the destination is stored in the storage unit; and a wireless device that is an RSU that wirelessly communicates with a mobile terminal; a first queue through which data originating from a specific mobile terminal passes; a second queue through which data originating from a normal mobile terminal other than the specific mobile terminal passes; Equipped with The mobile terminal is mounted on a vehicle or a drone, The route search data is transmitted from the mobile terminal, The control unit When it is determined that the amount of data flowing through the first link has exceeded a predetermined standard, even if new route search data flowing through the second queue is received, a registration refusal process is executed to refuse to set a new transmission route that passes through the link; transmitting data passing through the first queue to a destination in preference to data passing through the second queue; A network system that does not refuse to set up a new transmission route that passes through the first link when new route search data flowing through the first queue is received, regardless of whether the amount of data flowing through the first link exceeds a predetermined standard.

2. The network system described in claim 1, wherein the registration rejection process is a process of refusing to set up a new transmission route that passes through the first link even if the control unit receives the new route search data when the control unit determines that the amount of data communication through the first link exceeds a predetermined standard.

3. The network system according to claim 2, wherein when the control unit determines that the amount of data flowing through a second link, which is one of the plurality of links, exceeds a predetermined standard, the control unit executes a registration refusal process to refuse to set up a new transmission route that passes through the second link, even if new route search data is received.

4. The network system described in claim 1, wherein the registration rejection process is a process in which, when the control unit determines that the total amount of data flowing through the multiple links exceeds a predetermined standard, the control unit rejects the setting of a new transmission route that passes through the communication device itself, even if the new route search data is received.

5. 5. The network system according to claim 1, wherein the registration refusal process is executed by not acquiring the route information from the new route search data.

6. 6. The network system according to claim 1, wherein the registration refusal process is executed by not relaying the new route search data to another communication device.

7. a packet counter for counting packet data received via the link; 4. The network system according to claim 1, wherein the control unit determines whether or not the traffic volume exceeds a predetermined standard based on the detected value of the packet counter.

8. further comprising a communication traffic prediction unit that predicts future communication traffic based on input communication traffic data; 7. The network system according to claim 1, wherein the control unit determines whether the traffic volume of data flowing through the link exceeds a predetermined standard based on the data predicted value calculated by the traffic volume prediction unit.

9. A communication device to which other communication devices are communicatively connected via a plurality of links, a data relay processing unit that executes a process of relaying route search data having a specific communication device as a destination, the route search data being received via a first link that is one of the plurality of links, to a next communication device connected to a link different from the first link; a storage unit that stores route information including a source and a destination obtained from the route search data; a control unit that executes a process of transmitting route response data including the route information for determining a transmission route to a destination communication device to a source communication device when the destination of the received route search data is the device itself or when final route information from the device itself to the destination is stored in the storage unit; and a wireless device that is an RSU that wirelessly communicates with a mobile terminal; a first queue through which data originating from a specific mobile terminal passes; a second queue through which data originating from a normal mobile terminal other than the specific mobile terminal passes; Equipped with The mobile terminal is mounted on a vehicle or a drone, The route search data is transmitted from the mobile terminal, The control unit When it is determined that the amount of data flowing through the first link has exceeded a predetermined standard, even if new route search data flowing through the second queue is received, a registration refusal process is executed to refuse to set a new transmission route that passes through the link; transmitting data passing through the first queue to a destination in preference to data passing through the second queue; A communication device that does not refuse to set a new transmission route that passes through the first link when new new route search data flowing through the first queue is received, regardless of whether the amount of data flowing through the first link exceeds a predetermined standard.

10. A communication method for a communication device including a wireless device that is communicatively connected to other communication devices via a plurality of links and that performs wireless communication with a mobile terminal, a first queue through which data originating from a specific mobile terminal passes, and a second queue through which data originating from a normal mobile terminal other than the specific mobile terminal passes, a data relay processing step of relaying route search data having a specific communication device as a destination, the route search data being received via a first link that is one of the plurality of links, to a next communication device connected to a link different from the first link; a storage step of storing route information including a source and a destination acquired from the route search data in a storage unit; a response control step of executing a process of transmitting route response data including the route information for determining a transmission route to a destination communication device to a source communication device when the destination of the received route search data is the device itself or when final route information from the device itself to the destination is stored in the storage unit; a registration refusal processing step of executing a registration refusal process to refuse to set a new transmission route that passes through the link even when new new route search data flowing through the second queue is received when it is determined that the communication volume of data flowing through the first link has exceeded a predetermined standard; Equipped with the wireless device is an RSU; The mobile terminal is mounted on a vehicle or a drone, The route search data is transmitted from the mobile terminal, the communication device transmits data passing through the first queue to a destination in priority to data passing through the second queue; A communication method that does not reject the setting of a new transmission route that passes through the first link when new new route search data flowing through the first queue is received, regardless of whether the amount of data flowing through the first link exceeds a predetermined standard.

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