KR101715368B1 - Method and node for performing dynamic switching when node failure is occured in wireless sensor network - Google Patents

Abstract

In accordance with an embodiment of the present invention, there is provided a dynamic switching method for a node malfunction in a wireless sensor network, the method comprising the steps of: (a) detecting a malfunction of a previously connected parent node; (b) detecting a rank value which is an order value of an available time slot which is an unused time slot period of at least one neighboring node other than the malfunctioning parent node and a time slot period during which data is transmitted to its parent node; And (c) selecting one of the at least one neighboring node as a new parent node based on the detected available time slot and the rank value.

Description

METHOD AND NODE FOR PERFORMING DYNAMIC SWITCHING WHEN NODE FAILURE IS OCCURED IN WIRELESS SENSOR NETWORK FIELD OF THE INVENTION [0001]

[0001] The present invention relates to a method and a node for performing dynamic switching when an arbitrary node in a wireless sensor network malfunctions, and more particularly, to a method and a node for reducing a cost and a time for re- To a method and a node for performing dynamic switching.

Wireless Sensor Network technology is a wireless technology that can measure / detect various status and environmental information such as temperature, humidity, illuminance, pressure and so on remotely without constructing a separate wired network. Such a wireless sensor network can be used in areas or objects requiring human access, such as monitoring of environmental conditions, monitoring structures and building conditions, monitoring volcanic activity, precise plant cultivation, area and facility security, It can be used cheaply and effectively.

At least one wireless sensor network is defined for remotely monitoring and controlling objects. Each wireless sensor network is a multi-hop network in which a plurality of nodes having sensors and wireless communication modules are interconnected through a short-range wireless link in a distributed space. At this time, the node measures the circumstance and transmits it to the neighboring node or transmits the data received from the neighboring node to another neighboring node. Each wireless sensor network is connected to a separate base station through a wired / wireless network such as PCS (Personal Communication Services), WLAN (Wireless Local Area Network), xDSL (x Digital Subscriber Line), KORNET, Thus, even if the user does not go to the site, the user can access the central server connection and easily use the application service such as monitoring and management of the area and the object.

A data aggregation tree used in the wireless sensor network means a tree structure that merges data received from a plurality of nodes and transmits the merged data to the base station. In this data merge tree, each node has an object to receive data and an object to transmit data, and it operates to transfer and merge data to each designated route.

However, in a data merge tree, when a node fails due to a natural disaster or weather, child nodes for a failed node can not send their data to the base station, It is rearranged in a way that redesigns itself. However, this method has a problem in that it consumes much in terms of time and cost, and it may result in rearrangement of nodes not affected by the failure, which is very inefficient.

Japanese Patent Application Laid-Open No. 10-2014-0127904 (Publication date: April 4, 2014)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the related art, and it is an object of the present invention to provide a wireless sensor network in which, when a malfunctioning node occurs, only a relation between nodes in an area adjacent to a malfunctioning node is restructured, And to provide a method and a node for performing dynamic switching.

As a technical means for achieving the above-mentioned technical problem, a dynamic switching method for any node malfunction in the wireless sensor network, which is performed by a node included in a wireless sensor network, according to an embodiment of the present invention, Detecting a malfunction of a previously connected parent node; (b) detecting a rank value which is an order value of an available time slot which is an unused time slot period of at least one neighboring node other than the malfunctioning parent node and a time slot period during which data is transmitted to its parent node; And (c) selecting one of the at least one neighboring node as a new parent node based on the detected available time slot and the rank value.

According to another embodiment of the present invention, there is provided a node for performing dynamic switching in the event of an arbitrary node malfunction in a wireless sensor network, comprising: a memory for storing a program for performing dynamic switching when the random node malfunctions; And a processor for executing the program, wherein when the program is executed, the processor detects a malfunction of a previously connected parent node, and detects an unused time of at least one neighboring node other than the malfunctioning parent node The method includes detecting a rank value that is an order value of an available time slot that is a slot interval and a time slot interval that transmits data to a parent node of the mobile node and detects a rank value that is one of the at least one neighboring node based on the detected available time slot and rank value The neighbor node is selected as a new parent node.

