Communication system, node device, and communication path decision method

Abstract

To determine a communication route selected by giving priority to a preferential route.SOLUTION: Each node device has adjacent route information where routes between adjacent node devices are set as preferential routes or non-preferential routes in advance. A transmission destination node device refers to the adjacent route information to update a cumulative number of relays and a non-preferential cumulative number of relays in a route request packet broadcast from a source node device, and preferentially selects the route of a route request packet having the smallest non-preferential cumulative number of relays. When there is a plurality of routes having the same non-preferential cumulative number of relays, the transmission destination node device next selects the route of a route request packet having the smallest cumulative number of relays as an optimal route. When there is a plurality of routes having the same cumulative number of relays, the transmission destination node device next selects the route of a preferentially received route request packet as the optimal route, and unicasts a route response packet to the transmission destination node device via the selected optimal route to create a route table.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication system, a node device, and a communication path determination method that can determine a communication path between a source node device and a destination node device by prioritizing a preferred path when the paths between adjacent node devices in a network include a mixture of preferred and non-preferential paths. [Background technology]

[0002] An example of a routing protocol that determines a communication route that passes through multiple node devices that make up a network is the Open Shortest Path First (OSPF) routing protocol. The OSPF routing protocol is a link-state routing protocol that uses cost distance and enables flexible network control. The Ad hoc On-Demand Distance Vector (AODV) routing protocol is a reactive routing protocol that determines a communication route with a small number of hops between node devices.

[0003] Patent Document 1 describes a node device that, upon receiving a frame from another node, refers to a weighting table for each destination node and determines the node to which the frame should be forwarded. The node device determines the destination node according to the weight, and updates the weight according to the success or failure of forwarding the frame to the other node. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4888598 Summary of the Invention [Problem to be solved by the invention]

[0005] The OSPF routing protocol described above can build a network that emphasizes cost and distance, but the calculation cost of each node device is high. On the other hand, the AODV routing protocol does not require high calculation costs for each node device, but since the route is determined only by the number of hops of the node device, even if there is a large difference in bandwidth between the node devices, the number of hops is calculated as the same, so the route load may be concentrated between the node devices with narrow bandwidth.

[0006] However, when the AODV routing protocol is applied to a network in which the routes between node devices are a mixture of highly stable wired routes (preferred routes) and less stable wireless routes (non-preferred routes), as described above, the route is determined only by the number of hops. Therefore, when the number of hops of a communication route consisting only of wired routes is large and the number of hops of a communication route including a wireless route is small, a communication route including a wireless route is selected. As a result, there is a problem that a less stable communication route including a wireless route is selected even though there is a highly stable communication route consisting only of wired routes.

[0007] The present invention has been made in consideration of the above, and aims to provide a communication system, node device, and communication path determination method that can determine a communication path between a source node device and a destination node device by prioritizing a preferred path when the paths between adjacent node devices in a network include a mixture of preferred and non-preferential paths. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, a communication system according to the present invention is a communication system that determines a communication path between a source node device and a destination node device via the node devices in a network having a plurality of node devices, in which each node device presets, as neighboring path information, that each neighboring path between the source node device and the neighboring node device is either a preferred path or a non-preferred path, the source node device broadcasts a route request packet having a sequence number to the neighboring node device with the destination node device as a destination, a relay node device that receives and relays the route request packet refers to the neighboring path information, increments and updates the cumulative number of hops in the route request packet, and if the received neighboring path is a non-preferred path, further performs a hop number update process to increment and update the non-preferred cumulative number of hops in the route request packet, broadcasts the route request packet to other neighboring node devices, and The destination node device that receives a route request packet refers to the adjacent route information, performs the number of hops update process, and, among the route request packets received with the same sequence number, preferentially selects as the optimal route the route of the route request packet with the smallest non-priority cumulative number of hops, and if there are multiple routes with the same non-priority cumulative number of hops, performs route selection process for the optimal route in which the route of the route request packet with the smallest cumulative number of hops is next selected as the optimal route, and if there are multiple routes with the same cumulative number of hops, performs route selection process for the optimal route in which the route reply packet received first is next selected as the optimal route, and unicasts a route reply packet to the destination node device via the selected optimal route, and each node device, when it receives the route request packet, temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when it receives the route reply packet within a predetermined time, stores it as a route table between the source node device and the destination node device.

[0009] Furthermore, in the communications system of the present invention, in the above invention, when the relay node device receives route request packets having the same sequence number, it first records the route of the first-arriving route request packet in a temporary route table and broadcasts it, and when a later-arriving route request packet is received, it compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, it updates the route of the later-arriving route request packet as a temporary route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, it discards the later-arriving route request packet and maintains the contents of the current temporary route table.

[0010] In addition, in the communication system of the present invention, in the above invention, each node device, when receiving the route request packet, stores the incremented cumulative hop count and non-priority cumulative hop count of the route request packet in the temporary route table as the request side cumulative hop count and the request side non-priority cumulative hop count, respectively.

[0011] In addition, in the communication system of the present invention, in the above invention, the route reply packet is added with the answering side's cumulative relay number and the answering side's non-priority cumulative relay number, which correspond to the cumulative relay number and the non-priority cumulative relay number, respectively, and when each node device receives the route reply packet, it increments the answering side's cumulative relay number and the answering side's non-priority cumulative relay number in the route reply packet, stores the incremented answering side's cumulative relay number and the answering side's non-priority cumulative relay number in the temporary route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the temporary route table as a route table.

[0012] In addition, in a communication system according to the present invention, in a network having a plurality of node devices, each node device presets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path, and when a predetermined first node device and a predetermined second node device constituting the network are communicatively connected as a new adjacent path, the new adjacent path is preset as the adjacent path information, that the new adjacent path is either a preferred path or a non-preferred path, and the first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the new adjacent path is communicatively connected, and a cumulative number of hops and a non-preferred cumulative number of hops to the first or second node device, and the notification signal The other node device that receives the notification signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information in which the non-priority cumulative number of hops of existing route information stored in a routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information in which the cumulative number of hops of existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

[0013] In addition, in the above-mentioned invention, the communication system according to the present invention is characterized in that the notification signal is transmitted with information for identifying the node itself added thereto.

[0014] In addition, in the above-mentioned invention, the communication system according to the present invention is characterized in that it has a sequence number for identifying the notification signal in order to handle a case where the notification signal is transmitted a plurality of times.

[0015] In the communication system according to the present invention, the preferred route is a wired route, and the non-preferential route is a wireless route.

[0016] Further, a node device according to the present invention is a node device of a communication system that determines a communication route between a source node device and a destination node device via the node devices in a network having a plurality of node devices, and each node device presets, as neighboring route information, that each neighboring route between the source node device and the neighboring node device is either a preferred route or a non-preferred route, and when the node device is the source node device, the source node device broadcasts a route request packet having a sequence number to the neighboring node device with the destination node device as a destination, and when the node device is a relay node device that receives and relays the route request packet, the relay node device refers to the neighboring route information and increments the cumulative number of hops in the route request packet to update it, and when the received neighboring route is a non-preferred route, further performs a hop number update process of incrementing and updating the non-preferred cumulative hop number in the route request packet, and broadcasts the route request packet to other neighboring node devices. When the node device is the destination node device that received the route request packet, the destination node device refers to the adjacent route information, performs the number of hops update process, and, among the received route request packets having the same sequence number, preferentially selects as the optimal route the route of the route request packet with the smallest non-priority cumulative number of hops, and if there are multiple routes with the same non-priority cumulative number of hops, performs route selection process for the optimal route in which the route of the route request packet with the smallest cumulative number of hops is next selected as the optimal route, and if there are multiple routes with the same cumulative number of hops, performs route selection process for the optimal route in which the route reply packet received first is next selected as the optimal route, and unicasts a route reply packet to the destination node device via the selected optimal route, and each node device, when it receives the route request packet, temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when it receives the route reply packet within a predetermined time, stores it as a route table between the source node device and the destination node device.

