KR101647948B1 - A position tracking system, a position tracking apparatus and a position tracking method for a user device using visible light communication - Google Patents

Abstract

The present invention relates to a position tracking system, a position tracking device, and a position tracking method of a user device using visible light communication. A light receiving unit for receiving an optical signal from the outside and transmitting the optical signal to the controller; and a control unit for controlling the optical signal output of the optical transmitting unit, A position tracking device including a controller for acquiring position information of the user device based on the optical signal received by the receiver; A user device capable of transmitting and receiving an optical signal with the position tracking device; And a data base for storing position information corresponding to each of the plurality of illumination identifiers, wherein the optical transmitter is configured to cause the optical transmitter to output an optical signal including different illumination identifier information for a plurality of regions, , The different illumination identifiers represent different position information, and the user device outputs a response signal including illumination identifier information obtained from a transmission signal of the position tracking device, and the position tracking device Extracts illumination identifier information from the response signal, and acquires position information of the user device based on the extracted illumination identifier information.

Description

TECHNICAL FIELD [0001] The present invention relates to a position tracking system, a position tracking device, and a position tracking method for a user device using visible light communication,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position tracking system, a position tracking apparatus and a position tracking method for a user device using visible light communication, and more particularly, , A location tracking device and a location tracking method.

Location Based Service (LBS) is a technology that provides a variety of information and services useful to users based on user location. 2. Description of the Related Art In recent years, as the spread of smart devices has been activated, various location-based services have been performed by utilizing a positioning technology using a global positioning service (GPS), a Wi-Fi access point (AP), or a mobile communication base station.

The conventional positioning service mainly uses a GPS signal, and its application is limited in the indoor environment. In the case of the positioning method using GPS, it is difficult to receive the GPS signal in the indoor environment, and the positioning method using the received signal strength indicator (RSSI: Received Signal Strength Indicator) of the Wi- There is a problem that the pseudo range error becomes large due to signal attenuation caused by the wall surface, signal distortion due to an obstacle in the room, or multipath due to signal reflection.

Therefore, in recent years, a lighting infrastructure using a conventional fluorescent lamp or an incandescent lamp has been replaced with a light emitting diode (LED), which is a digital semiconductor element. As an alternative to overcome the inaccuracy of the existing indoor positioning, There is a discussion about positioning using a visible light communication technology that transmits information in the visible light frequency range of about 400 to 700 nm.

An object of the present invention is to provide a position tracking system, a position tracking device, and a position tracking method for guiding an accurate position of a user device by using visible light communication in an indoor environment where positioning using a GPS signal is difficult.

According to an aspect of the present invention, there is provided an optical communication system including an optical transmitter for outputting an optical signal based on a control command of a controller, a light receiver for receiving an optical signal from the outside and transmitting the optical signal to the controller, A position-tracking device including a controller for controlling the output and acquiring positional information of the user device based on the optical signal received by the optical receiver; A user device capable of transmitting and receiving an optical signal with the position tracking device; And a data base for storing position information corresponding to each of the plurality of illumination identifiers, wherein the optical transmitter is configured to cause the optical transmitter to output an optical signal including different illumination identifier information for a plurality of regions, , The different illumination identifiers represent different position information, and the user device outputs a response signal including illumination identifier information obtained from a transmission signal of the position tracking device, and the position tracking device Extracts illumination identifier information from the response signal, and acquires position information of the user device based on the extracted illumination identifier information.

According to another aspect of the present invention, there is provided an optical communication system including: an optical transmitter for outputting an optical signal based on a control command of a controller; A light receiving unit for receiving an optical signal from the outside and transmitting the optical signal to the controller; And a controller for controlling operations of the optical transmitter and the optical receiver, wherein the controller controls the optical transmitter to output an optical signal including different illumination identifier information for a plurality of regions, Wherein the light identifier indicates different position information, extracts the light identifier information from the response signal of the user device received by the light receiver, and acquires the position information of the user device based on the extracted light identifier information A device for tracking a position of a user device is provided.

According to another aspect of the present invention, there is provided a method of controlling a light emitting device, the method comprising: dividing an optical emission range of the optical transmitter into a plurality of regions and outputting optical signals including different illumination identifier information for each region; Receiving a response signal of the user device through the light receiving unit; Extracting illumination identifier information from the response signal; And acquiring position information of the user device based on the extracted illumination identifier information, wherein the different illumination identifiers indicate different position information.

