KR100833506B1 - An Path Recovery Mechanism and Apparatus using Candidate Node in AODV - Google Patents

Abstract

The AODV path recovery method using a candidate node according to the present invention is a path recovery method in which an intermediate node that detects a link loss of a next node while transmitting data from an originating node to a destination node in an ad hoc network finds a path to a destination. An address acquisition step of obtaining the address of the candidate node at a predetermined distance from the intermediate node on the path to the node and a data transmission step of transmitting data to the destination node to the address of the obtained candidate node. According to the present invention, the number of broadcast packets flowing into the network and the delay time at each node are reduced, and the bandwidth of the network is improved.

Description

An Path Recovery Mechanism and Apparatus using Candidate Node in AODV}

1 is a flowchart of a path recovery process of a conventional area search technique.

2 is a flowchart illustrating a path recovery process according to an embodiment of the present invention.

3 is a flowchart illustrating a path recovery process according to another embodiment of the present invention.

4 is a flowchart illustrating a path recovery process according to another embodiment of the present invention.

5 is a configuration of a path recovery apparatus according to an embodiment of the present invention.

6 is information for entering a conventional AODV routing table.

7 is information to be entered in the AODV routing table according to an embodiment of the present invention.

8 is a format of a route request message (RREQ message) according to an embodiment of the present invention.

9 is a format of a route response message (RREP message) according to an embodiment of the present invention.

The present invention relates to AODV path recovery, and more particularly, to an apparatus and method for AODV path recovery using candidate nodes in local search during AODV path maintenance.

Recently, due to the rapid improvement of wireless network technology, the application range and frequency of mobile wireless computing are rapidly increasing.

Mobile wireless networks are classified into a network having an infrastructure such as a base station or an access point and an ad hoc network without an infrastructure.

The characteristic of an ad hoc network is that there is no fixed infrastructure, so it must be able to carry data between mobile nodes. To this end, each mobile node in the ad hoc network must perform the function of a general router.

In addition, because each node in the ad hoc network is mobile, the network topology changes dynamically over time. In addition, the data transmission radius due to battery maintenance is limited, and has a low bandwidth and a high error rate.

Despite these drawbacks, the ad hoc network does not have an infrastructure, so it can be effectively used in special places such as disaster relief, battlefields and exhibition halls, or in general places without infrastructure.

Routing routing protocols in ad hoc networks are classified into three categories.

Routing routing protocols in the first ad hoc network There is a proactive or table-driven routing protocol.

For example, DSDV (Destination Sequenced Distance Vector), Optimized Link State Routing (OLSR), Topology Broadcast Based on Reverse-Path Forwarding (TBRPF), and the like.

Second, there are reactive or on-demand routing protocols. Examples include Dynamic Source Routing (DSR), Ad hoc On-Demand Distance Vector Routing (AODV), Temporally Ordered Routing Algorithm (TORA), and the like.

Finally, there is a hybrid protocol. Zone routing protocol (ZRP) is a representative example.

Ad hoc On-Demand Distance Vector Routing (AODV) is a typical demand-based routing protocol. When the source node needs to transmit data, it finds a routing path to the destination node. This process is called route discovery.

Once the path is found, data transfer occurs, and the node is frequently disconnected due to the frequent movement of nodes.

When a path break is found, the intermediate node on the path re-scans the path to the destination node and repairs the broken path. This is called local repair.

Fast local path recovery reduces the loss in data transmission, providing a seamless communication environment.

Path rescan is, in the worst case, a path retrieval that follows the full retrieval of the path by the source node, such as the path initialization setting.

The technical problem to be achieved by the present invention is to minimize the data transmission interruption by reducing the delay time using a candidate node when the path loss occurs while communicating using the AODV routing scheme in the Ad-hoc environment. In addition, by reducing the amount of the path request message (RREQ) that occurs when the path is lost to reduce the network traffic load and the network itself bandwidth burden.

One embodiment of the route path recovery method according to the present invention for achieving the above technical problem is a path for the intermediate node that recognizes the link loss of the next node during the data transmission from the source node to the destination node in the ad hoc network to find the path to the destination In a recovery method, an address acquiring step of acquiring an address of a candidate node at a predetermined distance from the intermediate node on a path to a destination node and a data transmitting step of transmitting data to the destination node using the acquired candidate node address Have

More preferably, if the address of the candidate node is not obtained, the method further includes a route rescanning message transmitting step of transmitting a message for rescanning the route to the destination node.

