KR101135201B1 - A rssi based location measurement method and system using acceleration location information in the wireless network - Google Patents

Abstract

The disclosed position measuring method and position measuring system generates a first position coordinate based on an RSSI value of a received signal transmitted from a node attached to an object requiring position measurement, and includes acceleration / position information included in a received signal from the node. An improved positional coordinate measurement is obtained by generating a second positional coordinate based on and generating a final third positional coordinate from the first and second positional coordinates.

Description

Rssi based location measurement method and system using acceleration location information in the wireless network}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and system for measuring position in a wireless network, and more particularly, to wireless environment characteristics, such as multipath fading, peripheral interference, mobility, irregular signal propagation characteristics, and the like, in a wireless network. The present invention relates to a RSSI (Received Signal Strength Indication) based location measurement method using acceleration location information to reduce location error caused by the location error.

In various environments, localization techniques are an important field for realizing various applications such as logistics management and material management based on location recognition. It is also possible to add a GPS (Global Positioning System) receiver or hardware for position recognition to the object of location recognition to measure the position, but this entails the problem of cost and resource constraints, There is a problem that the signal is not received in the basement or dense building area.

Commonly used location recognition methods include a Time Of Arrival (TOA) method, a Time Difference Of Arrival (TDOA) method, a Received Signal Strength Indication (RSSI) method, and the like.

The TOA method uses relations between distance and transmission time when the speed of propagation is known, and is used as a hardware ranging mechanism for measuring distance by measuring propagation time of propagation. However, the TOA method has the disadvantage that the speed of propagation is affected by external factors such as temperature, the transmitter and receiver must both be precisely synchronized, and expensive and energy-consuming electronics are required to accurately synchronize with satellite signals. There is this.

In order to overcome the exact synchronization requirements of the TOA method, the TDOA method has been proposed. In the TDOA method, each node has two transceivers with different propagation speeds. When the transmitter sends a message simultaneously with a fast radio wave signal and relatively slow ultrasound, the receiver receives the message through a radio device and an ultrasound device at different times, and the two signals are different. The distance between two nodes is measured based on the arrival time.

Finally, the RSSI method measures the strength of the received signal and associates it with the distance. In theory, the RSSI value in free space, i.e., the strength of the received signal, decreases in proportion to the square of the distance from the signal source to the signal destination. As a result, the node receiving the radio transmission may use the strength of the received signal to calculate the distance from the transmitter. However, due to the multipath fading, ambient interference, mobility, and irregular signal propagation characteristics in real space, since the desired signal, the interference signal, and the noise signal are received together, the RSSI value is sometimes about 50% ranging error. ) Can be generated.

The present invention has been made to solve the problems of the conventional RSSI-based position recognition technology, and provides a positioning method and a positioning system in an RSSI-based wireless network with improved performance using acceleration position information.

The position measuring method according to the present invention is an RSSI value-based position measuring method using acceleration / position information in a wireless network, the node including an acceleration sensing unit and including the acceleration / position information of the object from a node attached to the object of the position measurement. Transmitting a packet; Receiving the node packet using a plurality of coordinators, and transmitting a report packet including a RSSI value of the received packet and the acceleration / location information to a positioning server; Calculating first position coordinates of the node by using the RSSI value of the report packet received at the positioning server; Calculating second position coordinates of the node based on the acceleration / position information included in the report packet; And calculating final third position coordinates from the first and second position coordinates to determine final position coordinates of the object.

The acceleration / position information includes moving distance and moving azimuth information from an initial position of the object.

The node transmits the node packet only when the travel distance exceeds a preset threshold.

The positioning server determines the third position coordinate in consideration of an error in position measurement based on an RSSI value included in the first position coordinate and an error in position measurement based on acceleration / position information included in the second position coordinate. do.

The node packet includes a node identifier, a sequence number (SN), and acceleration / position information.

The report packet includes a coordinator identifier, an RSSI value when the node packet is received, and information on the node packet.

