KR20140014640A - Method of transmitting data for saving energy of sensor node in wireless sensor networks and system for performing the same - Google Patents

Abstract

Provided is a data transmission method which allows each sensor uses energy evenly by transmitting data to an adjacent node having more remaining energy. The data transmission method comprises the following steps of: broadcasting, by a first sensor node, a request to receiver (RTR) message to adjacent sensor nodes; transmitting, to the first sensor node, a clear to receiver (CTR) message from a second sensor node which has the most remaining energy among the adjacent sensor nodes which have received the RTR message; transmitting data from the first sensor node which has received the CTR message to the second sensor node; and transmitting, by the second node, first data of the first sensor node and second data of the second data to a destination node when the destination node is activated. Therefore, each sensor node can use energy evenly, thereby prolonging a lifespan of an entire sensor network. [Reference numerals] (AA) Start; (BB) End; (S710) Broadcast a request to receive (RTR) message; (S720) Transmit, by a second sensor node, a clear to receive (CTR) message to a first node; (S730) Transmit, by the first sensor node, data to the second sensor node; (S740) Transmit, by the second sensor node, data of the first and second sensor nodes to a destination node when the destination node is activated

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and system for transmitting data for energy saving of a sensor node in a wireless sensor network,

The present invention relates to a data transmission method and apparatus of a wireless sensor network, and more particularly, to a data transmission method and apparatus for saving energy of a sensor node in a wireless sensor network.

In wireless sensor networks, it is an important issue that sensor nodes use less energy and extend network time. A duty cycle is proposed to reduce the energy consumption of the sensor nodes. In low asynchronous duty cycles, each sensor node is independently activated and efficiently reduces energy when traffic is low. However, if the data to be transmitted increases, the transmitting node has to wait a lot of time until the activation time of the receiving node due to the low duty cycle. In this case, the energy used is larger than the energy used for data transmission. In order to solve this problem, the OC-MAC scheme has been proposed in which a transmitting node transmits data to a neighboring node having a larger residual energy than that of the neighboring node, switches to an inactive state, and collects and transmits data. However, the OC-MAC scheme chooses the node with the least residual energy among the nodes with larger residual energy than the node itself when selecting the neighbor node to delegate data. Therefore, the sensor nodes can not use energy in a balanced manner.

More specifically, in order to extend the network time in a wireless sensor network, the sensor node must save energy. To this end, a duty cycle technique has been proposed, which reduces energy use of the sensor node by converting the sensor node into an active state and an inactive state (Non-Patent Document 1). The activation time of the sensor node to which the duty cycle is applied is determined by duty. If the duty is large, the sensor node is active for most of the time. However, when low duty is applied, the sensor node is mostly inactive and the sensor node can receive data only when it is activated. Therefore, when the duty is low, the transmitting node has to wait a long time until the activation time of the receiving node. Is greater than the energy used for data transmission.

Due to the above problems, an OC-MAC (Opportunistic Cooperation MAC) technique has been proposed. The OC-MAC scheme transmits data to neighboring nodes through opportunistic data collaboration between transmitting nodes, and switches itself to an inactive mode to reduce energy consumption. However, the sensor node participating in the data collaboration selects the sensor node having the lowest energy among its neighbor nodes. The selected sensor node transmits the received data and its data to the neighboring sensor node, and if there is no sensor node to cooperate, the sensor node transmits the data delegated at the activation time of the receiving node and its own data.

However, as described above, the OC-MAC scheme selects a node having the least residual energy among the nodes having a larger residual energy than the node itself when selecting a neighbor node to which data is to be delegated. As a result, a node with a low residual energy consumes more energy again, and a node with a high residual energy consumes less energy, so that sensor nodes can not use energy in a balanced manner. As a result, even if some of the sensor nodes do not have residual energy, it is not easy to replace some sensors due to the characteristics of the sensor network equipment, so that they have limited power resources, have.

