KR100759312B1 - Link recovery method for hierarchical routing over lowpan - Google Patents

Abstract

A link recovery method for hierarchical routing on LoWPAN(Low Power Wireless Personal Area Networks) is provided to ensure connection state of a network by generating a bypass if route disconnection is generated. A first node finds a route disconnection between the first node and a parent node(S30). The first node requests a bypass route to a second node if the first node finds the route disconnection between the first node and the parent node(S40). The second node checks a route to a first common ancestral node with the first node(S50). If the route into the first common ancestral node is effective, bypass route generation is informed to the first node(S60).

Description

Link recovery method for hierarchical routing over LoWPAN}

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

1 and 2 are diagrams illustrating an example of a path disconnection occurring in a low power wireless personal area network (LoWPAN), respectively.

FIG. 3 is a flowchart schematically illustrating a path recovery method through the generation of a bypass path in a low power wireless personal area network (LoWPAN) according to an embodiment of the present invention.

4 is a flowchart illustrating a process of requesting a detour path by a node whose path with a parent node is disconnected according to an embodiment of the present invention.

5 is a flowchart illustrating a process of processing a bypass path request of a node receiving a bypass path request according to an embodiment of the present invention.

6 is a flowchart illustrating a detour path formation process of a first common ancestor node receiving a path validation packet according to an embodiment of the present invention.

7 is a flowchart illustrating a bypass path forming process of intermediate nodes receiving a path validity response packet according to an embodiment of the present invention.

8 is a flowchart illustrating a bypass path generation process of intermediate nodes receiving a bypass path notification packet according to an embodiment of the present invention.

9 illustrates a structure of a routing table for a bypass path according to an embodiment of the present invention.

10 is a diagram illustrating a process of generating a bypass path according to an embodiment of the present invention.

TECHNICAL FIELD The present invention relates to wireless networks, and more particularly, to a path recovery method for hierarchical routing using dynamic address assignment on Low Power Wireless Personal Area Networks (LoWPAN).

In general, a personal area network (PAN) is a concept that contrasts with a widely known local area network (LAN) or a long-distance network (WAN), so that each individual has a unique network, and a wireless sensor network and a home network, etc. It can be used in various fields. In an effort to implement such a PAN wirelessly, a high-speed wireless personal area network specification was introduced as the IEEE 802.15.3 standard, and low power wireless personal area network (LowPAN) as the IEEE 802.15.4-2003 standard. The standard has been published.

The interface identifier of the LoWPAN device is based on EUI-64 [EUI64]. The interface identifier can be used to create routing tables for multi-hop routing in LoWPAN. However, given the limited capabilities of LoWPAN devices (ie low power, limited memory space, small packet size), on-demand multi-hop routing using routing tables and EUI-64 identifiers ) Is difficult to use extensively. In addition, using a routing table becomes more difficult when a large number of devices are expected to be deployed in LoWPAN. In other words, the on-demand routing method can set up an efficient path in an ad-hoc or mesh type wireless network. However, in this routing method, each node has a routing table for relaying data packets. Must be equipped.

For example, in the on-demand routing method defined in RFC 3651, a transmitting node does not have information on all routing paths, and all nodes on the path distribute and store only routing paths up to the next hop in a routing table. This is a method for finding a path to a destination node from a point in time to transmit data. Therefore, each node needs to have a routing table.

However, LoWPAN devices have a limited memory space in most cases, and thus, it is difficult to establish a routing table in the limited memory space.

In order to solve the above problems, a hierarchical routing method using dynamic allocation of 16-bit short addresses has been developed. However, the conventional 16-bit short address dynamic allocation method has a problem in that communication is not possible due to disconnection with a network connected through the path when a path break occurs due to a communication environment or a node failure.

Therefore, the technical problem to be achieved by the present invention is to solve the problems of the prior art as described above, hierarchical in a low-power wireless personal area network (LoWPAN) that can ensure the connectivity of the network by creating a bypass path in the event of a path disconnection It is to provide a path recovery method for routing.

According to an aspect of the present invention, there is provided a path recovery method for hierarchical routing on Low Power Wireless Personal Area Networks (LoWPAN) including a plurality of hierarchical nodes. A node discovering a path break with a parent node of the first node; If the first node finds a path break with the parent node, requesting a detour path to the second node; Checking, by the second node, a path to a first common ancestor node with the first node; And notifying the first node of generating a detour path if the path to the first common ancestor node is valid as a result of the inspection.

The requesting the detour path to the second node may include collecting information of a neighbor node through a scan process; Selecting any one of the neighbor nodes; And transmitting a bypass path request packet to a selected node and waiting to receive a response packet corresponding to the bypass path request packet. In this case, the selected node becomes the second node.