[0017] Furthermore, the node device of the present invention is characterized in that, in the above invention, when the relay node device receives route request packets having the same sequence number, it first records the route of the first-arriving route request packet in a temporary route table and broadcasts it, and when a later-arriving route request packet is received, it compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, it updates the route of the later-arriving route request packet as a temporary route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, it discards the later-arriving route request packet and maintains the contents of the current temporary route table.

[0018] In addition, in the node device of the present invention, in the above invention, each node device, when receiving the route request packet, stores the incremented cumulative hop count and non-priority cumulative hop count of the route request packet in the temporary route table as the request side cumulative hop count and the request side non-priority cumulative hop count, respectively.

[0019] In addition, the node device of the present invention is characterized in that, in the above invention, the route reply packet is added with the cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side, which correspond respectively to the cumulative relay number and the non-priority cumulative relay number, and when each node device receives the route reply packet, it increments the cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side in the route reply packet, stores the incremented cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side in the temporary route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the temporary route table as a route table.

[0020] Furthermore, in a node device according to the present invention, in a network having a plurality of node devices, each node device pre-sets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path, and when a predetermined first node device and a predetermined second node device constituting the network are communicatively connected as a new adjacent path, the new adjacent path is pre-set as the adjacent path information that the new adjacent path is either a preferred path or a non-preferred path, and the first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the new adjacent path is communicatively connected, and a cumulative number of hops and a non-preferred cumulative number of hops to the first or second node device, and the notification signal The other node device that receives the notification signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information in which the non-priority cumulative number of hops of existing route information stored in a routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information in which the cumulative number of hops of existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

[0021] In the node device according to the present invention, in the above invention, the preferred path is a wired path, and the non-preferential path is a wireless path.

[0022] Further, a communication path determination method according to the present invention is a communication path determination method for determining a communication path between a source node device and a destination node device via a plurality of node devices in a network having the node devices, wherein each node device presets, as neighboring path information, that each neighboring path between the source node device and an adjacent node device is either a preferred path or a non-preferred path, the source node device broadcasts a route request packet having a sequence number to the adjacent node device with the destination node device as a destination, a relay node device receiving and relaying the route request packet refers to the neighboring path information, increments and updates the cumulative number of hops in the route request packet, and if the received adjacent path is a non-preferred route, further performs a hop number update process of incrementing and updating the non-preferred cumulative number of hops in the route request packet, broadcasts the route request packet to other adjacent node devices, and The destination node device that receives the route request packet refers to the adjacent route information, performs the number of hops update process, and, among the route request packets having the same sequence number that have been received, preferentially selects as the optimal route the route of the route request packet with the smallest non-priority cumulative number of hops, and if there are multiple routes with the same non-priority cumulative number of hops, performs route selection process for the optimal route in which the route of the route request packet with the smallest cumulative number of hops is next selected as the optimal route, and if there are multiple routes with the same cumulative number of hops, performs route selection process for the optimal route in which the route reply packet that was received first is next selected as the optimal route, and unicasts a route reply packet to the destination node device via the selected optimal route. Each node device, when receiving the route request packet, temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when receiving the route reply packet within a predetermined time, stores it as a route table between the source node device and the destination node device.

[0023] Furthermore, in the communication route determination method of the present invention, in the above invention, when the relay node device receives route request packets having the same sequence number, first records the route of the first-arriving route request packet in a temporary route table and broadcasts it, and when a later-arriving route request packet is received, it compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, it updates the route of the later-arriving route request packet as a temporary route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, it discards the later-arriving route request packet and maintains the contents of the current temporary route table.

[0024] In addition, in the communication route determination method of the present invention, in the above invention, each node device, when receiving the route request packet, stores the incremented cumulative relay count and non-priority cumulative relay count of the route request packet in the temporary route table as the request side cumulative relay count and the request side non-priority cumulative relay count, respectively.

[0025] In addition, the communication route determination method of the present invention is characterized in that, in the above invention, the route reply packet is added with the cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side, which correspond to the cumulative relay number and the non-priority cumulative relay number, respectively, and when each node device receives the route reply packet, it increments the cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side in the route reply packet, stores the incremented cumulative relay number of the answering side and the non-priority cumulative relay number of the answering side in the temporary route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the temporary route table as a route table.

[0026] Further, in a communication path determination method according to the present invention, in a network having a plurality of node devices, each node device pre-sets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path, and when a predetermined first node device and a predetermined second node device constituting the network are communicatively connected as a new adjacent path, the new adjacent path is pre-set as the adjacent path information, that the new adjacent path is either a preferred path or a non-preferred path, and the first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the node devices are communicatively connected as the new adjacent path, and a cumulative number of hops and a non-preferred cumulative number of hops to the first or second node device, and the notification The other node device that receives the signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information for which the non-priority cumulative number of hops of existing route information stored in a routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information for which the cumulative number of hops of existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

[0027] In addition, in the communication path determination method according to the present invention, the preferred path is a wired path, and the non-preferential path is a wireless path. Effect of the Invention

[0028] According to the present invention, when the routes between adjacent node devices in a network include a mixture of preferred routes and non-preferential routes, it is possible to determine a communication route between a source node device and a destination node device by giving priority to the preferred route. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a communication system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram showing the configuration of a node device. [Diagram 3] FIG. 3 is a flowchart illustrating a communication path determination process procedure of the node device. [Figure 4] FIG. 4 is a flowchart illustrating a detailed procedure of the route selection process shown in FIG. [Diagram 5] FIG. 5 is a diagram illustrating an example of route selection in a destination node device. [Figure 6] FIG. 6 is a diagram illustrating an example of route selection in a destination node device. [Figure 7] FIG. 7 is a diagram illustrating an example of route selection in a destination node device. [Figure 8] FIG. 8 is a diagram illustrating an example of a route selection in a destination node device. [Figure 9] FIG. 9 is a schematic diagram showing a schematic configuration of a communication system before a new route is connected. [Figure 10] FIG. 10 is a schematic diagram showing a schematic configuration of a communication system in which the new path is a wired path. [Figure 11] FIG. 11 is a flowchart illustrating an example of a process executed in a node device to which an adjacent path has been added. [Figure 12] FIG. 12 is a diagram illustrating an example of a format of the notification signal. [Figure 13] FIG. 13 illustrates an example of the routing table. [Figure 14] FIG. 14 is a diagram showing an example of a routing table from which the route information has been deleted. [Figure 15] FIG. 15 is a diagram showing the routing table in which the routes have been reconstructed. [Figure 16] FIG. 16 is a flowchart illustrating an example of a process executed in a node equipment that receives a notification signal. [Figure 17] FIG. 17 illustrates an example of the routing table. [Figure 18] FIG. 18 is a diagram showing an example of a routing table from which the route information has been deleted. [Figure 19] FIG. 19 is a diagram showing the routing table in which the routes have been reconstructed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0031] <Device configuration> FIG. 1 is a schematic diagram showing a general configuration of a communication system according to an embodiment of the present invention. In a network having a plurality of node devices 1 to 10, the communication system uses an AODV routing protocol to determine a communication path between a source node device and a destination node device via the node devices 1 to 10. In FIG. 1, the node device 1 is the source node device, and the node device 10 is the destination node device. When determining the communication path, the node devices 2 to 9 serve as relay node devices. As shown in FIG. 1, the node device 1 is connected to the node devices 2 and 6. The node device 10 is connected to the node devices 5, 8, and 9. The node devices 2, 3, 4, and 5 are connected to the node devices 1 and 3, the node devices 2 and 4, the node devices 3 and 5, and the node devices 4 and 10, respectively. The node device 6 is connected to the node devices 1, 7, and 9. The node devices 7, 8, and 9 are connected to the node devices 6 and 8, the node devices 7 and 10, and the node devices 6 and 10, respectively.

