JP2007036397A - Ad hoc network system and node device thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transmit an important message reliably to a specified node in a system in the ad hoc network system in which a plurality of nodes compose a network autonomously. <P>SOLUTION: In the ad hoc network system in which the plurality of nodes form the network autonomously, based on-demand routing protocols, each node has a route management table for holding route information containing a plurality of next transfer destination information 23 for relaying and transmitting the message to the specified node. The route information is generated regardless of the presence or absence of communication, and is held in the route management table. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ad hoc network system in which a plurality of nodes autonomously form a network, and in particular, urgency from any node constituting the ad hoc network toward a specific node in the ad hoc network. The present invention relates to an ad hoc network system that realizes transfer of a message that requires certainty and a node device thereof.

With the recent progress of wireless communication technology and the miniaturization and advancement of electronic devices, communication between communication devices is possible without using existing network infrastructure, compared to the conventional infrastructure type communication form. Interest in ad hoc network systems is growing. This ad hoc network differs from traditional fixed infrastructure networks (for example, communication networks configured to communicate via access points)
(1) Communication between objects and devices (2) Autonomous network can be built with a large number of objects and devices (3) Network can be built independent of existing communication infrastructure (4) Easy and temporary use While it has the feature that it is possible to construct a network that is capable of responding to changes in topology, it is required to be autonomous. At present, various routing protocols (ad hoc routing protocols) for effectively forming an ad hoc network have been proposed in order to satisfy the above characteristics and requirements (for example, Non-Patent Document 1 shown below). ~ 3 etc.).

  Further, holding of a plurality of routes from a transmission destination to a transmission source for the purpose of quick route restoration at the time of link disconnection is shown in the following Non-Patent Document 4 and Patent Documents 1 and 2 below.

  Here, Non-Patent Document 1 (DSR) and Non-Patent Document 2 (AODV) are documents showing an on-demand type routing protocol. According to these protocols, when a communication request occurs, a route from the transmission source to the transmission destination is set, and an environment for performing predetermined communication is provided.

  On the other hand, Non-Patent Document 3 (OLSR) is a document showing a proactive routing protocol. According to this protocol, by constantly exchanging route information, an environment is provided that allows communication to be started based on the route information held when a communication request occurs.

  Non-Patent Document 4 (AOMDV) is an extension of the protocol shown in Non-Patent Document 2 to multipath. This document describes a method (protocol) for obtaining a plurality of routes without overlapping links when there are overlapping links in the plurality of routes held. According to this technology, it is possible to solve the problem that the route cannot be repaired when there are overlapping links in a plurality of routes.

  On the other hand, Patent Document 1 discloses a route control method capable of creating or selecting a route with few duplicate links and duplicate nodes. Further, Patent Document 2 discloses a route control method that realizes quick route switching by holding an alternative route in advance in preparation for link disconnection due to deterioration of the quality of a link during communication.

Japanese Patent Laid-Open No. 2004-23440 JP 2004-282270 A DSR (Dynamic Source Routing): draft-ietf-manet-dsr-10. txt AODV (Ad Hoc On Demand Distance Vector Routing): RFC3561 OLSR (Optimized Link State Routing): RFC3626 AOMV (M. Marina, S, Das, “On-demand multipath distance vector routing in ad hoc networks,“ Proceedings of the International Conference on Network 1)

  However, the conventional ad hoc routing protocols shown in Non-Patent Documents 1 to 3 basically assume Best-effort type communication, and all communication is handled as the Best-effort type. For this reason, even if a communication requiring urgent communication occurs, the specification is such that if other communication is already present, the communication is processed sequentially from the communication that already exists. However, there was a problem that a delay occurred.

  In addition, in the on-demand type ad hoc routing protocol according to the prior art such as Non-Patent Documents 1 and 2, the table size at each node is maintained by maintaining the route to the destination only when communication occurs. And traffic for routing within ad hoc networks. However, in the on-demand type protocol, it is necessary to obtain a route to a transmission destination when communication occurs, and there is a problem that a delay required for route search becomes a large overhead in an urgent message.

