JP7740870B2 - Communication device, network system, and communication method - Google Patents

Description

The present invention relates to a communication device, network system, and communication method that performs data relay processing.

In inter-vehicle communication networks that use roadside units, traffic congestion and other factors can increase the number of users joining the network, resulting in localized congestion. Patent Document 1, for example, discloses technology for controlling traffic to alleviate such congestion.

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 heavily loaded device, and changes congestion control based on the results of this identification.

Japanese Patent Application Laid-Open No. 2018-137656

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

The present invention aims to provide a communication device, network system, and communication method that can avoid communication congestion and maintain high-quality communication conditions.

The present invention relates to a communication device that is communicatively connected to other communication devices via multiple links. The communication device includes: a data relay processing unit that relays route search data, which is received via a first link (one of the multiple links) and has a specific communication device as its destination, to a next communication device connected to a link different from the first link; a memory unit that stores route information including a source and 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 memory unit, transmits route response data to the source communication device that includes the route information for determining a transmission route to the destination communication device. If the control unit determines that the traffic volume of data flowing through the link exceeds a predetermined threshold, the control unit executes registration refusal processing to refuse to set a new transmission route that passes through the link, even if new route search data is received. This configuration effectively prevents communication congestion from progressing, while also setting a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system.

Preferably, the registration rejection process is a process in which, when the control unit determines that the amount of data flowing through the first link exceeds a predetermined threshold, the control unit rejects the establishment of a new transmission route that passes through the first link, even if the new route search data is received. This configuration makes it possible to avoid situations in which the amount of data flowing through the first link becomes congested, resulting in a decline in communication efficiency.

When the control unit determines that the amount of data flowing through a second link, which is one of the multiple links, exceeds a predetermined threshold, it preferably executes a registration refusal process that refuses to set up a new transmission route that passes through the second link, even if new route search data is received. This configuration can also avoid congestion in the communication state on the second link, making the communication state of the entire network system more stable.

Preferably, the registration rejection process is a process in which, if the control unit determines that the total amount of data flowing through multiple 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 situations in which the communication device itself becomes congested and is unable to perform relay processing.

The registration rejection process is preferably performed by not obtaining the route information from the new route search data. This configuration enables simple control to be used to prevent new transmission routes that pass through links with congested communication traffic from being registered.

The registration rejection process is preferably performed by not relaying the new route search data to other communication devices. This configuration enables simple control to be used to prevent new transmission routes that pass through congested links from being registered.

It is preferable that the communication device further includes a packet counter that counts packet data received via the link, and that the control unit determines whether the communication volume exceeds a predetermined standard based on the detected value of the packet counter. This configuration makes it possible to reliably detect the communication status of the link based on the detected value of the packet counter, and accurately determine whether the communication volume is congested.

It is preferable that the communication device further includes a wireless device that performs wireless communication with a mobile terminal, and that the route search data is transmitted from the mobile terminal. This configuration effectively avoids worsening communication congestion and ensures stable communication, even when used in roadside devices where the number of users participating in communication fluctuates frequently, such as vehicles, as they join and leave the communication range of the wireless device.

The communication device preferably 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 preferably prioritizes data communication originating from the specific mobile terminal over data communication 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 the intended destination, regardless of the usage status of the network system for the normal mobile terminal.

It is preferable that the communication device further comprises a communication traffic prediction unit that predicts future communication traffic based on input communication traffic data, and that 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 will be alleviated, thereby achieving more stable communication.

The present invention also relates to a network system in which a communication device is communicatively connected to multiple other communication devices via multiple links, wherein at least one of the multiple communication devices comprises: a data relay processing unit that relays route search data, which is received via a first link, one of the multiple links, and which has a specific communication device as its destination, to a next communication device connected to a link different from the first link; a memory unit that stores route information including a source and destination obtained from the route search data; and a control unit that, if the destination of the received route search data is the source communication device or if final route information from the source communication device to the destination communication device is stored in the memory unit, transmits route response data to the source communication device that includes 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, it 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, while also setting up a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system.