According to the embodiment of the present invention, the position of the user device in the indoor environment can be efficiently tracked by using the optical signal output from the lighting module, and various services using the optical signal, such as the indoor location tracking service and the indoor location guidance service, .

In addition, according to the embodiment of the present invention, the optical signal output from the position tracking device is divided into a plurality of regions, and the optical device can precisely track the position of the user device.

1 is a schematic diagram illustrating a system for tracking a position of a user device according to an embodiment of the present invention;
2 is a block diagram showing a configuration of a position tracking apparatus according to an embodiment of the present invention;
3 is a diagram showing an embodiment of a frame structure of a visible light signal output by the position tracking apparatus of the present invention.
4 is a view showing an embodiment in which the position tracking device of the present invention alternately transmits visible light signals to a plurality of areas.
5 illustrates an embodiment in which a plurality of regions are divided into sector units according to an embodiment of the present invention.
6 is a flowchart illustrating a method of tracking a location of a user device according to an embodiment of the present invention.

As used herein, terms used in the present invention are selected from general terms that are widely used in the present invention while taking into account the functions of the present invention. However, these terms may vary depending on the intention of a person skilled in the art, custom or the emergence of new technology. Also, in certain cases, there may be a term arbitrarily selected by the applicant, and in this case, the meaning thereof will be described in the description of the corresponding invention. Therefore, it is intended that the terminology used herein should be interpreted relative to the actual meaning of the term, rather than the nomenclature, and its content throughout the specification.

1 is a schematic diagram showing a system 1000 for tracking a location of a user device according to an embodiment of the present invention.

Referring to FIG. 1, a location tracking system 1000 of the present invention may include a location tracking device 1200, at least one user device 1400, and a database 1600.

The position tracking system 1000 of the present invention is for tracking the precise position of the user device 1400 in the indoor environment as well as in the outdoor environment and can be used for visibility communication between the position tracking device 1200 and the user device 1400 Light Communication) can be used.

Visible light communication is a method of using a visible light band signal of a wavelength of about 380 to 780 nm visible to the human eye as an information transmission medium instead of a conventional RF (Radio Frequency) band signal. On the transmission side of visible light communication, a digital light emitting device emitting visible light such as an LED can quickly switch on / off or perform intensity modulation of light to output information in visible light. On the visible light receiving side, visible light is received using a light receiving element such as a photodiode (PD), an image sensor, or an optical sensor, and information can be extracted from the received visible light to transmit and receive data.

A method of modulating / demodulating a visible light signal for storing or extracting information in visible light is divided into a baseband modulation in a baseband and a subcarrier modulation in which a subcarrier is transmitted using a subcarrier. ). ≪ / RTI > Typical examples of baseband modulation schemes include pulse coding using pulse characteristics such as line coding and position, width, and spacing of pulses. A typical example of a modulation technique using subcarriers is M-ary Phase Shift Keying (M-PSK), M-ary Phase Amplitude Modulation (M-PAM), and M-ary Quadrature Amplitude Modulation . In addition, on-off keying (OOK) modulation and pulse position modulation (PPM) are widely used in visible light communication. In addition, NRZ-OOK (Non-Return to Zero On Off Keying) (Pulse Width Modulation), Sub-Carrier Pulse Position Modulation (SC-PPM), Sub-Carrier Frequency Shift Keying (SCFSK), Pulse Amplitude Modulation (PAM), Amplitude Shift Keying (ASK) Phase Shift Keying) can be utilized.

Visible light communication is harmless to the human body because it uses visible light as a wireless communication medium. It is free from legal restrictions such as frequency permission, has no interference with ISM (Industrial, Scientific and Medical) frequency band, .

Especially, in case of visible light communication using LED, unlike conventional fluorescent lamps, it is environment-friendly because it does not contain mercury and has a long lifetime ranging from 50,000 to 100,000 hours with high efficiency of up to 100 lm / W. 70 ~ 90% energy savings can be achieved. In general, the human eye recognizes that the visible light flicker rate is more than 100 times per second, so it can not recognize the flicker of light. Therefore, using this principle, it is possible to maintain the illumination / Data communication becomes possible.

Hereinafter, the components of the position tracking system 1000 according to an embodiment of the present invention will be described.

First, the position tracking apparatus 1200 can track the position of the user device 1400 using visible light communication, and includes an optical transmitter 1220 for outputting a visible light signal, a light receiver (not shown) for receiving a visible light signal from the outside ). According to one embodiment, the location tracking device 1200 may be provided in combination with various types of lighting devices.