[0032] FIG. 2 is a functional block diagram showing the configuration of the node devices 1 to 10. As shown in FIG. 2, in the node devices 1 to 10, the storage unit 11, the control unit 12, the receiving units 13-1 to 13-n, and the transmitting units 14-1 to 14-n are connected to the packet relay processing unit 15. The packet relay processing unit 15 transmits the packets received by the receiving units 13-1 to 13-n from the corresponding transmitting units 14-1 to 14-n according to the information stored in the header of the packets under the control of the control unit 12. The control unit 12 controls the packet relay processing unit 15 according to the adjacent route information RD and the route table T stored in the storage unit 11, relays the packets, determines the optimal route, and sets the determined route table T. The receiving units 13-1 to 13-n and the transmitting units 14-1 to 14-n are respectively connected in pairs to the communication routes between the node devices and the other node devices, and perform transmission and reception processing between the node devices and the other node devices.

[0033] In addition, in this embodiment, a mixture of wired and wireless paths is permitted as paths between node devices. A wireless path is used between node devices 6 and 9, and a wired path is used between the other node devices.

[0034] In the outline of a general AODV routing protocol, first, a source node device broadcasts a route request packet (RREQ: Route Request) to adjacent node devices, and the node device that receives this route request packet broadcasts it to adjacent node devices other than the node device that received it, and this is repeated until the destination node device. At this time, the route request packet has an accumulated number of relays (number of hops) incremented each time it is forwarded. Then, the destination node device unicasts a route reply packet (RREP: Route Reply) to the source node device for the route indicated by the route request packet with the smallest number of relays among the multiple route request packets received. When each node device receives a route request packet, it temporarily stores a tentative route table including the source, destination, relay source, and relay destination, and when it receives a route reply packet within a predetermined time, it stores the tentative route table as a route table and deletes other tentative route tables. As a result, each node device uses the route table to determine a communication route between the source node device and the destination node device.

[0035] In contrast, in this embodiment, in addition to the cumulative relay count, additional information on the non-priority cumulative relay count is added to the route request packet. The non-priority cumulative relay count is the cumulative number of relays of a non-priority route, and the non-priority route may be, for example, a wireless route with low stability, but may also be a route with a slow communication speed or a narrow communication band. The wireless route is an unstable route that is greatly affected by the external environment on the route. The priority route is, for example, a wired route with high stability, and is not counted in the non-priority cumulative relay count. The priority route may be a route with a fast communication speed or a wide communication band. The distinction between the priority route and the non-priority route depends on, for example, whether it is a wired route or a wireless route, but the wireless route may be included in part of the priority route, or the wired route may be included in part of the non-priority route, depending on the band, external environment, and route configuration. In other words, any route may be set as a non-priority route.

[0036] Information on whether the adjacent path is a preferred path or a non-preferred path is set in advance as adjacent path information by each node device and held. For example, as shown in Fig. 1, the node device 6 has adjacent path information RD in the storage unit 11, and as the adjacent path information RD, paths between adjacent node devices "S (node ​​device 1)" and "N7 (node ​​device 7)" are set as preferred paths, and paths between adjacent node device "N9 (node ​​device 9)" are set as non-preferred paths. That is, each node device has in advance, as the adjacent path information RD, that each adjacent path between adjacent node devices is either a preferred path with high stability or a non-preferred path with low stability.

[0037] The node device 1, which is a source node device, broadcasts route request packets P11 and P16 having the same sequence number to the adjacent node devices 2 and 6, with the node device 10, which is a destination node device, as the destination.

[0038] The node devices 2 and 6, which are relay node devices that receive the route request packet, generate a route table T that temporarily stores the source, destination, relay source, and / or relay destination. Then, the node devices 2 and 6 refer to the adjacent route information RD, increment the cumulative number of hops in the route request packet to update it, and if the received adjacent route is a non-priority route, perform a hop number update process to further increment and update the non-priority cumulative number of hops in the route request packet, and broadcast the route request packet to the other adjacent node devices, the node devices 3, 7, and 9. The node devices 4, 5, and 8, which are relay node devices, perform the same process. Note that additional information on the non-priority cumulative number of hops is described in an extension in the TLV (Type, Length, Value) format.

[0039] Here, since the node device 6 transfers the route request packets P17 and P20 to the two adjacent node devices, node devices 7 and 9, respectively, two route tables T1 (with the node device 7 as the relay destination) and T2 (with the node device 9 as the relay destination) with different relay destinations are temporarily stored. Furthermore, since the node device 9 receives the route request packet P20 via a non-priority route, the node device 9 transmits a route request packet P21 with an incremented non-priority cumulative relay count to the node device 10. Note that the route request packet broadcast by the node device 1, which is the source node device, is assigned the same sequence number, and the route request packets broadcast by the node devices 2 to 9, which are relay node devices, are also assigned the same sequence number. Note that when the source node device retransmits the route request packet, it is broadcast with a different sequence number assigned.

[0040] Node device 10, which is the destination node device that received the route request packet, refers to adjacent route information RD and performs a hop count update process to update the cumulative hop count and non-priority cumulative hop count in the route request packet in the same manner as a relay node device, and selects as a priority the route of the route request packet with the smallest non-priority route cumulative hop count as the optimal route from among the route request packets P15, P19, and P21 that have been received and have the same sequence number, and if there are multiple routes with the same non-priority cumulative hop count, selects next as the optimal route the route of the route request packet with the smallest cumulative hop count, and if there are multiple routes with the same cumulative hop count, performs a route selection process for the optimal route to select next the route of the route request packet that was received earliest as the optimal route, and unicasts a route reply packet P30 to node device 1, which is the source node device, via the selected optimal route.

[0041] Specifically, the node device 10 receives three route request packets P15, P19, and P21 having the same sequence number via routes R1, R2, and R3. Then, the node device 10 selects the routes R1 and R2 of the route request packets P15 and P19 having the smallest non-priority cumulative hop count (value=0) as the optimal route. Furthermore, since there are multiple routes R1 and R2 having the same non-priority cumulative hop count, the node device 10 selects the route R2 of the route request packet P19 having the smallest cumulative hop count (value=4) as the optimal route. As a result, a route in which the priority route is prioritized, that is, a route with high stability, is selected as the optimal route. The node device 10 stores a route table T of the selected optimal route. Then, the node device 10 unicasts the route reply packet P30 to the node device 8 in order to transmit the route reply packet P30 to the node device 1, which is the source node device, via route R2.

[0042] Thereafter, the node devices 6, 7, and 8 that receive the route reply packet P30 store the temporary route table T that corresponds to the source, destination, relay source, and relay destination in the route reply packet P30 as the route table T, and delete the other temporary route tables T. For example, the node device 6 stores the route table T1 and deletes the route table T2. In addition, the other node devices 2, 3, 4, 5, and 9 delete the temporarily stored temporary route table T if they do not receive a route request packet within a predetermined time.