The position measuring system according to the present invention is an RSSI value-based position measuring system using acceleration / position information in a wireless network, and includes an acceleration sensing unit and is attached to an object of position measurement, and includes a node including acceleration / position information of the object. A node generating a packet and transmitting the packet through a wireless network; A plurality of coordinators having a fixed position, receiving the report packet to extract an RSSI value, and generating and transmitting a report packet including the extracted RSSI value and a node packet; Receiving a report packet to calculate the first position coordinates of the object based on the RSSI value and the second position coordinates of the object based on the acceleration / position information, the first and second position coordinates are fused and correlated, the final It includes; location measuring server for determining the third location coordinates that are position coordinates.

According to the position measuring method and the position measuring system of the present invention, it is possible to solve the problem of the positioning method based on the RSSI value due to radio environment characteristics, for example, multipath fading, ambient interference, mobility, irregular signal propagation characteristics, etc. By supplementing the information, improved RSSI-based position measurement is possible.

Acceleration / position information may be transmitted only when the displacement of the object exceeds a predetermined threshold value, thereby reducing power consumption required for the operation of the node and significantly reducing the band for wireless communication.

Hereinafter, with reference to the drawings, embodiments of a received signal strength based position measurement method and a position measurement system using acceleration / position information in a wireless network according to the present invention will be described.

1 is a block diagram of an embodiment of a position measuring system according to the present invention. The position measuring system of the present embodiment may operate in a wireless environment, for example, a wireless personal area network (WPAN) using a 2.4 Ghz frequency. 1, a location measurement server 100, a plurality of coordinators 110, and a plurality of nodes 120 are shown.

The plurality of nodes 120 are mounted on the objects that are the targets of the position measurement at the first known positions and are moved together with the objects. Thus, the positions of the plurality of nodes 120 are the positions of the objects. The number of coordinators 110 may be appropriately determined according to the size and shape of the management area. The position coordinates of the plurality of coordinators 110 are known values. That is, the plurality of coordinators 110 have a fixed position. The position coordinates of the plurality of coordinators 110 are stored in advance in the position measurement server 100. Even when the position of the coordinator 110 is changed while operating the system, the changed position is stored in the positioning server 100.

2 illustrates a configuration example of the node 120, the coordinator 110, and the location measurement server 100. The node 120 detects the movement of the object to generate the acceleration / position information, and the acceleration detection unit 121 and the control unit 122 receives the acceleration / position information from the acceleration detection unit 121 and generates a node packet including the same. And a communication unit 123 for transmitting the node packet to the plurality of coordinators 110. The acceleration detector 121 is for detecting acceleration / position information of the object and may include an acceleration sensor 124 and an acceleration detection module 125. The acceleration sensor 124, for example, refers to a sensor capable of detecting the direction and magnitude of acceleration in response to a force applied to the object as the object moves. The acceleration sensor 121 may be inertial, gyro, etc. in various ways. Recently, the acceleration sensor 121 may also be implemented in a chip form which is miniaturized and low power by Mems technology. The acceleration sensing module 125 receives acceleration information from the acceleration sensor 124 and generates acceleration / position information including a moving distance and a moving azimuth angle from an initial position of the object.

An example of a node packet generated by the controller 122 is shown in FIG. 3. Referring to FIG. 3, the node packet may include a node identifier (NODE ID) for identifying the node 120, a sequence number (SN), and acceleration / position information (SI). Reference numerals 126 and 127 denote power sections for operating the memory and node 120, respectively.

The coordinator 110 includes a communication unit 111 for receiving a node packet from the plurality of nodes 120 through an antenna and transmitting a report packet to the positioning server 100. The control unit 112 extracts the RSSI value from the node packet signals received from the plurality of nodes 120. The control unit 112 generates a report packet including information on the received node packet and the extracted RSSI value.

An example of a report packet generated by the controller 112 is shown in FIG. 4. Referring to FIG. 4, the report packet may include a coordinator identifier (Cordi id), an RSSI value (RSSI), and node packet information. In addition, when the RSSI value-distance conversion data is embedded in a memory (not shown) of the coordinator 110, the control unit 112 calculates a receiving distance from the RSSI value extracted using the packet, and reports the receiving distance by the packet. Can be included in The receiving distance is the distance between the node that sent the node packet and the coordinator that received it.