Korean Patent Laid-Open No. 10-2009-0059291 ("Sensor network power management method and sensor network power management system according to an event ", published by Electronics and Telecommunications Research Institute, June 11, 2009)

 Reducing Energy Consumption by Avoiding Reception of Duplicate Messages in Wireless Sensor Networks. Access Control, Media Access Control, Lim Mun - ho, Korea Database Association, Information Technology and Database Journal Vol.12 No.4, pp.13 ~ 24, 2005.

In order to solve the above problem, there is a need to use the energy of the sensor node in a balanced manner and to extend the life of the wireless sensor network by transmitting data to a neighboring node having a large residual energy among neighboring nodes. In other words, based on the existing OC-MAC scheme, by transmitting data to a neighboring node having a large amount of energy, the energy consumption of the sensor node can be reduced and the life of the wireless sensor network can be maintained for a long time.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above problems and to provide a wireless sensor network system and a wireless sensor network system, And to provide a data transmission method for energy saving of a sensor node that can extend the service life of the sensor node.

Another object of the present invention is to prolong the lifetime of the entire wireless sensor network by using the OC-MAC technique and transmitting energy to neighboring nodes having a large amount of residual energy so that each sensor node uses energy in a balanced manner. And to provide a data transmission system for energy saving of a sensor node.

According to another aspect of the present invention, there is provided a method of transmitting energy-saving data for a sensor node, the method comprising: transmitting a Request To Receiver (RTR) message to neighboring sensor nodes step; Transmitting a Clear To Receiver (CTR) message to the first sensor node from a second sensor node having the highest residual energy among neighbor sensor nodes receiving the RTR message; Transmitting the data to the second sensor node by the first sensor node receiving the CTR message; And transmitting the first data of the first sensor node and the second data of the second sensor node to the destination node in the activated state of the destination node. The transmitting of the CTR message may include calculating a backoff time of each neighboring sensor node so that the sensor node having the largest residual energy has a short backoff time; And transmitting the CTR message to the first sensor node after the neighboring sensor nodes have passed the backoff time. The step of calculating the backoff time may be characterized by calculating a backoff time based on the following equation.

Backoff time = ((own residual energy / (residual energy + residual energy of sensor node requesting cooperative communication)) * wait time for response request ^-1

Here, the step of transmitting data to the second sensor node may further include transmitting data to be transmitted by the first sensor node to the second sensor node.

According to another aspect of the present invention, there is provided a data transmission system for energy saving of a sensor node, comprising a Request To Receiver (RTR) broadcasted from a first sensor node to neighboring sensor nodes, And a second sensor node receiving the RTR message and transmitting the CTR message to the first sensor node, the remaining sensor node having the highest residual energy among the neighbor sensor nodes receiving the RTR message, The second sensor node receives the first data from the first sensor node and transmits the first data of the first sensor node and the second data of the second sensor node to the destination node in the active state of the destination node And transmits the data. Here, the second sensor node may include a calculation unit for calculating a backoff time so that the sensor node having the largest residual energy has a short backoff time; And a transmitter for transmitting a CTR message to the first sensor node after the backoff time has elapsed. Here, the calculating unit may calculate the backoff time based on the following equation.

Backoff time = ((own residual energy / (residual energy + residual energy of sensor node requesting cooperative communication)) * wait time for response request ^-1

Here, the first sensor node further transmits data to be transmitted by the first sensor node to the second sensor node.

According to the method and apparatus for data transmission for energy saving of a sensor node according to an embodiment of the present invention, when a specific sensor node transmits data to any one of neighboring nodes, Lt; / RTI > This allows each sensor node to use energy in a balanced manner, extending the lifetime of the entire sensor network. Therefore, the life of the entire sensor network becomes long, and the time and cost for replacing the sensor nodes can be greatly reduced.

