KR20090128274A - Method for measuring mobile node position in wireless sensor networks - Google Patents

Abstract

PURPOSE: A method for measuring a mobile node position in wireless sensor networks is provided to calculate the location information of a mobile node using a reference node weighted value having a minimum measurement error and to measure the exact location of the mobile node. CONSTITUTION: The number of a reference node corresponding to an initial distance measurement value is counted(204). A virtual distance measurement value corresponding to the number of the counted reference node is generated(214). A middle distance measurement value and a middle location measurement value are calculated using the linear combination of the generated virtual distance measurement value and the initial distance measurement value. Using a calculated measurement error, a reference node weighted value is calculated(218). The location information of a mobile node is calculated(222).

Description

How to measure the position of a mobile node in a wireless sensor network {METHOD FOR MEASURING MOBILE NODE POSITION IN WIRELESS SENSOR NETWORKS}

The present invention relates to a method of measuring a position of a mobile node in a wireless sensor network and a computer-readable recording medium recording a program for realizing the method. More particularly, the present invention relates to an initial distance measurement value obtained from a wireless sensor network. Inaccurate initial distance measurement value by improving the measurement error of the initial distance measurement value by using different virtual distance measurement values according to the number of reference nodes and calculating position information of the mobile node using the weight of each reference node having the minimum measurement error. A computer-readable recording medium recording a method for measuring the position of a mobile node in a wireless sensor network and a program for realizing the method, capable of accurately measuring the position of the mobile node with low complexity regardless of the number of reference nodes. It is about.

Advances in wireless communications and microelectronics technology have enabled wireless sensor networks between low-cost, ultra-small sensors. The wireless sensor network can be applied to various applications such as safety and security, environmental ecological monitoring, intelligent transportation system, automatic control of production process, warehouse logistics, and disaster relief.

In particular, the location information of the mobile node in the wireless sensor network is very important and needs to be basically provided. For example, among the recent applications of wireless sensor networks, sensor devices that are attached to patients for remote diagnosis of patient conditions in hospitals, sensor devices that are attached for safety to those who work in potentially dangerous industrial sites, or accessors Sensor devices for asset management and the like need to accurately measure accurate location information in order to accomplish their individual tasks in wireless sensor networks.

On the other hand, because of its inherent mobility, the mobile node (mobile sensor node) frequently changes its position in the operating environment. Therefore, the location should be able to be measured from time to time or in real time according to the needs of the application environment.

Such location information measurement technology includes a technology using a general location information measurement device. Global Positioning System (GPS) receivers, as is well known, are technologies that meet this need and provide highly accurate location information. The GPS receiver receives visual information of three or more satellites and estimates their time difference and estimates the receiver's instantaneous geographical position, or global coordinates, based on that distance. Although somewhat different depending on the receiving environment of the GPS receiver, location information with a tolerance of about 20 m may be measured in the GPS receiver. GPS receivers are quite effective outdoors because they are capable of receiving satellite signals. However, there is a drawback that the technology using the GPS receiver cannot be an effective technology for the indoor environment or an application service system requiring higher accuracy.

Due to such limitations in application and low accuracy, wireless sensor networks generally use a method for measuring the position of a mobile node (target node) by itself without using an external device.

In general, all sensor nodes deployed in a certain area have unique location information. In the sensor node called an anchor node or a reference node, geographical position information of each sensor node may be manually set at the initial stage of construction, or may be automatically set by a remote central server. On the other hand, a mobile node (target node) is attached to a movable object or person and is located at an arbitrary point at any point in the operating environment.

The method for measuring the position of the mobile node may be divided into a central measurement method and a variance measurement method according to a subject measuring the distance between the reference node and the mobile node.

First, referring to the central measurement method, these reference nodes periodically transmit or provide a message including their identification ID and location coordinates in a broadcast manner or unicast manner at the request of a neighbor node. The mobile node periodically receives all the location information of the surroundings and simultaneously measures the distance between each reference node and the mobile node. Here, the distance between the reference node and the mobile node is generally the received signal strength (RSS), time of arrival (TOA) or time of flight (TOF), arrival of a signal received from the reference node. It may be measured using a method such as TDOA (Time Difference of Arrival) or Angle of Arrival (AOA).

In addition, the variance measuring method, which is another operation method, is a method in which the mobile node periodically transmits its identification ID and the fixed-deployed reference node measures the distance from the mobile node.

In other words, as a position measurement method of the sensor network itself, the position measurement of the mobile node is performed at the mobile node itself in the case of the central measurement method, and in the case of the dispersion measurement method, all the distance measurement values measured by each reference node are collected. It is done at the central server.

On the other hand, as a representative position measuring method, the multilateration method uses the position information and the distance measurement of the reference node.

First, the multivariate survey method, which is a conventional positioning technique, generates a distance equation whose variables are unknown position coordinates of the mobile node with respect to the position information and distance measurement values of all received reference nodes, and linearizes them based on certain constraints. Next, the multivariate method calculates the optimal position information through a series of processes to equalize the terms including the unknown position coordinates and the constant terms and remove the constants of the terms. Here, as the number of distance measurement values increases, more accurate position data may be measured. Therefore, the position information of the mobile node may be determined as a coordinate value that minimizes the total sum of the measurement distance (measurement distance between the mobile node and the reference node) and the residual error of the estimated distance.

However, due to various obstacles installed in the field, especially in the indoor environment of the sensor network, there are considerable invisible distances and many multipaths between the mobile node and the reference node. The RF communication channel of such an operating environment has channel characteristics that vary in time such as fading, delay, interference, and noise. Therefore, there is a problem that a large error is included in the distance measurement estimated by each mobile node and the reference node.

The multivariate position measurement method, which is a conventional position measurement technique, may not only produce an optimal solution when the error is included in the distance measurement value, but may also cause a larger position error when the number of reference nodes is small. For example, the multivariate position measurement method does not yield any results when the number of reference nodes is two.

In a real operating environment, in addition to the characteristics of the RF communication channel, a plurality of reference node signals may be received depending on a region. In addition, the reference node signal changes according to network operation, such as receiving only three, two, or one signal. Therefore, considering the operating environment situation as well as the distance measurement error caused by invisible distance and channel fading, there is an urgent need for a method capable of accurately measuring the geographical position of the mobile node (target node).

Therefore, the prior art as described above has a problem that not only an optimal solution cannot be calculated when an error is included in the distance measurement, but also a larger position measurement error can be caused when the number of reference nodes is small. It is a subject of the present invention.

Accordingly, the present invention improves the measurement error of the initial distance measurement by using different virtual distance measurements according to the number of reference nodes corresponding to the initial distance measurement obtained in the wireless sensor network, and weights each reference node having the minimum measurement error. By calculating the position information of the mobile node using the method, the position measurement method of the mobile node in the wireless sensor network can accurately measure the position of the mobile node with low complexity regardless of the inaccurate initial distance measurement value or the number of reference nodes. And a computer readable recording medium having recorded thereon a program for realizing the method.

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 solve the problem, the present invention improves the measurement error of the initial distance measurement by using different virtual distance measurements according to the number of reference nodes corresponding to the initial distance measurement obtained in the wireless sensor network, and has a minimum measurement error. The location information of the mobile node is calculated using the weight of each reference node.

More specifically, the present invention provides a method for measuring a position of a mobile node, the method comprising: a reference node counting step of counting the number of reference nodes corresponding to an initial distance measurement obtained from the outside; Generating an intermediate distance measurement value and an intermediate distance measurement value by generating a virtual distance measurement value corresponding to the number of reference nodes and linearly combining the generated virtual distance measurement value and the obtained initial distance measurement value; A weight calculation step of calculating a measurement error based on the calculated intermediate position measurement value and the position information of the reference node and calculating a weight for each reference node using the calculated measurement error; And calculating position information of the mobile node using the calculated intermediate position measurement value and the calculated weight for each reference node.

The present invention may further include a previous position information checking step of checking whether the previous position information of the mobile node is available when the number of the counted reference nodes is less than a predetermined number. If the previous location information of the mobile node is not available, a weight for each reference node may be calculated using a ratio of the distance measurement value to the reference node less than the predetermined number.

On the other hand, the present invention, a mobile node position measurement system having a processor, the reference node counting function for counting the number of reference nodes corresponding to the initial distance measurement value obtained from the outside; An intermediate measurement calculation function of generating a virtual distance measurement value corresponding to the number of reference node counts and linearly combining the generated virtual distance measurement value and the obtained initial distance measurement value to calculate an intermediate distance measurement value and an intermediate position measurement value; A weight calculation function for calculating a measurement error based on the calculated intermediate position measurement value and the position information of the reference node and calculating a weight for each reference node using the calculated measurement error; And a computer-readable recording medium having recorded thereon a program for realizing a position information calculating function for calculating position information of the mobile node using the calculated intermediate position measurement value and the calculated weight for each reference node.

