KR20100066284A - Position tracking apparatus and method for a low power wpan/wban device - Google Patents

Abstract

PURPOSE: A position tracking apparatus and a method for a low power WPAN/WBAN device are provided to trace the position of a sensor node with low power. CONSTITUTION: A distance collection unit(110) collects the distance information of a plurality of anchor known nodes and each adjacent node to at least one sensor unknown node. A minimum distance calculation unit(120) respectively calculates a shortest path to the anchor node based on the distance information of the adjacent node. The minimum distance calculation unit select the sensor node having the shortest path from the anchor node and minimum distance as a parent node to manage them. A group separation unit(130) divides each node into a first group and a second group according whether their position is known or not. The controller selects a first sensor node nearest to a first group node to find the parent node.

Description

POSITION TRACKING APPARATUS AND METHOD FOR A LOW POWER WPAN / WBAN DEVICE}

TECHNICAL FIELD The present invention relates to a location tracking device, and more particularly, to a location tracking device and a method for easily tracking the location of a sensor node in a network having a few anchor nodes.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development. [Task Management No .: 2008-F-050-01, Title: WBAN In-body System and On] -body system development].

Wireless Personal Area Network (abbreviated as "WPAN") / Wireless Body Area Network (hereinafter abbreviated as "WBAN") consists of low power, low cost, small devices Means a kind of wireless sensor network. WPAN / WBAN sensor is a device that has a relatively short communication distance with low power and it is a hop-to-hop that transmits the sensor node's information to another node and the neighbor node passes back to its neighbor node. to communicate in a hop-based fashion.

On the other hand, in the sensor network, the method of tracking the position of a sensor node includes a distance measuring method and an angle measuring method between two nodes. Arrival, hereinafter abbreviated as " TOA, " measurement methods (e.g., US Patent Publication No. 2004-0235499, Ranging and positioning system, Ranging and positioning method, and radio communication apparatus).

The position calculation of the sensor node calculates the position of the sensor by triangulation method using the distance information between any sensor node and the anchor node whose position is to be tracked. The sensor network has a lot of network topology changes such as moving or adding sensor nodes, so it is often inefficient to install a sufficient number of anchor nodes in advance. In this case, the sensor node and the anchor node cannot communicate directly (one hop) but communicate in multihop. In other words, the distance between an anchor node and an arbitrary sensor node cannot be measured directly.

However, since the distance measured by the multi-hop has a lot of difference according to the spatial arrangement between the anchor node and the sensor node, there is a problem that a large position error occurs when estimating the position using the triangulation method using this distance.

의 시간 복잡도를 가지므로 위치를 결정하는데 많은 시간과 전력이 요구되는 문제점이 있다. Meanwhile, a method of using (Multidimensional Scaling, MDS) (for example, U.S. Patent Publication No. 2005-0080924 A1, Node localization in communication networks) is disclosed to improve such a problem.

Since there is a time complexity of, there is a problem that requires a lot of time and power to determine the location.

Accordingly, the present invention is to solve the above problems, the position location tracking system for tracking the position of the sensor node quickly and accurately by calculating the position with a low calculation complexity to recognize the position of the sensor node in the sensor and It is to provide a method.

In order to solve the above technical problem, a low-power WPAN / WBAN sensor location tracking device according to an embodiment of the present invention,

A measurement distance collector configured to collect and collect distance information of adjacent nodes, respectively, from a plurality of anchor nodes fixed in the sensor network and at least one sensor node whose location is not known; A shortest distance calculator configured to calculate shortest paths to the anchor nodes based on the collected distance information of adjacent nodes, and select and manage sensor nodes having the shortest path and the shortest distance to the anchor nodes as parent nodes; A group separation unit for separating each node into a first group having a location according to whether the location is determined, the anchor node being included in the first group, and a second group having no location; And selecting the first sensor node closest to the node of the first group in the second group to find the parent node thereof, and to the distance information (measurement value) of the shortest path to the anchor node of the first sensor. And a controller configured to reflect the estimated position of the parent node of the sensor node and the shortest path distance information of the anchor node, wherein the control unit applies a triangulation method to the corrected shortest path distance information of the first sensor node. It includes a control unit for identifying the position.