Selecting any one of the neighbor nodes includes: excluding a node of the neighbor node whose request is prohibited; And selecting a node having the shortest hop distance to the parent node during hierarchical routing among the remaining nodes except for the node whose request is prohibited.

The checking of the path to the first common ancestor node may include: sending, by the second node, a test packet to the first common ancestor node in unicast; The first common ancestor node recording a bypass path in a routing table of the first common ancestor node in response to the check packet; And transmitting, by the first common ancestor node, a path validity response packet to the second node.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the embodiments of the present invention, reference should be made to the accompanying drawings that illustrate embodiments of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

1 and 2 are diagrams illustrating an example of a path disconnection occurring in a low power wireless personal area network (LoWPAN), respectively.

1, 2 and 10, reference numerals A through K denote radio nodes in LoWPAN. Nodes A to K are low power communication devices each having a wireless communication function. The nodes A to K may be source nodes generating data or intermediate nodes relaying data between the source node and the target node in the middle of receiving or receiving data. In addition, each node may be connected to other nodes in a hierarchical structure.

First, referring to FIG. 1, FIG. 1 illustrates a case where a path between a node B and a node D is disconnected due to deterioration of a wireless environment or mobility of a node.

FIG. 2 shows a case in which all paths between the node D and the node E and the parent node (node A) are disconnected as the node B falls into an inoperable state due to a device failure or the like. Breakage of the path can be found in many cases. For example, it may be determined that a path disconnection occurs when packet transmission fails from a child node to a parent node for a predetermined time or more. As another example, when the packet transmission failure rate is more than a predetermined value (for example, 50%), it may be determined as a path disconnection. A child node refers to a node connected directly below this node to any one node (arbitrary node) in a hierarchical structure. The parent node is a concept in contrast to the child node, and refers to a node directly connected to the node with respect to any one node. Here, the connection does not mean a physical connection or a wired connection.

3 is a flowchart schematically illustrating a path recovery method for hierarchical routing in a low power wireless personal area network (LoWPAN) according to an embodiment of the present invention.

Referring to FIG. 3, in the path recovery method according to an embodiment of the present invention, one node (hereinafter, also referred to as a request node, for example, node E of FIG. 10) that forms a LoWPAN is a parent node (eg, FIG. 10). If it is found that the path with the node B) of 10 is disconnected (S30), a detour path is requested to the neighbor node (S40). The neighboring node means all or some of the nodes except for the own node.

 When a node (a requesting node, for example, node E of FIG. 10) that detects a path disconnection with a parent node has requested a bypass path (S40), the node receiving the request (eg, node C of FIG. 10) is connected with the requesting node. The path to the first common ancestor node (eg, node A of FIG. 10) is examined to determine whether the path is valid (S50). As a result of the check, if the path to the first common ancestor node is valid, the request node notifies the generation of the detour path (S60). In this case, the ancestor node refers to nodes connected to a parent of any one node (arbitrary node) in a hierarchical structure and includes the above-described parent node. The descendant node is a concept in contrast to the ancestor node, and refers to nodes that are connected to the child of any one node (arbitrary node) in the hierarchical structure. The first common ancestor node between the requesting node and the requesting node is a node that has a hierarchical hop distance closest to the requesting node among nodes that are ancestor nodes common to the requesting node and the requesting node.

4 is a flowchart illustrating an example of a detailed process performed at a node whose path to the parent node is disconnected according to an embodiment of the present invention.

Referring to FIG. 4, a node that finds that a path to a parent node is disconnected collects information of a neighbor node through a scan process and stores the information of the neighbor node in a neighbor table (S42). The scanning process may be a process of broadcasting a predetermined broadcast packet (eg, hello packet) to find a node responding to the broadcast packet. After the scan process excludes a node whose request is prohibited among neighboring nodes collected information (S43), the best node is selected among the remaining neighbor nodes (S44). Here, the criterion of the node whose request is prohibited is a descendant node of the request node or a top node registered in its routing table or a descendant node thereof.

 It is preferable that a request for generating a bypass path is not made to a node for which the aforementioned request is prohibited. Also, the criterion of the best neighbor node is preferably the node having the shortest hop-distance or hop-count to the parent node through hierarchical routing. This is a condition for minimizing the number of nodes that must maintain a routing table.

When the neighbor node is selected, a request packet is sent to the selected node to request a bypass path generation (S45), and waits to receive a response packet thereto (S46). After waiting for a predetermined time, the requesting node determines whether the detour path generation is successful (S47). If the detour path generation fails, the request node returns to step S44 and selects another neighbor node to request the detour path generation. On the other hand, if the bypass path generation is successful, the path recovery process may be completed (S48).

