KR20090093645A - Method of random network coding in wireless sensor network - Google Patents

Abstract

A random network coding method of a wireless sensor network is provided to transmit data by confirming whether a network coding method is applied in the node of wireless sensor network. A sensor node determines an adjacent node showing beacon signal to a transit node(S301). The sensor node confirms by transmitting data index information(S302). The sensor node determines whether a network coding method is applied(S303). The sensor node listens secretly data of the other sensor node through the opportunistic reception. The sensor node applies the network coding mode. And the normal transmission mode is applied(S305).

Description

Method of random network coding in wireless sensor network

The present invention relates to a random network coding method of a wireless sensor network. More particularly, a wireless sensor for transmitting data by checking whether a network coding scheme is applicable to a node of a mobile wireless sensor network. A random network coding method of a network.

Wireless sensor networks have many potential applications, such as environmental monitoring, target tracking, highway traffic information management, and building monitoring.

The wireless sensor network consists of a sensor node having a sensor module and a network module, and a plurality of sensor nodes are arranged in a corresponding region to form one network that operates organically. At this time, each sensor node collects, processes, and transmits information through sensing, and relay nodes located in the middle play a relay role of retransmitting the received data.

In general, the sensor node is installed in an inaccessible area, so it is difficult to replace or charge the battery. Thus, a major concern of research on wireless sensor networks is how long the network can be maintained with limited energy.

In the past, MAC protocols and routing protocols have been proposed in a manner that considers limited energy. A typical method is the AODV (Ad hoc On-demand Distance Vector) method through multi-hop routing in order to effectively transmit data to each server.

However, this has a disadvantage in that the number of transmissions of the sensor node is large and the throughput per sensor node is significantly reduced when the sensor node is moved. In particular, when a load is overloaded due to a heavy load on a specific path, a bottleneck may occur and the performance of the entire network may be seriously degraded.

Recently, researches for improving the transmission efficiency of a network using a network coding scheme have been conducted. In general, when data continuously sensed by each sensor node moves along a dynamic path, the relay node accumulates data transmitted from each sensor node in a storage space. In this case, in the relay node, throughput may be increased by reducing the number of transmissions of data using a network coding scheme.

Hereinafter, a description will be made by comparing the transmission times of a transmission method using a network coding and a general transmission method. FIG. 1A illustrates an exemplary embodiment of a general transmission scheme, and FIG. 1B illustrates an exemplary embodiment of a transmission scheme using a network coding scheme.

1A and 1B illustrate a case in which a relay node transmits data transmitted from a sensor node to another sensor node. That is, the relay node C transmits the data transmitted from the sensor node A (ie, a) to the sensor node B, and the data transmitted from the sensor node B (ie, b) to the sensor node A.

As illustrated in FIG. 1A, the relay node C transmits data transmitted from the sensor nodes A and B to each sensor node without using a network coding scheme, and a total of four transmissions are required.

As illustrated in FIG. 1B, the relay node C transmits data transmitted from the sensor nodes A and B to each sensor node using a network coding scheme, and a total of three transmissions are required.

In this case, the relay node C applies an exclusive logical product operation (XOR) to the data (ie, a and b) transmitted from the sensor nodes A and B and transmits the same to the sensor nodes A and B. Here, sensor node A is sent from relay node C. To decode the data of sensor node B (i.e., ). Similarly, sensor node B is sent from relay node C. To decode the data of sensor node A (ie, ).

Therefore, the transmission method using the network coding method of FIG. 1B may result in throughput improvement over the general transmission method of FIG. 1A.

In a transmission scheme using a network coding scheme, data transmitted from neighbor nodes of the relay node to the relay node should be overheared by opportunistic listening and stored for an arbitrary time. This is for neighboring nodes to decode their desired data from the data transmitted from the relay node.

However, when neighboring nodes are mobile, it may be difficult to overhear through opportunistic reception using a network coding scheme as the distance between nodes changes. That is, the neighbor node may not listen to the data transmitted to the relay node, and thus may not be able to decode data desired by the node from the relay node.

In a mobile wireless sensor network, the transmission method using the network coding method can expect the throughput to be reduced by reducing the number of transmissions of the network, but when the network coding method is not practically used, the transmission reliability of the network may be reduced. There is a limit to this.