The present invention also relates to a communication method for a communication device communicatively connected to other communication devices via multiple links, the method comprising: a data relay processing step for relaying route search data, the data being received via a first link that is one of the multiple links and having a specific communication device as its destination, to a next communication device connected to a link different from the first link; a storage step for storing route information including a source and destination obtained from the route search data in a storage unit; a response control step for transmitting route response data including the route information for determining a transmission route to the destination communication device to the source communication device, if the destination of the received route search data is the source communication device itself or if 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 for executing registration refusal processing to refuse to set a new transmission route that passes through the link, even if new route search data is received, when it is determined that the volume of data flowing through the link has exceeded a predetermined standard. This method effectively prevents communication congestion from progressing, while also setting a transmission route that is not congested even for new connection requests, thereby improving the communication quality of the entire network system.

The present invention provides a communication device, network system, and communication method that can avoid communication congestion and maintain high-quality communication conditions.

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; 1 is a block diagram showing an example of the configuration of a communication device according to an embodiment of the present invention; FIG. 4 is a schematic diagram illustrating control of a normal state of the communication device according to the present embodiment. FIG. 10 is a schematic diagram illustrating control of a congestion state of a communication device according to the present embodiment. 10 is a flowchart illustrating an example of a control flow regarding relay processing of the communication device of the present embodiment. 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. FIG. 10 is a schematic diagram showing a network system according to a first modified example. FIG. 10 is a schematic diagram illustrating data processing for each queue in a communication device according to a first modified example. 10 is a table illustrating an example of a route table held in a communication device according to a first modified example. A block diagram showing an example of the configuration of a communication device that determines the communication state based on a packet prediction value obtained using a learned model of the second variant example. 10 is a graph showing a communication state predicted by a communication device of a second modified example. FIG. 10 is a schematic diagram showing a network system according to a third modified example. FIG. 11 is a block diagram showing an example of the configuration of a communication device according to a fourth modified example. 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.

Embodiments of the present invention will be described below with reference to the drawings.

<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.

Note that while mobile terminals 101a-101d are shown in Figure 1 as examples of communication devices mounted on vehicles, this is not limiting. Mobile terminals 101a-101d may also be held by a walking user carrying a smartphone or other communication device, or by a user riding a bicycle. Alternatively, mobile terminals 101a-101d may be mounted on a drone that has autonomous traveling means or flying means. In other words, mobile terminals 101a-101d can be considered communication devices that are intended for movement.

The network system 1 of this embodiment includes multiple communication devices 10-1 to 10-7 and links 20-1 to 20-7 connecting the communication devices 10-1 to 10-7.

Communication devices 10-1 to 10-7 are node devices installed throughout the city. Each of communication devices 10-1 to 10-7 is equipped with one or more RSUs (Road Side Units) 110 as wireless devices. Communication devices 10-1 to 10-7 communicate with mobile terminals 101a to 101d via RSUs 110a to 110c. Note that in FIG. 1, the RSUs 110 are not shown for communication devices 10-2, 10-3, and 10-5 to 10-7. Also, in this embodiment, node devices communication device 10-1 and RSUs 110a to 110c are illustrated as separate devices, but communication device 10-1 and RSUs 110a to 110c may be integrated into one device.

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

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 one example, and multiple communication devices 10-1 to 10-7 may also be connected to each other in a mesh-like configuration.

The communication devices 10-1 to 10-7 connected by links 20-1 to 20-7 have common functions for establishing communication.

The links 20-1 to 20-7 that make up 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; 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) multi-hop format used in the field of wireless communications.

<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.

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

The control unit 11 reads data such as programs stored in the memory unit 12 and executes various controls to operate the communication device 10. These controls include, for example, processing related to route requests (RREQ) and route replies (RREP), processing to execute the functions of the packet relay processing unit 13, and processing to update data stored in the memory unit 12.

The storage unit 12 is composed of semiconductor memory or the like. The storage unit 12 stores various types of information for the functioning of the communication device 10. This information includes, for example, programs and data for executing the route search-related processes described below.

In this embodiment, the storage unit 12 stores a route table 121 for managing route entries, which are information for forwarding packets. Route entries are information for establishing routes between communication devices 10 when the communication devices 10 receive a route request (RREQ) and a route reply (RREP). The contents of route entries are described below.

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 with 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, so two of the receiving units 14-1 to 14-n and the transmitting units 15-1 to 15-n are connected to 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.

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

In this embodiment, the packet relay processing unit 13 includes packet counters 200-1 to 200-n corresponding to the receiving units 14-1 to 14-n. The packet counters 200-1 to 200-n are communication information acquisition units that count packets received by the receiving units 14-1 to 14-n. The receiving units 14-1 to 14-n and packet counters 200-1 to 200-n, each with the same number after a hyphen, correspond to each other.