The position tracking device 1200 can output information in a visible light signal. For example, the position tracking device 1200 includes a light source (e.g., LED) that outputs visible light, and controls the output of the light source by utilizing various modulation techniques as described above so that desired information is included in visible light, And outputs the visible light signal.

Here, the information included in the visible light signal may be an illumination identifier to which a unique value is assigned to each of the position tracking devices 1200. The user device 1400 of the present invention obtains the light identifier information from the visible light signal of the position tracking device 1200 and outputs a response signal including the obtained light identifier information as described later. Upon receiving the response signal from the user device 1400, the location tracking device 1200 can acquire the location information of the corresponding user device using the illumination identifier included in the response signal.

The user device 1400 includes various devices capable of performing transmission and reception of a visible light signal with the position tracking device 1200. For example, the user device 1400 may include a smart phone, a cellular phone, a navigation device, a digital broadcasting terminal, a personal digital assistant (PDA), a notebook computer, and the like.

Meanwhile, the database 1600 stores various information necessary for the location tracking device 1200 to track the location of the user device 1400. For example, the database 1600 may store location information corresponding to each of a plurality of illumination identifiers. According to one embodiment, the database 1600 may be connected to the location tracking device 1200 through a wired / wireless network to provide information, or may be included in the location tracking device 1200.

According to the embodiment of the present invention, the position tracking device 1200 divides the visible light emission range of the optical transmitter 1220 into a plurality of areas, and outputs optical signals including different illumination identifier information for each area have. 1, the position tracking device 1200 divides an area capable of emitting visible light into two areas, that is, a first area (Area 1) and a second area (Area 2) through an optical transmitter 1220, It is possible to output an optical signal including different illumination identifier information for each region. That is, the illumination identifier of the first visible light signal (Sig. 1) transmitted to the first region has a different value from the illumination identifier of the second visible light signal (Sig. 2) transmitted to the second region. The visible light signal transmitted in each area can be transmitted in the form of a beacon promised in advance between the position tracking device 1200 and the user device 1400. [

The user device 1400 receiving the visible light signal from the position tracking device 1200 transmits the corresponding response signal Ack. At this time, the response signal includes the illumination identifier information of the visible light signal received by the user device 1400. Upon receiving the response signal of the user device 1400, the location tracking device 1200 can acquire the location information of the user device 1400 using the illumination identifier information included in the response signal.

In the embodiment of FIG. 1, the user device 1400 can receive the second visible light signal (Sig. 2) and output the response signal (Ack) accordingly. The light identifier information of the second visible light signal (Sig. 2) may be included in the response signal (Ack). Upon receiving the response signal Ack of the user device 1400, the position tracking device 1200 can recognize that the corresponding response signal Ack includes the illumination identifier of the second visible light signal Sig. 2, It can be seen that the user device 1400 is located in the second area (Area 2) emitting the second visible light signal (Sig. 2).

According to one embodiment, there may be a plurality of location tracking devices 1200 within one location tracking system 1000, each location tracking device 1200 having a plurality of areas with different illumination identifier information It is possible to output an optical signal. If all the pieces of the light identifier information included in the optical signals output from the plurality of position tracking devices 1200 are different, the position tracking device 1200 transmits the light identifier information included in the response signal Ack to the corresponding user device It is possible to obtain the positional information of the position sensor 1400. However, if overlapping of the light identifier information is allowed between the optical signals output from the plurality of position tracking devices 1200, the position tracking device 1200 may detect the light identifier information included in the response signal Ack and the position identifier The location information of the corresponding user device 1400 can be acquired by using the combination of the installation location information of the user device 1400 and the location information of the user device 1400. The database 1600 stores data for acquiring location information of the user device 1400 using the illumination identifier information and other information according to the setting status of the location tracking system 1000. [

According to an embodiment of the present invention, the location tracking device 1200 acquiring location information of the user device 1400 can beam-form a visible light signal to the corresponding user device 1400 and transmit the beam. Specifically, the location tracking device 1200 determines whether the acquired location information of the user device 1400 matches the location information indicated by the illumination identifier of the optical signal output by the location tracking device 1200. The matching of the position information may be determined according to the matching of the illumination identifiers according to the embodiment. If the position information matches, the user device 1400 can know that it is located within the light emission range of the position tracking device 1200. At this time, the position tracking device 1200 can beam-transmit the visible light signal to the area corresponding to the corresponding illumination identifier, and transmit the data to the user device 1400 efficiently.