[0043] As a result, the route between the source node device and the destination node device is determined by the route table T stored in each of the node devices 1 to 10, and a two-way communication route is created.

[0044] If the source node device does not receive a route reply packet within a predetermined time after broadcasting a route request packet, it discards the packet addressed to the destination for which the route was requested. If a packet with the same destination is about to be sent, a route request packet with a new sequence number will be broadcast. If the node devices 2 to 9 do not receive a route reply packet within a predetermined time, they delete all temporarily stored route tables T.

[0045] Furthermore, when a relay node device receives multiple route request packets having the same sequence number from multiple node devices, it first records the route of the first route request packet in the temporary route table T and broadcasts it, and when it receives a later route request packet, it performs route selection processing of the optimal route by comparing the route of the first route request packet with the route of the later route request packet in the same manner as the destination node device, and if the route of the later route request packet is more optimal than the route of the first route request packet, it overwrites and updates the route of the later route request packet as the temporary route table T, and broadcasts the later route request packet. Also, if the route of the later route request packet is not more optimal than the route of the first route request packet, it discards the later route request packet and maintains the contents of the current temporary route table T. In this way, the relay node device performs route selection processing of the optimal route in the same manner as the destination node device, and performs forwarding of the route request packet and updating of the temporary route table based on the result.

[0046] Here, as described above, the route selection process for the optimal route refers to adjacent route information RD, updates the cumulative number of hops and non-priority cumulative number of hops in the route request packet, and, among the route request packets received with the same sequence number, preferentially selects as the optimal route the route of the route request packet with the smallest non-priority cumulative number of hops, and if there are multiple routes with the same non-priority cumulative number of hops, next selects as the optimal route the route of the route request packet with the smallest cumulative number of hops, and if there are multiple routes with the same cumulative number of hops, next selects as the optimal route the route of the route request packet received earliest.

[0047] <Control process of node equipment> Fig. 3 is a flowchart showing a communication path determination process procedure of the node devices 1 to 10. As shown in Fig. 3, when determining a communication path, each node device determines whether the node device itself is a source, a relay, or a destination (step S100).

[0048] If the node device itself is the sender (step S100: sender), it broadcasts a route request packet to adjacent node devices (step S101). It then determines whether or not a route response packet has been received within a predetermined time (step S102). If the route response packet has not been received within the predetermined time (step S102: No), the packet addressed to the destination for which the route was requested is discarded (step S103), and this process ends. On the other hand, if a route response packet has been received within the predetermined time (step S102: Yes), the route of this route response packet is determined and stored as a route table (step S104), and this process ends.

[0049] On the other hand, if the node device is a relay (step S100: relay), it determines whether or not a route request packet has been received (step S111). If a route request packet has not been received (step S111: No), this determination process continues. If a route request packet has been received (step S111: Yes), a temporary route table is created and temporarily stored (step S112). Then, the cumulative number of hops and the cumulative number of non-priority hops of the received route request packet are updated based on adjacent route information (step S113). Then, the received route request packet is broadcast to adjacent nodes (step S114).

[0050] Then, it is determined whether a route request packet with the same sequence number has been received (step S115). That is, it is determined whether a later route request packet with the same sequence number has been received. If a route request packet with the same sequence number has been received (step S115: Yes), the cumulative hop count and non-priority cumulative hop count of the received route request packet are updated based on adjacent route information (step S116). Then, based on the updated cumulative hop count and non-priority cumulative hop count, route selection processing for an optimal route is performed to select an optimal communication route (step S117). Then, if the route request packet having the selected optimal route is a later route request packet, this later route request packet is broadcast to adjacent node devices (step S118). Note that if the route of the first route request packet is the optimal route, the later route request packet is discarded. Also, if the route of the later route request packet is the optimal route, the tentative route table T is overwritten and updated. On the other hand, if a route request packet with the same sequence number has not been received (step S115: No), the process proceeds to step S119. The processes in steps S115 to S118 are repeated for the next subsequent route request packet within a predetermined period of time.

[0051] Then, it is determined whether or not a route response packet is received within a predetermined time after the route request packet is received (step S119). If a route response packet is received (step S119: Yes), a tentative route table corresponding to the route of the route response packet is determined as the route table and stored, and other tentative route tables are deleted (step S120). If a route response packet is not received (step S119: No), all tentative route tables are deleted (step S121), and this process is terminated.

[0052] On the other hand, if the node device itself is the destination (step S100: destination), it determines whether or not a route request packet has been received (step S131). If the route request packet has not been received (step S131: No), this determination process continues. If the route request packet has been received (step S131: Yes), a temporary route table is created and temporarily stored (step S132).

[0053] Then, it is determined whether or not a route request packet with the same sequence number has been received (step S133). If a route request packet with the same sequence number has been received (step S133: Yes), the process proceeds to step S132 to create a tentative route table. On the other hand, if a route request packet with the same sequence number has not been received (step S133: No), the cumulative hop count and non-priority cumulative hop count of the received route request packet are updated based on adjacent route information (step S134). Then, a route selection process is performed to select an optimal communication route based on the updated cumulative hop count and non-priority cumulative hop count (step S135). Then, the route cable of the selected route is determined and stored (step S136), and other tentative route tables are deleted (step S137). Then, a route reply packet is unicast via the selected route (step S138), and this process ends.

[0054] <Route selection process> Fig. 4 is a flowchart showing the detailed processing procedure of the route selection process shown in Fig. 3. As shown in Fig. 4, the node device preferentially selects a route with the smallest non-priority cumulative relay count (step S201). Then, it is determined whether there are multiple routes with the same non-priority cumulative relay count (step S202). If there are not multiple routes with the same non-priority cumulative relay count (step S202: No), the route with the smallest non-priority cumulative relay count is selected as the selected route, and the process returns to step S117 or step S135.

[0055] On the other hand, if there are multiple routes with the same non-priority cumulative relay count (step S202: Yes), the route with the smallest cumulative relay count is selected from the multiple selected routes (step S203). Then, it is determined whether there are multiple routes with the same cumulative relay count among the selected routes (step S204).

[0056] If there are no multiple routes with the same cumulative number of hops (step S204: No), the route with the smallest cumulative number of hops is selected as the selected route, and the process returns to step S117 or step S135. On the other hand, if there are multiple routes with the same cumulative number of hops (step S204: Yes), the route that was received first is selected as the selected route (step S205), the later route is discarded, and the process returns to step S117 or step S135.

[0057] <An example of route selection> 5 to 8 are diagrams showing an example of route selection in a destination node device. In FIG. 5, a destination node device "D" receives a route request packet from a source node device "S" for route R10 via only the preferred route, and a route request packet from the source node device for route R20 via a route including a non-preferential route. The cumulative number of hops for route R10 is "5", and the non-preferential cumulative number of hops is "0". The cumulative number of hops for route R20 is "3", and the non-preferential cumulative number of hops is "1". Since the non-preferential cumulative number is determined with priority, route R10 with the smallest non-preferential cumulative number of hops is selected.

[0058] In Fig. 6, the destination node device receives route request packets for routes R11 and R21, both of which have been sent from the source node device via non-priority routes. The cumulative number of hops for route R11 is "5", and the non-priority cumulative number of hops is "2". The cumulative number of hops for route R21 is "5", and the non-priority cumulative number of hops is "1". Since the non-priority cumulative number is determined with priority, route R21, which has the smallest non-priority cumulative number of hops, is selected.

