KR20090043196A - Method for identification and construction of network in sensor network environments - Google Patents

Abstract

The present invention relates to a network recognition and configuration method in a sensor network environment, wherein all nodes of a sensor network are recursively repeated a subset of the time allocated to each node at network recognition and configuration time to be assigned to a corresponding child node. In this way, each node is guaranteed a unique transmission time and transmits a node-specific recognition message for recognition at a unique time, thereby effectively eliminating the possibility of recognition failure due to internal radio interference and redundant operation of the sensor network. In particular, there is an effect that can increase the node recognition success rate.

Sensor Network, Routing, Parent Node, Child Node, Message, Broadcast, RSSI

Description

METHOOD FOR IDENTIFICATION AND CONSTRUCTION OF NETWORK IN SENSOR NETWORK ENVIRONMENTS}

The present invention relates to a network recognition and configuration method in a sensor network environment, and more particularly, to assign a unique time for each node in a sensor network to generate all node connections recognizable within a radio frequency range (RF). Accordingly, the present invention relates to a network recognition and configuration method in a sensor network environment that can increase the path recognition rate of each node and effectively reduce the number of unconnected nodes in the sensor network.

In general, after the first Sensor Node is installed or scattered, each node must establish a network by establishing a connection with each other, and each path in the established network becomes basic information for determining network routing. .

At this time, the recognized path becomes a factor that directly affects energy efficiency and reliable routing of the entire sensor network. Therefore, in the initial sensor network recognition phase, it is necessary to discover all possible connections between the nodes so that they can be considered for routing, and also to create unreliable nodes in the sensor network, ultimately forming a reliable and energy efficient sensor network. Should be.

In the related art, an advertisement message is transmitted from a top-level parent node, that is, a sink node, and a connection operation between the two nodes occurs through a response of a node receiving the advertisement message, and the advertisement message is completed after the connection operation is completed. The node receiving the succession of the advertisement function recursively repeats the above operations to sequentially support the sensor network recognition. The above process is caused by the operation between the parent node and the child node, which is independent of the control of the entire network.

That is, according to the related art, a plurality of nodes may attempt to transmit an advertisement message at a time point because it is impossible to control the time of the advertisement message in the entire sensor network, which is a range in which the transmission ranges of the two advertisement messages overlap. This results in the occurrence of RF interference and causes a reduction in the recognition rate, and there is a problem such that mutual recognition is impossible between nodes operating the advertisement message transmission at the same time.

In addition, the approach of allocating the advertising time of the child node internally by dividing a certain time to the child node that the parent node has accessed, since the minimum required time for the advertising operation for each child node exists, the number of child nodes that can be supported There is a problem of limiting.

In addition, even in the approach of a child node receiving the advertisement message, a random-backoff when a collision occurs due to the approach of two or more nodes, a collision that occurs when the received node approaches after a normal reception of the advertisement message. This is a solution to the problem, which is different from the collision resolution method of the message itself.) There is a limitation that all accesses (or paths) of all nodes are handled at the same level. In practice, not all nodes will be used equally in routing.

The present invention has been made to solve the above-described problem, an object of the present invention by assigning a unique time for each node in the sensor network to create all the node connections recognizable within the RF range to configure the network, the path of each node It is possible to increase the recognition rate, and to provide a network recognition and configuration method in a sensor network environment to effectively reduce the number of unconnected nodes in the sensor network.

Another object of the present invention is to provide a network recognition and configuration method in a sensor network environment that can effectively eliminate the possibility of recognition failure due to internal radio interference and redundant operation of the sensor network, and increase the node recognition success rate. have.