For the detour path generation request, the request node may determine that the detour path generation is successful when a successful response packet (eg, a path validity response packet, which will be described later) is normally received from the selected node (that is, the requested node). Can be. When the successful response packet is not received or the failure response packet is received for the bypass path generation request, the requesting node may determine that the bypass path generation has failed.

5 is a flowchart illustrating an example of a detailed process performed in a node that receives a bypass path request according to an embodiment of the present invention.

Referring to FIG. 5, when the selected node receives the bypass path request packet (S51), a unicast scheme checks a path packet (path validation packet) to see if the path to the first common ancestor node with the request node is valid. Confirm by transmitting to (S52).

After that, when the path validity response packet, which is a response to the path validation packet, arrives from the first common ancestor node (S53), it is determined that the path to the common ancestor node is valid, and the detour path is recorded in its routing table (S54). Informs the request node that the detour path generation was successful (S55). At this time, the node receiving the bypass path request may inform the requesting node that the bypass path generation was successful by transmitting a response packet (eg, a path valid response packet) to the request node.

If the path validity response packet for the check packet from the common ancestor node does not arrive (S53), it is determined that the path is invalid and notifies the requesting node that the detour path generation has failed (S56).

6 is a flowchart illustrating an example of a detailed process performed in a first common node that receives a path validation packet according to an embodiment of the present invention.

Referring to FIG. 6, when the first common ancestor node receives the path validation packet from the requested node (S61), after recording the detour path in its routing table (S62), the path validation response packet is sent to the requested node. It transmits (S63). In this case, the path validity response packet may be transmitted to the requested node via one or more intermediate nodes. Specifically, the first common ancestor node sends a path validity response packet to the next hop node on the hierarchical routing path towards the requested node. Then, the node receiving the path validity response packet retransmits the path validity response packet to the next hop node, and eventually the path validity response packet is transmitted to the requested node.

An example of the detailed process performed in the intermediate node that receives the path validity response packet is shown in FIG. 7.

Referring to FIG. 7, when an intermediate node located on a hierarchical routing path from a first common ancestor node to a requested node receives a path validity response packet (S71), after writing a detour path in its routing table (S71), S72) Retransmit the path validity response packet to the next hop node on the hierarchical routing path toward the requested node (S73). Through this iterative process, the nodes of the path from the first common ancestor node to the requested node store the routing table containing the detour path information.

Referring back to FIG. 6, the first common ancestor node that records the detour path in its routing table also transmits a detour path notification packet to its child node corresponding to the ancestor node of the detour path request node (S64). Then, the node receiving the detour route advertisement packet retransmits the detour route advertisement packet to the next hop node, and eventually the detour route advertisement packet is transmitted to the parent node of the requesting node.

An example of a detailed process performed at the intermediate node that receives the detour path advertisement packet is shown in FIG. 8.

Referring to FIG. 8, when an intermediate node located on a hierarchical routing path from a first common ancestor node to a requesting node receives a bypass route notification packet (S81), after recording the bypass route in its routing table (S82). In step S83, the detour path advertisement packet is retransmitted to the next hop node on the hierarchical routing path toward the node requesting the detour path. As described above, nodes in the path from the first common ancestor node to the bypass path request node store the routing table containing the bypass path information through an iterative process.

9 illustrates a structure of a routing table for a bypass path according to an embodiment of the present invention. The routing table is a table held by each of the nodes (eg, nodes C, A, and B in FIG. 10) involved in creating the bypass path, and destination nodes (eg, node E in FIG. 10) that should be delivered through the bypass path. , I, J and K) of the highest destination node (eg, node E of FIG. 10) and its node (eg, node E of FIG. 10) and its descendants (eg, nodes I, J and K of FIG. 10). The address of the forwarding node, i.e., the bypass path connection node (e.g., node C of FIG. 10), for routing to the network is recorded. Through this, when the data packet is transmitted, it is possible to determine whether it is a child node of the highest node recorded in the routing table, and then deliver the packet through the path specified in the routing. The addresses of the top destination node and the bypass path connection node may each consist of 16 bits.

FIG. 10 is a diagram illustrating a process of generating a bypass path through the method as described above. "10a" indicates a process in which node E, which has lost its path to the parent node B, requests a bypass path to node C. Thus, node E becomes the bypass path request node and node C becomes the requested node.

&Quot; 10b " represents a process in which node C, which has received a bypass path, checks a path validity to the first common ancestor node A with node E. That is, node C sends a check packet to node A in unicast to check whether the path from node C to node A is valid.