  On the other hand, in the pro-active type ad hoc routing protocol according to the prior art such as Non-Patent Document 3, since the route information is constantly exchanged, the traffic amount in the ad hoc network increases and the sensor node In such an ad hoc network composed of battery-powered nodes, there is a problem in that the battery is consumed by the process of transmitting and receiving information that is constantly exchanged and the process of received messages, which shortens the life of the node. It was. Further, as the number of nodes constituting the ad hoc network increases, there is a problem that the route information held in each node becomes enormous.

  In addition, the wireless network has a characteristic that the bit error rate of the wireless link is larger than that of the wired network, and the wireless link is frequently disconnected due to movement of surrounding objects or changes in radio wave conditions. On the other hand, in the above-described ad hoc routing protocol, predetermined communication is continued by performing rediscovery of a route after detecting a link failure. For this reason, it takes time to rediscover a route after a link failure, and there is a problem that the use of the protocol becomes a large overhead for communications that require urgency.

  In addition, as described above, in the techniques shown in Non-Patent Document 3 and Patent Documents 1 and 2, a link failure in which an alternative route is obtained in advance in order to reduce the time required to rediscover the route after the link failure. A quick response to is shown. However, the purpose of this means is to realize path switching as quickly as possible. When a link failure occurs, a message loss or delay due to retransmission occurs, and the communication that requires urgency satisfies that requirement. There was a problem that it could not be made.

  The present invention has been made in view of the above, and in an ad hoc network system in which a plurality of nodes autonomously configure a network, an ad hoc network system is configured from an arbitrary node constituting the ad hoc network system. It is an object of the present invention to provide an ad hoc network system that realizes reliable transmission of a message that requires urgency and certainty to a specific node in the network (hereinafter referred to as “critical message”) and its node device. .

  In order to solve the above-described problems and achieve the object, an ad hoc network system according to the present invention is an ad hoc network in which a plurality of node devices autonomously form a network based on an on-demand type routing protocol. In the system, the node device includes a route management table in which route information including a plurality of next transfer destination node information for relay transmission of a message directed to the specific node device is stored, and the route information It is generated regardless of the presence or absence and is stored in the route management table.

  According to the ad hoc network system according to the present invention, a path management table is provided that holds path information including a plurality of next transfer destination node information for relay transmission of a message directed to a specific node device, Since this route information is generated regardless of the presence / absence of communication and is held in the route management table, there is an effect that reliable transmission of an urgent message can be realized.

  Embodiments of an ad hoc network system and its node device according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

(Configuration of this system)
First, the system configuration of the ad hoc network system according to the present invention will be described. FIG. 1 is a diagram showing a configuration of an ad hoc network system of the present invention in which a plurality of nodes autonomously configure a network. In the ad hoc network system shown in the figure, nodes 101 constituting the system are connected by one or more wireless links 102, and between the wireless links 102, for example, the above-described on-demand type DSR or AODV The function is exhibited by executing predetermined communication based on the ad hoc routing protocol.

(Features of this system)
Next, features of this system will be described. In addition to the conventional on-demand ad hoc routing protocol, each node constituting the ad hoc network system according to the present invention searches for and holds a route between a source and a destination only when communication occurs. And has a function of searching and holding a route toward a specific node in the ad hoc network system regardless of the presence or absence of communication. In other words, each node in the ad hoc network system is configured at the time of startup and periodically at intervals of several tens of minutes to several hours (or about one day depending on the system). 3), a route search toward a specific node (for example, 101-y in the system configuration of FIG. 1) registered in the system is performed.

  Here, the above-described route search is a search procedure that makes it possible to hold a plurality of routes to a destination node, and is realized by extending or correcting the route search procedure in DSR or AODV. The For example, in the AODV route search procedure, regarding a broadcast message (Route Request) for searching for a destination node, if the message is duplicated, the message received later is unconditionally discarded. However, in the route search procedure according to the present invention, based on the information registered as the configuration information, a plurality of duplicately received messages may be received at the time of processing / transfer and at the time of response to the Route Request message. Response processing for the message is required.