In order to achieve the above object, a first aspect of the present invention provides a network recognition and configuration method in a sensor network environment in which at least one parent and child node are formed in a tree form based on one top-level parent node, (a) Transmitting, by the top parent node, an advertisement message including its node information; (b) a child node receiving the transmitted advertisement message, respectively, calculating an access time to its parent node according to a received strength value of the corresponding advertisement message; (c) each child node transmitting a response message to its parent node at the calculated access time, acquiring information necessary for a routing protocol, and performing path recognition; (d) assigning a unique transmission time to each parent node, including the top-level parent node, to transmit an advertisement message based on the child node to its child nodes; (e) each child node recursively transmitting the advertisement message repeatedly at the unique transmission time; And (f) when each parent node does not receive any response message from its child nodes, recursively transmits an end-of-recognition message to its parent parent node that allocated the corresponding transmission time, and recursively transmits the highest level parent node. It is to provide a network recognition and configuration method in a sensor network environment, characterized in that it comprises the step of transmitting to.

In this case, the node information preferably includes round information obtained by calculating a time at which one recognition operation occurs in one cycle and information required for a routing protocol.

Preferably, the step (b) may be calculated to give a first access time to a child node having a large reception strength value.

Preferably, in step (b), a child node whose reception strength value is less than or equal to a preset threshold may not transmit a response message to its parent node.

Preferably, in step (d), each parent node including the top-level parent node divides the time allotted to it by the number of child nodes that have sent the response message to give its own child nodes different unique transmission times. Can be assigned.

A second aspect of the present invention provides a recording medium having recorded thereon a program for executing the network recognition and configuration method in the above-described sensor network environment.

According to the network recognition and configuration method in the sensor network environment of the present invention as described above, by assigning a unique time for each node in the sensor network to generate all the node connections recognizable within the RF range to configure the network, The path recognition rate can be increased, and the number of unconnected nodes in the sensor network can be effectively reduced.

In addition, according to the present invention, there is an advantage that can result in greater energy reduction and transmission reliability increase in the sensor network field that requires the formation of a precise network and fixed installation applications that do not consider the movement.

In addition, according to the present invention, by guaranteeing the temporal uniqueness of the advertising message generated by each node for network recognition, it is possible to provide an environment that can be received without generating internal radio interference and other operations to all nodes within the RF range, Recognized paths are provided in the network as information of routing path determination and bypass path selection, so that the network routing protocol can perform more efficient and reliable path selection.

In addition, according to the present invention, by applying a reception strength (RSSI) value to the access order of each node, by giving the highest probability of access to the most stable path, the probability that the main path to configure the routing in the network is increased. There is an advantage to this.

In addition, according to the present invention, it is possible to increase the path recognition rate of each node, that is, the number of recognized paths per node, and also to reduce the number of unconnected nodes in the sensor network, and in particular, to recognize the main routing path. An increase in the success rate can be obtained, and the increase in the number of connection nodes and connection paths has the advantage of allowing more routing paths to be considered in the routing algorithm, thereby effectively reducing the network routing costs between operations.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention illustrated below may be modified in many different forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

1 is a conceptual diagram schematically showing a sensor network configuration for implementing a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention, Figure 2 is a sensor network environment in accordance with an embodiment of the present invention This is a conceptual diagram for explaining the operation state by time for the network recognition and configuration method.

1 and 2, a sensor network for implementing a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention is based on a sink node (S) as one top node. Thus, the first to fifth sensor nodes A to E, each of which includes at least one parent and child node, are configured in a tree form.

Here, the "parent node" is a node directly connected to the upper part of each node, for example, the parent node of the fourth and fifth sensor nodes (D and E) becomes the second sensor node (B), the first The parent node of the third to third sensor nodes A to C becomes the sink node S. FIG. Therefore, in the broadest sense, the lowest nodes, that is, nodes above the fourth and fifth sensor nodes D and E, may both be parent nodes.

On the other hand, the "child node" is a node directly connected below each node, for example, the child node of the sink node (S) becomes the first to third sensor nodes (A to C), the second sensor node The child node of (B) becomes the fourth and fifth sensor nodes D and E. Therefore, in the broadest sense, the highest node, that is, the node existing below the sink node S, may be child nodes.

Hereinafter, a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention will be described in detail.

First, after installing a plurality of sensor nodes in a desired location, the sink node S, which is a top node that receives a command to start network recognition from a user, has its own network information (or node information) required for recognition. Send a broadcast (broadcast) (recipient not specified).

