KR100832964B1 - Apparatus and method for dispersing data in wireless sensor network - Google Patents

Abstract

A data distribution method in a wireless sensor network and an apparatus thereof are provided to maximize the memory utilization of each node by making each node periodically confirm its own data collection space and distributing data to another node in case there is no spare space to collect data. The third node, a child node of the second node, confirms its own time value(S101). If the timer value is smaller than "2 x RTT(Round-Trip Time)", the third node transmits a memory alert message to the second node(S102). Receiving the memory alert message, the second node confirms its own data collection space and judges whether a spare space exists(S103). In case there is no spare space, the second node sends a transfer denial message to the third node(S105). However, if it is confirmed that there is a spare space, the second node sends a transfer permission message to the third node(S106). Based on the transfer permission message, the third node transmits the data stored in its own data collection space to the second node(S107). While transmitting the data, the third node confirms whether 1/3 of the data have been transmitted(S108). If so, the third node concludes data transmission(S110).

Description

Apparatus and method for dispersing data in wireless sensor network

1 is a block diagram showing a node of a wireless sensor network according to an embodiment of the present invention;

2 is a diagram illustrating a topology of a wireless sensor network according to an embodiment of the present invention;

3 is a signal flow diagram illustrating a data distribution method generated within one hop of a wireless sensor network according to an embodiment of the present invention;

4A illustrates a structure of a memory warning message of a wireless sensor network according to an embodiment of the present invention;

4b is a view showing the structure of a transmission rejection message of a wireless sensor network according to an embodiment of the present invention;

4c is a diagram showing the structure of a transmission approval message of a wireless sensor network according to an embodiment of the present invention; and

5 is a signal flow diagram illustrating a data distribution method generated in multi-hops of a wireless sensor network according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100: node 110: radio unit

120: RAM 130: processor

140: ROM 150: sensing unit

The present invention relates to a method and apparatus for data distribution in a wireless sensor network, and more particularly, to a method and apparatus for distributing data in a wireless sensor network to overcome memory constraints for each node constituting the wireless sensor network through data distribution. It is about.

The wireless sensor network refers to a network technology composed of sensor nodes having various sensing, data processing, and wireless communication functions to recognize the surrounding situation.

Such wireless sensor networks are currently applied to steel processes to enable location management of workers in hazardous areas, safety management for workers, and monitoring of environmental changes and abnormalities in specific areas. In addition, in a steel measurement application, the wireless sensor network transmits data requested from a sink other than periodically transmitted measurement data, or transmits data generated by an event.

In general, the nodes that make up a wireless sensor network typically include a processor of several MHz, a wireless radio section capable of speeds of tens to hundreds of Kbps, tens of Kbytes of ROM, and several Kbytes of RAM.

In particular, in a node having such a configuration, the RAM allows data collected by the sensing unit to be stored in a space other than the program execution space. In general, RAM is composed of 4Kbytes. It is composed of 2Kbytes.

On the other hand, in steel measurement applications, the wireless sensor network allows measurement data to be periodically transmitted and received, and the data transmitted to the query-driven, which is a method in which a node responds to a query of a sink, is increased.

In addition, steel metrology applications in wireless sensor networks are characterized by allowing all or some of the sensors to send data collected via queries to the sink.

In steel measurement applications of such wireless sensor networks, mobile sinks can cause nodes that cannot collect data due to lack of memory when large time intervals between queries in the sink and large amounts of data occur in a short period of time. .

In particular, such problems may arise in applications that can be used in steel mills, such as monitoring plant facilities or processes.

In addition, the nodes of the wireless sensor network are small, which causes limited resources such as a battery and a memory, and thus, nodes that cannot collect more data may occur when a large amount of data occurs in a short time.

An object of the present invention for solving the above problems is to provide a method and apparatus for data distribution in a wireless sensor network to prevent the occurrence of a node that is impossible to collect data in the wireless sensor network.

In order to achieve the above object of the present invention, a data distribution method of a wireless sensor network in which a plurality of nodes of the present invention is formed in a tree form includes a memory warning message of a node whose data collection space is less than or equal to a preset threshold. Transmitting; Checking, by the parent node, its memory space and transmitting a transmission acknowledgment message to a child node when its data collection space is greater than or equal to a preset threshold; And transmitting, by the child node, data stored in its data collection space to the parent node in response to the transmission approval message.