One embodiment of the route path recovery apparatus according to the present invention for achieving the above technical problem is a path for the intermediate node to recognize the link loss of the next node during the data transmission from the source node to the destination node in the ad hoc network to find the path to the destination A recovery apparatus, comprising: an address acquisition unit for acquiring an address of a candidate node at a predetermined distance from the intermediate node on a path to a destination node, and a data transmission unit for transmitting data to the destination node with the obtained candidate node address .

More preferably, if the address of the candidate node is not obtained, the apparatus further includes a route rescanning message transmitting unit which transmits a message for rescanning a route to the destination node to the source node.

Existing route recovery methods, such as reinitialization, where the source node re-directs the entire route directly, cause significant delays and excessive generation of route request messages (RREQs) sent for routing.

Also, in case of the path recovery process of the conventional local search method, the delay time increases when the hop number value (previous paper: number of hops = 10) that defines the local search range increases, and in the worst case, delay occurrence such as reinitialization occurs. cause.

There are also many path request messages (RREQ messages). This is a loss of network bandwidth, especially for mobile ad hoc networks using mobile links between links, which greatly affects the overall communication link environment.

The present invention defines a connection target node that is located near the lost node (two hop distance in the present invention) as a "candidate node", and performs a path recovery using a candidate node to perform delay time and RREQ. We devise a way to reduce the amount of messages to help improve bandwidth.

Hereinafter, a method and apparatus for AODV path recovery using the candidate node of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a path recovery process of a conventional area search technique. Referring to FIG. 1, an intermediate node (d) recognizes a link loss of a next node during data transmission from an originating node to a destination node in an ad hoc network. Recognizing the loss, the intermediate node (d) performs a local path search to find the destination node.

Local discovery is a method where the intermediate node (d) that recognizes the link loss of the next hop node performs a route search directly to the destination node on behalf of the source node.

The TTL value is used to broadcast the path discovery message up to n predetermined hops. If the n-hop local search does not find the destination node, a RERR (Route Error) message is generated, causing the source node to directly search for re-routing. In previous papers, the route request message (RREQ message) is based on 10 hops.

2 is a flowchart of a path recovery process according to an embodiment of the present invention. Referring to FIG. 2A, an intermediate node (d) recognizes a link loss of a next node during data transmission from an originating node to a destination node in an ad hoc network.

In case of securing and operating communication link using AODV routing protocol, if the link to the next hop node is lost due to the movement, loss, or absence of each node in the network, the path recovery procedure is operated for continuous packet transmission. do.

As a methodology, a node that is aware of a loss recovers a path link using a local search method, or a first originating node performs a new path search to recover a path to maintain a link.

According to the current AODV path recovery method defined in the IETF standard, many packets are generated for rerouting, which causes a large amount of network bandwidth loss.

In the present invention, to improve this, a candidate node is set on the AODV path, and when a path loss occurs, more efficient path recovery is possible. By using candidate nodes, it is possible to reduce broadcasting packets that are excessively introduced into the network.

Referring to FIG. 2B, the intermediate node d, which recognizes a loss of a link to a next node, broadcasts a path request message for finding a candidate node h. In the present invention, instead of proceeding in the order of directly searching for a destination node when a path recovery procedure is lost, a path request message (RREQ) for first finding a candidate node at a predetermined distance (for example, 2 hops) is generated. Occurs.

The intermediate node transmits a route request message that includes the destination node and finds a candidate node at a predetermined distance (for example, two hops away) from the intermediate node on a path to the destination node.

For example, the route request message broadcasts the route discovery message only up to four predetermined hops using a TTL value of four.

A node at a predetermined distance (for example, two hops away) on a path from a node that has recognized a path loss to a destination node is called a candidate node.

Instead of generating a route request message (RREQ) with a large range to find the destination node, it looks for connection candidate nodes in a relatively local (two-hop distance) region. When the candidate node h receives the route request message RREQ, it generates a new route response message RREP to recover the connection.

As described above, the present invention, unlike the conventional local recovery technology, performs a relatively small range of search, thereby reducing the latency and reducing the burden on the network bandwidth.

For example, the path request message may use a TTL value of 4 and an estination Only option. Latency is much reduced because only hops of 4 or less are expected. And because the Destination Only option is used, each node does not need to check the routing table.

The Route Request Message (RREQ) is a field for the original destination address called Origin-Destination IP Address with the addition of the Candidate Node (C) option. In the present invention, the TTL of the RREQ will be 4 or less, and only candidate nodes generate RREPs by checking the Destination Only field.

The number of occurrences of the route request message (RREQ) according to the present invention is as follows. In order to mathematically prove the difference in path request messages generated for link recovery, it is assumed that nodes in ad-hoc networks are uniformly present in all spaces.