On the other hand, the location tracking device in the sensor network according to an embodiment of the present invention to track the position of the WPAN / WBAN sensor node,

a) collecting and collecting distance information of adjacent nodes, respectively, from a plurality of anchor nodes having a location and at least one sensor node having no location; b) calculating the shortest paths to the anchor nodes based on the collected distance information of the adjacent nodes, and selecting and managing sensor nodes having the shortest path and the shortest distance to the anchor nodes as parent nodes; c) dividing each node into a first group of known locations depending on whether the node is located, the anchor node being included in the first group, and a second group of unknown locations; d) selecting a first sensor node adjacent to the node of the first group in the second group to find its parent node, and the first path to distance information (measurement) of the shortest path to the anchor node of the first sensor; Correcting by reflecting the estimated position of the parent node of the sensor node and the shortest path distance information for the anchor node; And e) determining a position of the first sensor node by applying triangulation to the corrected shortest path distance information.

According to the embodiment of the present invention by the above-described configuration, in the sensor network where the sensor nodes are randomly densely distributed, a small number of anchor nodes can be implemented to realize the location of the sensor node with low complexity, thereby achieving fast and accurate tracking at low power. .

As described above, according to an embodiment of the present invention, in the sensor network in which the sensor nodes are randomly distributed, the position of the sensor is easily calculated by simply calculating the position of the sensor through a few anchor nodes.

In particular, the shortest path for each anchor node is added, and the position is calculated one by one from the sensor node closest to each anchor node, and the position is calculated to reduce the complexity, and the position of the sensor node can be tracked quickly and accurately at low power.

In addition, according to an embodiment of the present invention, by detecting the location of the indoor firefighters with a lot of flame or by temporarily placing sensors in airports and department stores, it is possible to detect dangerous substances or contaminants, and install the anchor node 10 like a mountain. In the case of disposing a sensor node in a difficult area and the location of a large number of low-power implanters (implantor) in the human body there is an effect that can be utilized.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

Now, a description will be given of a low power WPAN / WAN sensor position tracking device and method according to an embodiment of the present invention in detail with reference to the drawings.

In the following description specific details of the location tracking apparatus and method of the present invention are presented to provide a more general understanding of the present invention, which is understood that the present invention may be readily implemented without these specific details and also by modification thereof. It will be apparent to those of ordinary skill in the art.

1 is a network configuration diagram schematically showing a location tracking device for tracking the location of a sensor according to an embodiment of the present invention.

Referring to FIG. 1, at least three anchor nodes when the location tracking device is a two-dimensional plane for estimating a location as a system for identifying location information of a sensor in a sensor network. 10, a plurality of sensor nodes 20 and a location tracking device 100. In addition, the present invention is not limited thereto and may include at least four anchor nodes 10 in the three-dimensional space.

The anchor node 10 is a fixed node that knows its position and serves as a reference point when calculating the position of the sensor node 20. The position of the anchor node 10 may be set artificially or by using a global positioning system (GPS), and may set its position after installation to perform a function as the anchor node 10. In general, it is preferable that the anchor node 10 has a structure with a low limit on the energy used.

The sensor node 20 transmits information sensed in various environments or physical systems or a specific event related to a sensor based on a wireless communication technology, and is a wireless node composed of a sensor, a processor, and a communication element.

The sensor node 20 may have a plurality of anchor nodes 10 in one network and may be in a fixed position or have mobility. The anchor node 10 is generally operated at low power with limited energy available and communicates hop-to-hop in association with the anchor node 10 and neighboring sensor nodes 20.

