KR20070050243A - Determination method of aggregation node in wireless sensor network - Google Patents

Abstract

The present invention relates to a method for determining a wireless sensor network aggregation node. The method for determining a wireless sensor network aggregation node includes a method for determining an aggregation node of a wireless sensor network system including a sink node and a plurality of sensor nodes. a) receiving data transmitted from the plurality of sensor nodes, (b) calculating a perma point using the positions of the plurality of sensor nodes, and setting up a set node using the ferma points; and (c The method for determining a wireless sensor network aggregation node comprising transmitting a query for setting the aggregation node set in the step (b) as an aggregation point.

According to the present invention, since the redundant transmission of the sensor nodes of the wireless sensor network can be prevented, the limited resources of each sensor node can be used for a longer time, which has the advantage of extending the overall life of the wireless sensor network.

Wireless Sensor Network, Aggregation Node, Ferma Point, Aggregation Point, Relay Node

Description

Determination method of aggregation node in wireless sensor network

1 is a conceptual diagram of Ferma points for determining a set node.

2 is a flowchart illustrating a process of determining an aggregate node in a sink node according to an embodiment of the present invention.

3 is a schematic diagram of a wireless sensor network topology according to an embodiment of the present invention.

4 and 5 are simulation diagrams showing the results of simulating the transmission energy consumption according to the position of the aggregation node.

6 and 7 are simulation diagrams showing the change of network life according to the total number of sensor nodes in the wireless sensor network.

Explanation of symbols on the main parts of the drawings

100: sink node 102, 104: sensor node

108: Ferma point (set point) 300: Sync node

310a to 310g: sensor node

The present invention relates to a method for determining a wireless sensor network aggregation node, and more particularly, to a method for determining a wireless sensor network aggregation node using a ferma point to determine a sensor node closest to a ferma point or a ferma point as an aggregation node. It is about.

Recently, due to the development of wireless communication and electronics technology, a network between low-cost, ultra-small sensors is possible. A network composed of these sensors is called a wireless sensor network.

Wireless sensor networks are used for ecological environment monitoring, intelligent environment monitoring, location awareness services, intelligent medical systems, and intelligent robotic systems, and are developing as a core technology of ubiquitous computing environment.

A wireless sensor network is a sensor node that senses, measures, and floods physical data such as light, sound, temperature, and motion in the physical space, and a central primary node (sink node, sink) that receives and analyzes data flooded from the sensor node. -node).

Sensor nodes typically include one or more sensors, actuators, microcontrollers, tens of kilobytes of EEPROM, several kilobytes of SRAM, hundreds of kilobytes of flash memory, analog-to-digital converters (ADCs), short-range wireless communication modules, and It consists of a power supply (energy source) for supplying power to these components.

Due to the limited resources of a sensor node, the lifetime of a wireless sensor network depends entirely on the life of the sensor node.

Since the sensor node's energy source is most often consumed by short-range wireless communication for transmitting collected data to the sink node, configuring the wireless sensor network to efficiently perform such wireless communication can extend the life of the wireless sensor network. It is a way.

This energy problem is recognized as one of the most important problems in the sensor network, and there are various ways to extend the life of the network.

In general, a method of giving a sleep time through the MAC protocol and a method of reducing the number of duplicate transmissions by performing aggregation are being studied.

In general, to obtain information from each sensor node, the sink node floods a query containing a certain command.

The sensor nodes corresponding to the flooding information collect data in its sensing radius according to the command included in the flooded information and transmit the data to the sink node.

In this case, since data is transmitted to the sink node by all sensor nodes corresponding to the flooding information, to prevent duplicate transmission using an aggregation point (or an aggregation node) in order to solve the problem of duplicate transmission of the same information to the sink node. Methods are being studied.

The method for improving energy efficiency through aggregation is a method of preventing redundant transmission by collecting data transmitted from each sensor node in a wireless sensor network at a predetermined point (aggregation node) and transmitting the data to the sink node.

The aggregation node (collective node) receives data transmitted from each sensor node, compresses or attaches the received data, and reduces the packet size to transmit to the sink node.

Since the energy consumption is different depending on the location of the sensor node configured to perform such a data collection, it is important to determine the most appropriate aggregation node.

Therefore, in recent years, as a method for setting or determining a set node, a method of performing aggregation by constructing a tree using a greedy algorithm and a method of performing aggregation by an opportunistic method are studied. Has been.

However, determining an aggregation node using the above-described method has a problem in that an overhead such as a tree configuration for selecting an aggregation node is required.