The control unit 11 determines whether the communication condition 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 condition 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 condition is congested is not limited to this. For example, the communication condition may be determined based on the number of packets per unit time (throughput), or other methods may be used to determine the communication condition.

When the communication state is congested, the control unit 11 executes control to relieve the congested state. Below, the control executed by the control unit 11 when the communication state is not congested will be referred to as normal state control, and the control executed by the control unit 11 when the communication state is congested will be referred to as congested state control.

<Normal state control>
First, control in a normal state will be described with reference to Fig. 3. Fig. 3 is a schematic diagram illustrating control in a 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.

In the example shown in Figure 3, the path costs of links 20-1 to 20-7 are all set to 1. Note that while the number of hops is used as the path cost, other indicators may also be used to determine communication priority. For example, a combination of information such as bandwidth and reliability, as in the Interior Gateway Routing Protocol (IGRP), may also be used.

When a route search begins, communication device 10-1, which is the sender, generates a route search packet that includes a route request (RREQ) message. The route search packet includes a sender ID "1.1" that identifies communication device 10-1 itself and 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 sent to all nodes connected to communication device 10-1. In the example of Figure 1, communication device 10-1 sends a route search packet to communication device 10-2 and communication device 10-7.

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

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

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.

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

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 communication device 10-1 to communication device 10-3. In the example of Figure 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 the preset expiration date expires. After the expiration date has passed, the same process is performed, and a search is made for a route with a low total cost (hereinafter sometimes referred to as an appropriate route).

<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 communication device 10-2 on the link 20-1 is congested, and the communication state of the communication device 10-7 is not congested.

After determining that the communication state is congested, the control unit 11 of communication device 10-2 sets the route table 121 to reject new registrations. This means that even if communication device 10-2 receives a route search packet containing 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.

In this state, even if communication is established between RSU 110c and mobile terminal 101c and communication device 10-1 sends a route search packet to communication device 10-2, no route entry will be created in communication device 10-2, and the route search packet will not be forwarded to communication device 10-3. Therefore, a route response packet will not be sent from communication device 10-3 to communication device 10-1.

On the other hand, since communication conditions are not congested for communication device 10-7, the normal control described above is performed. The route search 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, and route entries are stored in each of communication devices 10-4 to 10-7. As shown in the route table for communication device 10-3 in Figure 4, the total cost for the counterclockwise route is "5." Having received the route search 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.

Since communication device 10-1 does not receive a route response packet for the clockwise route, it sets the transmission route based on the route response packet received on the counterclockwise route. Communication device 10-2 rejects the new registration, so the counterclockwise route, with a total path cost of "5," is ultimately set as the transmission route for transmitting packets from communication device 10-1 to communication device 10-3. Since the communication conditions on the counterclockwise route are not congested, stable communication is possible, and it is possible to avoid a situation in which the communication conditions become even more congested on the clockwise route as well.

Note that for communications from mobile terminal 101a (communication device 10-1) to communication device 10-3 and from mobile terminal 101b (communication device 10-1) to communication device 10-3, the clockwise route with a total cost of "2" continues even during congestion control. In this example, even in a congested state, already established transmission routes are maintained until their expiration dates.

<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.

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 proceeds to step S2, where it causes the packet relay processing unit 13 to perform relay processing (step S1: No).

In step S2, the packet relay processing unit 13 performs packet relay processing to relay the route search packet to the next communication device 10 (e.g., communication device 10-3) after reflecting the path cost in the total cost in the route search packet, as described above (step S2). At the same time, the control unit 11 performs 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 obtained from the route search packet (step S3).

In step S1, if the control unit 11 determines that the destination in the route search packet is itself, it proceeds to step S4 (step S1: Yes). In step S4, the control unit 11 executes a response control process to send a route response packet to the communication device 10 that is the sender (step S4).

After processing step S3 or step S4, the control unit 11 determines whether the communication volume is equal to or greater than a set threshold to determine whether communication is in a normal state or a congested state (step S5). For example, the control unit 11 monitors the detection values of 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 (e.g., 90%) of the expected stream volume. Note that the set threshold is not limited to this method. For example, the set threshold may also 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.

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 step S6, where the control unit 11 controls the congestion state.

Next, the flow of control for the congested state in step S6 will be described with reference to Figure 6. Figure 6 is a flowchart showing an example of the flow of control for the congested state in the communication device 10 of this embodiment. When control for the congested state is initiated, 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). The control unit 11 then executes a relay stop process to not forward a route search packet to other communication devices 10 even if it 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.