The sensor node 20 and the anchor node 10 measure the distances of neighboring adjacent nodes, respectively, and transmit the measured distances to the location tracking device 100.

The location tracking device 100 may include location information of surroundings, location information of the anchor node 10, a sensor node 20 adjacent to the anchor node 10, and another sensor node 10 ′ adjacent to the sensor node 20. Manages distance information between the two, and has a function of tracking the position of the sensor node 20 periodically or aperiodically.

To this end, the location tracking device 100 includes a measurement distance collector 110, a shortest distance calculator 120, a group separator 130, and a controller 140.

The measurement distance collector 110 collects and collects measured distance information between adjacent nodes from the anchor node 10 and the sensor node 20, respectively.

The shortest distance calculator 120 finds the shortest path from each sensor node 20 to the anchor node 10 based on the collected distance information between adjacent nodes and calculates the distance of the shortest path. At this time, the shortest distance calculator 120 manages an adjacent node having the shortest path and the shortest distance closest to the anchor node 10 as the "parent node."

The group separator 130 separates a group of sensor nodes 20 into a group (hereinafter, referred to as “G _u ”) and a group of unknown location (hereinafter, referred to as “G _k ”). do. That is, the G _u group refers to a group in which the location of the sensor node is known, and the G _k group refers to a group in which the location of the sensor node is not known.

The controller 140 selects one sensor node 20 adjacent (closest to) the G _u group in the G _k group, and selects a distance of the shortest path to the anchor node 10 of the selected sensor node 20. Correction is performed by reflecting the estimated position of the parent node of the sensor node 20 and the shortest path distance to the anchor node 10. The controller 140 calculates the position of the sensor node 20 by applying the corrected distance to the triangulation method.

The controller 140 repeatedly performs the process of correcting and calculating the shortest distance until the position estimation of all the sensor nodes of the G _u group is completed.

On the other hand, Figure 2 is an exemplary view showing a triangulation method for determining the position of the sensor node according to an embodiment of the present invention.

Referring to FIG. 2, a sensor network according to an embodiment of the present invention includes three anchor nodes (first, second and third anchor nodes) and two sensor nodes n _i and n _j . Here, it is assumed that the sensor node n _i to determine the position is in direct communication distance with the first anchor node and the second anchor node and is connected in two hops with the third anchor node via n _j .

, 앵커 노드2와 노드 n_i와 거리

는 직접 측정가능하며 측정된 거리를 각각

와

라고 한다. 제3 앵커 노드와 n_i와 거리

는 직접 측정할 수 없으며, 제3 앵커 노드와 센서 노드 n_j 간 거리

와 센서 노드 n_j와 센서 노드 n_i와 거리

를 이용하여 추정할 수 있다. At this time, the distance between the first anchor node and the sensor node n _i

, The distance between anchor node 2 and node n _i

Is directly measurable and each of the measured

Wow

It is called. Distance from third anchor node n _i

Cannot be measured directly, and the distance between the third anchor node and the sensor node n _j

With sensor node n _j and distance with sensor node n _i

It can be estimated using.

는 다음의 수학식 1과 같이

혹은

보다 크고 그 두 개의 합보다 같거나 작다. The position of the sensor node n _i is calculated by triangulation using the position of the three anchor nodes and the three distance information. Here, the distance between the third anchor node and the sensor node n _i

Is as shown in Equation 1 below.

or

Is greater than or equal to the sum of the two.

의 추정치

는

와 같거나 작으며 추정 치의 오차에 따라 센서 노드 n_i의 추정위치에 오차가 발생되므로 앵커 노드와의 거리를 정확하게 추정하는 것이 요구된다. From Equation 1

Estimate of

Is

Since the error occurs at the estimated position of the sensor node n _i according to the error of the estimate, it is required to accurately estimate the distance from the anchor node.