1 is a conceptual diagram showing data transmission in the OC-MAC scheme.
2 is an exemplary diagram of a sensor node arrangement in a sensor network.
3 is a conceptual diagram illustrating a transmission process of the OC-MAC scheme when a sensor node is arranged as shown in FIG.
4 is a conceptual diagram illustrating a transmission process of a data transmission method for energy saving of a sensor node according to an embodiment of the present invention when a sensor node is arranged as shown in FIG.
5 and 6 are exemplary views of a topology of a sensor network, respectively.
7 is a flowchart illustrating a data transmission method for energy saving of a sensor node according to an embodiment of the present invention.
8 is a detailed flowchart of the CTR message transmission step of FIG.
9 is a block diagram illustrating a configuration of a data transmission system for energy saving of a sensor node according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

OC - MAC ( Opportunistic Cooperation MAC )technique

First, the existing OC-MAC scheme will be described in more detail below.

To extend the lifetime of wireless sensor networks, a duty cycle has been proposed and related techniques have been studied. In the duty cycle, the transmitting node waits in an idle listening state until the activation time of the receiving node for data transmission. There is a problem that the energy consumed for waiting the active state of the receiving node at the low duty cycle is larger than the energy used for data transmission. To solve this problem, the OC-MAC scheme in the asynchronous duty cycle reduces energy consumption through cooperative communication between the transmitting node and the neighboring nodes.

1 is a conceptual diagram showing data transmission in the OC-MAC scheme.

As shown in FIG. 1, two transmitting nodes b and c wait for a receiving node a to occur for data transmission. The sensor node c broadcasts a Request To Receiver (RTR) message to find a neighbor node to which its data is to be delegated. The sensor node b receiving the RTR compares its residual energy with the residual energy of the sensor node c. If the residual energy of the node is less than the remaining energy of the request node, it ignores the RTR request and broadcasts the RTR message to delegate its own data. If the residual energy of the node is greater than the remaining energy of the request node, the node waits for the backoff calculated by Equation (1) and transmits a CTR (Clear To Receiver) message to allow data delegation.

The sensor node c receiving the CTR message transmits its data to the sensor node b and switches to the inactive state to save energy. The sensor node b broadcasts the RTR message to delegate its own data and the data of the received sensor node c. This process is repeated until there is no neighbor node to cooperate with, and data is transmitted when the receiving node a occurs.

Data transmission method for energy saving of sensor node

In the data transmission method for energy saving of the sensor node according to the embodiment of the present invention, when a specific sensor node delegates its data to at least one of its neighboring nodes, as in the above-described OC-MAC technique, It is possible to use the energy usage of the sensor node in a balanced manner by transmitting data to the sensor node having a large amount of residual energy instead of the sensor node having the value.

FIG. 2 is an exemplary view of a sensor node arrangement of a sensor network, and FIG. 3 is a conceptual diagram illustrating a transmission process of an OC-MAC scheme when a sensor node is arranged as shown in FIG. 4 is a conceptual diagram illustrating a transmission process of a data transmission method for energy saving of a sensor node according to an embodiment of the present invention when the sensor node is arranged as shown in FIG. 3 to 4, R denotes RTR, C denotes CTR, A denotes ACK, and B denotes a Beacon message.

In Figure 2, the number in the circle means the residual energy. The sensor node a is the source node and the sensor node d is the destination node. In the environment of FIG. 2, FIG. 3 shows a transmission process of the OC-MAC scheme. The sensor node a that generates the data to be transmitted requests the cooperative communication by broadcasting the RTR message, and the sensor nodes c and b receiving the broadcast RTR message perform a backoff by the time calculated by Equation (1) CTR message. The sensor node b having less residual energy transmits a CTR message to a before c. The sensor node a receiving the CTR transmits its own data (DATA 1) to the sensor node b. After that, the sensor node b broadcasts the RTR for cooperation request, and the sensor node c receives the data (DATA 1) of the sensor node a and the data (DATA 2) of the sensor node b. Then, when the destination node d is activated, the sensor node c transmits its own data (DATA 3), the data of the sensor node a (DATA 1), and the data of the sensor node b (DATA 2).