After the relay stop process of step S12, the control unit 11 determines whether the communication volume is less than the set threshold (step S13). Here, it determines whether the communication congestion 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 judgment criterion for 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 lower set threshold (e.g., 80%) than the set threshold of step S5 from the perspective of determining whether the congestion has been reliably alleviated.

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 monitoring 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 processing in step S14.

When the process proceeds to step S14, the control unit 11 executes a process to cancel the registration refusal that refuses the registration of new route entries in the route table 121 of the storage unit 12 (step S14). The control unit 11 then executes a process to cancel the relay stop that does not forward route search packets to other communication devices 10 even if the packets are received (step S15). After the process of step S15, the control unit 11 ends control of the congested state.

In the above embodiment, the destination communication device 10-3 sends the route response packet, but it is also possible for a communication device 10 that has final route information regarding the route to the destination communication device to send the route response packet. In that case, the route response packet can be sent to all communication devices 10 connected to that communication device 10.

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 is equipped with: 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 the 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., the 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., the communication device 10-3) if the destination of the received route search packet is the source communication device 10 (e.g., the communication device 10-3) or if final route information from the source communication device 10 to the destination communication device 10 (e.g., the communication device 10-3) 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.

Furthermore, 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 relays a route search packet (route search data) received via link (first link) 20-1, which is one of multiple links 20-1 to 20-7, and destined for a specific communication device 10-3, to the next communication device 10-3 connected to link 20-3, which is different from link 20-1; a storage step that stores route information including the source and destination acquired from the route search packet in a storage unit 12; a response control step that, if the destination of the received route search packet is the source communication device 10-1 or if final route information from the source communication device to the destination is stored in the storage unit 12, executes processing to transmit a route response packet (route response data) to the source communication device 10-1, the route response packet including route information for determining a transmission route to the destination communication device 10-3; and a registration refusal processing step that, if it is determined that the communication volume of data flowing through links 20-1 to 20-7 has exceeded a predetermined standard, executes registration refusal processing to refuse to set a new transmission route that passes through link 20-1, even if new route search data is received.

With this configuration and method, even if a new route search is requested when the communication status of any of 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 link 20-1 from becoming even more congested. Furthermore, the new transmission route from the source to the destination will also avoid link 20-1, which is in a congested communication status, achieving stable communication conditions.

In addition, the registration rejection process in this embodiment is performed by not obtaining route information from new route search packets.

As a result, no route information is acquired, and the data in the route search packet sent to the next communication device 10-3 is not updated. 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. Simple control can be used to prevent new transmission routes that pass through link 20-1 from being registered.

In addition, the registration rejection process in this embodiment is executed by not relaying the new route search data to the next communication device 10-3 (another communication device) connected to link 20-2, which is different from link 20-1.

As a result, new route search packets will no longer be relayed from communication device 10-2 to the next communication device 10-3, meaning that new route search packets will no longer reach their destinations and new route response packets will no longer be sent to the source. Simple control can be used to prevent new transmission routes that pass through link 20-1 from being registered.

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.

This allows the communication status of link 20 to be reliably detected based on the detection value of packet counter 200, making it possible to accurately determine whether or not the link is congested.

Next, we will explain a variation of the above embodiment. Note that in the following explanation, components that are common or similar to those in the above embodiment will be assigned the same reference numerals, and their explanation may be omitted.

<First Modification>
FIG. 7 is a schematic diagram showing a network system 1a according to a first modified example. The mobile terminals 101a to 101c in FIG. 7 are communication devices mounted on ordinary vehicles. The priority mobile terminal 201a is a communication device mounted on a vehicle in which communication with the network system 1a is given priority over the mobile terminals 101a to 101c mounted on ordinary vehicles. The vehicle in which the priority mobile terminal 201a is mounted is assumed to be, for example, an ambulance that provides high public benefit and should be given priority. The communication device 10 or the RSUs 110a to 110c distinguish between the mobile terminals 101a to 101c mounted on ordinary vehicles and the 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 the signal output by the priority mobile terminal 201.

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

Figure 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 Figure 8 omits the illustration of the mobile terminal 101c, with which communication has not been established.