In addition, since the topology information of the wireless sensor network is needed to determine the aggregation node, a lot of additional information exchange between the sink node and the sensor node is required, and thus, a large amount of time and resources are consumed in determining the aggregation node.

In addition, there is a problem in that it is not possible to accurately calculate the position of the aggregation node that provides the optimum efficiency.

An object of the present invention is to provide a method for determining an aggregate node of a wireless sensor network using Ferma points that can minimize time and resource consumption and at the same time ensure optimal efficiency in order to solve the problems of the prior art as described above. It is done.

In order to achieve the above object, according to a preferred embodiment of the present invention, in a method of determining an aggregation node of a wireless sensor network system including a sync node and a plurality of sensor nodes, (a) the plurality of nodes; Receiving data transmitted from a sensor node of the sensor node; (b) calculating a Fermat point using the positions of the plurality of sensor nodes, and setting an aggregation node using the Fermat point; And (c) transmitting a query for setting the set node set in step (b) as the set point.

Hereinafter, exemplary embodiments of a method for determining a wireless sensor network aggregation node will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of Ferma points for determining a set node.

With reference to the accompanying drawings will be described in detail the concept of the Ferma point and the method of calculating the Ferma point.

As shown in FIG. 1, one sink node P ₁ 100, a sensor node P ₂ 102, and a sensor node P ₃ 104 exist at any three points in the sensing field, and the sensor node P ₂ ( 102, when the sensing data is transmitted from the P ₃ (104) to the sink node P ₁ (100), in order to minimize the transmission energy consumption of the sensor network from the sensor node P ₂ (102) and the sensor node P ₃ (104) When data is transmitted to the sink node P ₁ (100), a data aggregation point (hereinafter, referred to as an 'aggregation point') that minimizes a transmission distance (i.e., the total number of hops to be transmitted) must be determined. .

The aggregation point is a specific point in the sensor network and refers to an aggregation point of sensing data transmitted from a sensor node that collects and transmits information in its sensing radius.

That is, the aggregation node receives the sensing data transmitted from each sensor node and compresses or attaches the sensing data to reduce the size of the packet and transmits it to the sink node at once, or performs a series of calculations using the sensing data transmitted from each sensor node. After executing, the result is transmitted to the sink node.

Therefore, when using the aggregate node in the sensor network, the sensor node P ₂ (102) and sensor node P ₃ (104) for transmitting the sensing data does not transmit its own sensing data to the sink node P ₁ (100), but aggregate If a node does not exist at a node located at a point or a collection point, the sensing data is transmitted from the collection point to a node at the nearest location (hereinafter referred to as a 'gathering node').

Through this process, redundant data transmission can be eliminated and the energy efficiency of the sensor node can be improved.

Determining the aggregation point to minimize the sensing data transmission distance is solved by finding the point where the sum of the distances connecting the sensor node 102 and 104 and the sync node 100 and the data aggregation point in a straight line is minimum. .

As a method of determining an aggregation point that can minimize the sensing data transmission distance, the present invention proposes an aggregation point determination method using Fermat's Point.

Pierre de Fermat found the point where the sum of the distances to each vertex of the triangle was the smallest and proved it.

The Ferma point is defined as the point at which the cabinet between each vertex (ie two sensor nodes and sink nodes) and the Ferma point is 120 degrees.

However, when any of the cabinets of the triangle is 120 degrees or more, the vertices of the cabinet are defined as Ferma points.

This point is called the point of Ferma, and it is possible to reduce the overlapped transmission to the minimum by determining the aggregation point using the Ferma point.

Accordingly, as shown in FIG. 1, the sink node P ₁ (x ₁ , y ₁ ) 100, the sensor node P ₂ (x ₂ , y ₂ ) 102, and the sensor node P ₃ (x ₃ , y ₃ ) ( 104) when the Fermat points present in the interior of △ P ₁ P ₂ P ₃ and △ P ₁ P ₂ P ₃ to the vertex to as x (x, y) (108 ), Fermat point x (108) and each The relationship with the nodes 100, 102, 104 is defined by equation (1).

In order to calculate the Fermat point according to the definition of the Fermat point as described above, an equilateral triangle is first constructed on three sides of ΔP ₁ P ₂ P ₃ .

ΔP ₁ P ₂ The coordinates of the new vertex of each equilateral triangle drawn on three sides of P ₃ are coordinates T ₁ (x ₁ ', y ₁ ') (110) and T ₂ (x ₂ ', y, respectively, according to equation (2). ₂ ') 112, T3 (x ₃ ', y ₃ ') (114).