The position measuring server 100 generates final position coordinates of the plurality of nodes 120 using the communication unit 101 which receives the report packet from the plurality of coordinators 110 and the RSSI value and the acceleration / position information of the report packet. The control unit 102 is included. The configuration manager 103 manages information on the overall configuration required when the controller 102 generates the position coordinates. For example, the configuration manager 103 manages basic information for generating the position coordinates such as the position coordinates of the coordinator 110, the RSSI value-distance conversion information, the size of the management region of the position tracking, and the frequency distortion pattern for each management region. It is. The output management unit 104 provides and displays the final position coordinates to the user. The controller 102 may control the communication unit 101 to transmit the final position coordinates to the location tracking client 10. The position measuring client 10 may perform a function of providing and displaying the finally measured position coordinates to a user or an operator.

5 is a flowchart illustrating an embodiment of a position measuring method according to the present invention. Hereinafter, a position measuring method using the above-described position measuring system will be described with reference to FIG. 5. For convenience of explanation, a process of determining the final position coordinates of one node will be described, and the term “node 120” used below means Node 01 in FIG. 1.

The node 120 is attached to the object to be managed by the position at the initial position and moves with the object. An initial location may be set in memory 126 of node 120. When the object starts to move, the acceleration sensor 124 detects the acceleration information in response to the movement inertia of the node 120. Based on the acceleration information, the acceleration detection module 125 generates acceleration / position information including a distance and a moving azimuth angle at which the node 120 is moved from the initial position. The generated acceleration / position information may be stored in the memory 126. As an algorithm for generating the acceleration / position information, a navigation algorithm using a three-axis acceleration sensor used in a known autonomous navigation apparatus can be employed, so a detailed description thereof will be omitted. The acceleration sensor 121 using the acceleration sensor 124 may detect its own position and moving direction by itself without external help such as transmission and reception of radio waves if only an initial position is given. The controller 122 generates a node packet including acceleration / position information. The node packet is periodically transmitted to the plurality of coordinators 110 through the communication unit 123.

The controller 122 may control the communication unit 123 to transmit the node packet only when the position change amount of the node 120 according to the generated acceleration / position information is larger than the threshold. If the position change of the node 120 is smaller than the threshold, the node packet may not be transmitted. Since the node 120 is attached to the object and moved, the power supply unit 127 may be, for example, a battery. The transmission of the packet from the node 120 to the coordinator 110 is by radio transmission, which consumes a lot of battery during radio transmission. If the position change amount of the node 120 does not reach the threshold, the usage of the battery may be reduced by not transmitting the node packet. In addition, although the acceleration sensor 124 has its own error, when the position change amount of the node 120 is small, the ratio of the error with respect to the position change amount becomes relatively large, and thus the position accuracy may be degraded. The threshold value may be appropriately selected in consideration of required positioning accuracy of the object and an error of the acceleration sensor 124. As described above, the controller 122 generates a node packet and controls the communication unit 123 to transmit to the plurality of coordinators 110 when the position change of the node 120 is greater than the threshold and the transmission period is reached. It is possible to reduce the power consumption required for the operation of 120, it is possible to significantly reduce the band for wireless communication.

The plurality of coordinators 110 receives the node packet, and extracts the RSSI value of the received signal. In addition, a report packet of the type shown in FIG. 4 is generated and transmitted to the positioning server 100.

The location measurement server 100 determines the first location coordinates of the node 120 based on the RSSI value included in the report packet, and generates the second location coordinates of the node 120 based on the acceleration / position information. And the 3rd position coordinate which is the last position coordinate of the node 120 is calculated from a 1st, 2nd position coordinate.

In order to determine the first position coordinate of the node 120, the positioning server 100 withdraws the RSSI values from the report packet received from the plurality of coordinator 110, using the built-in RSSI-distance conversion table Yields Here, the reception distances refer to distances from the node 120 to the plurality of coordinators 110. The first position coordinate of the node 120 based on the RSSI value is determined by using the position coordinates of the plurality of coordinators 110 and the reception distances from the node 120 converted from the RSSI values to the plurality of coordinators 110. do. In theory, the RSSI value is inversely proportional to the square of the receiving distance, so if there are RSSI values transmitted from a plurality of coordinators whose position coordinates are known, for example, using a polygon center of gravity, triangulation, etc. The location of node 120 may be determined. Hereinafter, a method using the center of gravity of the polygon will be described as an example.