At this time, among the information included in the advertisement message is required in the present invention (Round) (that is, a value synchronized in the network, and calculates the time when one recognition operation occurs in one cycle.) Field One, and other information will be necessary information for the routing protocol to be used by the sensor network, which may be different depending on the routing algorithm.

Subsequently, the child node receiving the broadcasted advertisement message calculates the access time to the corresponding parent node according to the strength of the received strength of the received advertisement message (RSSI), and responds to the corresponding access time. By transmitting, each parent and child node get each other information necessary for routing protocol and the path is recognized.

That is, the child node receiving the broadcast message transmitted from the sink node S, which is the highest node, measures the strength of the received strength message (RSSI) value of the received advertisement message, calculates the access time to the corresponding parent node. Calculate

Referring to FIG. 2, the time before the end of the access time from (T21) to (T22) after the transmission of the advertisement message is small from (T21) when the reception strength (RSSI) value is large along the time axis ( Divides the range up to T22), and attempts to transmit a response to the parent node at the access time calculated according to its received strength (RSSI) value.

All response times are between (T21) and (T22). In addition, since the response time is generated according to the reception strength (RSSI) value, a child node having the same reception strength (RSSI) value may occur, or duplication of access time may occur due to other delays. In this case, a random random interval after the failure is attempted to send a response again.

For example, referring to the example of calculating the access time, if "(T21) has a time of 1.0, (T22) has a time value of 1.2, and the receivable RSSI intensity according to the RF chip is -100 to 0 [dBm]. And there is no threshold setting of RSSI. ", If the received RSSI is -80 [dBm], the access time is 1.16.

On the other hand, the reason for giving priority to the child node having a large reception strength (RSSI) value is that the child node having a large reception strength (RSSI) value is more likely to be a physically adjacent child node, which directly affects the transmission / reception success rate. As a result, there is a high probability of being an efficient and highly reliable path to be considered first when selecting a routing path, thereby increasing the probability of generating a connection by giving more responsive transmission opportunities.

When the path recognition is completed, the child nodes have information of the corresponding parent node through the broadcasted advertisement message, and each parent node knows the information of the corresponding child nodes by receiving a response transmission from the corresponding child nodes. Here, the number of child nodes that respond is essential for the next step.

After the path recognition is performed as described above, each parent node allocates a unique time to transmit each advertisement message for recursively repeating the path recognition function based on its own child nodes.

That is, as a part corresponding to (T23) of FIG. 2, each parent node transmits an advertisement message based on the child node to all the child nodes, that is, assigning a unique transmission time that guarantees uniqueness in the entire sensor network. Proceed.

Meanwhile, the entire time T24 shown in FIG. 2 is called a slot in the present invention, and one slot becomes the minimum unit including all operations T20 to T23 required in the path recognition step.

Referring to FIG. 1, the sink node S, which is the highest node, has three first to third sensor nodes A to C as direct child nodes. The sink node S is "1/1" as in (T10), the first sensor node A is "1/3" as in (T11), and the second sensor node B is (T12) and As shown in (T13), the third sensor node C has an assigned unique transmission time of "3/3" as shown in (T13).

Here, the denominator "1" in the time "1/1" allocated to the sink node S, which is the most significant node, means that the time of the molecule "1" of the time of "1", which is a continuous infinite time Is divided into a unit of "1" and means a time corresponding to "1" within each divided unit. In addition, since the total size of the divided unit is "1", that is, all the time is allocated to the sink node (S).

For example, in the case of the second sensor node B, "2/3" to "3" is an infinite time divided by the unit of "3", and "2" is the second time in the divided unit. It means that it is assigned to the sensor node (B).

That is, each parent node including the top node sink node S allocates its own time by dividing its own time by the number of child nodes, that is, the number of child nodes that sent a response to the corresponding access time. will be. Here, it should be noted that "x / y" does not mean dividing one slot internally, but "x" slot among "y" slots, which is a method of not dividing a certain time internally.