  In the route search procedure described above, when a node that already holds a route to a destination receives a Route Request message from another node, a response to the Route Request message (on behalf of the destination) ( (Route Reply) message is notified, and the amount of traffic generated by route search processing in the ad hoc network can be reduced.

(Route management table)
FIG. 2 is a chart showing an example of a route management table in the node 101 in the ad hoc network system. In the figure, the path management table is composed of an identifier 21 of a transmission source node, an identifier 22 of a transmission destination node, an identifier 23 of a next hop (transfer destination) node, a status flag 24, a lifetime 25, and other 26 elements. It is possible to hold (register) up to N routes (N is an arbitrary natural number and a value specified in the configuration information) for a plurality of specific nodes specified in the information (see FIG. 3 described later). It has become. Note that, for a route addressed to a specific node, NULL is set in the identifier of the transmission source node in order to receive a message from an arbitrary transmission source node.

(Configuration information)
FIG. 3 is a table showing an example of configuration information defined in advance for each node. In the configuration information shown in the figure, an identifier 31 (31-1, 31-2,..., 31-AA) of a specific node for which an arbitrary number of registrations is permitted, and the number of routes (hops) to the specific node The maximum number of allowed routes 32, a re-search cycle (route management cycle for a specific node) 33 until a route to a specific node is re-searched, a route life (effective period) 34 for a normal route, etc. are defined. . This configuration information is set in each node constituting the ad hoc network system, and serves as reference information for creating a route management table to be described later.

(Transfer processing at each node related to the message for the destination node)
Next, refer to FIGS. 1 to 6 for processing at each node when the node 101-x (see FIG. 1) in the ad hoc network notifies an important message directed to the specific node 101-y (see FIG. 1). To explain. Here, FIG. 4 is a diagram showing an example of a processing sequence of an urgent message directed to the specific node 101-y, and FIG. 5 is a diagram showing an example of a route at the time of forwarding the urgent message toward the specific node 101-y. FIG. 6 is a diagram showing an example of a control header added to a message. In the example of the route illustrated in FIG. 5, the case where two transmission routes 103 indicated by hatching arrows are secured for each node is illustrated as an example for the urgent message for the specific node 101-y. Needless to say, the present invention is not limited to a single transmission path, and can be applied to a transfer process that secures three or more transmission paths.

  In FIG. 4, the node 101-x that is the message transmission source, for example, based on a communication request from its own application, sends an emergency message for the specific node 101-y with a control header as shown in FIG. Referring to its own route management table, it transmits to all the routes toward node 101-y (that is, all of the next hop (forwarding destination) nodes having 101-y as the identifier of the destination node) (FIG. 4). SQ101). Here, the sequence number in the control header is for uniquely identifying the transfer message, and is incremented by the node 101-x as the transmission source every time the message is transmitted.

  Subsequently, the node 101-a and the node 101-b that have received the urgent message from the node 101-x refer to their own route management table in the same manner as described above and transfer messages to all the routes toward the node 101-y. Processing is performed (SQ102, SQ103 in FIG. 4). Here, for example, the node 101-c receives the duplicate urgent message for the node 101-y (see the duplicate message reception point 104 shown in FIG. 5), but the node 101-c which is a relay node. Determines itself for duplicate messages. Specifically, the node 101-c confirms the duplication of the received message based on the information including the sequence number, the identifier of the transmission source node, and the identifier of the transmission destination node included in the control header of the received urgent message. If the received message is not a duplicate message, message transfer processing is performed (SQ104 in FIG. 4). If the received message is a duplicate message, the duplicate message is discarded (SQ105 in FIG. 4).

  Further, the node 101-y which is the transmission destination node sets a sequence number and an identifier of the transmission source node included in the control header of the critical message received in the same manner as the relay node (nodes 101-a, b, c). Check for duplicate received messages based on the information. At this time, if the received message is a new message, a predetermined application is notified (SQ106 in FIG. 4), whereas if it is a received message, the received message is discarded (SQ107 in FIG. 4). ).