"10c" responds by sending the first common ancestor node A by sending a path validation response packet to the requested node C for the path validation packet, and bypassing the nodes leading to the path to the request node E. The process of notifying the detour path generation by transmitting the notification packet is shown. Node C, which has received the path validity response packet from the first common ancestor node A, records a routing table for the bypass path as shown in FIG. Node B, which has received the detour route advertisement packet from the first common ancestor node A, also records a routing table as shown in FIG. 9, and the first common ancestor node A also has a routing table as shown in FIG. 9. Record it. Accordingly, the packet to be delivered to the destination nodes E, I, J or K through the node B may be delivered to the destination nodes E, I, J or K through the node C which is a bypass path connection node. . Thus, when the bypass path is created, node C acts as the parent node of node E.

As described above, according to the exemplary embodiment of the present invention, only nodes (for example, nodes A, B, and C of FIG. 10) that are involved in the creation of the detour route do not need to have a routing table at all nodes A to K. The short routing table as shown in FIG. 9 may be provided. Therefore, due to the limited memory space of the device of the LoWPAN, even if a path break occurs in a LoWPAN environment where it is difficult to have a long routing table, the path to the disconnected node can be recovered by creating a bypass path.

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, which are also implemented in the form of a carrier wave (for example, transmission over the Internet). It also includes. 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. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

According to the present invention as described above, by utilizing a dynamically allocated short address (for example, 16-bit address) on a low-power wireless personal area network (LoWPAN), due to deterioration of the communication environment or failure of the device when using hierarchical routing Even if a path break occurs, the network connectivity can be guaranteed by restoring a path to the node that was disconnected through the creation of a bypass path.

Claims (10)

A path recovery method for hierarchical routing on Low power Wireless Personal Area Networks (LoWPAN) having a plurality of hierarchical nodes, The first node discovering a path break with the parent node of the first node; If the first node finds a path break with the parent node, requesting a detour path to the second node; Checking, by the second node, a path to a first common ancestor node with the first node; And And informing the first node of generating a detour path if the path to the first common ancestor node is valid as a result of the check. The method of claim 1, wherein requesting a bypass path to the second node comprises: Collecting information of neighbor nodes through a scan process; Selecting any one of the neighbor nodes; And Transmitting a bypass path request packet to a selected node, and receiving a response packet corresponding to the bypass path request packet, And wherein the selected node becomes the second node. The method of claim 1, wherein the selected node becomes the second node. The method of claim 2, wherein selecting one of the neighbor nodes Excluding a node of the neighbor node whose request is prohibited; And Selecting a node having the shortest hop distance to the parent node in the hierarchical routing among the remaining nodes except the node forbidden from the request, wherein the path for hierarchical routing on the low power wireless personal area network is selected. Recovery method. The method of claim 1, wherein checking the path to the first common ancestor node comprises: Sending, by the second node, unicast a check packet to the first common ancestor node; The first common ancestor node recording a bypass path in a routing table of the first common ancestor node in response to the check packet; And And sending, by the first common ancestor node, a path validity response packet to the second node. The method of claim 4, wherein the transmitting of the path validity response packet to the second node comprises: Sending, by the first common ancestor node, the path validity response packet to the next hop node on the hierarchical routing path towards the second node; And The node receiving the route validity response packet writing a detour route in its routing table; And And the node receiving the path validity response packet retransmitting the path validity response packet to a next hop node on a hierarchical routing path towards the second node. Path recovery for hierarchical routing on a network. The method of claim 5, wherein the notifying the first node of the detour path generation comprises: And when the second node receives the path validity response packet, determining that the path to the first common ancestor node is valid, wherein the path recovery method is for hierarchical routing on a low power wireless personal area network. . The method of claim 4, wherein the path recovery method And when the first common ancestor node writes a detour path in its routing table, sending a detour path advertisement packet to the parent node. The path for hierarchical routing on a low power wireless personal area network. Recovery method. 8. The method of claim 7, wherein transmitting a detour route advertisement packet to the parent node Sending, by the first common ancestor node, the bypass route advertisement packet to the next hop node on the hierarchical routing path towards the first node; The node receiving the detour path advertisement packet recording a detour path in its routing table; And And retransmitting the bypass route advertisement packet to a next hop node on the hierarchical routing path directed to the first node by the node receiving the bypass route advertisement packet. Path recovery methods. The method of claim 4, wherein the routing table is A method for path recovery for hierarchical routing on a low power wireless personal area network comprising an address of a top destination node and an address of a bypass path connection node. 10. The method of claim 9, wherein the address of the highest level destination node and the address of the bypass path connection node are A path recovery method for hierarchical routing on a low power wireless personal area network, each 16 bits.

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