One embodiment of the present invention can limit the number of updates as much as possible by updating only the nodes in the vicinity of the malfunction node that are part of the data merge tree affected by the node malfunction, Lt; / RTI >

1 is a structural diagram of a wireless sensor network system according to an embodiment of the present invention.
2 is a tree structure diagram of some nodes constituting a wireless sensor network according to an embodiment of the present invention.
3 is a block diagram illustrating internal components of a node in accordance with an embodiment of the present invention.
4 is a tree structure diagram for explaining available time slots according to an embodiment of the present invention.
5 is a tree structure diagram for explaining a first dynamic switching operation performed according to an embodiment of the present invention.
6 is a tree structure diagram for explaining a second dynamic switching operation performed in accordance with an embodiment of the present invention.
7A and 7B are tree diagrams for explaining a third dynamic switching operation performed according to an embodiment of the present invention.
FIG. 8 is a graph for comparing the delay time during a node malfunction between an embodiment of the present invention and an ideal embodiment.
FIG. 9 is a flowchart illustrating a method of performing dynamic switching when a node malfunctions in a wireless sensor network according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

In this specification, the term " part " includes a unit realized by hardware, a unit realized by software, and a unit realized by using both. Further, one unit may be implemented using two or more hardware, or two or more units may be implemented by one hardware. On the other hand, 'to' is not limited to software or hardware, 'to' may be configured to be an addressable storage medium, and may be configured to play one or more processors. Thus, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, the components and components may be implemented to play back one or more CPUs in a device or a secure multimedia card.

Hereinafter, definitions of terms referred to in this specification will be described.

A "node" is an entity that constitutes a network, and may refer to a sensor that can be connected to a server or other node through a network. However, the present invention is not limited to this, and the "node" may be either a computer or a portable terminal. Here, the computer includes, for example, a notebook computer, a desktop computer, a laptop computer, and the like, each of which is equipped with a web browser (WEB Browser), and the portable terminal may be a wireless communication device , Personal Communication System (PCS), Global System for Mobile communications (GSM), Personal Digital Cellular (PDC), Personal Handyphone System (PHS), Personal Digital Assistant (PDA), International Mobile Telecommunication (IMT) Based wireless communication apparatuses such as a W-CDMA (Code Division Multiple Access) -2000, a W-CDMA (W-Code Division Multiple Access), and a Wibro (Wireless Broadband Internet) terminal. The term "network" may also be used in a wired network such as a local area network (LAN), a wide area network (WAN) or a value added network (VAN) And may be implemented in all kinds of wireless networks, such as communication networks.

The "parent node" means an ancestor node previously specified for an arbitrary node in a tree structure composed of a plurality of nodes, and an arbitrary node can be an object to which data is transmitted. The term "child node " means a lower node previously designated for an arbitrary node in a tree structure, and an arbitrary node may be an object receiving data. Also, "sibling node" means a neighboring node of a horizontal relationship, not a relation of transmitting and receiving data.

A " timeslot "means a communication schedule that is given to achieve time synchronization in the operation of nodes included in a wireless sensor network. A time slot is divided into a plurality of sub-slots. A time slot is assigned to each node, and data can be transmitted only in a time slot period allocated to the node. In addition, the same or different timeslots may be assigned to each node depending on the location of the node in the tree structure. These timeslots allow the wireless sensor network to efficiently use energy through wake up / sleep modes. That is, by repeating the active state and the inactive state, necessary communication is performed only for a predetermined time period, thereby suppressing the energy use of the node.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, a wireless sensor network system 10 according to an embodiment of the present invention includes at least one node 100 and a base station 200.

Here, the wireless sensor network system 10 can be designed in the form of a data merge tree structure. That is, the data transmitted from the lowest node 100 to the upper node 100 may be transmitted and merged, and the result of merging data of all the nodes 100 may be received in the base station 200.

At this time, each of the nodes 100 is designated in advance for the parent node 100 and the child node 100, and is activated only when data transmission / reception is required according to the schedule determined by the time slot, Reception, merging, transmission, and the like.

With reference to FIG. 2, a description will be given of the principle that nodes of the data merge tree structure operate according to a schedule determined by a time slot.