(Reverse route information registration processing to the route management table)
Next, referring to FIG. 1, FIG. 4, and FIG. 7 for registration processing of route information (hereinafter referred to as “reverse route”) from the destination node to the source node when an urgent message directed to a specific node is transferred. To explain. FIG. 7 is a diagram illustrating an example of a route management table in which reverse route information is registered. Now, focusing on the nodes 101-a, 101b, 101c, etc. in FIG. 1, these nodes function as relay nodes that transfer critical messages for the specific node 101-y. For example, when the nodes 101-a and 101b transfer an urgent message from the node 101-x to the node 101-y (SQ102 and SQ103 in FIG. 4), the route toward the node 101-x is transferred to the path management table. Register with. Specifically, as shown in FIG. 7, the source node 101-x of the urgent message directed to the specific node 101-y is set as the destination node, and the adjacent node that forwarded the urgent message toward itself is set as the next hop. Register as a (forwarding destination) node in the route information table. Similarly, the node 101-c registers the route toward the node 101-x in the route management table when transferring the urgent message from the node 101-x toward the node 101-y (SQ104 in FIG. 4). To do. Similarly, the node 101-y registers route information for the node 101-x (a plurality of nodes exist).

  Each of the nodes 101-a, 101-b, and 101-c receives the urgent message from the node 101-x to the node 101-y, and the node 101- registered in the path management table. When the route information for x is less than the maximum number of routes N (the specified value in the configuration information shown in FIG. 3), the route information is registered in the route management table. Do not register route information.

  Moreover, it is preferable to provide the lifetime defined in the configuration information for the registered route information. That is, by making the route information to be added valid route information only for the specified time, the table size held in each node can be reduced (set to “T1” in the example shown in FIG. 7). Similarly, with respect to the reverse route, it is possible to reduce the traffic amount by holding up to N pieces of route information (specified by the configuration information) for the specific node.

  In this way, when the reverse route information similar to the transfer route information is registered in each node, along with the transfer of the critical message to the specific node 101-y, the specific node 101-y to the node 101- message transfer from x (other specific nodes different from the specific node 101-y to other transmission source nodes different from the node 101-x) and path information (nodes) Based on the route information to 101-y and the reverse route information to node 101-x), forwarding processing to a plurality of next hop (forwarding destination) nodes is performed.

  Note that the maximum number of routes (N) defined by the configuration information may be different for each node. In the example shown in FIG. 7, both the maximum number of routes registered as route information and reverse route information are shown as the same N, but they need not be the same, and these values may be different. .

  As described above, according to this embodiment, each node has a path management table in which path information including a plurality of next transfer destination node information for relaying and transmitting a message directed to a specific node is held. Since this route information is generated regardless of the presence / absence of communication and is held in the route management table, reliable transmission of the critical message is realized.

  In addition, according to this embodiment, when transferring an urgent message having a specific request condition directed to a specific node, each node transmits the same message to a plurality of next transfer destination nodes held in the route management table. Since the information transmission is performed, the frequency of the urgent message transmission increases, and the urgent message transmission is realized.

  Further, according to this embodiment, each node temporarily stores the route (reverse route) information returning from the transmission destination node to the transmission source node in the route management table when the urgent message for the specific node is transferred. Therefore, the time required for route search is limited, and quick transmission of an important message is realized.

  Further, according to this embodiment, each node is provided with configuration information including information on the identifier of the specific node and the maximum number of routes allowed as the number of routes (hops) to the specific node. Since the route information to be held in the route management table is determined based on the configuration information, the route information held in each node can be controlled even when the number of nodes constituting the ad hoc network system increases. And increase in route information can be suppressed.

  Further, according to this embodiment, since each node discards the duplicate message received by itself based on the information on the maximum number of routes held in the configuration information, the traffic in the ad hoc network system is The amount can be suppressed.