Assuming that all nodes are evenly distributed, the RREQ messages sent by the nodes are spread all over the circle space with the radius of the product of the TTL and the average distance between the nodes.

RTL: RREQ TTL of traditional recovery

4: TTL of the proposed scheme

N: 4 / RTL * 100 (% of packets compared to existing scheme)

As shown in the above equation, as RTL increases, N also decreases, making it more efficient for existing solutions. Since the TTL is set to 10 as the basis of the existing scheme, it can be expected that 40% of packets will be reduced.

Referring to FIG. 2C, the candidate node unicasts the path response message to the d node. The path response message includes at least one of a candidate node option and a candidate node address.

The intermediate node receives a path response message that includes the address of the candidate node. The path response message may include at least one of a candidate node option and a candidate node address.

Referring to FIG. 2D, the intermediate node d adds the address of the candidate node h to the routing table and transmits data to the destination node to the candidate node h.

Recognizing the loss of an adjacent node, the intermediate node (d) has a routing table that contains the address of a candidate node at a predetermined distance (eg, two hops) from itself.

If there is no transmission of the path response message from the candidate node h, the intermediate node d sends a path error message (RRER message) to the source node to rescan the path by itself.

For example, the link recovery time according to the present invention is as follows.

RT (AODV) = T (RREQ) + T (RREP) + a (T (RERR) + T (SDT) + T (RTO))

RT (AODV) = total recovery time

T (RREQ) = RREQ occurrence time

T (RREP) = RREP occurrence time

a = probability of a local recovery failure

T (RERR) = RERR occurrence time

T (SDT) = source recovery time

T (RTO) = Request Time Over Time

In the present invention, since the number of route request messages (RREQ) is small, the RREQ generation time T (RREQ) becomes smaller than before, and the existing method estimates the distance to 10 hops, whereas the proposed method requires only 4 hops or less. The Request Time Over time, T (RTO), is also significantly reduced.

In addition, the Destination Only option eliminates the need for each node to examine the routing table.

3 is a flowchart illustrating a path recovery process according to another embodiment of the present invention. Referring to FIG. 3, an intermediate node that recognizes a link loss of a next node during data transmission from an originating node to a destination node in an ad hoc network performs a route search to a destination.

The intermediate node transmits a route request message for finding a candidate node at a predetermined distance (for example, two hops away) from the intermediate node on the route to the destination node (S301).

The intermediate node receives a path response message containing the candidate node's address from the candidate node.

The intermediate node adds the candidate node address to the routing table and transmits data to the destination node as the candidate node (S303).

If there is no transmission of the path response message from the candidate node, the intermediate node transmits a path error message to rescan the path to the source node (S304).

4 is a flowchart illustrating a path recovery process according to another embodiment of the present invention. Referring to FIG. 4, in an ad hoc network, an intermediate node that detects a link loss of a next node during data transmission from a source node to a destination node performs route search to a destination, and the intermediate node goes to the destination node. The address of the candidate node at a predetermined distance from the intermediate node on the path is obtained (S401).

The intermediate node transmits data to the destination node to the address of the obtained candidate node (S402).

If the intermediate node fails to obtain the address of the candidate node, it transmits a message to the source node to re-discover the route to the destination node (S403).

5 is a block diagram of a path recovery apparatus according to an embodiment of the present invention. Referring to FIG. 5, the path recovery apparatus includes a path request message transmitter 510, a path response message receiver 520, a data transmitter 530, and a path rescan message transmitter 540.

 The route request message transmitter 510 transmits a route request message to find a candidate node at a predetermined distance (for example, two hops away) from the intermediate node on the route to the destination node. The path response message receiver 520 receives a path response message including the address of the candidate node from the candidate node.

The path request message transmitter 510 and the path response message receiver 520 may obtain an address of a candidate node at a predetermined distance (for example, two hops away) from the intermediate node on a path to a destination node. do.

The data transmitter 530 transmits data destined for the destination node to the candidate node. Add the candidate node address to the routing table.

 If there is no transmission of the path response message from the candidate node, the path rescanning message transmitter 540 transmits a path error message to rescan the path by the source node.

6 is information for entering a conventional AODV routing table. Referring to FIG. 6, the existing routing table does not have address information of nodes at a predetermined distance (for example, two hops).

Therefore, new information in the routing table, that is, the address of the candidate node, must be known. Therefore, the following candidate node address information is added to the routing table. Add it to the routing table with Candidate Node IP Address.