The positioning server 100 uses the position coordinates of the plurality of coordinators 110 as a center point to calculate the first position coordinates of the node 120 based on the RSSI values, and based on the RSSI values of each of the plurality of coordinators 110. Draw a plurality of circles whose radius is the receiving distance. The coordinates of the center of gravity of the polygons connecting the intersection points of the circles are determined as the first position coordinates of the node 120. It will be appreciated by those skilled in the art that two-dimensional position coordinates require at least three intersections to form a polygon. 6 shows an example of determining the first position coordinates in this way. 6, "C" represents a coordinator. The number displayed next to the plurality of coordinators marked with "C" is the position coordinate of each coordinator. Circles having a radius of the received distance converted using the RSSI value received from a plurality of coordinators are drawn, and the intersection points of these circles are marked with "○". The number displayed next to the plurality of coordinators marked with "C" is the position coordinate of each coordinator. The coordinates of the center of gravity of the polygons connecting the intersections can be obtained most simply by taking the arithmetic mean of the coordinates of the intersections. In Figure 6, ① indicates the first position coordinates determined by the above process. In addition, various methods may be applied, such as a method of taking an average value of coordinates of the intersection points by giving a constant weight to the intersection points, for example, a method of taking an average value with a larger weight as the conversion distance based on the RSSI value is closer.

In order to determine the second position coordinates of the node 120, the positioning server 100 extracts the acceleration / position information from the report packet of the node 120. Since the acceleration / position information includes moving distance information and moving azimuth information based on the initial position of the node 120, the second position coordinates of the node 120 may be determined based on the acceleration / position information. In Fig. 6, ② indicates the second position coordinate.

Next, the positioning server 100 correlates and fuses the first position coordinates and the second position coordinates to generate tertiary position coordinates which are current position coordinates of the node 120. The first position coordinate is set by the correlation between the pre-embedded RSSI value and the distance. The coordinator combines the desired signal with the interference signal and the noise signal due to radio environment factors such as multipath fading, ambient interference, mobility, and irregular signal propagation characteristics. Received at field 110, the RSSI value has an error. This error is contained in the first positional coordinates. The position measurement server 100 adopts a method of reducing the position measurement error by correcting the first position coordinates using the second position coordinates based on the acceleration / position information to generate the third position coordinates. Errors in positioning based on RSSI values and those based on acceleration / position information are based on the error range specified in the specifications of the hardware used. In addition, it can be applied by adjusting the error range according to the application environment through preliminary experiment before installation / operation.

Referring to FIG. 6, when the error of the first position coordinate based on the RSSI value is t1, the node 120 may expect that the radius t1 exists inside the circle C1 based on the first position coordinate. . In addition, when the error of the second position coordinate based on the acceleration / position information is t2, the node 120 may expect to exist inside the circle C2 having a radius t2 around the second position coordinate. Therefore, based on the first position coordinate and the second position coordinate, it can be expected that the actual position of the node 120 is present in the region C3 where the circle C1 and the circle C2 overlap. Here, the area of the area C3 is smaller than the area of the circle C1 and the area of the circle C2. Therefore, when the RSSI value and the acceleration / position information are used together, the node 120 may be used rather than the individual information. It can be seen that the accuracy of the position can be improved.

The location measurement server 100 may determine any point in the area C3 as the third location coordinate that is the final location coordinate of the node 120. For example, if the error t1 of the first position coordinate based on the RSSI value and the error t2 of the second position coordinate based on the acceleration / position information are the same, the positioning server 100 may determine the first position coordinate and the second position coordinate. The coordinate of the midpoint of the line L1 to connect can be determined as a 3rd position coordinate. In addition, if the error t1 of the first position coordinate based on the RSSI value and the error t2 of the second position coordinate based on the acceleration / position information are different from each other, the third position sin table may be determined using these proportional relations. For example, an intersection point between a line L2 connecting two intersection points P1 and P2 of a circle C1 and a circle C2 and a line L1 connecting a first position coordinate and a second position coordinate ( P3) can be determined as the tertiary position coordinate. If the circle C1 and the circle C2 do not intersect due to the accumulated error or the like, the midpoint of the line L1 may be determined as the third position coordinate.