Prior to a specific description, the operation conventions given in the wireless sensor network system 10 will be described. Each node 100 in the wireless sensor network can receive data in only one time slot period and data transmission and reception can not be performed in the same time slot period. In addition, the merge of data performed at an arbitrary node can be performed in a perfect merge such that the sizes of data packets transmitted from each node are all the same. Each node includes identification information called a rank value. The rank value means the number of data links to which one node is connected to another node or the order value of a time slot period in which a node transmits data to its parent node. For example, a node given a rank value k is configured to have one parent node and k-1 child nodes. The k-rank node collects data from the child node during the k-1th time slot period from the first node, and transmits the merged data to the parent node during the k-th time slot period.

2, first, since the lowest-ranked nodes have only one data link and the data is transmitted to the parent node in the first time slot period, the rank value is given as 1. In the first time slot period, the parent node receiving the data has two data links and the data is transmitted to the parent node in the second time slot period, so that the rank value is given as 2. In this manner, a node having a rank value of 3 transmits data in a third time slot period. A node having a rank value of 4 receives data from all child nodes in a previous time slot period, merges the received data, and transmits the merged data to the base station 200 in a fourth time slot period. As a result, in the example of FIG. 2, it can be determined that a time delay corresponding to a total of four time slot periods occurs until all the data is transmitted from the lowermost node to the base station 200.

In the wireless sensor network system 10, if a malfunction occurs in any one of the nodes, the malfunctioning node can not receive data transmitted from the child node or can not transmit the received data to the parent node Lt; / RTI > Here, a malfunction of a node means that a node can perform a full function in performing data transmission and reception, such as when a mechanical fault occurs in a node due to a natural disaster or weather, or when the node does not operate due to power exhaustion This means the operating state in all cases where it disappears. It is also possible to include a case where the connection relationship is released from the parent node by a dynamic switching operation of a parent node, which will be described later, as a malfunction of the node.

If a node malfunctions, it is important for the child node to find a new parent node to send the data to. At this time, an embodiment of the present invention aims at reducing network time and cost by allowing a child node of a malfunctioning node to perform dynamic switching to find a new parent node only in the vicinity of a node where a malfunction occurs.

With reference to FIG. 3, the elements included in the node 100 for achieving this object will be described in detail.

Each node 100 may be configured to include a memory for storing a program (or an application) for performing dynamic switching when a parent node malfunction occurs, and a processor for executing the above program. Here, the processor may perform various functions according to the execution of the program stored in the memory. The modules included in the processor for performing each function may be referred to as a parent node malfunction detection unit 110, a neighbor node information detection unit 120, And may be represented by a switching unit 130.

The parent node malfunction detection unit 110 may detect malfunction of the parent node of the connected parent node. For example, it is possible to determine whether a parent node is malfunctioning by overhearing a transmission / reception packet of a parent node. Or whether or not the parent node malfunctions according to whether an acknowledgment (ACK) message for data transmitted to the parent node is received or not.

The neighbor node information detection unit 120 detects available timeslots and rank values of neighboring nodes in position. Since each node 100 stores information on neighboring nodes located at neighboring positions in advance, it is possible to detect available time slots and rank values of neighboring nodes from previously stored information. Alternatively, it is possible to detect the time slot and the rank value by receiving the location identification information of the neighboring node and transmitting the query data to the neighboring node.

Here, the available time slot means a time slot period that is not utilized by the corresponding node among the intervals before the time slot period in which the node operates. This will be described in detail with reference to FIG.

In FIG. 4, the node C has a rank value of 2. Therefore, data is transmitted in the second time slot. Therefore, although the first time slot period can receive data from the child node, the child node is not used due to the absence of the child node. At this time, the first time slot of node C is called an available time slot. An indication of the available time slot may be indicated by "{} ". Accordingly, the number 1 is indicated on the right side of the node C in brackets.

The parent node switching unit 130 selects one of the neighboring nodes as a new parent node based on the detected available time slot and the rank value.

First, the parent node switching unit 130 may select a new parent node using the first dynamic switching operation. Specifically, when the node 100 has a rank value equal to or greater than its own rank value of at least one neighbor node and a first neighbor node having an available time slot exists, the first neighbor node is selected as a new parent node . At this time, if there are a plurality of first neighbor nodes, the first neighbor node having the lowest rank value may be selected as a new parent node.