A transmission process of a data transmission method for energy saving of a sensor node according to an embodiment of the present invention is shown in FIG. In the data transmission method for energy saving of the sensor node according to the embodiment of the present invention, the backoff time for transmitting the CTR can be obtained by taking the reciprocal of the equation (1) as shown in the following equation (2).

Based on Equation (2), the sensor node having the largest residual energy among the neighbor nodes first transmits the CTR. Referring to FIG. 4, the sensor node a desires to delegate data broadcasts the RTR as in the conventional method. Based on Equation (2), the sensor node c and the sensor node b receive the CTR and transmit the CTR to the sensor node a before the sensor node b. The sensor node a receives its own data (DATA 1) to the sensor node c. Since the sensor node b transmits data to the sensor node c, the conventional OC-MAC technique transmits the data (DATA 1) and the data (DATA 2) twice. However, the sensor node b transmits only the data The number of transmissions can be reduced. In the wireless sensor network, the energy cost for data transmission is large, and if the number of transmissions is reduced, the sensor node can save energy.

In the conventional OC-MAC scheme, data is transmitted to a node having a small residual energy among neighboring nodes, and then the data is sequentially transmitted to a node having a large residual energy. However, according to the data transmission method for saving energy of the sensor node according to the embodiment of the present invention, the data is directly transmitted to the node having a large residual energy, so that the number of transmissions of the intermediate nodes can be reduced. Assuming that energy 1 is consumed in data transmission, in the conventional OC-MAC scheme, the sensor node b uses 2 energy for data transmission, but in the embodiment of the present invention, the number of transmissions decreases and uses 10,000 energy.

FIG. 7 is a flowchart illustrating a data transmission method for energy saving of a sensor node according to an exemplary embodiment of the present invention, and FIG. 8 is a detailed flowchart illustrating a CTR message transmission step in FIG.

7, in data transmission in a sensor network according to an exemplary embodiment of the present invention, a data transmission method for energy saving of a sensor node includes a first sensor node transmitting a RTR (Request To Receiver message (S710). That is, a first sensor node, which means a specific sensor node among a plurality of sensor nodes, determines whether or not it is ready to receive data transmission to neighboring sensor nodes in order to search for a neighboring sensor node to transmit its data You can broadcast an RTR message that asks you. 2, a specific sensor node a that desires to delegate data can broadcast an RTR message to sensor nodes b and c, which are neighbor sensor nodes.

In operation S720, the second sensor node having the largest residual energy among the neighboring sensor nodes receiving the RTR message may transmit a CTR (Clear To Receive) message to the first sensor node. The sensor node, which receives the data of the first sensor node among the neighboring sensor nodes that have received the RTR message broadcasted by the first sensor node, transmits a CTR message to the first sensor node, Can be displayed. Here, the step S720 of transmitting the CTR message may include a step S721 of calculating the backoff time of each neighboring sensor node so that the sensor node having the largest remaining energy has a short backoff time, And transmitting the CTR message to the first sensor node after the back-off time has elapsed (S723).

2, a first sensor node (sensor node a in FIG. 2) may transmit a RTR message to neighboring sensor nodes (sensor node b and sensor node c in FIG. 2). Here, the neighboring sensor node b and neighboring sensor node c that have received the RTR message can calculate the respective backoff time so that the sensor node having the largest residual energy has a short backoff time (S721). Here, the backoff time calculating step S721 may calculate the backoff time based on Equation (2). The backoff time is calculated based on Equation (2) as described above. If the backoff time is calculated based on Equation (2) as described above, the backoff time of the sensor node can be calculated so that the sensor node having a larger residual energy has a shorter backoff time.

After that, the sensor node b and the sensor node c can transmit the CTR message to the first sensor node (sensor node a in Fig. 2) after the calculated backoff time elapses, respectively. If the backoff time is calculated based on Equation (2), the backoff time of the sensor node having a large amount of residual energy is calculated to be shorter, so that the backoff time of the sensor node c is shorter, The CTR message can be transmitted to the first sensor node (sensor node a in Fig. 2) before the node b. Therefore, the sensor node c becomes the second sensor node in FIG.