On the other hand, the acquired location information of the user device 1400 may not coincide with the location information indicated by the illumination identifier of the optical signal output by the location tracking device 1200. When a plurality of position tracking devices 1200 exist in the position tracking system 1000, the response signal Ack of the user device 1400, which is output corresponding to the visible light signal of the other position tracking device, ). ≪ / RTI > In this case, the position tracking apparatus 1200 does not perform the beamforming, thereby increasing stability and reliability of data transmission.

As described above, the location tracking system 1000 of the present invention can perform more precise location tracking and efficient data transmission by dividing the optical emission range of the location tracking device 1200 into a plurality of areas.

2 is a block diagram showing a configuration of a position tracking apparatus 1200 according to an embodiment of the present invention.

2, the location tracking apparatus 1200 may include a controller 1210, an optical transmitter 1220, a light receiver 1230, a memory 1240, and a communication unit 1250.

First, the optical transmitter 1220 outputs a visible light signal based on a control command of the controller 1210. As described above, the controller 1210 can store information in a visible light signal using baseband modulation or subcarrier modulation. The light transmitting unit 1220 may include various LED modules, according to an exemplary embodiment of the present invention. According to the embodiment of the present invention, the optical transmitter 1220 may include a plurality of illumination modules to transmit different visible light signals to a plurality of areas. The controller 1210 may group one or more lighting modules and output different visible light signals for each group. However, the present invention is not limited to this, and the visible light signal transmission to a plurality of regions may be performed using one illumination module.

The light receiving unit 1230 receives the visible light signal from the outside and transmits it to the controller 1210. The light receiving unit 1230 can demodulate the received visible light signal and extract the information included in the corresponding signal. For example, the light receiving section 1230 may include a light receiving element and a demodulation circuit. At this time, a photodiode or the like can be used as the light receiving element. The light receiving element can receive the visible light signal and convert it into an electrical signal. The demodulation circuit can demodulate the electric signal output from the light receiving element. According to another embodiment, the demodulation circuit may be omitted in the light receiving unit 1230, but the controller 1210 may perform the demodulation function instead. Information contained in the visible light signal can be extracted from this demodulated electrical signal, which can be performed in the light receiver 1230 or the controller 1210.

The memory 1240 may store various programs and data for driving the position tracking device 1200. The memory 1240 may store data semi-permanently or temporarily. Also, the memory 1240 may be provided in a form embedded in the position tracking device 1200 or in a detachable form. Examples of the memory 1240 include a hard disk drive (HDD), a solid state drive (SSD), a flash memory, a ROM (Read-Only Memory), a RAM This can be.

The communication unit 1250 is a structure for the location tracking device 1200 to transmit and receive data to / from an external device. The location tracking device 1200 can access the wired / wireless network through the communication unit 1250 and can receive information from a database connected to the network.

The communication unit 1250 may include various communication modules such as wired / wireless communication. In case of wireless communication, the communication unit 1250 may include a mobile communication module or a short-range communication module. 3G, 4G mobile communication such as CDMA, GSM, CDS, cdmaOne, HSCSD, CDMA2000, UMTS, WCDMA, EV-DO, HSDPA, HSPA +, LTE, LTE-advanced, WiMAX, Wibro, It is possible to perform communication by connecting to the mobile communication network according to various standards such as specifications. In the case of the short-range communication module, data can be transmitted / received to / from an external device via a short-distance communication method including Wi-Fi, bluetooth, and zigbee.

The location tracking device 1200 of the present invention can be used as an access point for wireless communication of a user device. That is, the location tracking device 1200 transmits and receives data to and from the user device using the optical transmitter 1220 and the optical receiver 1230, and can transmit and receive the data to and from the external network using the communication unit 1250. Accordingly, the location tracking device 1200 can serve as an access point that relays the user device to perform communication with the external network.

The controller 1210 controls the overall operation of the position tracking device 1200. That is, the controller 1210 may perform arithmetic operation and processing of various information and may control the operation of each component of the position tracking apparatus 1200. The operation of the position tracking device 1200 may be interpreted to be performed under the control of the controller 1210 unless otherwise mentioned in the following description.

The controller 1210 may be implemented as a computer or similar device depending on the hardware, software, or combination thereof. The controller 1210 may be provided in the form of an electronic circuit that processes an electrical signal to perform a control function, and may be provided in a form of a program that drives a hardware controller 1210 in software.

FIG. 3 shows an embodiment of a frame structure of a visible light signal output by the position tracking apparatus of the present invention.