In general, if the number of coordinators 110 is increased, that is, narrowing the interval between the coordinators 120 may improve the accuracy of the first position coordinates of the node 120 based on the RSSI value. However, increasing the number of coordinators 110 is very expensive. In addition, due to environmental constraints, it may be difficult to install an appropriate number of coordinators. According to the present invention, by using the acceleration / position information to correlate with the position coordinates based on the RSSI value to correct the mutual error by using a small number of coordinator 110 while improving the position coordinates based on the RSSI value of the object You can get the position coordinates.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments, rather than to limit the scope of the invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

1 is a block diagram of an embodiment of a position measuring system according to the present invention.

FIG. 2 is a block diagram of a node, a coordinator, and a positioning server shown in FIG. 1. FIG.

3 is a diagram illustrating an example of a node packet.

4 illustrates an example of a report packet.

5 is a flow chart of an embodiment of a position measuring method according to the present invention.

FIG. 6 is a diagram for explaining an example of determining first, second, and third position coordinates. FIG.

<Explanation of symbols for the main parts of the drawings>

10 ...... Positioning client 100 ...... Positioning server

110... … Coordinator 120... … Node

121... … Acceleration detection unit 122. … Control

123... … Communication unit 124. … Acceleration sensor

125... … Acceleration detection module 126... … Memory

127... … Power supply

Claims (10)

An RSSI value-based location measurement method using acceleration / location information in a wireless network, Transmitting a node packet including acceleration / position information of the object from a node having an acceleration sensing unit and attached to the object of position measurement; Receiving the node packet using a plurality of coordinators, and transmitting a report packet including a RSSI value of the received packet and the acceleration / location information to a positioning server; Calculating first position coordinates of the node by using the RSSI value of the report packet received at the positioning server; Calculating second position coordinates of the node based on the acceleration / position information included in the report packet; And calculating a final cubic position coordinate from the first position coordinate and the second position coordinate and determining the final third position coordinate as the final position coordinate of the object. The method of claim 1, The acceleration / position information includes a movement distance and a moving azimuth information from an initial position of the object. 3. The method of claim 2, And the node transmits the node packet only when the moving distance exceeds a preset threshold. The method according to any one of claims 1 to 3, The positioning server determines the third position coordinate in consideration of an error in position measurement based on an RSSI value included in the first position coordinate and an error in position measurement based on acceleration / position information included in the second position coordinate. Position measurement method. The method according to any one of claims 1 to 3, The node packet includes a node identifier, a sequence number (SN), and acceleration / position information. And the report packet includes a coordinator identifier, an RSSI value when the node packet is received, and information about the node packet. An RSSI value-based location measurement system using acceleration / location information in a wireless network, A node having an acceleration sensing unit and attached to an object for position measurement, the node generating a node packet including acceleration / position information of the object and transmitting the same through a wireless network; A plurality of coordinators having a fixed position, receiving the node packet to extract an RSSI value, and generating and transmitting a report packet including the extracted RSSI value and the node packet; The report packet is received to calculate a first position coordinate of the object based on the RSSI value and a second position coordinate of the object based on the acceleration / position information, and the final position coordinate of the object is determined from the first and second position coordinates. Position measurement system comprising; a positioning server for determining the third position coordinates. The method of claim 6, The acceleration / position information includes a moving distance and moving azimuth information from an initial position of the object. The method of claim 7, wherein And the node controlling unit to transmit the node packet only when the moving distance exceeds a preset threshold. 9. The method according to any one of claims 6 to 8, The positioning server determines the third position coordinate in consideration of an error in position measurement based on an RSSI value included in the first position coordinate and an error in position measurement based on acceleration / position information included in the second position coordinate. Position measuring system. 9. The method according to any one of claims 6 to 8, The node packet includes a node identifier, a sequence number (SN), and acceleration / position information. The report packet includes a coordinator identifier, an RSSI value at the time of receiving the node packet, and the node packet information.

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