[0059] In Fig. 7, the destination node device receives route request packets for routes R12 and R22, both of which have been sent from the source node device via non-priority routes. The cumulative number of hops for route R12 is "5", and the non-priority cumulative number of hops is "1". The cumulative number of hops for route R22 is "3", and the non-priority cumulative number of hops is "1". The non-priority cumulative number of hops is determined as a priority, but since both have the smallest non-priority cumulative number of hops at "1", the cumulative number of hops is then determined as a priority. Then, route R22, which has the smallest cumulative number of hops at "3", is selected.

[0060] In Fig. 8, the destination node device receives route request packets for routes R13 and R23, both of which have passed through non-priority routes from the source node device. The cumulative number of hops for route R13 is "5", and the non-priority cumulative number of hops is "1". Furthermore, the cumulative number of hops for route R23 is "5", and the non-priority cumulative number of hops is "1". The non-priority cumulative number of hops is determined as a priority, but since both have the smallest non-priority cumulative number of hops at "1", the cumulative number of hops is then determined as a priority. However, since both cumulative numbers of hops are the same at "5", route R13 is selected for the route request packet that arrived first (earliest).

[0061] In this embodiment, it is possible to determine a highly stable communication route that avoids non-priority routes such as wireless routes without imposing a large calculation load. In particular, when wireless routes are mixed into a wired network as emergency backup routes, it is possible to determine a highly stable communication route that avoids communication routes including wireless routes.

[0062] In addition, the route selection determination process calculation for the communication route is mainly performed by the destination node device, and is only performed by a portion of relay node devices to which route request packets are sent from multiple relay sources, thereby reducing the calculation load on the node devices.

[0063] <Processing when a new route is connected> Fig. 9 is a schematic diagram showing a general configuration of a communication system before a new path is connected. Compared to the communication system in Fig. 1, the communication system in Fig. 9 shows a state before the wireless path between node devices 6 and 9 is connected so as to be able to communicate as a new adjacent path. Node device 6 is connected to node devices 1 and 7. Node device 9 is connected to node device 10. In the communication system shown in Fig. 9, when the wireless path between node devices 6 and 9 is connected so as to be able to communicate as a new adjacent path, the communication system shown in Fig. 1 is configured.

[0064] Fig. 10 is a schematic diagram showing a schematic configuration of a communication system in the case where the new route is a wired route. In the communication system shown in Fig. 9, when the wired route between the node devices 6 and 9 is connected so as to be able to communicate with each other as a new adjacent route, the communication system shown in Fig. 10 is configured.

[0065] First, when the node device 6 and the node device 9 are connected to be able to communicate with each other as a new adjacent route, the new adjacent route is preset as adjacent route information RD to indicate that the new adjacent route is either a preferred route or a non-preferential route.

[0066] 11 is a flowchart for explaining an example of a process executed in a node device to which an adjacent path has been added. When the process of this flowchart is started, the following steps are executed.

[0067] In step S301, the control unit 12 determines whether or not an adjacent path to another node device has been newly established, and if it is determined that an adjacent path has been newly established (step S301: Yes), the process proceeds to step S302, and otherwise (step S301: No), the process repeats the process of step S301. For example, as in Figs. 9 to 1, if the node device 6 and the node device 9 are connected by a wireless path, the process is determined as Yes and the process proceeds to step S302. Similarly, as in Figs. 9 to 10, if the node device 6 and the node device 9 are connected by a wired path, the process is determined as Yes and the process proceeds to step S302.

[0068] In step S302, the control unit 12 determines whether or not both of the node devices at both ends of the newly established adjacent route have an existing adjacent route in addition to the newly established one. If it is determined that there is an existing adjacent route (step S302: Yes), the control unit 12 proceeds to step S303, and otherwise (step S302: No) ends the process. For example, in the case of node device 9, since there is an existing adjacent route in addition to the newly established adjacent route, the control unit 12 proceeds to step S303. Note that this step is a process for preventing a node device with one adjacent route from transmitting a notification signal (RLINK (Route Link) signal), for example.

[0069] In step S303, the control unit 12 acquires the node ID of the node device itself. For example, in the case of the node device 9, the control unit 12 acquires “09” from the storage unit 11 as the node ID.

[0070] In step S304, the control unit 12 stores the node device ID of the node device itself acquired in step S303 and a sequence number for identifying the notification signal in each field of the RLINK signal. FIG. 12 is a diagram showing an example of a format of a notification signal when the node device 6 and the node device 9 are connected by a wireless path as shown in FIG. 1. As shown in FIG. 12, for example, in the case of the node device 9, the control unit 12 stores the node ID "09" and the sequence number "01" in each field of the RLINK signal. Note that the identifier field indicates that a node that receives the RLINK signal recognizes that this signal is an RLINK signal as a notification signal and is connected to be able to communicate as a new adjacent path. Furthermore, the RLINK signal has a cumulative number of hops and a non-priority cumulative number of hops of the path.

[0071] In step S305, the control unit 12 sets the cumulative relay count of the RLINK signal to an initial value of "1." For example, in the case of the node device 9, whether the node device 9 is connected via a wireless route as in Fig. 1 or via a wired route as in Fig. 10, the control unit 12 sets the cumulative relay count to the initial value of "1" in either case.

[0072] In step S306, the control unit 12 determines whether the newly established adjacent route is a wireless route or not, and if it is a wireless route (step S306: Yes), the process proceeds to step S307, otherwise (step S306: No), the process proceeds to step S308. For example, if the node device 9 is connected to a wireless route as in Fig. 1, the process proceeds to step S307, and if the node device 9 is connected to a wired route as in Fig. 10, the process proceeds to step S308.

[0073] In step S307, the control unit 12 sets the non-priority cumulative relay count of the RLINK signal to “1.” For example, when the node device 9 is connected to the wireless path as shown in FIG. 1, the control unit 12 sets the non-priority cumulative relay count to “1.”

[0074] In step S308, the control unit 12 transmits (broadcasts) an RLINK signal to other node equipments via the transmission units 14-1 to 14-n. For example, in the case of the node equipment 9, the control unit 12 transmits an RLINK signal from a transmission unit corresponding to an adjacent route having the node equipment 10 as a destination.

[0075] In step S309, the control unit 12 erases the existing route information stored in the routing table according to the cumulative number of hops and the non-priority cumulative number of hops of the RLINK signal. Fig. 13 is a diagram showing an example of a routing table held by the node device 9 in Fig. 9. The control unit 12 erases the existing route information having a non-priority cumulative number of hops that is two or more greater than the non-priority cumulative number of hops of the RLINK signal, and the existing route information having a cumulative number of hops that is two or more greater than the cumulative number of hops of the RLINK signal.

[0076] For example, when node device 6 and node device 9 are connected via a wireless path as shown in FIG. 1, the control unit 12 erases existing route information stored in the routing table that is two or more greater than the non-priority cumulative hop count "1" of the RLINK signal. In this case, there is no corresponding existing route information, so there is no route information to erase. In addition, the control unit 12 erases route information with node devices 1 to 4, 6, and 7 as destinations, which is existing route information that is two or more greater than the cumulative hop count "1" of the RLINK signal, from the existing route information stored in the routing table.