The node transmitting a memory warning message to its parent node may include a timer value calculated according to the following equation and an RTT value which defines a time for which data transmitted from the node can reach the sink. In addition, when the timer value is less than or equal to 2 times the RTT value, it is determined that the data collection space is less than the predetermined threshold, characterized in that for transmitting the memory warning message.

T = time since the data space was freed by the previous query,

M = the size of the total data collection space,

m = currently occupied data collection space

The step of the node transmitting a memory warning message to its parent node, characterized in that for transmitting the TTL field included in the memory warning message to have a predetermined value.

Preferably, the data distribution method of the wireless sensor network further comprises the step of transmitting a transmission rejection message to the child node when the parent node receiving the memory warning message is a data collection space of less than a predetermined threshold. It features.

Preferably, the data distribution method of the wireless sensor network further comprises the step of terminating the data transmission when the child node transmits 1/3 of the data stored in its data collection space to the parent node. do.

In order to achieve the above object of the present invention, a data distribution method of a wireless sensor network in which a plurality of nodes of the present invention is formed in a tree form includes a memory warning message of a node whose data collection space is less than or equal to a preset threshold. Transmitting; Checking, by the parent node, its memory space, and transmitting the memory warning message to all nodes of the wireless sensor network except the child node when its data collection space is less than or equal to a preset threshold; When the parent node receives a transmission grant message corresponding to the transferred memory warning message from at least one node, randomly selecting one node and transferring the transmission grant message received from the node to the child node; And transmitting, by the child node, data stored in its data collection space to the node selected by the parent node via the parent node.

The transmitting of the memory warning message to all nodes of the wireless sensor network except for the child node by the parent node may cause the TTL field value of the memory warning message provided from the child node to be subtracted by a predetermined value. Characterized in that.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in describing in detail the operating principle of the preferred embodiment of the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In addition, the same reference numerals are used for parts having similar functions and functions throughout the drawings.

1 is a block diagram showing a node of a wireless sensor network according to an embodiment of the present invention.

Referring to FIG. 1, a node 100 of a wireless sensor network may include a radio unit 110, a RAM 120, a processor 130, a ROM 140, and a sensing unit 150.

Herein, the radio unit 110 performs wireless communication between the nodes 100, and performs a memory alert message (Memory Alert Msg.), A transfer permission message (Transfer Permission Msg.), And a transfer denial message (Transfer Denial) according to data distribution. Msg.) Performs a function of transmitting and receiving between the nodes (100).

The RAM 120 includes a program execution space and a storage space for data collected by the sensing unit 150, and the ROM 140 stores the execution program.

The processor 130 determines whether the free space exists in the data collection space of the RAM 120 at a predetermined cycle or in real time, and if it is determined that the free space does not exist, the data is distributed through the radio unit 110. Perform the function.

Next, the data distribution method of the node having such a configuration will be described in detail.

2 is a diagram illustrating a topology of a wireless sensor network according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the wireless sensor network may be configured as a tree structure in which a plurality of nodes are connected based on one sink. FIG. 2 defines, for example, node 1 (100a) as a sink, node 2 (100b), node 3 (100c), and node 4 (100d) as nodes connected to the sink, and the dotted lines shown in FIG. Indicates a wireless connection between

Each node 100 of the wireless sensor network includes a timer value and a round-trip time (RTT) value for managing the size of the data collection space.

Here, the timer value is a value calculated from Equation 1 below, and is an expected time value until the size of the data collection space is less than or equal to a preset threshold.

T = time since the data space was freed by the previous query,

M = the size of the total data collection space,

m = currently occupied data collection space

The RTT value defines the time that the data transmitted from the node can reach the sink, which can be easily measured during communication with the sink. Such an RTT value means a sufficient time for the node 100 to attempt communication with the neighboring node 100 to prevent the data collection space included in the node 100 from being below a preset threshold.

As such, each node 100 of the wireless sensor network including the timer value and the RTT value may adjust the usage of the memory space through data distribution using the included timer value and the RTT value.

3 is a signal flow diagram illustrating a data distribution method generated within one hop of a wireless sensor network according to an embodiment of the present invention.

4A, 4B, and 4C are diagrams illustrating structures of a memory warning message, a transmission rejection message, and a transmission approval message of a wireless sensor network according to an exemplary embodiment of the present invention.

Referring to FIG. 3 of these drawings, between two neighboring nodes in a wireless sensor network, that is, node 2 (100b) and node 3 (100c) included in one hop, for example, of node 2 (100b). When the node 3 (100c), which is a child node, detects its timer value and determines that the timer value is less than twice the RTT value (S101), a memory alert message is sent to the node 2 (100b) of its parent node (Memory Alert). Msg.) Is transmitted (S102).