Thereafter, the first sensor node receiving the CTR message may transmit data to the second sensor node (S730). 2, the first sensor node (sensor node a in FIG. 2) that has received the CTR message from the second sensor node (sensor node c in FIG. 2) DATA 1) to the second sensor node (sensor node c in FIG. 2).

In the above description, only the case where the first sensor node, which means a specific sensor node, is the sensor node a in FIG. 2 has been described. However, each sensor node can transmit its own data to the neighboring sensor nodes as the first sensor node.

Then, the second sensor node may transmit the first data of the first sensor node and the second data of the second sensor node to the destination node in the active state of the destination node (S740). That is, in the asynchronous duty cycle technique, when the destination node finally receiving the data reaches the activation state, the second sensor node transmits the second data, which is its own data, and the second sensor node received from the first sensor node 1 data to the destination node. Here, the step S740 of transmitting data to the second sensor node may further transmit the data to be transmitted by the first sensor node to the second sensor node. Here, the data to be transmitted further may include data previously received from the other sensor node by the first sensor node.

2, when the destination node (sensor node d in FIG. 2) is activated, the second sensor node (sensor node c in FIG. 2) The first data received from the sensor node a in FIG. 2 and the second data of the second sensor node may be transmitted (S740). In addition, the second sensor node (sensor node c in FIG. 2) may further transmit the data of the sensor node b received from the sensor node b to the destination node.

The data transmission method for energy saving of the sensor node according to an embodiment of the present invention shows better performance in a high density environment. The following example demonstrates this.

5 and 6 are exemplary views of a topology of a sensor network, respectively.

In FIGS. 5 and 6, it is assumed that the sensor node e is a destination node and the sensor nodes b, c, and d are active and have data to be transmitted. At this time, the OC-MAC scheme transmits data as shown in FIG. 5, and the data transmission method according to an embodiment of the present invention can transmit data as shown in FIG.

In the OC-MAC scheme, the sensor node a can transmit its own data to the sensor node d via the RTR and the CTR, and the sensor node d can transmit its own data and the data of the sensor node a to the sensor node b. The sensor node b receiving the data transmits the data to the sensor node c as described above, and when the destination node e is activated, the data of a, b, c, and d are transmitted to e and a total of 10 transmissions occur . However, as shown in FIG. 6, the data transmission method according to an embodiment of the present invention transmits data to the sensor nodes a, b, and d to c, so that a total of seven transmissions occur and three transmissions are reduced have.

In the above example, only a small number of sensor nodes exist. However, when there are more sensor nodes and the density of the sensor nodes is increased and the number of neighboring nodes is increased, the number of data delivery transmissions of the intermediate nodes is further decreased . This can extend the life of the network by reducing the energy use of the sensor nodes. In addition, sensor node with low energy of remaining energy participates in data transfer, and sensor node with large residual energy receives data directly without consuming energy, so energy of sensor node can be used in a balanced manner.

In the asynchronous duty-cycle wireless sensor network environment, the sensor node has to wait a long time to transmit data, and the energy consumed at this time is larger than the energy used for data transmission. As described above, in the data transmission method according to an exemplary embodiment of the present invention, in the OC-MAC scheme that proposes a data cooperative technique, a sensor node having a large residual energy among neighbor nodes participates in data delegation, Can be used.

Data transmission system for energy saving of sensor node

9 is a block diagram illustrating a configuration of a data transmission system for energy saving of a sensor node according to an embodiment of the present invention.

9, a data transmission system 900 for energy saving of a sensor node according to an embodiment of the present invention includes a first sensor node 910, a second sensor node 920, a neighboring sensor node 920 -1, and 920-2, and a destination node 930.