For example, with reference to FIG. 5, it is assumed that a malfunction occurs at the node D. FIG. At this time, the node F detects that its parent node malfunctions and tries to select a new parent node among the neighboring nodes. In this case, a node having a rank value equal to or higher than the rank value 1 of the node F and having an available time slot has a rank value 2, a node C having the first time slot as an available time slot and a rank value 3, There exists a node B having a time slot as an available time slot. However, since the rank value of the node C is lower than the rank value of the node B, the node F selects the node C as the new parent node. This is because it is good to leave available time slots of the node with the highest rank value for later use.

In addition, the parent node switching unit 130 may select a new parent node using the second dynamic switching operation. Specifically, when at least one second neighbor node having an order value of an available time slot interval of at least one neighbor node is lower than its own rank value, the node 100 sets an order value of the highest available time slot interval as The second neighboring node having a rank value equal to or higher than the order value of the time slot period of the selected second neighboring node can be released.

For example, with reference to FIG. 6, it is assumed that a malfunction has occurred in the node B. FIG. The node D originally had a rank value of 2. If a malfunction occurs at node B at that moment, node D loses its parent node. At this time, only the node C having the available time slot exists. However, the order value of the available time slot period of the node C is 1. That is, node D can transmit data to node C only in the first time slot period. However, since the node D has a rank value of 2 and is receiving data from the node F in the first time slot period, the node C can not be designated as the parent node. Therefore, the node D selects the node C as the parent node and at the same time releases the connection to the node F which is the child node having the rank value equal to or higher than the order value of the available time slot period of the node C (i.e., 1).

Meanwhile, in the case of the second dynamic switching operation shown in FIG. 6, the node D finds a new parent node, but the node F loses its parent node, and thus a new parent node must be found by itself.

In addition, the parent node switching unit 130 may select a new parent node using the third dynamic switching operation. Specifically, the node 100 may select a nearest neighbor node in the base station 200 as a new parent node when there is no neighboring node having an available time slot among at least one neighboring node. In this case, the node 100 receives its rank value from the parent node or the base station 200 on the basis of the connection relationship between nodes included in the path from the base station 200 to the lowest node included therein Update or update itself.

For example, with reference to Figs. 7A and 7B, it is assumed that the second dynamic switching operation of Fig. 6 occurs. In the case of FIG. 6, node F is faced with the situation of finding a new parent node. At this time, none of the neighboring nodes C, D, E, and G have available time slots. Accordingly, as shown in FIG. 7A, the node F selects the node C located closest to the base station 200 as the parent node. In this case, the rank values of the nodes A, C, and F are newly aligned. That is, the node C can not simultaneously receive data from the nodes D and F. Since the third available time slot interval exists in the node A, the rank value of the node C is updated to 3, and the rank value of the node F is updated 2 < / RTI > In this case, the node G can select the node F as its new parent node through the first dynamic switching operation method as shown in FIG. 7B.

By performing dynamic switching of the other node in case of malfunction of the arbitrary node in this manner, the delay time required for the data transmission / reception operation of the wireless sensor network can be minimized. Referring to FIG. 8, an embodiment of the present invention is represented by ADA, and an ideal embodiment is represented by DEDA. As shown in FIG. 8, it can be seen that the delay time graph of one embodiment of the present invention is very close to the graph of the ideal embodiment. Specifically, it can be seen that the delay time of the embodiment of the present invention is about 6% lower than that of the ideal embodiment.

Hereinafter, with reference to FIG. 9, a dynamic switching method in the case of a node malfunction in a wireless sensor network according to an embodiment of the present invention will be described in detail.

The following method is performed by the node 100 described with reference to FIG. 3, and thus includes all of the methodical features described with reference to FIG. 3, even if there are somewhat omitted parts below.

First, each node 100 detects a malfunction of a previously connected parent node (S900).

Next, the node 100 detects available time slots and rank values of at least one neighbor node (S910).

Finally, the node 100 performs switching by selecting any one of the neighboring nodes as a new parent node based on the available time slot and rank value (S920). At this time, it is possible to simply select a new parent node through switching, but the connection with the child node may be additionally released depending on the surrounding situation. It is also possible to update the rank value if it is necessary to update the rank value of each node 100 in the link reaching the base station 200 after the connection to the new parent node.

As described above, according to the embodiment of the present invention, the number of updates can be limited as much as possible by updating only the nodes in the vicinity of the malfunction node, which is a part of the data merge tree affected by the node malfunction, Can be maintained.