3 is a flowchart illustrating a method of estimating a position of a sensor node according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the position tracking device 100 according to an exemplary embodiment of the present invention may first measure adjacent positions measured at each sensor node 20 in order to periodically or aperiodically estimate the position of the sensor node 20. The distance measurement data is collected (S301). The distance measurement can be calculated by measuring the TOA between two nodes and considering the propagation speed.

The location tracking apparatus 100 calculates the shortest path and the shortest path distance for each anchor node 10 from the collected adjacent node distance information (S302). Here, the shortest path distance is calculated as the sum of the distances between the two nodes along the shortest path from the sensor node 20 to the anchor node 10.

The location tracking apparatus 100 separates and groups the sensor nodes 20 into G _k groups in which positions are identified and G _Guk groups in which positions are not identified (S303). In the initial stage, the anchor node 10 is included in the G _k group and the sensor node 20 is included in the G _uk group. When classifying the group, the location tracking apparatus 100 may classify the group into subgroups based on the anchor node 10 and calculate a location in the subgroups classified to reduce the computational complexity. The detail group should include at least three anchor nodes and two sensor nodes in the two-dimensional plane as shown in FIG. 1.

Next, the location tracking apparatus 100 selects the closest (adjacent) sensor node u between the G _k group and the G _uk group and finds a parent node p corresponding to the sensor node u (S304).

In addition, the position tracking apparatus 100 corrects the shortest path distance measurement for the anchor node 10 of the sensor node u in consideration of the estimated position of the parent node p and the shortest path distance measurement for the anchor node 10 of p. (S305).

Subsequently, the position tracking apparatus 100 estimates the position of the sensor node u using triangulation from the corrected distance information and the position information of the anchor node 10 (S306).

If the positioning device 100 is shut down is not present to determine whether the sensor node 20 to a location in the G _uk group is present (S307, Yes), and the more there (S307, No), the S304 Repeat step S307.

That is, the position tracking device 100 calculates the position by finding the node closest to the G _k group and correcting the shortest path distance until the G _uk group becomes 0 in order to estimate the positions of all the sensor nodes 20. Repeat it.

Meanwhile, a method of finding the closest node between two groups G _k and G _uk according to an embodiment of the present invention will be described with reference to FIG. 4.

4 is a flowchart illustrating a method of finding adjacent nodes between two groups according to an embodiment of the present invention.

가 최소가 되는 센서 노드를 찾고 그 센서 노드를 노드 u라고 한다(S401). 즉, 센서 노드 u를 G_uk 그룹에서 삭제하고 G_k 그룹에 포함시킨다(S402). Referring to the accompanying Figure 4, ensure that any neighbor node n _j of sensor nodes n _i of the position tracking device (100) G _uk group according to an embodiment of the present invention belong to the G _k group, wherein G _k groups If you belong to

The sensor node is found to be the minimum and the sensor node is called node u (S401). That is, the sensor node u is deleted from the group G _uk and included in the group G _k (S402).

In addition, the parent node of the sensor node u may be known from the shortest path calculated in step S302 of FIG. 3, which is referred to as node p (S403).

의 복잡도를 갖는다.As described above, the shortest path calculation for one anchor may use a proven method such as a Dijkstra algorithm. In any graph G = (V, E), if V is the number of nodes and E is the number of adjacent nodes, then the shortest path calculation for one anchor is

Has the complexity of

On the other hand, Figure 5 is a flow chart illustrating a position correction method of the sensor node u according to an embodiment of the present invention.

Referring to FIG. 5, a process of correcting the shortest distance with respect to the anchor of the sensor node u according to an embodiment of the present invention from the position and the shortest distance information of its parent node p is shown.

,

,

를 각각 계산하고(S501, S502), 앵커 노드(10)에 대한 최단경로 측정거리

,

,

으로부터 노 드u의 최단경로에 대한 측정거리

,

,

를 부모 노드 p의 위치를 고려하여 보정하는 것은 다음의 수학식 2와 같다.The position tracking device 100 may determine the distance between the estimated position of the node p and the anchor node 10 from the position of the parent node estimated in FIG. 4.