7 is information to be entered in the AODV routing table according to an embodiment of the present invention. Existing routing tables do not have address information of nodes at a certain distance (for example, two hops away).

Therefore, new information in the routing table, that is, the address of the candidate node, must be known. Therefore, the following candidate node address information is added to the routing table. Add it to the routing table with Candidate Node IP Address.

8 is a format of a route request message (RREQ message) according to an embodiment of the present invention. Referring to FIG. 8, the route request message (RREQ message) is added with a Candidate Node (C) option and a field for the original destination address called Origin-Destination IP Address is added to the route request message (RREQ message).

Preferably, the TTL of the route request message (RREQ message) will be 4 or less, and only the candidate node (Candidate Node) generates the route response message (RREP) by checking the Destination Only field.

The number of occurrences of the route request message (RREQ message) according to the present invention is as follows. To mathematically prove the difference between the path request message (RREQ message) occurring for link recovery, it is assumed that the nodes in the ad hoc network are uniformly present in all spaces.

Assuming that all nodes are evenly distributed, the path request message (RREQ message) sent by the node is spread all over the circle space with the radius of the product of the TTL and the average distance between the nodes.

RTL: RREQ TTL of traditional recovery

4: TTL of the proposed scheme

N: 4 / RTL * 100 (% of packets compared to existing scheme)

As described above, since the TTL is set to 10 in the conventional paper, the present invention can be expected to reduce the packet by about 40% than the conventional method.

9 is a format of a route response message (RREP message) according to an embodiment of the present invention. Referring to FIG. 9, the route response message (RREP message) has a candidate node (C; Candidate Node) option and a candidate node address (Candidate Node IP address) added thereto.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, in the efficient AODV path recovery method using the candidate node according to the present invention, when a path loss occurs while communicating using the AODV routing technique in an Ad-hoc environment, the delay time is reduced by using the candidate node. Minimize transmission interruptions. In addition, by reducing the amount of the path request message (RREQ) generated when the path is lost, the network traffic load and the bandwidth burden of the network itself is reduced.

The efficient AODV path recovery method using the candidate node according to the present invention can be applied to all environments that constitute Ad-hoc networks using AODV routing in the future, and ensures efficient network maintenance in the ubiquitous environment in the future.

Claims (13)

In the path recovery method for the intermediate node that finds the link loss of the next node during the data transmission from the source node to the destination node in the ad hoc network to find the path to the destination, An address acquiring step of acquiring an address of a candidate node at a distance of a hop number determined smaller than the number of hops between the intermediate node and the destination node on a path to the destination node; And And a data transmission step of transmitting data to the destination node to the address of the obtained candidate node. The method of claim 1, wherein the obtaining address comprises: A route request message transmitting step of transmitting a route request message for finding a candidate node two hops away from the intermediate node on the route to the destination node; And And a path response message receiving a path response message including an address of the candidate node from the candidate node. The method of claim 2, wherein the route request message, Path recovery method characterized in that the TTL (Time To Live) value 4. The method of claim 2, wherein the path response message, And at least one of a candidate node option and a candidate node address. The method of claim 1, And if the address of the candidate node is not obtained, transmitting a path rescanning message to the source node to send a message to rescan the route to the destination node. The method of claim 1, And the intermediate node has a routing table that includes addresses of candidate nodes at a distance of hops less than the number of hops between itself and the destination node. In the path recovery device for the intermediate node that detects the link loss of the next node during the data transmission from the source node to the destination node in the ad hoc network, to find the path to the destination, An address acquisition unit for obtaining an address of a candidate node at a distance of hops less than the number of hops between the intermediate node and the destination node on a path to the destination node; And And a data transmitter for transmitting data to the destination node to the address of the acquired candidate node. The method of claim 7, wherein the address acquisition unit, A path request message transmitter including the destination node and transmitting a path request message to find a candidate node two hops away from the intermediate node on a path to the destination node; And And a path response message receiving unit for receiving a path response message including the address of the candidate node from the candidate node. The method of claim 8, wherein the route request message, Path recovery device characterized in that the TTL (Time To Live) value 4. The method of claim 8, wherein the path response message, And at least one of a candidate node option and a candidate node address. The method of claim 7, wherein If the address of the candidate node is not obtained, the route recovery apparatus further comprises a route re-discovery message transmitter for transmitting a message to the source node to re-discover the route to the destination node. The method of claim 7, wherein And the intermediate node has a routing table including an address of a candidate node at a distance of hops less than the number of hops between itself and the destination node. A computer-readable recording medium having recorded thereon a program for executing the method according to any one of claims 1 to 6.

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