Therefore, in a mobile wireless sensor network, it is necessary to apply a data transmission method of a relay node differently depending on whether or not a network coding method is available.

Therefore, the above-described conventional technology has a problem in that the network coding scheme cannot be collectively applied in the mobile wireless sensor network, and an object of the present invention is to solve such a problem.

Accordingly, an object of the present invention is to provide a random network coding method of a wireless sensor network for transmitting data by checking whether a network coding scheme is applicable to a node of a mobile wireless sensor network.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In order to achieve the above object, the present invention provides a network coding method comprising the steps of: determining a relay node through measurement strength of a beacon signal; Determining whether to apply network coding by checking data index information of the relay node based on data index information of neighbor nodes; And transmitting data to the relay node according to the determination result.

In addition, the present invention provides a sensor node having a processor, the function of determining the relay node through the measurement strength of the beacon signal; Determining whether to apply network coding by checking data index information of the relay node based on data index information of neighbor nodes; And a computer-readable recording medium having recorded thereon a program for realizing a function of transferring data to the relay node according to the determination result.

As described above, the present invention has an effect of maximizing data transmission efficiency according to a random network coding scheme in a mobile wireless sensor network.

In addition, the present invention has the effect of applying a random network coding to reduce the number of transmissions and prevent the load from being overloaded on a particular path.

In addition, the present invention has the effect of increasing the efficiency of the wireless sensor network and improve the throughput per sensor node.

1A is a diagram illustrating an embodiment of a general transmission scheme;

1B is a diagram illustrating an embodiment of a transmission scheme using a network coding scheme;

2 illustrates an embodiment of a wireless sensor network according to the present invention;

3 is a flowchart illustrating a random network coding method of a wireless sensor network according to the present invention;

4 is a graph illustrating random network coding performance in FIG. 3.

* Explanation of symbols for the main parts of the drawings

210: sensor node A 220: sensor node B

230: sensor node C 240: sensor node D

250: Sensor node E

The above objects, features, and advantages will become more apparent from the detailed description given hereinafter with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention pertains may share the technical idea of the present invention. It will be easy to implement. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

As shown in FIG. 2, in the wireless sensor network according to the present invention, a sensor node A 210, a sensor node B 220, a sensor node C 230, a sensor node D 240, and a sensor node E 250 are described. ) Is included. At this time, each sensor node attempts to transmit its data to the server through a multi-hop method when sensing in its own jurisdiction. Here, the data of each sensor node is sensing information of each sensor node, 'a' for sensor node A 210, 'b' for sensor node B 220, 'c' for sensor node C 230, and a sensor. Assume that 'd' is the node D 240.

In addition, the server periodically broadcasts the beacon signal, each sensor node measures and stores the strength of the beacon signal received from the server to determine the location of the server, and its relay probability, 0 <p <1 ) Is determined by calculating.

In particular, the present invention applies a basket routing algorithm when routing data through a relay node. The basket routing algorithm is hop-based multihop routing that integrates sensor node mobility into the routing design. In the present invention, since the basket routing algorithm is well known to those skilled in the art, a detailed description thereof will be omitted.

Hereinafter, for convenience of description, a case in which the sensor node A 210 transmits its data a to the sensor node B 220 will be described. Therefore, those skilled in the art will be able to easily understand each sensor node through the following description.

First, a case in which the sensor node A 210, which is a transmitting node, transmits data to a relay node (assuming the sensor node E 250 in the present invention) will be described.

The sensor node A 210 attempts to transmit its sensing information (a) to the server upon detection in its jurisdiction, and for this purpose, neighboring neighbor nodes (ie, sensor node B 220 and sensor node C). 230, the sensor node D 240 and the sensor node E 250 broadcast a Request-To-Send (RTS) signal.

At this time, each neighbor node determines whether or not to receive data transmitted in a given timeslot based on the relay probability p. Each neighbor node that has determined the reception includes the measurement strength of the beacon signal received from the server in the ACK (ACKnowledgement) signal and transmits it to the sensor node A 210.

Thereafter, the sensor node A 210 receives the ACK signal of each neighbor node, compares the measurement strength of the beacon signal included in the ACK signal, and determines the neighbor node representing the strongest beacon signal as the relay node. Herein, it is assumed that the sensor node representing the strongest beacon signal is 'sensor node E 250'.