In Equation 2, d ₁₂ , d ₂₃ , and d ₃₁ are defined as the distances between vertices P ₁ (100), P ₂ (102), and P ₃ (104), and α ₁ (116), α ₂ (118), α ₃ (120) is defined as the angle between the straight line P ₁₂ (a straight line connecting P ₁ (100) and P ₂ 102), straight line P ₂₃ , and straight line P ₃₁ with the reference plane.

Next, the straight lines P ₁ T ₁ and P ₂ (102) connecting P ₁ (100) and T ₁ (110), and the straight lines P ₂ T ₂ and P ₃ (104) and T ₃ connecting T ₂ (112). When constructing a straight line P ₃ T ₃ connecting 114, the intersection of the three straight lines becomes the Ferma point X 108.

Therefore, the coordinates of the Ferma point are calculated by Equation 3 below.

However, if any of the angles of the triangle whose sensor nodes P ₂ 102, sensor node P ₃ 104, and sink node P ₁ 100 are vertices is 120 degrees or more, the Ferma point has an angle of 120 degrees or more. It is defined as a vertex.

2 is a flowchart illustrating a process of determining an aggregation node in a sink node according to an embodiment of the present invention.

With reference to the accompanying Figure 2 will be described in detail the aggregation node determination process in the sink node according to an embodiment of the present invention.

Hereinafter, a process of determining an aggregate node in the sink node 100 will be described based on the case where sensing data is transmitted from two sensor nodes 102 and 104.

The sink node 100 receives data transmitted from the sensor nodes 102 and 104 (S200) and uses a location information of the sensor nodes 102 and 104 to transmit the data, such as the Ferma point (set point) 108. To calculate (S202).

The location information of the sensor nodes 102 and 104 may be configured to be stored in the sink node 100 when the sensor network is configured. Alternatively, the sensor node 102 may be configured to sense data transmitted from the sensor nodes 102 and 104. Location information of the 102 and 104 may be included and transmitted to the sink node 100.

Since the method of calculating the Ferma point using the positions of the sink node 100 and the two sensor nodes 102 and 104 has been described above, a detailed description thereof will be omitted.

After calculating the Ferma point, the sink node 100 determines whether a sensor node exists at a position corresponding to the Ferma point using the sensor network information (S204).

As a result of determining whether the sensor node exists, if the sensor node exists at the corresponding position, the sink node 100 sets the corresponding sensor node as a set node (S208), and includes the result in an interest query. In order to transmit the sensing data to the sensor nodes (102, 104) (S210).

If, as a result of determining whether the sensor node is present in the sink node 100, if the sensor node does not exist at the corresponding position, the sink node 100 searches for the sensor node closest to the Ferma point using the sensor network information. In step S206, the closest sensor node is set as a set node (S208), and the result is included in an interest query and transmitted to the sensor nodes 102 and 104 that transmit sensing data (S210).

The sensor node (or sensor node closest to the Ferma point) that receives the interest query transmitted from the sink node 100 resets its state to function as the aggregation node. The sensing data transmission sensor nodes 102 and 104 receiving the interest query transmitted from the sink node 100 transmit their sensing data to the aggregation node after receiving the query.

The aggregation node aggregates or compresses the sensing data transmitted from the two sensor nodes 102 and 104, or transmits a result calculated using the two data to the sink node 100.

Since the number of transmissions can be reduced by this process, the energy efficiency of the sensing data transmission sensor nodes 102 and 104 is improved, and as a result, the lifespan of the sensor network is increased.

3 is a configuration diagram of a wireless sensor network topology according to an exemplary embodiment of the present invention, and FIGS. 4 and 5 are simulation diagrams showing the results of simulating transmission energy consumption according to the location of an aggregation node.

For the transmission energy consumption simulation, a sensor network topology of the type shown in FIG. 3 is constructed and used.

As shown in FIG. 3, the sensor network topology used in the transmission energy consumption simulation includes one sink node 300 and 10,000 sensor nodes in a sensor field of 1000m * 1000m width and is located on the boundary of the sensor field. All sensor nodes except the sensor node are configured to have six neighboring nodes connected in a hexagonal shape.

That is, the sensor node 310C having a coordinate of (10, 10) has six sensor nodes 310a, 310b, 310d, 310e, 310f, and 310g connected in a hexagonal shape as neighboring neighbor nodes. All sensor nodes are placed.