The present invention may further include a previous position information checking function for checking whether the previous position information of the mobile node is available when the number of the counted reference nodes is less than a predetermined number. And if a previous location information of the mobile node is not available, a computer-readable program having a program for realizing a function for calculating a weight for each reference node using a ratio of distance measurement values for the reference nodes less than the predetermined number. Provide a record carrier.

The present invention may further include a measurement error checking function for checking whether the calculated measurement error is minimum when the counted reference node number is a predetermined number, and the position when the calculated measurement error is minimum. A computer readable recording medium having recorded thereon a program for realizing the function of proceeding to an information calculating function and proceeding to the virtual distance measurement value generating function if the calculated measurement error is not minimum is provided.

In addition, the present invention, if the number of the counted reference node exceeds a predetermined number, the distance measurement value setting function to set the number of the counted reference node to the number of minimum distance measurement value and proceed to the virtual distance measurement value generation function ; A reference node set selection function for selecting a reference node set having a minimum mean square error by using the measurement error calculated in the weight calculation function; If it is determined whether the number of elements of the selected reference node set is the predetermined number, and if the identified number of elements is the predetermined number, the process proceeds to the position information calculating function, and if the number of identified elements is not the predetermined number A computer readable recording medium having recorded thereon a program for further realizing the function of generating a partial reference node set for generating a partial reference node set.

As described above, the present invention improves the measurement error of the initial distance measurement by using different virtual distance measurement values according to the number of reference nodes corresponding to the initial distance measurement obtained in the wireless sensor network, and for each reference node having a minimum measurement error. By calculating the position information of the mobile node using the weight, the position of the mobile node can be accurately measured with low complexity regardless of the incorrect initial distance measurement value or the number of reference nodes.

That is, in the present invention, the distance measurement value is alleviated or the distance measurement value is reduced through a refinement process of repeating a new generation of a virtual distance measurement value and arithmetic averaging of the distance measurement value received by a mobile node or a reference node. There is an effect that can provide an improvement in accuracy.

In addition, the present invention contributes to the position information of the mobile node through an iterative process of generating partial reference node sets and calculating intermediate position measurements and weights thereof based on a minimum distance measurement error (MSE). It is effective to select the reference node set with the minimum error among all reference node sets.

In addition, since the position information can be calculated as the weighted linear combination of the intermediate position measurement values of these reference node sets by their weights, the present invention has few reference nodes or various distance measurements such as noise, fading, and multipath. Even when an error is included and even when there are many reference nodes, there is an effect of providing a method of calculating and determining the position information of the mobile node with high accuracy with low complexity.

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.

1 is a configuration diagram of an embodiment of a sensor network and an application system to which the present invention is applied.

As shown in FIG. 1, the sensor network 110 and the application system 130 are connected through a broadband integrated network 120. Here, the sensor network 110 includes first to n th reference nodes 111 to 114, a mobile node 115, and a sink node 116. In addition, the application system 130 is connected to the user terminal 131, and is connected to the sink node 116 of the sensor network 110 through the broadband integrated network 120.

Referring to the sensor network 110 in detail, the first to n-th reference nodes 111 to 114 are fixed sensor nodes, and include unique reference node identifiers (IDs) and geographic location information mapped to the reference node IDs (for example, For example, position coordinate values).

Next, the mobile node 115 has a unique mobile node identifier (ID), and there is mobility that can be located at any point at any point in time. In addition, the mobile node 115 may be attached to people and objects that move continuously or from time to time (Nomadic).

The sink node 116 is a source of the sensor network 110 and simultaneously connects the sensor network 110 and a transmission network (for example, a broadband integrated network) that is a fixed network. The sink node 116 collects sensor data of a sensor node (for example, the first to n th reference nodes 111 to 114 or the mobile node 115), and collects the collected sensor data into the broadband integrated network 120. Transfer to the application system 130 through). In addition, the sink node 116 performs a function of transmitting a query of the application system 130 to the sensor node.

In contrast, the application system 130 connected to the broadband integrated network 120 provides a specific application service to the user through the user terminal 131 using the sensor data transmitted from the sink node 116.

On the other hand, the position measurement of the above-described mobile node 115 is divided into two cases depending on the subject and the operating method of the sensor network 110.

First, a case in which the mobile node 115 measures its position is as follows. First, the first to nth reference nodes 111 to 114 broadcast or unicast their IDs and position information (position coordinates). The mobile node 115 receives the transmitted reference node ID and the location information and measures the distance from the first to nth reference nodes 111 to 114.

Second, a case where the application system 130 measures the position of the mobile node 115 is as follows. First, the mobile node 115 broadcasts a message including its mobile node ID with a timestamp at the time of transmission. The first to n th reference nodes 111 to 114 receive the broadcasted message and measure the distance to the mobile node 115. The first to n th reference nodes 111 to 114 transmit their position information together with the measured distance measurement to the application system 130 through the broadband integrated network 120 via the sink node 116.

In short, the geographic location of the mobile node 115 depends on the subject and the manner in which the sensor network 110 operates. That is, the geographical position may be estimated by the mobile node 115 itself, or the geographical position may be measured by the positioning function of the application system 130.

2 is a flowchart illustrating a method for measuring a position of a mobile node in an application system according to the present invention.

The method for measuring the position of the mobile node 115 shown in FIG. 2 is based on the initial state of the first to n th reference nodes 111 to 114 transmitted by the application system 130 from the first to n th reference nodes 111 to 114. The present invention relates to a method of measuring the position of the mobile node 115 using distance measurement values and position information.

Application system 130 detects a location measurement event for mobile node 115 (202). The detected position measurement event may be periodically generated by a timer of the application system 130. In addition, the location measurement event may be generated as a query (Query) by the application module of the application system 130.

Subsequently, the application system 130 collects data information (eg, reference node ID or mobile node ID, time stamp, initial distance measurement and location information for the reference node, etc.) necessary for the location measurement and the collected data. The number N of reference nodes corresponding to the initial distance measurement value among the information is counted (204). The application system 130 collects initial distance measurement values and location information for the reference node for the location measurement event for a predetermined time.

If location measurement events for multiple mobile nodes exist at the same time, the application system 130 counts the number N of reference nodes collected for a certain time interval for each mobile node. That is, for the mobile node 115 to be measured, the application system 130 calculates the number N of position information of the reference node associated with the same mobile node ID and time stamp. In addition, when the number of mobile nodes is large, the application system 130 may count the number of reference nodes at time intervals that are independent of each other for each mobile node 115.

Application system 130 checks the number N of counted reference nodes (206). The application system 130 follows different procedures according to the number N of reference nodes for each mobile node. This procedure will be described separately according to the number of reference nodes (N).

First, if the check result 206, the number of counted reference nodes is two (N = 2), the application system 130 checks whether the previously calculated position information is available. If the calculated location information is not available, the application system 130 is based on the received data information of the first and second reference nodes 111 and 112 (the location information of the reference node and its initial distance measurement). A weight determination process is performed, and then position information of the mobile node 115 is calculated.

Second, if the check result 206, the number of the reference node is three (N = 3), the application system 130 performs the correction process and the weight calculation process of the initial distance measurement. The initial distance measurement correction process and the weight calculation process reduce the error of the initial distance measurement. This process is repeated until a minimum mean square error is obtained, based on the minimum mean square error (MSE), otherwise a fixed number of times. If the minimum mean square error is calculated or the number of iterations is completed, the application system 130 calculates the geographical position of the mobile node by performing a position information calculation process based on the intermediate position measurement value and the weight obtained in the weight calculation process. .

Third, if the check result 206, the number of the reference node is three (N> 3), the application system 130 sets the number (S) of the partial reference node set to the number (N) of the reference node and collects A process of correcting the initial distance measurement value and reducing the number of minimum distance measurement values (S) is performed so that the initial distance measurement value has higher accuracy. The application system 130 repeatedly calculates a partial reference node set having a minimum mean square error and its weight, which has a large influence on the estimation of the position of the mobile node, and then calculates accurate position information from the partial reference node set and its weight. .

In short, the location information calculation process depends on the number of reference nodes for each mobile node. Hereinafter, the process of calculating the location information will be described in detail.

As a result of the check 206, if the number N of reference nodes is two, the application system 130 checks whether the previously calculated position information is available (208). Here, the available case is when the period is considerably shorter in periodic positioning by a timer (eg, usually within a few seconds, but may be chosen differently depending on the application model).