[0077] When the node device 6 and the node device 9 are connected by a wired route as shown in FIG. 10, the control unit 12 erases existing route information stored in the routing table that is greater than the non-priority cumulative hop count "0" of the RLINK signal by two or more. In this case, there is no corresponding existing route information, so there is no route information to erase. Also, among the existing route information stored in the routing table, route information with the node devices 1 to 4, 6, and 7 as destinations, which is existing route information greater than the cumulative hop count "1" of the RLINK signal by two or more, is erased. FIG. 14 is a diagram showing an example of a routing table from which route information has been erased. As shown in FIG. 14, route information with the node devices 1 to 4, 6, and 7 as destinations is erased. In this embodiment, the criterion for erasing existing route information is set to two or more in consideration of the possibility of route shortening by AODV, but other criteria may be set depending on the routing protocol and the advantages and disadvantages of updates.

[0078] The same process is also executed in the node device 6 to which the adjacent route is newly established.

[0079] By the above process, when a new route is connected, an RLINK signal having an identifier indicating that a route has been newly established, its own node ID, and including the cumulative number of hops and the cumulative number of non-priority hops can be transmitted to other node devices. In addition, since the process of step S302 is arranged to determine whether or not an existing route exists, if the number of branches has increased and no new route is created, it is possible not to transmit the RLINK signal.

[0080] After the route information is deleted, if a communication request is made to a destination included in the deleted route information, the route is reconstructed by a route request packet (RREQ). Fig. 15 is a diagram showing a routing table in which the route of node device 10 is reconstructed when node device 6 and node device 9 are connected by a wired route as shown in Fig. 10. In Fig. 15, route information (hatched route information) with node devices 1, 2, 6, and 7 as destinations is reconstructed.

[0081] Fig. 16 is a flowchart for explaining an example of a process executed in a node device that has received a notification signal. When the process shown in Fig. 16 is executed, the following steps are executed.

[0082] In step S401, the control unit 12 determines whether or not an RLINK signal has been received, and if it is determined that an RLINK signal has been received (step S401: Yes), the process proceeds to step S402, and otherwise (step S401: No), the process of step S401 is repeated. For example, in the node device 10, if an RLINK signal has been received, the result is determined as Yes, and the process proceeds to step S402.

[0083] In step S402, the control unit 12 determines whether or not there is an existing adjacent path other than the adjacent path through which the RLINK signal was received, and if it is determined that there is an existing adjacent path (step S402: Yes), the process proceeds to step S403, otherwise (step S402: No), the process ends. For example, in the case of node device 10, since there are existing adjacent paths with node devices 5 and 8 other than node device 9 through which the RLINK signal was received, the result is Yes, and the process proceeds to step S403.

[0084] In step S403, the control unit 12 acquires the node ID and sequence number of the received RLINK signal. For example, in the case of the node device 10, "09" is acquired as the node ID from the node ID field, and "01" is acquired as the sequence number. If an RLINK signal with the same ID has been received immediately before, the acquired node ID indicates that it has been transmitted in duplicate, and therefore the subsequently received RLINK signal is ignored.

[0085] In step S404, the control unit 12 determines whether the received RLINK signal is unprocessed or not, and if it is determined that it is unprocessed (step S404: Yes), the process proceeds to step S405, and otherwise (step S404: No), the process ends. For example, in the node device 10, if the acquired sequence number is an unprocessed number, the result is determined as Yes, and the process proceeds to step S405.

[0086] In step S405, the control unit 12 acquires the cumulative relay count and the non-priority cumulative relay count of the received RLINK signal. For example, in the case of the node device 10 shown in Fig. 1, the cumulative relay count is acquired as "1" and the non-priority cumulative relay count is acquired as "1". On the other hand, in the case of the node device 10 shown in Fig. 10, the cumulative relay count is acquired as "1" and the non-priority cumulative relay count is acquired as "0".

[0087] In step S406, the control unit 12 adds (increments) "1" to the cumulative number of relays acquired in step S405. For example, in the case of the node device 10, "1" is added to the cumulative number of relays, so that the cumulative number becomes "2".

[0088] In step S407, the control unit 12 refers to the adjacent route information RD, determines whether the adjacent route through which the RLINK signal was received is a wireless route, and proceeds to step S408 if it is a wireless route (step S407: Yes), and proceeds to step S409 otherwise (step S407: No). For example, in the case of node device 10, the adjacent route between node device 9 through which the RLINK signal was received is a wired circuit, so the control unit 12 proceeds to step S409.

[0089] In step S408, the control unit 12 adds (increments) "1" to the non-priority cumulative relay count acquired in step S403.

[0090] In step S409, the control unit 12 restores the cumulative relay count and non-priority cumulative relay count added in steps S406 and S408 to the cumulative relay count and non-priority cumulative relay count of the RLINK signal, and transmits (broadcasts) them to other node devices. For example, in the case of the node device 10 in Fig. 1, an RLINK signal in which "2" is stored in the cumulative relay count and "1" is stored in the non-priority cumulative relay count is transferred to the node devices 5 and 8. On the other hand, in the case of the node device 10 in Fig. 10, an RLINK signal in which "2" is stored in the cumulative relay count and "0" is stored in the non-priority cumulative relay count is transferred to the node devices 5 and 8.

[0091] In step S410, the control unit 12 compares the current non-priority cumulative relay count added in step S408 with the non-priority cumulative relay count of each existing route information stored in the routing table, and proceeds to step S411 if there is existing route information that is two or more greater than the current non-priority cumulative relay count (step S410: Yes), and proceeds to step S412 otherwise (step S410: No). FIG. 17 is a diagram showing an example of a routing table. For example, the node device 10 in FIG. 9 has the routing table shown in FIG. 17. In this FIG. 17, in the case of the node device 1 with ID:01 as the destination, the node device 8 with ID:08 as the forwarding destination, the cumulative relay count is "4", and the non-wired cumulative relay count is "0". In the case of the node device 10 in FIG. 10, the non-priority cumulative relay count added in step S408 is "0", and there is no existing route information that is two or more greater than "0" in the non-priority cumulative relay count stored in the routing table, so it is determined as No and proceeds to step S412. If there is existing route information stored in the routing table with a non-priority cumulative hop count that is two or more greater than "0", it is deleted.

[0092] In step S412, the control unit 12 compares the current cumulative number of hops added in step S406 with the cumulative number of hops of each existing route information stored in the routing table, and if there is existing route information that is two or more greater than the current cumulative number of hops (step S412: Yes), the process proceeds to step S413, otherwise (step S412: No), the process ends. In the case of the node device 10, the cumulative number of hops to which "1" was added in step S406 is "2", and existing route information that is two or more greater than "2" exists in the cumulative number of hops stored in the routing table, so the result is determined as Yes and the process proceeds to step S413.

[0093] In step S413, the control unit 12 deletes from the routing table existing route information whose cumulative hop count is 2 or more than "2". Fig. 18 is a diagram showing an example of the routing table from which the corresponding route information has been deleted from Fig. 17. For example, in the case of node device 10, as shown in Fig. 18, route information whose destinations are node devices 1 to 3 and 6 is deleted.

[0094] After the route information is deleted, if a communication request is made to a destination included in the deleted route information, the route is reconstructed by a route request packet (RREQ). Fig. 19 is a diagram showing a routing table in which the route of node device 10 is reconstructed when node device 6 and node device 9 are connected by a wired route as shown in Fig. 10. In Fig. 19, route information (hatched route information) with node device 1 and node device 6 as destinations is reconstructed.