The first sensor node 910 refers to a specific sensor node among a plurality of sensor nodes included in the data transmission system of the sensor network. The first sensor node 910 broadcasts a request to receiver (RTR) message to neighboring sensor nodes 920, 920-1 and 920-2 and receives a CTR Receiver) message to the second sensor node (920).

Here, the second sensor node 920 refers to a sensor node having the greatest residual energy among the neighboring sensor nodes 920, 920-1, and 920-2 of the first sensor node 910. The second sensor node 920 receives the RTR message and the remaining energy among the neighboring sensor nodes 920, 920-1, and 920-2 is the largest, and the first sensor node 910 transmits CTR Receiver) message. Here, the second sensor node 920 may include a calculator 921 for calculating a backoff time such that the sensor node having the largest residual energy has a short backoff time, And a transmission unit 923 for transmitting the CTR message to the first sensor node. Here, the calculating unit 921 may calculate the backoff time based on Equation (2). Therefore, the sensor node having the largest residual energy among the neighboring sensor nodes 920, 920-1, and 920-2 may be the second sensor node 920. [

As a result, the second sensor node 920 has all of the data of the second sensor node 920 and the data of the first sensor node 910 as described above. The second sensor node 920 may transmit the data of the first sensor node 910 and the second sensor node 920 to the destination node 930 in the active state of the destination node 930. [ In addition, the first sensor node 910 may further transmit data to be transmitted by the first sensor node 910 to the second sensor node 930. Here, the data to be transmitted may include data previously received by the first sensor node 910 from another sensor node.

The specific operation of the data transmission system 900 according to an embodiment of the present invention is based on the data transmission method according to the embodiment of the present invention described above.

Claims (8)

In the data transmission method in the sensor network,
The first sensor node broadcasting a Request To Receiver (RTR) message to neighbor sensor nodes;
Transmitting a clear to receiver (CTR) message to the first sensor node by a second sensor node having the highest residual energy among the neighboring sensor nodes that have received the RTR message;
The first sensor node receiving the CTR message transmitting data to the second sensor node; And
And the second sensor node transmitting the first data of the first sensor node and the second data of the second sensor node to the destination node in an activated state of the destination node. Data transmission method for
2. The method of claim 1, wherein transmitting the CTR message comprises:
Calculating each backoff time by the neighboring sensor nodes such that the sensor node with the highest residual energy has a short back off time; And
And transmitting the CTR message to the first sensor node after the neighboring sensor nodes have passed the backoff time.
3. The method of claim 2, wherein calculating the backoff time comprises:
Wherein the backoff time is calculated based on the following equation.
Backoff time = ((own residual energy / (residual energy + residual energy of sensor node requesting cooperative communication)) * wait time for response request ^-1
The method of claim 1, wherein transmitting data to the second sensor node comprises:
Wherein the first sensor node further transmits data to be transmitted by the first sensor node to the second sensor node.
In the data transmission system in the sensor network,
The first sensor node receives a Request To Receiver (RTR) message broadcast to neighboring sensor nodes and has the highest residual energy among the neighboring sensor nodes that receive the RTR message, and clear to the first sensor node. Receiver) includes a second sensor node for transmitting a message,
The second sensor node receives the first data from the first sensor node and transmits the first data of the first sensor node and the second data of the second sensor node to the destination node in an active state of the destination node. A data transmission system for energy saving of a sensor node.
6. The method of claim 5, wherein the second sensor node
A calculator configured to calculate a backoff time such that the sensor node having the most residual energy has a short back off time; And
And a transmitter for transmitting a CTR message to the first sensor node after the backoff time has elapsed.
7. The apparatus of claim 6, wherein the calculating unit
Wherein the backoff time is calculated based on the following equation.
Backoff time = ((own residual energy / (residual energy + residual energy of sensor node requesting cooperative communication)) * wait time for response request ^-1
6. The method of claim 5, wherein the first sensor node
Wherein the first sensor node further transmits data to be transmitted by the first sensor node to the second sensor node.

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