,

)를 결정한다(210). 즉, 참조노드(111)의 전체 개수(K)가 2개이고 이전에 산출된 위치정보가 이용가능하지 않다면, 제1 및 제2 참조노드(111 및 112)에 대한 가중치(

,

)는 제1 및 제2 참조노드(111 및 112)에 대한 거리측정치의 비율로서 정의된다. 제1 및 제2 참조노드(111 및 112)의 위치정보가 각각

이고 그에 대한 초기 거리측정치가 각각

이면, 제1 및 제2 참조노드(111 및 112)에 대한 가중치(

,

)는 하기의 [수학식 1]과 같다.If the check result 208, the previously calculated position information is not available, the application system 130 uses the distance measurement ratio for the first and second reference nodes 111 and 112, 1] as the reference node weight (

,

(210). That is, if the total number K of the reference nodes 111 is two and previously calculated location information is not available, the weights for the first and second reference nodes 111 and 112 (

,

Is defined as the ratio of the distance measurement to the first and second reference nodes 111 and 112. The location information of the first and second reference nodes 111 and 112 is respectively

And the initial distance measurements for

, Weights for the first and second reference nodes 111 and 112 (

,

) Is as shown in Equation 1 below.

및

는 제1 참조노드에 대한 초기 거리측정치,

및

는 제1 및 제2 참조노드에 대한 가중치를 나타낸다.here,

And

Is the initial distance measurement for the first reference node,

And

Denotes weights for the first and second reference nodes.

,

)를 이용하여 이동노드(115)의 위치정보를 산출한다(212). 참조노드(111 및 112)의 개수가 두 개이고 이전에 산출된 위치정보가 이용가능하지 않다면, 응용시스템(130)은 제1 및 제2 참조노드에 대한 가중치(

,

)와 제1 및 제2 참조노드(111 및 112)의 위치정보(

)를 하기의 [수학식 2]에 적용하여 이동노드(115)의 위치정보(

)를 산출한다.In addition, the application system 130 may determine a weight value for the first and second reference nodes.

,

In operation 212, position information of the mobile node 115 is calculated. If the number of reference nodes 111 and 112 is two and the previously calculated location information is not available, the application system 130 may determine the weights for the first and second reference nodes.

,

) And location information of the first and second reference nodes 111 and 112 (

) Is applied to the following [Equation 2] position information of the mobile node 115 (

) Is calculated.

은 이동노드의 위치정보,

,

는 제1 및 제2 참조노드의 위치정보를 나타낸다.here,

Is the location information of the mobile node,

,

Denotes location information of the first and second reference nodes.

Equation 2 is a result of estimating the position of the mobile node 115 based on two initial distance measurements. As a result, it is estimated that the mobile node 115 is located on a straight line where the position coordinates of the first and second reference nodes 111 and 112 are connected to each other.

)는

로서 정의된다.On the other hand, if the check result 208, the previously calculated position information is available, the application system 130 is "214" which is a process of generating a virtual distance measurement value for the case that the number of reference nodes is 3 (N = 3) Perform the process. Here, the previously calculated position information is newly set as position information of a new third reference node. In addition, the distance measurement value for the newly set third reference node 113 (

)

It is defined as

)의 초기(미정(未精)) 거리측정치(

)에 대해, 각 초기 거리측정치에 대한 간접적인 거리인 가상 거리측정치(

)를 산출한다(214). 응용시스템(130)은 하기의 [수학식 3] 내지 [수학식 8]과 같이, 선형화 최소자승 기법을 이용하여 참조노드의 초기 거리측정치로부터 이동노드의 가상 위치측정치를 산출하고, 산출된 이동노드의 가상 위치측정치와 참조노드의 위치 간 거리차를 이용하여 가상 거리측정치(

)를 생성한다. 여기서, 간접적인 거리 산출은 가상 거리측정치(

)를 의미하며, 초기 거리측정치(

)에 대한 정확도를 개선하기 위함이다. 하기의 [수학식 3] 내지 [수학식 8]을 참조하여 가상 거리측정치(

)의 산출 과정을 살펴보기로 한다.On the other hand, if the check result 206, the number of reference nodes (N) is three, the application system 130 is a reference node set selected by a predetermined criterion among the initial distance measurement collected in the process "204" (

Initial (undecided) distance measurement of

), A virtual distance measure (indirect distance to each initial distance measure)

Is calculated (214). The application system 130 calculates the virtual position measurement value of the mobile node from the initial distance measurement value of the reference node by using the linearized least squares technique, as shown in Equations 3 to 8 below, and calculates the calculated mobile node. The virtual distance measurement value is calculated by using the distance difference between the virtual position measurement

) Here, the indirect distance calculation is a virtual distance measurement (

), The initial distance measurement (

To improve accuracy). With reference to [Equation 3] to [Equation 8] below the virtual distance measurement value (

Let's look at the calculation process of.

는 초기 거리측정치,

는 참조노드의 위치좌표,

및

는 이동노드의 초기 위치좌표를 나타낸다.here,

Is the initial distance measurement,

Is the position coordinate of the reference node,

And

Denotes the initial position coordinate of the mobile node.

)에 대해, 각각의 참조노드와 이동노드(115) 간의 거리측정치에 대한 거리방정식은 하기의 [수학식 4]와 같이 정리된다.Reference node set selected by a certain standard

), The distance equation for the distance measurement between each reference node and the mobile node 115 is summarized as Equation 4 below.

As a constraint for linearization of the least-squares method, when the distance equation for the k-th reference node is applied to Equation 4 above, a linearized distance equation such as Equation 5 below is obtained.

및

는 k번째 참조노드의 위치좌표를 나타낸다.here,

And

Denotes the position coordinate of the kth reference node.

)를 산출한다. 즉, 상기의 [수학식 5]를 벡터형식으로 표현하고 양변을 정리하면, k번째 참조노드를 제한조건으로 하는 가상 위치측정치(

)는 최소자승 기법에 따라 하기의 [수학식 6]과 같이 산출된다.The application system 130 is a constraint for the linearization of the least-squares technique. The application system 130 uses the distance equation for the k-th reference node to calculate the virtual position measurement (

) Is calculated. In other words, if Equation 5 is expressed in a vector form and both sides are arranged, a virtual position measurement value having the k th reference node as a constraint condition (

) Is calculated according to Equation 6 below according to the least-squares technique.

Here, T represents a transpose of the matrix.

와 행렬

는 각각 (K-1)×2 행렬과 (K-1)×1 행렬로서, 하기의 [수학식 7]과 같이 표현된다.procession

And matrix

Are (K-1) x 2 matrices and (K-1) x 1 matrices, respectively, and are expressed as shown in Equation 7 below.

와 행렬

는

인 요소를 포함하지 않는다.Where matrix

And matrix

Is

Does not contain the element

은,

의 차원이 3인 경우에는 선형적인 역행렬을 통해 계산되고, 그 차원이 3을 초과한 경우에는 행렬

의 무어-펜로즈 의사 역(Moor-Penrose pseudo inverse) 행렬을 통해 계산된다.Determinant in Equation 6 above

silver,

If the dimension of is 3, the linear inverse is calculated. If the dimension exceeds 3, the matrix is calculated.

Calculated by the Moor-Penrose pseudo inverse matrix.

)는 k번째 참조노드를 제한조건으로 하는 가상 위치측정치(

)와 초기 거리측정치(

)가 하기의 [수학식 8]에 적용되어 계산된다. 그러므로 응용시스템(130)은 이동노드(115)의 가상 위치측정치와 참조노드(111)의 위치 간의 거리로서 가상 거리측정치(

)를 산출한다.Therefore, the virtual distance measurement (

) Is a virtual position measurement (

) And the initial distance measurement (

) Is calculated by applying to Equation 8 below. Therefore, the application system 130 may determine the virtual distance measurement value as the distance between the virtual position measurement of the mobile node 115 and the position of the reference node 111.

) Is calculated.

는 가상 거리측정치,

및

는 이동노드의 가상 위치측정치의 위치좌표를 나타낸다.here,

Is a virtual distance measure,

And

Denotes the position coordinate of the virtual position measurement of the mobile node.

)를 생성하는 "214" 과정은 모든 k 즉,

에 대해서 반복된다.Virtual distance measure (

"214" process for every k, i.e.

Is repeated for.

로서 정의된 참조노드집합에 대해 수행된다.If the total number K of the reference nodes 111 is 2 and the previous position measurement is valid, the process "214" sets the previous position value to be the position coordinate of the third reference node and the distance measurement value therefor.

It is performed on the reference node set defined as.