Then, the sensor node A 210 transmits its data 'a' to the sensor node E 250, and receives the ACK signal from the sensor node E 250, and then ends the transmission.

In addition, when the sensor node A 210 transmits its data to the sensor node E 250 but does not receive the ACK signal, the sensor node A 210 transmits its data directly to the server. At this time, when the sensor node A 210 transmits data to the relay node and the server but does not receive the ACK signal, the sensor node A 210 determines that the data transmission has failed, and retransmits its data through the binary exponential backoff (BEB). .

On the other hand, when sensor node A 210 transmits data to sensor node E 250, neighbor nodes (i.e., sensor node C 230 and sensor node D 240) sneak through opportunity reception. The data a of A 210 is stored for a certain time.

In addition, the larger the number of neighbor nodes overhearing through opportunistic reception, the better, and other neighbor nodes not intercepting through opportunistic reception remain idle until the end of transmission.

In addition, in the present invention, since data is transmitted only between specific sensor nodes and not delivered to a server, a hop count indicating the number of hops to which data is transmitted is prevented in order to prevent a loop phenomenon in which repetitive transmission is performed between specific sensor nodes. (hop count) field is used. That is, the relay nodes apply a loop-free mechanism that does not transfer the same data to the sensor node that previously delivered the same data to the current relay node for data exceeding the preset hop count field value, so that the data can be transmitted to the server. .

When the transmission of the sensor node A 210 is completed as described above, a sensor node having data to be transmitted in the next time slot is arbitrarily selected and attempts to transmit data in the above manner. At this time, since each sensor node has mobility, its position changes over time, and the position of the server is determined again by measuring a new beacon signal from the server.

Next, a case in which the sensor node E 250, which is a transmission node, transmits data to the relay node (sensor node B 220 to be described later) will be described.

In particular, the sensor node E 250 is a sensor node that must transmit a plurality of data, unlike the sensor node A 210. The sensor node E 250 may apply network coding to maximize the throughput of data transmission, thereby transmitting a plurality of data at once. That is, sensor node E 250 includes data 'a' of sensor node A 210, data 'b' of sensor node B 220, data 'c' of sensor node C 230, and sensor node D 240. Network-coded data "d" 'Is sent to each sensor node at once.

At this time, each sensor node by intercepting the data of the neighbor nodes through the opportunistic reception and stores for a predetermined time, the 'node transmitted from the sensor node E (250) You can decode the data you want from '. That is, when the sensor node A 210 transmits its data a to the sensor node E 250 in FIG. 2, the neighbor nodes (that is, the sensor node B 220, the sensor node C 230, and the sensor) are transmitted. Node D 240] must receive and store the data a of sensor node A 210 even though the data is not transmitted by sensor node A 210 to itself.

However, the sensor node E 250 may not apply the network coding scheme collectively due to a neighbor node that does not overhear by opportunistic reception. That is, when the sensor node A 210 transmits its data a to the sensor node E 250 in FIG. 2, the sensor node B 220 is connected to the sensor node C 230 and the sensor node D 240. Compared to the sensor node A (210) far away, it may not be possible to hear by the opportunistic reception.

In this case, when the sensor node B 220 does not overhear through the opportunistic reception, the sensor node B 220 is transferred from the sensor node E 250. Cannot decode the data they want.

To this end, the sensor node E 250 checks whether the network coding is to be applied and then randomly applies it. This means that network coding is applied randomly because the eavesdropping through opportunistic reception can be changed according to the relay probability.

First, sensor node E 250 determines a relay node by broadcasting an RTS signal to neighbor nodes. That is, the sensor node E 250 receives the ACK signal from each neighbor node, compares the measurement strength of the beacon signal included in the ACK signal, and determines the neighbor node representing the strongest beacon signal as the relay node. Herein, it is assumed that the sensor node representing the strongest beacon signal is 'sensor node B 220'.

In particular, the sensor node E 250 transmits 'index information for data held in the storage space that has been eavesdropped through a previously performed opportunistic reception' (hereinafter referred to as "data index information") from each neighbor node. Receive.

Accordingly, the sensor node E 250 based on the data index information of the sensor node A 210, the sensor node C 230, and the sensor node D 240, the data index information of the sensor node B 220 that is a relay node. If it is determined that the data of the sensor node A 210 is overheard through opportunistic reception, the network coding method is applied to the data ' 'Is transmitted to the sensor node B (220).