[0095] According to the above process, when an RLINK signal is received, the value of the cumulative number of relays is added with "1" and transferred to another node device, and the value of the cumulative number of relays to which "1" has been added is compared with the existing cumulative number of relays stored in the routing table, and if the existing cumulative number of relays is 2 or more larger, the route information is deleted. Similarly, when an RLINK signal is received, the value of the non-priority cumulative number of relays is added with "1" and transferred to another node device, and the value of the non-priority cumulative number of relays to which "1" has been added is compared with the existing non-priority cumulative number of relays stored in the routing table, and if the existing non-priority cumulative number of relays is 2 or more larger, the route information is deleted. As a result, when a new adjacent route is added, only routes where a new route may exist can be deleted, so that route optimization can be performed quickly even when wired routes and wireless routes are mixed. In this embodiment, the criterion for deleting existing route information is set to 2 or more in consideration of the possibility of route shortening by AODV, but other criteria may be set depending on the routing protocol and the advantages and disadvantages of updates.

[0096] In addition, in this embodiment, when a new adjacent path is connected, it is possible to determine a highly stable communication path that avoids non-priority paths such as wireless paths without imposing a large calculation load. In particular, when wireless paths are mixed into a wired network as emergency backup paths, it is possible to determine a highly stable communication path that avoids communication paths including wireless paths.

[0097] In addition, the route selection determination process calculation for the communication route is mainly performed by the destination node device, and is only performed by a portion of relay node devices to which route request packets are sent from multiple relay sources, thereby reducing the calculation load on the node devices.

[0098] In the above embodiment, an example was shown in which route information satisfying the conditions was deleted in steps S309 and S413, but this route information may be subject to update without being deleted, and updated at a predetermined update timing. Specifically, the following form may be adopted. A flag (optimizable flag) indicating that the route information is subject to update is provided, and in steps S309 and S413, if the conditions are satisfied, the optimizable flag is set to "valid". Thereafter, if the optimizable flag is "valid" when a data packet is received, a route search is performed and the optimizable flag is changed to "invalid". By adopting such a form, packet loss caused by the deletion of route information can be suppressed.

[0099] In the above embodiment, the AODV routing protocol has been described as an example, but the present invention is not limited to this, and can be applied to any distance vector routing protocol that determines a communication route based on the number of hops (number of relays). For example, the present invention can be applied to RIP (Routing Information Protocol) and IGRP (Interior Gateway Routing Protocol).

[0100] In the above embodiment, when each node device receives a route request packet, the source, destination, relay source, and relay destination are stored in the temporary route table T. In addition to these, the route table T may store the cumulative relay count and non-priority cumulative relay count added to the route request packet as the cumulative relay count (request side) and non-priority cumulative relay count (request side).

[0101] This allows each node device to grasp the cumulative number of relays and the cumulative number of non-priority relays between the source node device 1 and its own node device, and each node device can use this as route information when communicating with the source node device 1.

[0102] In the above embodiment, the additional information of the non-priority cumulative hop count is added to the route request packet in addition to the cumulative hop count, but the additional information of the non-priority cumulative hop count may be added to the route reply packet P30 in addition to the cumulative hop count. Specifically, a relay node device that receives the route reply packet P30 transmitted from the node device 10 that is the destination node device increments and updates the cumulative hop count (answer side) in the route reply packet P30 in the same manner as when the route request packet is received, and if the received adjacent route is a non-priority route, performs a hop count update process (answer side) that further increments and updates the non-priority cumulative hop count (answer side) in the route reply packet, and unicasts the route reply packet to other adjacent node devices. The node devices 6, 7, and 8 that receive the route reply packet P30 store the temporary route table T corresponding to the source, destination, relay source, and relay destination in the route reply packet P30 as the route table T, and also store the cumulative number of relays (answer side) and the non-priority cumulative number of relays (answer side) in the route reply packet P30.

[0103] This allows the relay node device to hold information on the cumulative number of hops and the non-priority cumulative number of hops from the node device itself to the destination node device. This information can be used for a route reply by the relay node device as specified in IETF RFC3561 "Ad hoc On-Demand Distance Vector (AODV) Routing" 6.6.2. In addition, by obtaining the cumulative number of hops (answer side) and the non-priority cumulative number of hops (answer side), the node device 1, which is the source node device, can obtain information on the stability of the route to the destination node device, and can estimate the communication speed and determine the need for route update.

[0104] Although the embodiment and modifications to which the present inventors have applied the invention have been described above, the present invention is not limited by the description and drawings that form a part of the disclosure of the present invention according to the present embodiment. In other words, other embodiments, examples, operation techniques, etc. made by those skilled in the art based on the present embodiment are all included in the scope of the present invention. [Explanation of symbols]

[0105] 1~10 Node equipment 11 Storage section 12 Control section 13-1~13-n Receiver 14-1~14-n Transmitter 15 Packet relay processing unit P11~P21 Route request packets P30 Route Reply Packet R1, R2, R3, R10~R13, R20~R23 route RD adjacent route information T, T1, T2 routing table

Claims

1. A communication system for determining a communication path between a source node device and a destination node device via a plurality of node devices in a network, comprising: Each node device presets, as adjacent path information, whether each adjacent path between adjacent node devices is a preferred path or a non-preferred path, The source node device broadcasts a route request packet having a sequence number to adjacent node devices with the destination node device as the destination; a relay node device that receives and relays the route request packet refers to the adjacent route information, increments and updates the cumulative number of hops in the route request packet, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the route request packet, and broadcasts the route request packet to other adjacent node devices; the destination node device that has received the route request packet refers to the adjacent route information, performs the number of hops update process, and, from among the received route request packets having the same sequence number, preferentially selects as an optimal route the route of the route request packet having the smallest non-priority cumulative number of hops, and if there are multiple routes having the same non-priority cumulative number of hops, selects next as the optimal route the route of the route request packet having the smallest cumulative number of hops, and if there are multiple routes having the same cumulative number of hops, performs route selection process for the optimal route to select next as the optimal route the route of the route request packet received earliest, and unicasts a route reply packet to the destination node device via the selected optimal route; A communication system characterized in that, when each node device receives a route request packet, it temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when it receives the route reply packet within a specified time, it stores it as a route table between the source node device and the destination node device.

2. 2. The communications system according to claim 1, wherein, when a relay node device receives a route request packet having the same sequence number, it first records the route of the first-arriving route request packet in a tentative route table and broadcasts it, and, when a later-arriving route request packet is received, it compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, it updates the route of the later-arriving route request packet as a tentative route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, it discards the later-arriving route request packet and maintains the contents of the current tentative route table.

3. The communication system described in claim 1, characterized in that when each node device receives the route request packet, it stores the incremented cumulative hop count and non-priority cumulative hop count of the route request packet in the temporary route table as the request side cumulative hop count and the request side non-priority cumulative hop count, respectively.

4. A cumulative relay number on the answering side and a non-priority cumulative relay number on the answering side corresponding to the cumulative relay number and the non-priority cumulative relay number, respectively, are added to the route reply packet, The communication system described in claim 1, characterized in that when each node device receives the route reply packet, it increments the cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the route reply packet, stores the incremented cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the temporary route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the temporary route table as a route table.

5. In a network having a plurality of node devices, each node device preliminarily sets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path; When a predetermined first node device and a predetermined second node device that configure the network are connected to each other so as to be able to communicate with each other as a new adjacent route, the new adjacent route is preset as adjacent route information to indicate that the new adjacent route is either a preferred route or a non-preferential route; The first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the new adjacent path is connected so as to be capable of communication, and a cumulative relay number and a non-priority cumulative relay number to the first or second node device; Another node device that receives the notification signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information in which the non-priority cumulative number of hops in the existing route information stored in a routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information in which the cumulative number of hops in the existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

6. 6. The communication system according to claim 5, wherein information for identifying the node itself is added to the notification signal before transmission.