4 and 5 are simulation diagrams showing the results of simulating the transmission energy consumption according to the location of the aggregation node.

X-axis and Y-axis in Fig. 4 represents the X, Y coordinates of the node, Z-axis represents the degree of energy consumption.

Therefore, the point with the lowest coordinate on the Z axis becomes the point with the lowest energy consumption.

4 illustrates the transmission energy consumption when sensor node P ₂ flooding sensing data is located at (20, 980), sensor node P ₃ is located at (980,980), and sink node P ₁ is located at (0,0). It is a simulation diagram simulating the amount.

In FIG. 4, the Ferma point is calculated by Equation 3, and since all the cabinets of ΔP ₁ P ₂ P ₃ are less than 120 degrees, the position of the Ferma point X in this case is (215,781).

However, since there is no sensor node with the coordinates exactly matching the Ferma point, the sink node P ₁ selects the sensor node having the (220,780) coordinate closest to the Ferma point (215,781) as the aggregation node.

Looking at the simulation result, it can be seen that the energy consumption degree is the lowest when setting the sensor node located at (220,780) as a set node as shown.

FIG. 5 simulates transmission energy consumption when sensor node P ₂ flooding sensing data is located at (650,550), sensor node P ₃ is located at (980,980), and sink node P ₁ is located at (0,0). One simulation diagram.

In FIG. 5, since the internal angle of the sensor node P ₂ of ΔP ₁ P ₂ P ₃ is greater than or equal to 120 degrees, the Ferma point is calculated as P ₂ (650,550), and thus the sink node is selected as the sensor node P ₂ as the aggregation node. .

Looking at the simulation result, it can be seen that the energy consumption degree is the lowest when setting the sensor node P ₂ located at (650,550) as a set node as shown in FIG.

6 and 7 are simulation diagrams showing the change of network life according to the total number of sensor nodes in the network.

In more detail, FIG. 6 is a simulation diagram comparing the lifespan of the sensor network according to the present invention and the lifespan of the sensor network according to the GIT method according to the total number of nodes when the sink node is located at (0,0). 7 is a simulation diagram comparing the lifetime of the sensor network according to the present invention and the lifetime of the sensor network according to the GIT method according to the total number of nodes when the sink node is located at (0,0).

Network lifetime is defined as the total number of rounds until all sources have completed sending to the sink node.

The sensor field used in the simulation was set to a width of 100m * 100m.

As shown in FIG. 6 and FIG. 7, it can be seen that the network life is increased when a larger number of nodes are arranged in the sensor field of the same area, that is, when the density of nodes is large.

In addition, when compared with the existing GIT method, it can be seen that the network life of the sensor network using the aggregation point determination method according to the present invention significantly improved.

In addition, comparing FIG. 6 and FIG. 7, it can be seen that the network life is improved when the sink node is located at (50,50) rather than when it is located at (0,0).

That is, when the sink node is located in the center of the sensor field, since the sink node can have more valid paths than when present in the outer part of the sensor field, the network life is increased.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

As described above, according to the method of determining a set node using Ferma points according to the present invention, there is an advantage in that data transmission energy of a sensor node using a low power battery can be saved.

In addition, according to the present invention has the advantage that the life of the sensor network is increased by saving the data transmission energy of the sensor node.

In addition, according to the present invention there is an advantage that efficient routing can be performed using only local information without collecting information on the sensor network topology.

Claims (4)

A method for determining an aggregation node of a wireless sensor network system including a sink node and a plurality of sensor nodes, (a) receiving data transmitted from the plurality of sensor nodes; (b) calculating a Fermat point using the positions of the plurality of sensor nodes, and setting an aggregation node using the Fermat point; And and (c) transmitting a query for setting the set node set in step (b) as the set point. The method of claim 1, In step (b), (b1) identifying positions of the plurality of sensor nodes; (b2) calculating a Ferma point using the positions of the sink nodes and the positions of the plurality of sensor nodes identified in (b1); And and (b3) setting a set node using the Ferma point coordinates calculated in step (b2). The method of claim 2, Step (b3), It is determined whether there is a sensor node having the same coordinates as the Ferma point coordinates calculated in step (b2), and if there is a sensor node having the same coordinates, the sensor node is set as a set node, and the sensor node having the same coordinates And detecting a sensor node having a coordinate value closest to the Ferma point coordinate and setting the set node as a set node. The method of claim 1, And the sink node is located at the center of the wireless sensor network system.

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