In the first variant, in order to prioritize communications with the priority mobile terminal 201a, the route table 121 is managed based on source IDs that can identify each of the mobile terminals 101a-101c and the priority mobile terminal 201a. The source ID for mobile terminal 101a is set to "1.1.1b", the source ID for mobile terminal 101b is set to "1.2.1b", and the source ID for priority mobile terminal 201a is set to "1.3.1a".

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

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

Figure 9 is a table showing examples of route tables 121a-121b stored in the communication device 10 of the first modified example. As shown in Figure 9, the communication device 10 of the first modified example has multiple route tables 121a-121b corresponding to the first queue 250a and the second queue 250b.

The control unit 11 determines whether the communication condition is congested based on the total stream volume, without distinguishing between the multiple first queues 250a and second queues 250b. In the example of Figure 7, whether the communication condition is congested is determined based on the total number of packets originating from mobile terminals 101a-101b and the number of packets originating from priority mobile terminal 201a. If the control unit 11 determines that the communication condition is congested, the above-mentioned congested state control is executed.

In the example of Figure 7, if the 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 connects to one of RSUs 110a-110c. Note that the clockwise transmission route will continue for priority mobile terminal 201a and mobile terminals 101a-101b.

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

This effectively avoids communication congestion and ensures stable communication, even when used in cases where there is a large fluctuation in the number of users joining and leaving the communication range of RSUs 110a-110c (for example, the number of mobile terminals 101a-101c and priority mobile terminal 201a).

The communication device 10 of the first variant also includes a first queue 250a through which data originating from the specific priority mobile terminal 201a passes, and a second queue 250b through which data originating from normal mobile terminals 101a-101c other than the specific priority mobile terminal 201a passes. Regardless of whether the volume of data flowing through the link 20 exceeds a predetermined threshold, data communication originating from the specific priority mobile terminal 201a is prioritized over data communication originating from normal mobile terminals 101a-101c.

This allows data from the priority mobile terminal 201a, which has circumstances that require communication priority, to be sent reliably to the intended destination, regardless of the usage status of the network system 1a of the other mobile terminals 101a-101c.

<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.

As shown in FIG. 10, in the second variant, the number of packets detected by the packet counter 200 of the packet relay processing unit 13 is input to the LSTM (Long short-term memory) unit 300. The LSTM unit 300 calculates a packet prediction value for 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 also be trained on time series data of communication volume calculated based on congestion information, in addition to time series data of packet data.

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

In this way, the communication device 10 of the second variant further includes an LSTM unit 300 as a traffic volume prediction unit that predicts future traffic volume based on input traffic volume time series data. The control unit 11 determines whether the traffic volume 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.

This means that even if communication is not currently congested, if there is a high probability that it will become congested in the future, communication congestion will be alleviated, resulting in more stable communication.

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

<Third Modification>
12 is a schematic diagram showing a network system 1b of a third modified example. The third modified example differs 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.

In the example shown in Figure 12, communication device 10-1 is connected to three links 20-1, 20-2, and 20-8. Here, as in the above embodiment, if communication on a transmission route passing through link 20-1 becomes congested, the above-mentioned congested state control (registration refusal processing) is executed. In the third variant, if communication on a transmission route passing through link 20-8 also becomes congested in this state, registration distance processing is executed to prevent new registration of the transmission route passing through link 20-8.

In this way, when the communication device 10 of the third variant determines that the amount of data flowing through link 20-8 (second link), which is one of the multiple links 20-1, 20-2, and 20-8, exceeds a predetermined standard, it executes processing 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 that transmitted the second new route search data, even if the second new route search data is received from link 20-8.

This prevents communication congestion on different links 20-8 and makes communication across the entire network system 1b more stable.

<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 passing through the packet relay processing unit 13 (the total of the packet counters) exceeds a predetermined standard will be described.

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

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.

In the example shown in FIG. 13, packet data input from the receiving unit 14-1 is output from the transmitting unit 15-4 via the packet relay processing unit 13, packet data input from the receiving unit 14-2 is output from the transmitting unit 15-3 via the packet relay processing unit 13, packet data input from the receiving unit 14-3 is output from the transmitting unit 15-2 via the packet relay processing unit 13, and packet data input from the receiving unit 14-4 is output from the transmitting unit 15-1 via the packet relay processing unit 13.

The switch unit 130 of the communication device 10a is set with a backplane capacity (e.g., 300 Mbps) as a performance value. 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 variant, the control unit 11 executes a process to switch between normal state control and tight state control 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 via the packet relay processing unit 13 whether the amount of streams exceeds the predetermined standard.