,

,

Are respectively calculated (S501, S502), the shortest path measurement distance to the anchor node 10

,

,

Distance from node u to the shortest path

,

,

Is corrected in consideration of the position of the parent node p as in Equation 2 below.

That is, the position tracking device 100 considers the calculated distance between the estimated position of the parent node p and the anchor node 10 and the shortest path distance measurement value of the corresponding node, as shown in Equation 2 above. The shortest path distance with respect to may be corrected (S503).

On the other hand, Figure 6 shows the process of changing from the G _uk group to the G _k group according to the embodiment of the present invention.

Referring to FIG. 6, as the location tracking device 100 according to an embodiment of the present invention detects the positions of the sensor nodes 20 of the sensor network, the sensor nodes 20 are moved from the G _uk group to the G _k group. Show that you are changing.

It is assumed that the sensor network according to an embodiment of the present invention has three anchor nodes 10 and five sensor nodes 20.

First, (a) of FIG. 6 shows an anchor node included in a G _k group represented by a square (■) as an initial state, and a plurality of sensor nodes included in a G _uk group represented by a circle (○). (b) indicates that the nearest sensor nodes as an anchor node (■) are included in a group G _k from the nodes in the group G _uk (●) is included in the group G _k. And, (c) to (f) is, which according to an embodiment of the present invention as the case of (b) all of the sensor node 20 by including in the G _uk group one by one G _k groups, such as is included in G _k groups This means that the location tracking device 100 calculates the positions of all the sensor nodes 20.

On the other hand, Figure 7 is a graph showing the simulation results showing the position tracking error according to an embodiment of the present invention.

Referring to FIG. 7, a graph shows a simulation result of a matlab for a position error estimated by correcting the position error and the shortest path distance without correcting the shortest path distance to the anchor node 10. Shows.

The simulation environment assumes a plane of 100m x 100m and places anchor nodes 10 at four edges (((0,0), (100,0), (0,100), (100,100)). The sensor nodes 20 were randomly arranged on the plane, but experimented by changing 20 from 40 to 200. In addition, it is assumed that the communication distance (coverage) between the anchor node 10 and the anchor node 10 is 30 m or less.

As a result of the simulation, when the number of sensor nodes 20 is 40, the minimum number of adjacent nodes is 4, and in the case of the STP method which estimates the position without correcting the shortest path distance, the position estimation error is 74m and the distance is estimated as in the present invention. In case of correction and estimation, 43m distance error is shown. In addition, when the number of sensor nodes 20 is 200, the distance error of 1.4m for the STP method and 1.1m for the method according to the present invention is shown, respectively. It can be seen that can be estimated.

As described above, according to the embodiment of the present invention, the sensor node 20 has an effect of facilitating the location of the sensor network by simply calculating the position of the sensor through a few anchor nodes in a randomly distributed sensor network. .

In particular, it calculates the shortest path for each anchor node, calculates the position by sequentially adding one from the sensor node closest to each anchor node, and reduces the complexity, and the distance information between sensors in the space with a few anchor nodes 10 There is an effect of facilitating the location tracking of the sensor node 20 by using.

Although the embodiments of the present invention have been described above, the present invention is not limited only to the above embodiments, and various other changes are possible.

For example, in the exemplary embodiment of the present invention illustrated in FIG. 1, a two-dimensional plane including at least three anchor nodes and two sensor nodes has been described as an example. However, the present disclosure is not limited thereto and may further include at least one anchor node 10. Can be. Thus, there is an advantage of facilitating the positioning of the sensor node 20 in a three-dimensional space, such as inside a building.

Further, according to an embodiment of the present invention, the sensor is located in an area where it is difficult to detect dangerous substances or contaminants by temporarily placing a sensor in a location of an indoor firefighter with a high flame, an airport or a department store, or to install an anchor node 10 such as a mountain. When arranging the node 20, there is an effect that can be utilized, such as the location of a number of small output implanter (implantor) in the human body.