  Further, according to this embodiment, the configuration information further includes information indicating the lifetime of the route information, and the route information held in the route management table is managed based on the lifetime. An increase in route information and a reduction in traffic volume can be managed effectively.

  Further, according to this embodiment, each node constituting the ad hoc network holds a plurality of routes destined for a specific node in advance, and when a message destined for the specific node is generated or received, Since transmission and transfer processing are performed based on a plurality of stored route information, the required urgency and certainty can be ensured even in a wireless and multi-hop communication environment.

  In this embodiment, for the specific server (specific node) that receives the urgent message, an example (see FIG. 3) set in the configuration information is shown. However, a service search procedure or the like is introduced. Thus, the identifier of the specific server may be acquired after startup.

  As described above, the present invention is useful as an ad hoc network system having a message transfer function that requires urgency and certainty from an arbitrary node constituting the system to a specific node in the system.

It is a figure which shows the structure of the ad hoc network system of this invention in which a some node autonomously comprises a network. It is a chart which shows an example of the path | route management table in the node 101 in an ad hoc network system. It is a graph which shows an example of the configuration information prescribed | regulated previously by each node. It is a figure which shows an example of the process sequence of the important message toward specific node 101-y. It is the figure which showed on the system block diagram of FIG. 1 the example of a path | route at the time of the transfer of the critical message toward specific node 101-y. It is a figure which shows an example of the control header added to a message. It is a figure which shows an example of the route management table in which reverse route information was registered.

Explanation of symbols

21 identifier of source node 22 identifier of destination node 23 identifier of next hop (forwarding destination) node 24 status flag 25 lifetime 26 other 31 identifier of specific node 32 maximum path 33 re-search period (path management period for specific node)
101-a, 101-b, 101-c node 101-y specific node 101-x source node 102 wireless link 103 transmission path 104 duplicate message reception location

Claims (10)

In an ad hoc network system in which multiple node devices autonomously form a network based on an on-demand routing protocol,
The node device includes a route management table in which route information including a plurality of next transfer destination node information for relay transmission of a message directed to a specific node device is held,
The ad hoc network system, wherein the route information is generated regardless of the presence or absence of communication and is held in the route management table.   The node device performs broadcast transmission to a plurality of next transfer destination nodes held in the route management table when transferring an urgent message having a specific request condition toward the specific node device. The ad hoc network system according to claim 1, wherein:   The node device temporarily holds, in the route management table, route (reverse route) information returning from the transmission destination node to the transmission source node when the urgent message directed to the specific node device is transferred. The ad hoc network system according to claim 1 or 2, characterized in that The node device includes configuration information including information on an identifier of the specific node device and a maximum number of routes allowed as the number of routes (hops) to the specific node device.
The ad hoc network system according to claim 1, wherein the node device determines route information to be held in the route management table based on the configuration information.   5. The ad hoc network system according to claim 4, wherein the node device discards a duplicate message received by the node device based on information on a maximum number of paths held in the configuration information. The configuration information further includes information indicating the lifetime of the route information,
6. The ad hoc network system according to claim 4 or 5, wherein the node device manages route information held in the route management table based on the lifetime. In a node device constituting an ad hoc network system that autonomously forms a network based on an on-demand routing protocol,
Provided with a route management table that holds route information including a plurality of next transfer destination node information for relay transmission of a message directed to a specific node device different from itself,
The node device, wherein the route information is generated regardless of the presence or absence of communication and is held in the route management table.   The broadcast transmission is performed to a plurality of next transfer destination nodes held in the route management table when transferring an urgent message having a specific request condition toward the specific node device. 8. The node device according to 7.   The node device temporarily holds, in the route management table, route (reverse route) information returning from the transmission destination node to the transmission source node when the urgent message directed to the specific node device is transferred. The node device according to claim 7 or 8, wherein the node device is characterized in that: Configuration information including information on the identifier of the specific node device and the maximum number of routes allowed as the number of routes (hops) to the specific node device,
10. The node device according to claim 7, wherein route information to be held in the route management table is determined based on the configuration information.

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