)와 초기 거리측정치(

)를 선형결합하여 중간 거리측정치(

)를 산출한다(216). 이는 초기 거리측정치(

)에 대한 정확도를 향상시키고, 잡음 및 간섭 등의 원인에 대한 거리오차를 완화하기 위함이다. "216" 과정을 구체적으로 살펴보면, 응용시스템(130)은 가상 거리측정치(

)와 초기 거리측정치(

)에 대한 산술평균치를 하기의 [수학식 9]와 같이 산출한다.On the other hand, the application system 130 is the virtual distance measurement value generated in the "214" process (

) And the initial distance measurement (

) By linearly combining the intermediate distance measurements (

Is calculated (216). This is the initial distance measurement (

This is to improve the accuracy of), and to mitigate the distance error for the sources of noise and interference. Looking specifically at the "216" process, the application system 130 is a virtual distance measurement (

) And the initial distance measurement (

The arithmetic mean value for) is calculated as shown in Equation 9 below.

는 중간 거리측정치,

는 가상 거리측정치를 나타낸다.here,

Is the intermediate distance measurement,

Represents a virtual distance measurement.

)와 참조노드(111)의 위치정보(

)를 이용하여 중간 위치측정치(

)를 산출한다. 그리고 응용시스템(130)은 중간 위치측정치(

) 및 참조노드의 위치정보를 기초로 하여 측정오차를 산출하고 그 산출된 측정오차를 이용하여 참조노드별 가중치(

)를 산출한다(218).The application system 130 then measures the intermediate distance (

) And the location information of the reference node 111 (

With the intermediate position measurement (

) Is calculated. And the application system 130 is the intermediate position measurement (

) And the measurement error is calculated based on the location information of the reference node and the weight of each reference node (

Is calculated (218).

)와 참조노드(111)의 위치정보(

)로부터 가장 큰 거리측정치(

)인 최단 거리방정식을 구한다. 그리고 응용시스템(130)은 그 가장 큰 거리측정치(

)의 최단 거리방정식을 제한조건을 이용하는 선형화 최소자승 기법에 따라 중간 위치측정치(

)를 하기의 [수학식 10]과 같이 산출한다.Specifically, the application system 130 is a distance measurement (

) And the location information of the reference node 111 (

Largest distance measurement from

Find the shortest distance equation And the application system 130 has the largest distance measurement (

The intermediate position measurement () according to the linearized least-squares method using the constraint of the shortest distance equation

) Is calculated as shown in Equation 10 below.

와 행렬

는 (K-1)×2와 (K-1)×1인 행렬로서, 하기의 [수학식 11]과 같이 표현된다.Where T represents the transpose of the matrix,

And matrix

Are matrixes of (K-1) × 2 and (K-1) × 1, and are expressed as shown in Equation 11 below.

와 행렬

에서

인 요소는 포함되지 않고,

는 가장 큰 거리측정치,

와

는 가장 큰 거리측정치(

)와 관련된 참조노드의 위치정보를 나타낸다.procession

And matrix

in

Element is not included,

Is the largest distance measure,

Wow

Is the largest distance measurement (

) Indicates location information of the reference node.

)를 산출한다. 응용시스템(130)은 이동노드(115)의 중간 위치측정치(

), 중간 거리측정치(

) 및 참조노드(111)의 위치정보(

)로부터 하기의 [수학식 12]와 같이 계산된 거리차의 합을 이용하여 가중치(

)를 위한 거리측정오차인 평균제곱오차(MSE)를 계산한다.The application system 130 calculates the mean square error and inversely proportions to the measurement error.

) Is calculated. The application system 130 may measure the intermediate position of the mobile node 115 (

), The intermediate distance measurement (

) And location information of the reference node 111 (

) By using the sum of the distance differences calculated as in Equation 12 below.

Calculate the mean square error (MSE), which is the distance measurement error for.

는 평균제곱오차,

는 중간 위치측정치,

및

는 중간 위치측정치의 위치좌표를 나타낸다.here,

Is the mean squared error,

Is an intermediate position measurement,

And

Indicates the position coordinate of the intermediate position measurement value.

)를 하기의 [수학식 13]과 같이 참조노드집합의 크기로 정규화한 값으로 결정한다. 즉, 응용시스템(130)은 중간 위치측정치와 참조노드 위치 간 평균제곱오차(MSE)를 하기의 [수학식13]과 같이 참조노드집합의 개수로 정규화한다.Therefore, the application system 130 is weighted (

) Is determined as a value normalized to the size of the reference node set as shown in [Equation 13] below. That is, the application system 130 normalizes the mean square error (MSE) between the intermediate position measurement value and the reference node position by the number of reference node sets as shown in Equation 13 below.

는 참조노드집합의 크기를 나타낸다.here,

Denotes the size of the reference node set.

)는

로 대체된다. 반면, 정해진 횟수 동안의 반복 수행 과정에서, 중간 거리측정치(

)만이

로 대체된다.Application system 130 checks whether the mean square error (MSE) is the minimum (220). If the check result 220, the mean square error (MSE) is not the minimum, the application system 130 performs again from the "214" process. That is, the application system 130 repeatedly performs "214" to "220" process until the mean square error (MSE) is minimum or for a predetermined number of iterations. The processes "214" to "220" are performed when the minimum mean square error (MSE) is used as a reference to reduce the error of the distance measurement. Here, if the number of iterations is the first in the iteration process of finding the minimum mean square error (MSE), the mean square error (MSE) is set to the minimum value and the intermediate distance measurement value (

)

Is replaced by. On the other hand, during the repetition process for a predetermined number of times, the intermediate distance measurement (

Only

Is replaced by.

) 및 그 가중치(

)를 기초로 하여 이동노드(111)의 위치정보를 산출한다(222). 즉, 응용시스템(130)은 중간 위치측정 치(

) 및 그 가중치(

)에 의한 정규화 선형결합을 이용하여 하기의 [수학식 14]와 같이 이동노드(115)의 위치정보를 산출한다. 여기서, 위치정보는 지리적 위치좌표일 수 있다. 이러한 이동노드(115)의 위치정보는 참조노드의 전체 개수(K)가 두 개이고 이전에 산출된 위치정보가 이용가능한 경우, 또는 참조노드의 전체 개수(K)가 세 개 이상인 경우에 하기의 [수학식 14]와 같이 구해진다.On the other hand, if the check result 220, the mean square error (MSE) is the minimum, the application system 130 is the intermediate position measurement (

) And its weight (

Based on the position information of the mobile node 111 is calculated (222). That is, the application system 130 is the intermediate position measurement value (

) And its weight (

Using the normalized linear combination by) to calculate the position information of the mobile node 115 as shown in Equation 14 below. Here, the location information may be geographic location coordinates. The location information of the mobile node 115 is described below when the total number K of reference nodes is two and the previously calculated location information is available, or when the total number K of reference nodes is three or more. (14) is obtained.

는 이동노드의 위치정보,

는 k번째 참조노드를 제한조건으로 하는 중간 위치측정치,

는 k번째 부분 참조노드집합,

은 "218" 과정에서의 개별 가중치 산출을 위해 고려된 참조노드집합의 개수를 나타낸다.here,

Is the location information of the mobile node,

Is an intermediate position measurement with the k th reference node as the constraint,

Is the kth partial reference node set,

Denotes the number of reference node sets considered for calculating individual weights in the process of "218".

In the above Equation 14, each weight of the numerator lowers the ratio of the intermediate position measurement with a large error and considers the fact that each reference node set has a different importance and contributes to the mobile node positioning result. This is to increase the ratio of the intermediate position measurement. The normalization of the denominator weights in Equation (14) can make all the magnitudes of the errors relative.

On the other hand, if the check result 206, the number of reference nodes (N) is three or more (N> 3), the application system 130 is the number of reference nodes (N) as the number of minimum distance measurement (S) Set 224.

)를 산출하고, 그 산출된 가상 거리측정치(

)와 초기 거리측정치(

)에 대한 선형결합 과정을 수행한다. 여기서, "226" 과정은 2회 연속적으로 반복되는 것으로 제한할 수 있다. 횟수 제한은 여러 과정으로 나뉘어 있는 후속 처리 과정의 처리시간 및 부하를 고려해서, 평균제곱오차(MSE)의 1차적인 완화를 이루기 위한 것이다. 2번째 처리 과정이 반복될 때, 중간 거리측정치(

)는 가상 거리측정치를 생성하는 과정을 위해 1차 갱신된 초기 거리측정치(

)로 대체된다. 즉,

와 같이 설정된다.And so that the initial distance measurement has a higher accuracy, the application system 130 generates the virtual distance measurement and calculates the intermediate distance measurement in the same manner as the procedures "214" and "216" (226). That is, the application system 130 is a virtual distance measurement (

), And the calculated virtual distance measurement (

) And the initial distance measurement (

Perform a linear combination process for Here, the process "226" may be limited to being repeated twice in succession. The number limit is intended to achieve first order mitigation of the mean square error (MSE), taking into account the processing time and load of subsequent processes that are divided into processes. When the second process is repeated, the intermediate distance measurement (

) Is the first updated initial distance measure (

Is replaced by). In other words,

Is set as follows.