The embodiments of the present invention are not limited to the above-described apparatuses and / or methods, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a network configuration diagram schematically showing a location tracking device for tracking the location of a sensor according to an embodiment of the present invention.

2 is an exemplary view showing a triangulation method for determining the position of the sensor node according to an embodiment of the present invention.

3 is a flowchart illustrating a method of estimating a position of a sensor node according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a method of finding adjacent nodes between two groups according to an embodiment of the present invention.

5 is a flowchart illustrating a position correction method of a sensor node u according to an exemplary embodiment of the present invention.

6 shows a process of changing from a G _uk group to a G _k group according to an embodiment of the present invention.

7 is a graph showing a simulation result showing a position tracking error according to an embodiment of the present invention.

Claims (10)

A measurement distance collector configured to collect and collect distance information of adjacent nodes, respectively, from a plurality of anchor nodes fixed in the sensor network and at least one sensor node whose location is not known; A shortest distance calculator configured to calculate shortest paths to the anchor nodes based on the collected distance information of adjacent nodes, and select and manage sensor nodes having the shortest path and the shortest distance to the anchor nodes as parent nodes; A group separation unit for separating each node into a first group having a location according to whether the location is determined, the anchor node being included in the first group, and a second group having no location; And Selecting a first sensor node closest to the node of the first group in the second group to find its parent node, the first sensor to the distance information (measurement) of the shortest path to the anchor node of the first sensor node It includes a control unit for correcting by reflecting the estimated position of the parent node of the node and the shortest path distance information for the anchor node, The control unit is a control unit for determining the position of the first sensor node by applying triangulation to the corrected shortest path distance information Location tracking device comprising a. The method of claim 1, The control unit, Positioning apparatus, characterized in that to determine the position sequentially by calculating the position of the n-th sensor node of the second group from the corrected distance information. The method according to claim 1 or 2, The control unit, If the location of the sensor node is known to remove from the second group, the location tracking device to include in the first group. The method of claim 2, The shortest distance calculation unit, And calculating the shortest path distance information as a sum of distances between at least two nodes along the shortest path from the sensor node to the anchor node. The method of claim 2, The group separator, Classify the first group and the second group into subgroups based on each of the anchor nodes; The control unit is a location tracking device, characterized in that for calculating the position independently in the sub-group. The method of claim 5, The shortest path calculation for one anchor node is

Location, wherein V denotes the number of nodes and E denotes the number of adjacent nodes, respectively. In the method for the location tracking device in the sensor network to track the location of the WPAN / WBAN sensor node, a) collecting and collecting distance information of adjacent nodes, respectively, from a plurality of anchor nodes having a location and at least one sensor node having no location; b) calculating the shortest paths to the anchor nodes based on the collected distance information of the adjacent nodes, and selecting and managing sensor nodes having the shortest path and the shortest distance to the anchor nodes as parent nodes; c) dividing each node into a first group of known locations depending on whether the node is located, the anchor node being included in the first group, and a second group of unknown locations; d) selecting a first sensor node adjacent to the node of the first group in the second group to find its parent node, and the first path to distance information (measurement) of the shortest path to the anchor node of the first sensor; Correcting by reflecting the estimated position of the parent node of the sensor node and the shortest path distance information for the anchor node; And e) determining a position of the first sensor node by applying triangulation to the corrected shortest path distance information; Location tracking method comprising a. The method of claim 7, wherein After step e), And calculating the positions of the n-th sensor nodes of the second group from the corrected distance information to determine the positions sequentially. The method of claim 7, wherein C), In the case of a two-dimensional plane, it is divided into subgroups based on at least three anchor nodes, or In the case of a three-dimensional plane location tracking method characterized in that divided into subgroups based on at least four said anchor node. The method of claim 9, Step e), If the location of the sensor node is known, removing it from the second group and including it in the first group.

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