7. 6. The communication system according to claim 5, further comprising a sequence number for identifying said notification signal in order to cope with a case where said notification signal is transmitted a plurality of times.

8. the preferred route is a wired route; 8. The communication system according to claim 1, wherein the non-preferential path is a wireless path.

9. A node device of a communication system that determines a communication path between a source node device and a destination node device via a plurality of node devices in a network, the node device comprising: Each node device presets, as adjacent path information, whether each adjacent path between adjacent node devices is a preferred path or a non-preferred path, When the node device is the source node device, the source node device broadcasts a route request packet having a sequence number to adjacent node devices with the destination node device as the destination; If the node device is a relay node device that receives and relays the route request packet, the relay node device refers to the adjacent route information, increments and updates the cumulative number of hops in the route request packet, and if the received adjacent route is a non-priority route, further performs a hop number update process to increment and update the non-priority cumulative number of hops in the route request packet, and broadcasts the route request packet to other adjacent node devices. If the node device is the destination node device that received the route request packet, the destination node device refers to the adjacent route information, performs the number of hops update process, and selects, as an optimal route, the route of the route request packet with the smallest non-priority cumulative number of hops among the received route request packets having the same sequence number, and if there are multiple routes with the same non-priority cumulative number of hops, selects next as the optimal route the route of the route request packet with the smallest cumulative number of hops, and if there are multiple routes with the same cumulative number of hops, performs route selection process for the optimal route to select next as the optimal route the route of the route request packet received earliest, and unicasts a route reply packet to the destination node device via the selected optimal route. Each node device is characterized in that when it receives the route request packet, it temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when it receives the route reply packet within a specified time, it stores it as a route table between the source node device and the destination node device.

10. 10. The node device according to claim 9, wherein, when receiving route request packets having the same sequence number, the relay node device first records the route of the first-arriving route request packet in a tentative route table and broadcasts it, and, when receiving a later-arriving route request packet, compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, updates the route of the later-arriving route request packet as a tentative route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, discards the later-arriving route request packet and maintains the contents of the current tentative route table.

11. The node device according to claim 9, characterized in that, when each node device receives the route request packet, the cumulative relay count and the non-priority cumulative relay count of the incremented route request packet are stored in the temporary route table as the cumulative relay count on the request side and the non-priority cumulative relay count on the request side, respectively.

12. A cumulative relay number on the answering side and a non-priority cumulative relay number on the answering side corresponding to the cumulative relay number and the non-priority cumulative relay number, respectively, are added to the route reply packet, The node device according to claim 9, characterized in that, when each node device receives the route reply packet, it increments the cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the route reply packet, stores the incremented cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the temporary route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the temporary route table as a route table.

13. In a network having a plurality of node devices, each node device preliminarily sets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path; When a predetermined first node device and a predetermined second node device that configure the network are connected to each other so as to be able to communicate with each other as a new adjacent route, the new adjacent route is preset as adjacent route information to indicate that the new adjacent route is either a preferred route or a non-preferential route; The first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the new adjacent path is connected so as to be capable of communication, and a cumulative relay number and a non-priority cumulative relay number to the first or second node device; Another node device that receives the notification signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, further performs a hop number update process to increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information in which the non-priority cumulative number of hops in the existing route information stored in the routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information in which the cumulative number of hops in the existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

14. the preferred route is a wired route; 14. The node device according to claim 9, wherein the non-preferential path is a wireless path.

15. A communication path determination method for determining a communication path between a source node device and a destination node device via a plurality of node devices in a network, the method comprising: Each node device presets, as adjacent path information, whether each adjacent path between adjacent node devices is a preferred path or a non-preferred path, The source node device broadcasts a route request packet having a sequence number to adjacent node devices with the destination node device as the destination; a relay node device that receives and relays the route request packet refers to the adjacent route information, increments and updates the cumulative number of hops in the route request packet, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the route request packet, and broadcasts the route request packet to other adjacent node devices; the destination node device that has received the route request packet refers to the adjacent route information, performs the number of hops update process, and, from among the received route request packets having the same sequence number, preferentially selects as an optimal route the route of the route request packet having the smallest non-priority cumulative number of hops, and if there are multiple routes having the same non-priority cumulative number of hops, selects next as the optimal route the route of the route request packet having the smallest cumulative number of hops, and if there are multiple routes having the same cumulative number of hops, performs route selection process for the optimal route to select next as the optimal route the route of the route request packet received earliest, and unicasts a route reply packet to the destination node device via the selected optimal route; A communication route determination method characterized in that, when each node device receives the route request packet, it temporarily stores the source, destination, relay source and / or relay destination in a temporary route table, and when it receives the route reply packet within a specified time, it stores it as a route table between the source node device and the destination node device.

16. 16. The communication route determination method according to claim 15, wherein, when a relay node device receives route request packets having the same sequence number, it first records the route of the first-arriving route request packet in a tentative route table and broadcasts it, and, when a later-arriving route request packet is received, it compares the route of the first-arriving route request packet with the route of the later-arriving route request packet to perform route selection processing for the optimal route, and if the route of the later-arriving route request packet is more optimal than the route of the first-arriving route request packet, it updates the route of the later-arriving route request packet as a tentative route table and broadcasts the later-arriving route request packet, and if the route of the later-arriving route request packet is not more optimal than the route of the first-arriving route request packet, it discards the later-arriving route request packet and maintains the contents of the current tentative route table.

17. The communication route determination method described in claim 15, characterized in that when each node device receives the route request packet, it stores the incremented cumulative relay count and non-priority cumulative relay count of the route request packet in the temporary route table as the request side cumulative relay count and the request side non-priority cumulative relay count, respectively.

18. A cumulative relay number on the answering side and a non-priority cumulative relay number on the answering side corresponding to the cumulative relay number and the non-priority cumulative relay number, respectively, are added to the route reply packet, The communication route determination method according to claim 15, characterized in that, when each node device receives the route reply packet, it increments the cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the route reply packet, stores the incremented cumulative number of hops on the answering side and the non-priority cumulative number of hops on the answering side in the tentative route table corresponding to the source, destination, relay source and / or relay destination in the route corridor packet, and stores the tentative route table as a route table.

19. In a network having a plurality of node devices, each node device preliminarily sets, as adjacent path information, that each adjacent path between adjacent node devices is either a preferred path or a non-preferred path; When a predetermined first node device and a predetermined second node device that configure the network are connected to each other so as to be able to communicate with each other as a new adjacent route, the new adjacent route is preset as adjacent route information to indicate that the new adjacent route is either a preferred route or a non-preferential route; The first and second node devices broadcast, to other adjacent node devices, a notification signal having information indicating that the new adjacent path is connected so as to be capable of communication, and a cumulative relay number and a non-priority cumulative relay number to the first or second node device; Another node device that receives the notification signal refers to the adjacent route information, increments the cumulative number of hops in the notification signal to update it, and if the received adjacent route is a non-priority route, performs a hop number update process to further increment and update the non-priority cumulative number of hops in the notification signal, broadcasts the notification signal to other adjacent node devices, and erases or updates existing route information in which the non-priority cumulative number of hops in the existing route information stored in a routing table is greater than the non-priority cumulative number of hops stored in the notification signal, and erases or updates existing route information in which the cumulative number of hops in the existing route information stored in the routing table is greater than the cumulative number of hops stored in the notification signal.

20. the preferred route is a wired route; 20. The method for determining a communication path according to claim 15, wherein the non-priority path is a wireless path.

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