For example, the sensor node E 250 checks 'a, b, c, d' from the data index information of the sensor node A 210, the sensor node C 230, and the sensor node D 240, and the sensor If 'a, b, c, d' is also confirmed in the data index information of the node B 220, it is determined that the sensor node B 220 overheard the data of the sensor node A (210) through opportunistic reception. .

On the other hand, if the sensor node E 250 determines that the data of the sensor node A 210 has not been overheard through opportunistic reception, the sensor node E 250 may convert the data 'a' into the sensor node B (a general transmission method without applying network coding). 220).

For example, the sensor node E 250 checks 'a, b, c, d' from the data index information of the sensor node A 210, the sensor node C 230, and the sensor node D 240, and the sensor If 'b, c, d' is also confirmed in the data index information of the node B 220, it is determined that the sensor node B 220 does not overhear the data of the sensor node A (210) through opportunistic reception.

3 is a flowchart illustrating a random network coding method of a wireless sensor network according to the present invention.

As shown in FIG. 3, the sensor node E 250, which is a transmitting node, includes neighbor nodes (ie, sensor node A 210, sensor node B 220, sensor node C 230, and sensor node D 240). )] To broadcast the RTS signal. At this time, the sensor node E 250 receives the ACK signal from each neighbor node, compares the measurement strength of the beacon signal included in the ACK signal, and determines the neighbor node representing the strongest beacon signal as the relay node (S301). Here, a case where the relay node is determined as the sensor node B 220 will be described.

In particular, the sensor node E 250 receives the data index information along with the ACK signal from the sensor node B 220 and checks it (S302).

Subsequently, sensor node E 250 relays sensor node B, which is a relay node, based on data index information of neighbor nodes (ie, sensor node A 210, sensor node C 230, and sensor node D 240). The data index information of 220 is checked to determine whether to apply a network coding scheme (S303). That is, the sensor node E 250 applies a network coding scheme in case of sniffing data of the sensor node A 210 through opportunistic reception (S304), and applies a general transmission scheme in the opposite case (S305). .

4 is a graph illustrating random network coding performance in FIG. 3.

As shown in FIG. 4, the x-axis represents 'Target SIR' and the y-axis represents 'Number of Succesive Packets'.

① shows the best performance when 100% network coding is performed by the relay node that is excessively transmitted to the server, and ⑦ shows the lowest performance because the packet is always transmitted in one direction.

② to ⑥ are cases of performing random network coding, and show performance according to% of performing network coding for each.

In the simulation of FIG. 4, it can be seen that the performance is improved by about 1.5 times as a result of comparing the highest performance of each.

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

Claims (7)

In the network coding method, Determining a relay node through the measurement strength of the beacon signal; Determining whether to apply network coding by checking data index information of the relay node based on data index information of neighbor nodes; And Transmitting data to the relay node according to the determination result Random network coding method of wireless sensor network. The method of claim 1, The data index information, The random network coding method of the wireless sensor network, characterized in that the 'index information for the data held in the storage space that has been overtaken through the previously performed opportunistic reception. The method of claim 1, The relay node, The random network coding method of a wireless sensor network, characterized in that one of the neighboring nodes indicating the measurement strength of the strongest beacon signal. The method according to any one of claims 1 to 3, The determining of whether to apply the network coding, Wireless network, characterized in that the network node is applied to check the data index information of the relay node based on the data index information of the neighbor node, when the relay node overhears the data of the neighbor node through the opportunistic reception. Random network coding method of sensor network. The method of claim 4, wherein The step of transmitting data to the relay node, And coding the data corresponding to the data index information of the neighbor node through an exclusive OR operation and transmitting the data to the relay node. The method according to any one of claims 1 to 3, Determining whether to apply the network coding, Checking the data index information of the relay node based on the data index information of the neighbor node, if the relay node does not overhear the data of the neighbor node through the opportunistic reception, characterized in that the general transmission method is applied. Random network coding method of a wireless sensor network. On a sensor node with a processor, Determining a relay node through the measurement strength of the beacon signal; Determining whether to apply network coding by checking data index information of the relay node based on data index information of neighbor nodes; And A function of transmitting data to the relay node according to the determination result A computer-readable recording medium having recorded thereon a program for realizing this.