One embodiment of the present invention may also be embodied in the form of a recording medium including instructions executable by a computer, such as program modules, being executed by a computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer-readable medium can include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes any information delivery media, including computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transport mechanism.

While the methods and systems of the present invention have been described in connection with specific embodiments, some or all of those elements or operations may be implemented using a computer system having a general purpose hardware architecture.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

10: Wireless sensor network system
100: node
200: Base station

Claims (16)

A method of dynamic switching in the event of a malfunction of any node in the wireless sensor network, which is performed by a node included in a wireless sensor network,
(a) detecting a malfunction of the connected parent node;
(b) detecting a rank value which is an order value of an available time slot which is an unused time slot period of at least one neighboring node other than the malfunctioning parent node and a time slot period during which data is transmitted to its parent node; And
(c) selecting one of the at least one neighboring node as a new parent node based on the detected available time slot and a rank value,
The step (c)
Further comprising the step of releasing the connection to the child node after the parent node is selected. The method according to claim 1,
The step (c)
(c-1) if the first neighboring node having a rank value equal to or greater than its own rank value of the at least one neighboring node and having an available time slot exists, the first neighboring node is selected as a new parent node The method comprising the steps of: dynamically switching at any node malfunction in a wireless sensor network. 3. The method of claim 2,
The step (c-1)
And selecting a first neighboring node having a lowest rank value as a new parent node when a plurality of the first neighboring nodes exist. delete The method according to claim 1,
The step (c)
(c-2) if at least one second neighbor node having an order value of an available time slot interval of the at least one neighbor node is lower than its own rank value, 2 selecting a neighbor node as a new parent node and releasing a connection to a child node having a rank value equal to or higher than the order value of the time slot period of the selected second neighbor node, Dynamic switching method during malfunction. The method according to claim 1,
The malfunction of the parent node can be prevented,
A mechanical failure of the parent node or a disconnect of the parent node itself. The method according to claim 1,
The step (c)
(c-3) selecting a neighboring node closest to the base station as a new parent node if there is no neighboring node having an available time slot among the at least one neighboring node. Dynamic switching method during malfunction. 8. The method of claim 7,
The step (c-3)
And updating the rank value of the node based on a connection relation between nodes included in the path from the base station to the lowest node after the parent node is selected. Switching method. A node for performing dynamic switching upon malfunction of an arbitrary node in a wireless sensor network,
A memory storing a program for performing dynamic switching when the random node malfunctions; And
And a processor for executing the program,
The processor, when performing the program,
Detecting a malfunction of the connected parent node,
Detecting a rank value which is an order value of an available time slot which is an unused time slot period of at least one neighboring node other than the malfunctioning parent node and a time slot period during which data is transmitted to its parent node,
Selecting one of the at least one neighboring node as a new parent node based on the detected available time slot and rank value,
A node that performs dynamic switching upon malfunction of any node in the wireless sensor network that disconnects the child node after selecting the parent node. 10. The method of claim 9,
The processor comprising:
Selecting a first neighboring node as a new parent node if a first neighboring node having a rank value equal to or greater than its own rank value of the at least one neighboring node and having an available time slot is present, A node that performs dynamic switching when an arbitrary node malfunctions. 11. The method of claim 10,
The processor comprising:
Wherein the first neighboring node having the lowest rank value is selected as a new parent node when a plurality of the first neighboring nodes exist. delete 10. The method of claim 9,
The processor comprising:
When there is at least one second neighbor node having an order value of an available time slot interval that is lower than its own rank value among the at least one neighbor node, the second neighbor node having the order value of the highest available time slot interval Selecting a parent node and releasing a connection to a child node having a rank value equal to or higher than the order value of the selected second neighbor node. 10. The method of claim 9,
The malfunction of the parent node can be prevented,
A node performing dynamic switching upon malfunction of any node in the wireless sensor network, including a mechanical fault of the parent node or a disconnect of the parent node itself. 10. The method of claim 9,
The processor comprising:
Wherein the neighboring node closest to the base station is selected as a new parent node when there is no neighboring node having an available time slot among the at least one neighboring node. 16. The method of claim 15,
The processor comprising:
After selecting the parent node, the base station updates its rank value based on a connection relationship between nodes included in the path from the base station to the lowest node included in the base station. Node.

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