That is, when it is determined that the data collection space is a preset threshold through the timer value and the RTT value, the node 3 100c transmits a memory warning message indicating that the data collection space is insufficient to the parent node 100b. will be.

Here, node 3 (100c) transmits a memory warning message having a structure as shown in FIG. 4A to node 2 (100b), with its ID '3' in the node ID field and '1' in the TTL field. Can be set and transmitted.

Accordingly, when the memory warning message is transmitted from the node 3 (100c), the node 2 (100b) checks its data collection space (S103), and determines whether there is free space in its data collection space (S104).

The node 2 (100b), such as the node 3 (100c), if its own timer value is less than twice the RTT value, when the data collection space is confirmed below the preset threshold, there is free space in the data collection space In step S105, the transmission rejection message (Transfer Denial Msg.) Is transmitted to the node 3 (100c).

Here, the node 2 100b may transmit a transmission rejection message having the structure as shown in FIG. 4B to the node 3 100c, but may transmit a message in which the node ID of the sender and the node ID of the receiver are sequentially recorded after the message type. . That is, the node 2 100b may transmit, for example, a transmission rejection message that records '2' as the sender's node ID and '3' as the receiver's node ID.

However, if the timer value is more than twice the RTT value and the data collection space of the node 2 (100b) is determined to be above the preset threshold, the node 2 (100b) determines that the free space exists in the data collection space and transmits the transmission acknowledgment message (Transfer). Permission Msg.) Is transmitted to node 3 (100c) (S106).

Here, node 2 (100b) transmits a transmission rejection message having a structure as shown in Figure 4c to node 3 (100c), the node ID of the sender and the node ID of the receiver after the message type in the same manner as the transmission rejection message You can send the recorded message. That is, the node 2 100b may transmit a transmission rejection message in which '2' is recorded as the sender's node ID and '3' as the receiver's node ID.

Accordingly, the node 3 (100c) transmits the data stored in its data collection space to the node 2 (100b) in accordance with the received transmission approval message, to secure the free space according to the data collection (S107).

Then, while the third node 100c transmits data to the second node 100b, the third node 100c determines whether one third of the data included in the second node 100b is transmitted to the second node 100b (S108), and the corresponding amount of data. If is transmitted, the data transmission in progress is terminated (S110).

However, if one third of the data included in the node 3 (100c) is not transmitted to the node 2 (100b), one third of the data included in the node 2 (100b) by continuing to perform the data transmission that was being performed To be transmitted (S109).

5 is a signal flow diagram illustrating a data distribution method generated in multi-hops of a wireless sensor network according to an exemplary embodiment of the present invention.

Referring to FIG. 5, each node constituting the wireless sensor network determines whether there is free space in its data collection space according to a predetermined cycle or in real time, and if it is determined that the free space does not exist, the data is determined. It is possible to distribute and store its data to neighboring nodes where space is available in the collection space.

Among the nodes performing such an operation, as an example, a method of distributing the data centering on the node 3 (100c) will be described. First, the node 3 (100c) determines that the determined timer value is 2 times or less than the RTT value (S201). In step S202, the memory warning message is transmitted to the node 2 100b which is its parent node. Here, node 3 (100c) transmits a memory warning message having a structure as shown in FIG. 4A to node 2 (100b), with its ID '3' in the node ID field and '1' in the TTL field. Can be set and transmitted.

In response to the memory warning message provided from the node 3 (100c), the node 2 (100b) checks its memory space (S203), and when it is determined that the data collection space of the memory space includes the free space, the above-described FIG. If it is determined that the data collection space does not include the free space, all nodes (nodes except node 3) 100a and 100d constituting the wireless sensor network are configured from the node 3 (100c). Deliver the provided memory warning message (S205, S206).

Here, the node 2 (100b) subtracts the TTL field value of the memory warning message provided from the node 3 (100c) by '1' so that the corresponding TTL field value is changed to '0', and then wirelessly transmits the changed memory warning message. It can be delivered to all nodes of the sensor network. This is for limiting the transmission range of the memory warning message to 2 hops. In consideration that the memory warning message is sent only to the initial parent node, the node that wants to distribute data from the node whose hop counter from sink is larger than itself This is to prevent the transmission acknowledgment message from being received, thereby avoiding overhead in data distribution and data distribution.