Figure 1 shows the time allocated through the repetition of the process as shown above, basically after the transmission of the advertising message of each parent node, the time allocation for the response of the child node is made between the child node and the parent node No overlap of the advertised hours occurs.

In addition, the fact that each parent node allocates time to the child node may mean that each parent node passes the right of the time to the child nodes. In addition, sibling nodes such as the first sensor node A and the second sensor node B of FIG. 1 do not have time overlapping regardless of their hops after the initial time allocation is different. . This is because the time each parent node allocates to the child node is a subset of the time allocated to it.

Meanwhile, the round among the fields transmitted through the path recognition process is used to calculate the allocation time and has a value of 1 as one slot time passes. This is the synchronized value of child nodes recognized in the sensor network. A method of calculating its own slot time (unique time) using the assigned value and the transmitted period value is shown in Equation 1 below.

Period% denominator == numerator

When the above Equation 1 is satisfied, it becomes the operation slot time of the corresponding child node. However, "%" is a remainder operation and "==" means a comparison operation.

In the example of "3/3" in the third sensor node C of FIG. 1, since "R% 3 == 3", when the period becomes a multiple of 3, the intrinsic slot time is the fourth sensor. In the case of "2/6" in the node D, the "2" th time becomes the unique slot time of the fourth sensor node D during the time division of "6" units by "R% 6 == 2". .

On the other hand, the allocation operation in the above-mentioned assignment process of the unique transmission time is assigned by a simple operation by using the number of child nodes received a response message to the numerator and denominator value of the time in (T23) of FIG. Will be That is, the formula for calculating the specific value is shown in Equation 2 below.

"는 연속된 무한한 시간을 "y"라는 단위로 나누고 각 분할된 단위 내에서 "x"번째에 해당하는 시간을 의미하고, "B*M"은 자식노드에게 할당되는 분모의 값이며, "A+(N*B)"는 자식노드에게 할당되는 분자의 값이다.here, "

"" Divides the infinite infinite time into "y" units and means the "x" time within each divided unit, "B * M" is the value of the denominator assigned to the child node, and "A + (N * B) "is the value of the molecule assigned to the child node.

In addition, A is the value of the numerator assigned by the current node, B is the value of the denominator assigned by the current node, M is the total number of child nodes that sent the response message, and N (0≤N≤M-1, Parent node randomly assigned from 0 to M-1 in the order of access) means the unique number of the child node that sent the response message.

When the value calculated by Equation 2 is transmitted to the child nodes, all child nodes are given a time corresponding to a subset of the allocation time held by the parent node, thereby ensuring uniqueness of all child nodes. Advertising message transmission time (that is, unique transmission time) is guaranteed.

After that, each child node performs network recognition by recursively repeating the advertisement message transmission at the assigned unique transmission time, and the recognition process is recursively until the parent node does not receive a response message after transmitting the advertisement message. Is repeated.

As such, in the case of a node that does not receive any response after the broadcast of the advertisement message, the end-of-recognition message is reported to the parent node (assigned node). When receiving the termination report, recursively repeats the operation of reporting termination to its parent parent node. As a result, when the sink node S, the highest node, receives the termination report, all nodes in the sensor network receive the termination report. This means that the transmission is completed, so that the recognition process is completed.

In addition, the present invention can be used in a multi-channel environment. That is, the method of the present invention is applied to a sensor network environment using a multi-channel to receive a preferred channel reference for each node, and transmit a multi-channel transmission node.

3 is a conceptual diagram illustrating an application state in a multi-channel to a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention.

Referring to FIG. 3, in the method of applying the present invention to a multi-channel, all nodes search for a channel and receive RX (receive) as the most preferred channel before recognition is started in the step of installing a plurality of sensor nodes at a desired position. Stand-by), and the broadcast transmission operation of the advertisement message, which is the step (T20) of FIG. 2, may be performed by executing all channels.

In this way, a slot having a multi channel support format will be as shown in FIG. 3 (T30). In this case, the fields coming and going in the broadcast transmission and path recognition process of the advertisement message from the sink node (S), which is the top node, need to include the reception channel information of each node and will also be required as routing information.