)를 산출하고, 그 산출된 중간 위치측정치를 이용하여 평균제곱오차(MSE), 및 그 가중치를 산출한다(228). 즉, 최소 거리측정치의 개수(S)가 참조노드의 개수(N)인 경 우(S=N)에, 응용시스템(130)은 "226" 과정에서 산출된 중간 거리측정치(

)와, "228" 과정에서 산출된 중간 위치측정치(

)를 이용하여 평균제곱오차(MSE) 및 가중치를 산출한다. "228" 과정은 이동노드(115)의 위치추정에 큰 영향을 미치는 즉, 최소 평균제곱오차(MSE)를 가진 부분 참조노드집합에 대해 반복적으로 수행된다. 여기서, 구해진 평균제곱오차(MSE)가 최소 평균제곱오차(MSE)로 설정된다. 평균제곱오차(MSE) 및 가중치 산출 과정은 S개의 부분 참조노드집합 각각에 대해 수행되고, 최소 평균제곱오차(MSE) 및 그와 관련된 부분 참조노드집합이 선정된다.In addition, the application system 130 uses the intermediate distance measurement value calculated in the process of "226" and uses the intermediate position measurement value (Equation 10] to [Equation 13] above.

), And the mean square error (MSE) and its weight are calculated using the calculated intermediate position measurement (228). That is, when the number S of the minimum distance measurements is the number N of the reference nodes (S = N), the application system 130 calculates the intermediate distance measurement values calculated in the process of "226".

) And the intermediate position measurements ("228")

) Is used to calculate the mean square error (MSE) and weight. The process " 228 " is repeatedly performed on the partial reference node set having a large influence on the position estimation of the mobile node 115, i.e., having the minimum mean square error (MSE). Here, the obtained mean square error MSE is set to the minimum mean square error MSE. The mean square error (MSE) and weighting process are performed for each of the S partial reference node sets, and the minimum mean square error (MSE) and its associated partial reference node sets are selected.

The application system 130 selects the reference node set having the minimum mean square error (MSE) using the calculated mean square error (MSE) (230).

The application system 130 checks whether the number S of the selected minimum distance measurements is three (232). That is, the process "232" is repeated until the number S of the minimum distance measurements is 3 (S = 3). Here, S = 3, that is, the number of three represents the minimum number of reference node sets that can be measured.

As a result of the check 232, if the number of selected minimum distance measurements (S) is not three, the application system 130 has a portion having a size as small as one for a reference node set having a minimum mean square error (MSE). To generate the reference node set, set S = S-1 (234).

The application system 130 generates a partial reference node set according to the number S of the minimum distance measurements reduced by one (236). And the application system 130 performs again from the "228" process.

)에 대해 그 크기가 적어도 하나만큼 작은 부분 참조노드집합을 생성한다. 응용시스템(130)은 참조노드집합(

)의 각 원소를 하나씩 순차적으로 제거함으로써, 그 크기가 1개만큼 작은 부분 참조노드집합을 생성할 수 있다. 만약, 참조노드집합(

)의 크기가 L개라면, L-1개의 크기를 가진 부분 참조노드집합은 L개의 서로 다른 부분집합으로 이루어질 수 있다. 예를 들면, 참조노드집합(

)이 참조노드(111)의 위치정보(

)와 같이 L개의 원소를 포함하는 것이라면, 그 부분집합들은 하기의 [수학식 15]와 같은 형태로 이루어진다.Looking specifically at the process "236", the application system 130 is a reference node set having a minimum mean square error (MSE) selected in the process "230" (

Creates a partial reference node set whose size is at least one. Application system 130 is a reference node set (

By removing each element of) sequentially, one can generate a partial reference node set that is as small as one size. If the reference node set (

If L) is L, the L-1 partial reference node set may be composed of L different subsets. For example, the reference node set (

Location information of this reference node 111.

If it contains L elements, such subsets are formed as shown in [Equation 15] below.

)은 원래의 참조노드집합(

)에서 그 첫 번째 원소를 제외한 나머지 원소들로 이루어진 것이다. "236" 과정에서 생성된 이들 부분 참조노드집합(

)은 각각의 중간 위치측정치 및 가중치를 산출하기 위해 "228" 과정부터 다시 수행한다.As a result, when k = 1, the partial reference node set (

) Is the original reference node set (

) Is made up of elements other than the first element. The partial reference node set created in the process of "236" (

) Is performed again from the "228" process to calculate each intermediate position measurement and weight.

)에서 첨자 번호(k)는 편의상 최초의 것으 로부터 생성된 순으로 부여하기로 한다. 예를 들어, L개의 참조노드로 이루어진 초기 참조노드집합을

이라면, 그의 부분집합에 대한 번호는

에 이어서

와 같이 L개만큼 순차적으로 부여된다. 다시 이들 중에서 임의의 집합에 대한 부분집합에 대한 번호는

와 같이 L-1개만큼 순차적으로 이어진다. Where the partial reference node set (

Subscript number (k) is given for convenience in the order in which it is generated from the first one. For example, an initial reference node set consisting of L reference nodes

If the number for his subset is

Followed by

As shown in the order of L number. Again, the numbers for subsets of any of these

As shown in the sequence as L-1.

) 및 그 가중치(

)의 정규화 가중 선형결합을 이용하여 하기의 [수학식 16]과 같이 이동노드(115)의 위치정보(

)를 산출한다(238). 그러므로 응용시스템(130)은 개선된 거리측정치와 최소 평균제곱오차의 참조노드집합에 대해서만 이동노드의 위치정보를 고려하기 때문에 정확한 위치정보를 사용자에게 제공할 수 있다.As a result of the check 232, if the number S of the selected partial reference node sets is three, the application system 130 calculates all intermediate position measurement values calculated in the process of "228".

) And its weight (

Using the normalized weighted linear combination of the position information of the mobile node 115 as shown in [Equation 16]

Is calculated (238). Therefore, the application system 130 may provide accurate location information to the user because the location information of the mobile node is considered only for the reference node set of the improved distance measure and the minimum mean square error.

는 k번째 참조노드를 제한조건으로 하는 중간 위치측정치,

는 k번째 부분 참조노드집합,

은 "218" 과정에서의 개별 가중치 산출을 위해 고려된 참조노드집합의 개수를 나타낸다.here, Is the location information of the mobile node,

Is an intermediate position measurement with the k th reference node as the constraint,

Is the kth partial reference node set,

Denotes the number of reference node sets considered for calculating individual weights in the process of "218".

), 참조노드(111)의 위치정보 및 그의 가중치를 기초로 하여 전술된 "208" 내지 "212" 과정, "214" 내지 "222" 과정, 또는 224" 내지 "238" 과정 중 어느 하나의 과정에 따라 이동노드(115)의 위치정보를 산출한다.As described above, the position measurement of the mobile node 115 is made by several methods based on the intermediate position measurement value, the reference node position information, and its weight, depending on the number of reference nodes considered. That is, the application system 130 may determine the intermediate position measurement value according to the number of reference nodes 111.

), Any one of the above-described processes "208" to "212", "214" to "222", or 224 "to" 238 "based on the position information of the reference node 111 and its weight. According to the calculation, the position information of the mobile node 115 is calculated.

After the position information of the mobile node 115 is calculated in the process of "212", "222", and "238", the application system 130 checks whether there is an interrupt for the position measurement (240).

As a result of the check 240, if there is an interrupt for the position measurement, the application system 130 performs again from the "206" process. That is, the application system 130 repeatedly performs the position measurement process. On the other hand, if there is no interruption for the position measurement, the application system 130 terminates the position measurement process.

3 is a flowchart illustrating a method for measuring a position in a mobile node according to the present invention.

The method for measuring the position of the mobile node illustrated in FIG. 3 relates to a process in which the mobile node 115 measures its position using distance measurement values and position information of the reference node 111. Here, when the minimum distance measurement is three or more (S> 3), only the smallest four distance measurement may be used to reduce the processing burden of the mobile node 115. Other processing may be performed in the same manner as the above-described positioning process.

The mobile node 115 detects a location measurement event for the mobile node 115 itself (302).

Subsequently, the mobile node 115 collects data information necessary for position measurement (for example, reference node ID or mobile node ID, time stamp, initial distance measurement and position information for the reference node, etc.) and the collected data. The number N of reference nodes corresponding to the initial distance measurement value among the information is counted (304). The mobile node 115 collects initial distance measurement values and location information for the reference node for the location measurement event for a predetermined time.