If the detection values of packet counters 200-1 to 200-4 can be obtained, the amount of stream passing through the packet relay processing unit 13 (switch unit 130) can be detected. In some cases, a packet counter may also be placed in each of transmitters 15-1 to 15-4, and the amount of packet data on both the input and output sides may be directly monitored to obtain the amount of stream.

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

The control of the congestion state performed by the communication device 10a in the fourth variant differs from that of the above embodiment and the first to third variants. In the fourth variant, when the control unit 11 of the communication device 10a determines that the total communication volume of data flowing through multiple links 20-1 to 20-4 exceeds a predetermined standard, the communication device 10a performs a registration refusal process that refuses to set up a new transmission route that passes through the communication device 10a itself, even if new route search data is received, until the congestion state is lifted.

The registration rejection process prevents the establishment of a new transmission route that passes through all links 20-1 to 20-4 by not acquiring route information from new route search packets and not relaying packet data to other communication devices 10. In other words, even if route search packets are received from all links 20-1 to 20-4 connected to communication device 10a, route information is not registered and relay processing of the route search packets is not performed. Because a transmission route that passes through communication device 10a is not established, it is possible to effectively prevent situations in which the backplane capacity is reached and relay processing at communication device 10a is not performed.

<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.

The backplane capacity, which is a performance specification value of the switch unit 130 shown in Figure 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 designated as packet data 1, shown by the dashed line in Figure 14. Packet data on the transmission route flowing from link 20-2 to link 20-1 via communication device 10a-2 is designated as packet data 2, shown by the dashed line in Figure 14.

In 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. Therefore, the control unit 11 will not determine that a congestion state exists, and normal state control will be executed.

In contrast, 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, exceeding the specified standard of 90 Mbps, and congestion control will be implemented to prevent the establishment of a transmission route that passes through communication device 10a-2.

In the communication device 10a-2 of the fifth variant, new route registrations are not performed for transmission routes that pass through links 20-1, 20-2, and 20-8, and forwarding of route search packets is also halted until the congestion state is resolved. This prevents the traffic flowing through the switch unit 130 of the communication device 10a-2 from reaching the backplane capacity (100 Mbps), and sets a new transmission route that does not pass through the communication device 10a-2, stabilizing the communication state throughout the network system.

In addition, the fourth and fifth variants can also be configured with the first queue 250a and second queue 250b described in the first variant, or with a communication volume prediction unit such as the LSTM unit 300 described in the second variant. In these cases, as in the fourth and fifth variants, the determination of whether the state is normal or congested is made based on all data passing through the packet relay processing unit 13.

The above describes embodiments and variations of the present invention, but the present invention is not limited to the above embodiments and can be modified as appropriate. Furthermore, the series of processes in the above-described embodiments and variations can be executed by hardware or software. When a series of processes is executed by software, the programs that make up the software are installed onto a computer or the like from a network or recording medium. The computer may also be a computer built into dedicated hardware. The computer may also be a computer that can execute various functions by installing various programs, such as a general-purpose personal computer.

1, 1a, 1b Network system 10-1 to 10-7 Communication device 11 Control unit 12 Storage unit 15 Packet relay processing unit (data relay processing unit)
20-1 to 20-9 Links 101a to 101c, 201a Mobile terminals 110a to 110c RSUs (Radio Units)
200 Packet counter 250a First queue 250b Second queue 300 LSTM unit (communication volume prediction unit)

Claims (10)

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. The network system described in claim 1, wherein the registration rejection process is a process in which, when the control unit determines that the amount of data flowing through the first link exceeds a predetermined standard, the control unit rejects the establishment of a new transmission route that passes through the first link, even if the new route search data is received. The network system described in claim 2, wherein the control unit, when determining that the amount of data flowing through a second link, which is one of the multiple links, exceeds a predetermined standard, executes a registration refusal process that refuses to set up a new transmission route that passes through the second link, even if new route search data is received. The network system described in claim 1, wherein the registration refusal process is a process in which, when the control unit determines that the total amount of data flowing through multiple links exceeds a predetermined standard, the control unit refuses to set up a new transmission route that passes through the communication device itself, even if the new route search data is received. A network system according to any one of claims 1 to 4, wherein the registration rejection process is executed by not acquiring the route information from the new route search data. A network system according to any one of claims 1 to 5, wherein the registration rejection process is performed by not relaying the new route search data to other communication devices. 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. 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. 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. 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 .