In addition, if the RF chip supports a carrier sensing function, it is possible to increase the probability of avoiding collision by performing carrier sensing when transmitting the response of the above-described path recognition step.

In addition, in the above-described path recognition step, a threshold value of a reception strength (RSSI) value is set in advance so as not to transmit a response for reception below a threshold value. You can also add ways to reduce the burden depending on the requirements of your sensor network system.

In addition, the present invention is an algorithm for a network recognition and configuration method for the first time in the field of sensor networks, and is generally applicable to all sensor networks undergoing a process of recognizing the network after the sensor node is installed or sprayed.

On the other hand, the network recognition and configuration method in the sensor network environment according to an embodiment of the present invention can also be implemented as computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored.

For example, the computer-readable recording medium may be a ROM, a RAM, a CD-ROM, a magnetic tape, a hard disk, a floppy disk, a removable storage device, a nonvolatile memory (Flash memory). Optical data storage, and the like, and also implemented in the form of a carrier wave (eg, transmission over the Internet).

The computer readable recording medium can also be distributed over computer systems connected over a computer network so that the computer readable code is stored and executed in a distributed fashion.

While a preferred embodiment of a network recognition and configuration method in a sensor network environment according to the present invention has been described above, the present invention is not limited thereto, but the scope of the claims and the detailed description of the invention and the accompanying drawings are various. It is possible to carry out the transformation by the branch and this also belongs to this invention.

1 is a conceptual diagram schematically showing a sensor network configuration for implementing a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention.

2 is a conceptual diagram illustrating a time-by-hour operation state for a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention.

3 is a conceptual diagram illustrating an application state in a multi-channel to a network recognition and configuration method in a sensor network environment according to an embodiment of the present invention.

Claims (7)

In a sensor network environment in which at least one parent and child node are formed in a tree form based on one top-level parent node, (a) the top-level parent node transmitting a broadcast message including its node information; (b) a child node receiving the transmitted advertisement message, respectively, calculating an access time to its parent node according to a received strength value of the corresponding advertisement message; (c) each child node transmitting a response message to its parent node at the calculated access time, acquiring information necessary for a routing protocol, and performing path recognition; (d) assigning a unique transmission time to each parent node, including the top-level parent node, to transmit an advertisement message based on the child node to its child nodes; (e) each child node recursively transmitting the advertisement message repeatedly at the unique transmission time; And (f) When each parent node does not receive any response message from its child nodes, it recursively transmits an end-of-recognition message to its parent parent node that allocated the corresponding transmission time to the top-level parent node. Network recognition and configuration method in the sensor network environment comprising the step of delivering. The method of claim 1, The node information is a value synchronized with the network, and includes round information obtained by calculating a time at which one recognition operation occurs in one cycle and information necessary for a routing protocol. Way. The method of claim 1, The step (b) is a network recognition and configuration method for a sensor network environment, characterized in that the calculation to give the first access time to the child node having a large reception strength value. The method of claim 1, In step (b), a child node whose reception strength is less than or equal to a preset threshold does not transmit a response message to its parent node. The method of claim 1, In step (d), each parent node including the top-level parent node divides the time allocated to it by the number of child nodes that have sent the response message, and allocates different unique transmission times to its own child nodes. Network recognition and configuration method in the sensor network environment characterized in that. The method of claim 1, In the step (d), the unique transmission time is assigned to each of the following equation (3), the network recognition and configuration method in the sensor network environment.

here,

Is the number of consecutive infinite times divided into y units and means the xth time within each divided unit, A is the value of the numerator assigned to the current node, B is the value of the denominator assigned by the current node , M is the total number of child nodes that sent the response message, and N (0≤N≤M-1, the parent node randomly assigned from 0 to M-1 in the order of access) is the child node that sent the response message Means a unique number. A non-transitory computer-readable recording medium having recorded thereon a program capable of executing the method of any one of claims 1 to 6.

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