The mobile node 115 checks 306 the number N of counted reference nodes. The mobile node 115 follows different procedures according to the number N of reference nodes for each mobile node. This procedure will be described separately according to the number of reference nodes (N).

First, if the check result 306, the number of the counted reference node is two (N = 2), the mobile node 115 checks whether the previously calculated position information is available. If the calculated position information is not available, the mobile node 115 is based on the received data information of the first and second reference nodes 111 and 112 (position information of the reference node and initial distance measurement thereof). A weight determination process is performed, and then position information of the mobile node 115 is calculated.

Second, when the check result 306, the number of the reference node is three (N = 3), the mobile node 115 performs the correction process and the weight calculation process of the initial distance measurement. The initial distance measurement correction process and the weight calculation process reduce the error of the initial distance measurement. This process is repeated until a minimum mean square error is obtained, based on the minimum mean square error (MSE), otherwise a fixed number of times. If the minimum mean square error is calculated or the number of iterations is completed, the mobile node 115 calculates the geographic position of the mobile node by performing a location information calculation process based on the intermediate position measurement value and the weight obtained in the weight calculation process. .

Third, if the check result 306, the number of the reference node is three (N> 3), the mobile node 115 sets the number of minimum distance measurement (S) to four and the collected initial distance measurement is higher A process of correcting the initial distance measurement value and reducing the number of minimum distance measurement values S is performed to have accuracy. The mobile node 115 recursively obtains the partial reference node set having the minimum mean square error and its weight, which have a large influence on the position estimation of the mobile node, and then calculates the accurate position information from the partial reference node set and its weight. .

In short, the location information calculation process depends on the number of reference nodes for each mobile node. Hereinafter, the process of calculating the location information will be described in detail.

As a result of the check 306, if the number N of reference nodes is two, the mobile node 115 checks whether the previously calculated position information is available (308). Here, the available case is when the period is considerably shorter in periodic positioning by a timer (eg, usually within a few seconds, but may be chosen differently depending on the application model).

,

)를 결정한다(310).If the check result 308, the previously calculated position information is not available, the mobile node 115 uses the distance measurement ratios for the first and second reference nodes 111 and 112, 1] as the reference node weight (

,

(310).

,

)를 이용하여 이동노드(115)의 위치정보를 산출한다(312). 참조노드(111 및 112)의 개수가 두 개이고 이전에 산출된 위치정보가 이용가능하지 않다면, 이동노드(115)는 제1 및 제2 참조노드에 대한 가중치(

,

)와 제1 및 제2 참조노드(111 및 112)의 위치정보(

)를 상기의 [수학식 2]에 적용하여 이동노드(115)의 위치정보(

)를 산출한다.In addition, the mobile node 115 may have a weight value for the first and second reference nodes.

,

The location information of the mobile node 115 is calculated using the reference numeral 312. If the number of reference nodes 111 and 112 is two and the previously calculated position information is not available, the mobile node 115 may use the weights for the first and second reference nodes.

,

) And location information of the first and second reference nodes 111 and 112 (

) Is applied to the above [Equation 2] position information of the mobile node 115 (

) Is calculated.

Equation 2 is a result of estimating the position of the mobile node 115 based on two initial distance measurements. As a result, it is estimated that the mobile node 115 is located on a straight line where the position coordinates of the first and second reference nodes 111 and 112 are connected to each other.

)는 로서 정의된다.On the other hand, if the check result 308, the previously calculated position information is available, the mobile node 115 is the process of generating a virtual distance measurement value for the case where the number of the reference node is three (N = 3) "314 "Perform the process. Here, the previously calculated position information is newly set as position information of a new third reference node. In addition, the distance measurement value for the newly set third reference node 113 (

) It is defined as

)의 초기(미정(未精)) 거리측정치(

)에 대해, 각 초기 거리측정치에 대한 간접적인 거리인 가상 거리측정치(

)를 산출한다(314). 이동노드(115)는 상기의 [수학식 3] 내지 [수학식 8]과 같이, 참조노드의 초기 거리측정치로부터 선형화 최소자승 기법에 의해 이동노드의 가상 위치측정치를 산출하고, 산출된 이동노드의 가상 위치측정치와 참조노드의 위치 간 거리차를 이용하여 가상 거리측정치(

)를 생성한다.On the other hand, if the check result 306, the number (N) of the reference node is three, the mobile node 115 is a reference node set selected by a predetermined criterion among the initial distance measurement collected in the "304" process (

Initial (undecided) distance measurement of

), A virtual distance measure (indirect distance to each initial distance measure)

Is calculated (314). The mobile node 115 calculates a virtual position measurement value of the mobile node by a linearized least-squares technique from the initial distance measurement value of the reference node as shown in Equations 3 to 8, and calculates the calculated position of the mobile node. By using the distance difference between the virtual position measurement and the position of the reference node,

)

로서 정의된 참조노드집합에 대해 수행된다.If the total number K of the reference nodes 111 is 2 and the previous position measurement is valid, the process "314" sets the previous position value to the position coordinate of the third reference node and the distance measurement value therefor.

It is performed on the reference node set defined as.

)와 초 기 거리측정치(

)를 선형결합하여 중간 거리측정치(

)를 산출한다(316). 이는 초기 거리측정치(

)에 대한 정확도를 향상시키고, 잡음 및 간섭 등의 원인에 대한 거리오차를 완화하기 위함이다. "316" 과정을 구체적으로 살펴보면, 이동노드(115)는 가상 거리측정치(

)와 초기 거리측정치(

)에 대한 산술평균치를 상기의 [수학식 9]와 같이 산출한다.On the other hand, the mobile node 115 is a virtual distance measurement value generated in the "314" process (

) And initial distance measurement (

) By linearly combining the intermediate distance measurements (

Is calculated (316). This is the initial distance measurement (

This is to improve the accuracy of), and to mitigate the distance error for the sources of noise and interference. Looking specifically at the "316" process, the mobile node 115 is a virtual distance measurement (

) And the initial distance measurement (

The arithmetic mean value for) is calculated as shown in Equation 9 above.

)와 참조노드(111)의 위치정보(

)를 이용하여 중간 위치측정치(

)를 산출한다. 그리고 이동노드(115)는 중간 위치측정치(

) 및 참조노드의 위치정보를 기초로 하여 측정오차를 산출하고 그 산출된 측정오차를 이용하여 참조노드별 가중치(

)를 산출한다(318).And the moving node 115 is the intermediate distance measurement (

) And the location information of the reference node 111 (

With the intermediate position measurement (

) Is calculated. And the mobile node 115 is an intermediate position measurement (

) And the measurement error is calculated based on the location information of the reference node and the weight of each reference node (

318 is calculated.

)와 참조노드(111)의 위치정보(

)로부터 가장 큰 거리측정치(

)인 최단 거리방정식을 구한다. 그리고 이동노드(115)는 그 가장 큰 거리측정치(

)의 최단 거리방정식을 제한조건을 이용하는 선형화 최소자승 기법에 따라 중간 위치측정치(

)를 상기의 [수학식 10]과 같이 산출한다.Specifically, the mobile node 115 is a distance measurement (

) And the location information of the reference node 111 (

Largest distance measurement from

Find the shortest distance equation And the mobile node 115 is the largest distance measurement (

The intermediate position measurement () according to the linearized least-squares method using the constraint of the shortest distance equation

) Is calculated as shown in Equation 10 above.

)를 산출한다. 이동노드(115)는 이동노드(115)의 중간 위치측정치(

), 중간 거리측정치(

) 및 참조노드(111)의 위치정보(

)로부터 상기의 [수학식 12]와 같이 계산된 거리차의 합을 이용하여 가중치(

)를 위한 거리측정오차인 평균제곱오차(MSE)를 계산한다.The mobile node 115 calculates the mean square error and inversely proportions to the measurement error.

) Is calculated. The mobile node 115 is an intermediate position measurement of the mobile node 115 (

), The intermediate distance measurement (

) And location information of the reference node 111 (

) By using the sum of the distance differences calculated as shown in Equation 12 above.

Calculate the mean square error (MSE), which is the distance measurement error for.

)를 상기의 [수학식 13]과 같이 참조노드집합의 크기로 정규화한 값으로 결정한다. 즉, 이동노드(115)는 중간 위치측정치와 참조노드 위치 간 평균제곱오차(MSE)를 상기의 [수학식13]과 같이 참조노드집합의 개수로 정규화한다.Therefore, the mobile node 115 has a weight (

) Is determined as a value normalized to the size of the reference node set as shown in Equation 13 above. That is, the mobile node 115 normalizes the mean square error (MSE) between the intermediate position measurement value and the reference node position by the number of reference node sets as shown in Equation 13 above.