The nodes of the wireless sensor network, that is, the node 1 (100a) and the node 4 (100d) received the memory warning message from the node 3 (100c) checks their memory space (S207), the free space in the data collection space Figure out if it exists.

Here, FIG. 4 assumes that free space exists in the data collection spaces of both the node 1 (100a) and the node 4 (100d) according to an embodiment, and each of the node 1 (100a) and the node 4 (100d) corresponds to this. The transmission approval message is transmitted to the node 2 (100b) (S209, S210). However, in another embodiment, if there is no free space in the data collection space of both node 1 (100a) and node 4 (100d), node 1 (100a) and node 4 (100d) sends a rejection message to node 2 ( 100b), the node 2 (100b) transmits the transmission rejection message to the node 3 (100c), the series of data distribution process is terminated.

On the other hand, the node 1 (100a) and the node 4 (100d) for transmitting the transmission approval message to the node 2 (100b), while transmitting a transmission approval message having a structure as shown in Figure 4c to the node 2 (100b), Each node ID is recorded as the sender node ID, and the ID of node 2 100b is recorded as the receiver node ID.

When the node 2 100b receives a transmission acknowledgment message from at least one node in response to the memory warning message transmission processes S205 and S206, the node 2 100b randomly selects one node (S211) and transmits a transmission acknowledgment message provided from the selected node. To node 3 (100c) (S212).

When the data is transmitted from the node 3 (100c) in response to the transmitted approval message (S213), the node 2 (100b) transmits the data to the selected node 1 (100a) (S214), and the node 3 (100c). Is stored in the data collection space of the node 1 (100a).

On the other hand, the node 3 (100c) transmitting data determines whether 1/3 of the data to be transmitted is transmitted (S215), and if the corresponding amount of data has been transmitted, terminates the data transmission being performed (S218), and the corresponding amount. If the data is not transmitted, the data transmission is continuously performed so that one third of the included data amount is transmitted to the node 3 (100c) via the node 2 (100b) (S216 and S217).

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art.

The method and apparatus for distributing data in a wireless sensor network according to the present invention as described above, each node constituting the wireless sensor network whether or not the data collection space in accordance with a real time or a predetermined period through the timer value and the RTT value In this case, if there is no free space in the corresponding data collection space, data is distributed to other nodes, thereby maximizing the memory utilization efficiency of nodes including the restricted memory.

Claims (7)

In the data distribution method of a wireless sensor network in which a plurality of nodes are formed in a tree form, Transmitting a memory warning message to a parent node of a node whose data collection space is less than or equal to a preset threshold; Checking, by the parent node, its memory space and transmitting a transmission acknowledgment message to a child node when its data collection space is greater than or equal to a preset threshold; And And transmitting, by the child node, data stored in its data collection space to the parent node in response to the transmission approval message. The method of claim 1, The node sending a memory warning message to its parent node, When the timer value is less than twice the RTT value, including the timer value calculated according to the following equation and the RTT value that defines the time that the data transmitted from the node can reach the sink; And determining that a data collection space is equal to or less than the preset threshold, and transmitting the memory warning message.

T = time since the data space was freed by the previous query, M = the size of the total data collection space, m = currently occupied data collection space The method of claim 1, The node sending a memory warning message to its parent node, And transmitting the TTL field included in the memory warning message to have a preset value. The method of claim 1, And transmitting, by the parent node receiving the memory warning message, a transmission rejection message to the child node when its data collection space is less than or equal to a preset threshold. The method of claim 1, And when the child node transmits 1/3 of data stored in its data collection space to the parent node, terminating the data transmission. In the data distribution method of a wireless sensor network in which a plurality of nodes are formed in a tree form, Transmitting a memory warning message to a parent node of a node whose data collection space is less than or equal to a preset threshold; Checking, by the parent node, its memory space, and transmitting the memory warning message to all nodes of the wireless sensor network except the child node when its data collection space is less than or equal to a preset threshold; When the parent node receives a transmission grant message corresponding to the delivered memory warning message from at least one node, randomly selects one node among the at least one node provided and receives the transmission grant message received from the node. Delivering to the child node; And And transmitting, by the child node, data stored in the data collection space of the child node to the node selected by the parent node via the parent node. The method of claim 6, The step of forwarding the memory alert message to all nodes of the wireless sensor network except for the child node by the parent node, And transmitting the TTL field value of the memory warning message received from the child node by a predetermined value.

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