)는

로 대체된다. 반면, 정해진 횟수 동안의 반복 수행 과정에서, 중간 거리측정치(

)만이

로 대체된다.The mobile node 115 checks whether the mean square error (MSE) is the minimum (320). If the check result 320, the mean square error (MSE) is not the minimum, the mobile node 115 performs again from the "314" process. That is, the mobile node 115 repeatedly performs "314" to "320" processes until the mean square error (MSE) is minimum or for a predetermined number of repetitions. The processes "314" to "320" are performed when the minimum mean square error (MSE) is used as a reference to reduce the error of the distance measurement. Here, if the number of iterations is the first in the iteration process of finding the minimum mean square error (MSE), the mean square error (MSE) is set to the minimum value and the intermediate distance measurement value (

)

Is replaced by. On the other hand, during the repetition process for a predetermined number of times, the intermediate distance measurement (

Only

Is replaced by.

) 및 그 가중치(

)를 기초로 하여 이동노드(111)의 위치정보를 산출한다(322). 즉, 이동노드(115)는 중간 위치측정치(

) 및 그 가중치(

)에 의한 정규화 선형결합을 이용하여 상기의 [수학식 14]와 같이 이동노드(115)의 위치정보를 산출한다. 여기서, 위치정보는 지리적 위치좌표일 수 있다. 이러한 이동노드(115)의 위치정보는 참조노드의 전체 개수(K)가 두 개이고 이전에 산출된 위치정보가 이용가능한 경우, 또는 참조노드의 전체 개수(K)가 세 개 이상인 경우에 상기의 [수학식 14]와 같이 구해진다.On the other hand, if the check result 320, the mean square error (MSE) is the minimum, the mobile node 115 is the intermediate position measurement (

) And its weight (

Based on the calculated position information of the mobile node 111 (322). That is, the mobile node 115 is the intermediate position measurement (

) And its weight (

Using the normalized linear combination by) to calculate the position information of the mobile node 115 as shown in [Equation 14]. Here, the location information may be geographic location coordinates. The location information of the mobile node 115 is described in the case where the total number of reference nodes (K) is two and previously calculated location information is available, or when the total number of reference nodes (K) is three or more. (14) is obtained.

On the other hand, if the check result 306, the number (N) of the reference node is three or more (N> 3), the mobile node 115 determines the number (S) of the minimum distance measurement value (N) Set to 324. For example, the mobile node 115 sets the number S of minimum distance measurements to four.

)를 산출하고, 그 산출된 가상 거리측정치(

)와 초기 거리측정치(

)에 대한 선형결합 과정을 수행한다. 여기서, "326" 과정은 2회 연속적으로 반복되는 것으로 제한할 수 있다. 횟수 제한은 여러 과정으로 나뉘어 있는 후속 처리 과정의 처리시간 및 부하를 고려해서, 평균제곱오차(MSE)의 1차적인 완화를 이루기 위한 것이다. 2번째 처리 과정이 반복될 때, 중간 거리측정치(

)는 가상 거리측정치를 생성하는 과정을 위해 1차 갱신된 초기 거리측정치(

)로 대체된다. 즉,

와 같이 설정된다.And, so that the initial distance measurement has a higher accuracy, the mobile node 115 generates a virtual distance measurement and calculates an intermediate distance measurement in the same manner as the processes "314" and "316" (326). That is, the mobile node 115 is a virtual distance measurement (

), And the calculated virtual distance measurement (

) And the initial distance measurement (

Perform a linear combination process for Here, the process of "326" may be limited to being repeated twice in succession. The number limit is intended to achieve first order mitigation of the mean square error (MSE), taking into account the processing time and load of subsequent processes that are divided into processes. When the second process is repeated, the intermediate distance measurement (

) Is the first updated initial distance measure (

Is replaced by). In other words,

Is set as follows.

)를 산출하고, 그 산출된 중간 위치측정치를 이용하여 평균제곱오차(MSE), 및 그 가중치를 산출한다(328). 즉, 최소 거리측정치의 개수(S)가 참조노드의 개수(N)인 경우(S=N)에, 이동노드(115)는 "326" 과정에서 산출된 중간 거리측정치(

)와, "328" 과정에서 산출된 중간 위치측정치(

)를 이용하여 평균제곱오차(MSE) 및 가중치를 산출한다. "328" 과정은 이동노드(115)의 위치추정에 큰 영향을 미치는 즉, 최소 평 균제곱오차(MSE)를 가진 부분 참조노드집합에 대해 반복적으로 수행된다. 여기서, 구해진 평균제곱오차(MSE)가 최소 평균제곱오차(MSE)로 설정된다. 평균제곱오차(MSE) 및 가중치 산출 과정은 S개의 부분 참조노드집합 각각에 대해 수행되고, 최소 평균제곱오차(MSE) 및 그와 관련된 부분 참조노드집합이 선정된다.The mobile node 115 uses the intermediate distance measurement value calculated in step 326 to calculate the intermediate position measurement value using Equation 10 to Equation 13 above.

) Is calculated and the mean square error (MSE) and its weight are calculated using the calculated intermediate position measurement (328). That is, when the number S of the minimum distance measurements is the number N of the reference nodes (S = N), the mobile node 115 determines the intermediate distance measurement value calculated in the process of "326".

) And the intermediate position measurement ("328")

) Is used to calculate the mean square error (MSE) and weight. The process "328" is repeatedly performed on a partial reference node set having a large influence on the estimation of the position of the mobile node 115, that is, having a minimum mean square error (MSE). Here, the obtained mean square error MSE is set to the minimum mean square error MSE. The mean square error (MSE) and weighting process are performed for each of the S partial reference node sets, and the minimum mean square error (MSE) and its associated partial reference node sets are selected.

The mobile node 115 selects the reference node set having the minimum mean square error (MSE) using the calculated mean square error (MSE) (330).

The mobile node 115 checks whether the number S of the selected minimum distance measurements is three (332). That is, the process "332" is repeated until the number S of the minimum distance measurements is 3 (S = 3). Here, S = 3, that is, the number of three represents the minimum number of reference node sets that can be measured.

As a result of the check 332, if the number S of the selected minimum distance measurement exceeds 3, the mobile node 115 has a size as small as 1 with respect to the reference node set having the minimum mean square error (MSE). In order to generate an excitation partial reference node set, S = S-1 is set (334).

The mobile node 115 generates a partial reference node set according to the number S of the minimum distance measurements reduced by one (336). And the mobile node 115 performs again from the "328" process.

)에 대해 그 크기가 1만큼 작은 부분 참조노드집합을 생성한다. 이동노드(115)는 참조노드집합(

)의 각 원소를 하나씩 순차적으로 제거함으로써, 그 크기가 1개만큼 작은 부분 참조노드집합을 생성할 수 있다. 만약, 참조노드집합(

)의 크기가 L개라면, L-1개의 크기를 가진 부분 참조노드집합은 L개의 서로 다른 부분집합으로 이루어질 수 있다. 예를 들면, 참조노드집합(

)이 참조노드(111)의 위치정보(

)와 같이 L개의 원소를 포함하는 것이라면, 그 부분집합들은 상기의 [수학식 15]와 같은 형태로 이루어진다.Looking at the process "336" in detail, the mobile node 115 is a reference node set (MSE) having the minimum mean square error (MSE) selected in the process "330" (

Creates a partial reference node set whose size is as small as 1. The moving node 115 is a reference node set (

By removing each element of) sequentially, one can generate a partial reference node set that is as small as one size. If the reference node set (

If L) is L, the L-1 partial reference node set may be composed of L different subsets. For example, the reference node set (

Location information of this reference node 111.

If it contains L elements, such subsets are formed in the form of [Equation 15] above.

)은 원래의 참조노드집합(

)에서 그 첫 번째 원소를 제외한 나머지 원소들로 이루어진 것이다. "336" 과정에서 생성된 이들 부분 참조노드집합(

)은 각각의 중간 위치측정치 및 가중치를 산출하기 위해 "328" 과정부터 다시 수행한다.As a result, when k = 1, the partial reference node set (

) Is the original reference node set (

) Is made up of elements other than the first element. The partial reference node set created in the process of "336" (

) Is performed again from the “328” process to calculate each intermediate position measurement and weight.

) 및 그의 가중치(

)의 정규화 가중 선형결합을 이용하여 상기의 [수학식 16]과 같이 이동노드(115)의 위치정보(

)를 산출한다(338).As a result of the check 332, if the number S of the selected partial reference node sets is three, the mobile node 115 calculates all intermediate position measurement values calculated in the process of "328".

) And its weight (

Location information of the mobile node 115 as shown in [Equation 16] using the normalized weighted linear combination of

Is calculated (338).

), 참조노드(111)의 위치정보 및 그의 가중치를 기초로 하여 전술된 "308" 내지 "312" 과정, "314" 내지 "322" 과정, 또는 324" 내지 "338" 과정 중 어느 하나의 과정에 따라 이동노드(115)의 위치정보를 산출한다.As described above, the position measurement of the mobile node 115 is made by several methods based on the intermediate position measurement value, the reference node position information, and its weight, depending on the number of reference nodes considered. That is, the mobile node 115 is the intermediate position measurement value according to the number of reference nodes 111 (

), Any one of the above-described "308" to "312" process, "314" to "322" process, or 324 "to" 338 "process based on the location information of the reference node 111 and its weight. According to the calculation, the position information of the mobile node 115 is calculated.

After the position information of the mobile node 115 is calculated in steps "312", "322", and "338", the mobile node 115 checks whether there is an interrupt for the position measurement (340).

As a result of the check 340, if there is an interrupt for the position measurement, the mobile node 115 performs the process again from "306". That is, the mobile node 115 repeatedly performs the position measurement process. On the other hand, if there is no interruption for the position measurement, the mobile node 115 terminates the position measurement process.

이지만, 본 발명에서는 26개(

)만이 고려되기 때문에, 그 복잡도가 상당히 줄어들 수 있다. 여기서,

는

일 때 0 이고,

일 때

값을 가진다.Meanwhile, according to the present invention, when the number of reference nodes is large, according to the position measuring process of the mobile node 115 through iterative weight calculation, the complexity of the weight calculation may be considerably lowered. For example, in the conventional positioning technique, when there are N = 7 collected reference nodes and distance measurements, the size of the set of possible reference nodes that affect the final position information is 99 pieces.

However, in the present invention, 26 (

Since only) are considered, the complexity can be significantly reduced. here,

Is

0 when

when

Has a value.

Therefore, according to the position measuring method according to the present invention, even when there are few reference nodes or significant mean square errors such as noise, fading, and multipath are included, the distance measurement can be refined and contribute to the position information of the mobile node. Since the reference node set with the minimum error among all the reference node sets can be used, it is possible to calculate the location information of the mobile node with high accuracy even at low complexity.

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.

1 is a configuration diagram of an embodiment of a sensor network and an application system to which the present invention is applied;

2 is a flowchart illustrating a method for measuring a position of a mobile node in an application system according to the present invention;

3 is a flowchart illustrating a method for measuring a position in a mobile node according to the present invention.

* Explanation of symbols for the main parts of the drawings

110: sensor network 111 to 114: reference node

115: mobile node 116: sink node

120: broadband integrated network 130: application system

131: user terminal

Claims (19)

In the method of measuring the position of the mobile node, A reference node counting step of counting the number of reference nodes corresponding to the initial distance measurement obtained from the outside; Generating an intermediate distance measurement value and an intermediate distance measurement value by generating a virtual distance measurement value corresponding to the number of reference nodes and linearly combining the generated virtual distance measurement value and the obtained initial distance measurement value; A weight calculation step of calculating a measurement error based on the calculated intermediate position measurement value and the position information of the reference node and calculating a weight for each reference node using the calculated measurement error; And Calculating position information of the mobile node using the calculated intermediate position measurement value and the calculated weight for each reference node; Position measurement method of the mobile node comprising a. The method of claim 1, If the number of the reference node counted is less than a predetermined number, further comprising the step of checking the previous location information to determine whether the previous location information of the mobile node is available, The weight calculation step, And if the previous position information of the mobile node is not available, a weight for each reference node is calculated using a ratio of the distance measurement value to the reference node less than the predetermined number. The method of claim 2, The location information calculating step, And if the counted number of reference nodes is less than a predetermined number, calculating position information of the mobile node by weighted linear combination of the position information of the reference nodes. The method of claim 1, The intermediate measurement calculation step, Generating a virtual distance measurement value corresponding to the counted number of reference nodes; Calculating an intermediate distance measurement value by linearly combining the generated virtual distance measurement value with the obtained initial distance measurement value; And Calculating an intermediate position measurement value using the calculated intermediate distance measurement value and position information of the reference node; Position measurement method of the mobile node comprising a. The method of claim 4, wherein The virtual distance measurement generation step, The virtual position measurement of the mobile node is calculated from the initial distance measurement value of the reference node using a linearized least-squares method, and the virtual distance measurement value is calculated by using the calculated distance between the calculated position of the mobile node and the reference node. Position measurement method of a mobile node, characterized in that for generating. The method of claim 5, wherein The virtual distance measurement generation step, As a constraint for the linearized least-squares method, a distance equation with respect to the reference node is used. The method of claim 4, wherein The intermediate distance calculation step, And calculating the arithmetic mean value of the generated virtual distance measurement value and the obtained initial distance measurement value to calculate the intermediate distance measurement value. The method of claim 4, wherein The weight calculation step, And calculating the intermediate position measurement value according to a linearized least-squares technique using a shortest distance equation as a constraint. The method of claim 2, The previous location information checking step, And if the previous location information of the mobile node is available, designating the available old location information as the new location information of the reference node and proceeding to generating the virtual distance measurement value. The method of claim 4, wherein If the count of the reference node is a predetermined number further comprises a measurement error checking step of checking whether the calculated measurement error is the minimum, And if the calculated measurement error is minimum, proceed to the location information calculation step, and if the calculated measurement error is not minimum, proceed to the virtual distance measurement value generation step. The method of claim 4, wherein A distance measurement setting step of setting the number of reference node counts as the minimum distance measurement value and proceeding to generating the virtual distance measurement value if the number of the counted reference nodes exceeds a predetermined number; A reference node set selection step of selecting a reference node set having a minimum mean square error using the measurement error calculated in the weight calculation step; It is determined whether the number of elements of the selected reference node set is the predetermined number, and if the identified number of elements is the predetermined number, the process proceeds to the position information calculating step, and if the number of identified elements is not the predetermined number, Steps to create a partial reference node set that creates a reference node set Position measurement method of a mobile node further comprising. The method of claim 11, wherein The partial reference node set generating step, And generating the partial reference node set from the reference node set having the minimum mean square error. The method of claim 12, The partial reference node set generating step, And generating a new partial reference node set by reducing the number of elements by at least one less than the reference node set having the minimum mean square error. The method according to any one of claims 10 to 13, The weight calculation step, And calculating the mean square error between the calculated intermediate position measurement value and the reference node position by the number of the reference node sets. The method of claim 14, The location information calculating step, And calculating the position information of the mobile node by normalizing the calculated intermediate position measurement value and the calculated weight for each reference node and performing weighted linear combination. In a mobile node positioning system having a processor, A reference node counting function for counting the number of reference nodes corresponding to the initial distance measurement obtained from the outside; An intermediate measurement calculation function of generating a virtual distance measurement value corresponding to the number of reference node counts and linearly combining the generated virtual distance measurement value and the obtained initial distance measurement value to calculate an intermediate distance measurement value and an intermediate position measurement value; A weight calculation function for calculating a measurement error based on the calculated intermediate position measurement value and the position information of the reference node and calculating a weight for each reference node using the calculated measurement error; And A position information calculation function for calculating position information of the mobile node using the calculated intermediate position measurement value and the calculated weight for each reference node. A computer-readable recording medium having recorded thereon a program for realizing this. The method of claim 16, If the counted number of reference nodes is less than a predetermined number, further comprising a previous position information checking function for checking whether the previous position information of the mobile node is available, The weight calculation function, Computer-readable recording of a program for realizing a function for calculating a weight for each reference node by using a ratio of distance measurement values to reference nodes less than the predetermined number if the previous position information of the mobile node is not available. media. The method of claim 16, If the number of the counted reference node is a predetermined number further comprises a measurement error checking function for checking whether the calculated measurement error is the minimum, The computer-readable recording medium having recorded thereon a program for realizing the function of proceeding to the position information calculating function if the calculated measurement error is minimum, and proceeding to the virtual distance measurement value generating function if the calculated measurement error is not minimum. . The method of claim 16, A distance measurement value setting function for setting the number of reference node counts as the minimum distance measurement value and proceeding to the virtual distance measurement value generation function when the number of the counted reference nodes exceeds a predetermined number; A reference node set selection function for selecting a reference node set having a minimum mean square error by using the measurement error calculated in the weight calculation function; It is determined whether the number of elements of the selected reference node set is the predetermined number, and if the identified number of elements is the predetermined number, the process proceeds to the position information calculating function, and if the number of identified elements is not the predetermined number, Partial Reference Node Set Creation Function to Create Reference Node Set A computer-readable recording medium that records a program for further realization.

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