When transmitting a visible light signal, the position tracking apparatus of the present invention can transmit a frame to a corresponding area by storing light identifier information (Light ID Info.) In the frame. The illumination identifier information is uniquely allocated to each of the divided regions of the optical emission range of the position tracking apparatus, and different illumination identifier information may be allocated to different regions. In the frame of FIG. 3, the illumination identifier information may be replaced with region information, sector information, or the like that indicates a physical location according to the embodiment.

The user device receiving the transmitted frame extracts the illumination identifier information in the received frame and outputs a response signal including the extracted illumination identifier information. The location tracking device receiving the response signal of the user device can acquire the location information of the user device using the illumination identifier included in the response signal.

FIG. 4 shows an embodiment in which the position tracking apparatus of the present invention alternately transmits visible light signals to a plurality of regions. 4 (a) shows an embodiment in which the position tracking apparatus divides the light emission range into two regions to output visible light signals. Fig. 4 (b) shows an example in which the position tracking apparatus divides the light emission range into three regions, And outputs a signal.

Referring to FIG. 4, the position tracking apparatus of the present invention can alternately output each visible light signal corresponding to a plurality of regions in a predetermined period Tp. Referring to FIG. 4A, the position tracking apparatus alternately outputs visible light signals to the first area (Area 1) and the second area (Area 2), and outputs the current visible light output to the first area and the next visible light output Can be maintained at a predetermined period Tp. Similarly, referring to FIG. 4B, the position tracking apparatus alternately outputs visible light signals to the first area (Area 1), the second area (Area 2), and the third area (Area 3) The time interval between the current visible light output and the next visible light output for the region can be maintained at a predetermined period Tp. This applies equally to visible light output for the second region and the third region.

According to an embodiment of the present invention, the position tracking device can set the period Tp to 5 ms or less. Having an alternating period of less than 5 ms, the human eye can not sense the flickering of light, so it can always appear to emit light in all areas and prevent flickering.

When the position tracking apparatus receives the response signal to the specific region (the first region in the case of FIG. 4) while alternately outputting the visible light signal for each region, the visible light signal is irradiated to the region (first region) And can be transmitted.

FIG. 5 shows an embodiment in which a plurality of areas are divided into sector units according to an embodiment of the present invention.

According to the embodiment of the present invention, the position tracking device 1200 can divide the optical radiation range of the optical transmitter 1220 into various types of regions and output a visible light signal. For example, referring to FIG. 5, the position tracking apparatus 1200 divides the optical radiation range of the optical transmitter 1220 into a plurality of sectors (Sector 1, Sector 2, Sector 3, and Sector 4) It is possible to output a visible light signal including different illumination identifier information. In order to divide the light emission range into a plurality of sectors in this manner, the optical transmitter 1220 may include a plurality of illumination modules.

6 is a flowchart illustrating a method of tracking a position of a user device according to an embodiment of the present invention. Each step of Fig. 6 can be controlled by the controller of the position tracking device.

First, the position tracking apparatus outputs an optical signal including different illumination identifier information for a plurality of regions (S110). The location tracking device can divide the optical radiation area of the optical transmitter into a plurality of areas of various types, and different illumination identifier information is allocated to each divided area. The illumination identifier information may indicate location information for each divided area, or physical location information. In the embodiment of the present invention, the illumination identifier information may be replaced with area information indicating a physical location, sector information, and the like.

Next, the position tracking apparatus receives the response signal of the user device through the light receiving unit (S120). As described above, when the user device receives the optical signal in step S110, it acquires the light identifier information from the optical signal, and outputs a response signal including the acquired light identifier information. The position tracking device can receive a response signal output from the user device using a light receiving element such as a photodiode.

Next, the location tracking device extracts the illumination identifier information from the response signal (S130). The optical receiver of the location tracking device can demodulate the received optical signal and extract information contained in the signal. A demodulation circuit for this purpose may be included in the light receiving unit or the controller of the position tracking apparatus. The position tracking apparatus can acquire frame information of a response signal from the electric signal demodulated by the demodulation circuit and extract the illumination identifier information in the frame.

Next, the location tracking device obtains the location information of the user device based on the extracted illumination identifier information (S140). When all the illumination identifiers are mapped one-to-one with each one of the location information in the location tracking system, the location tracking device can obtain location information of the user device using only the acquired illumination identifier information. However, when the overlapping of the light identifiers is allowed between the optical signals output from the plurality of position tracking devices in the position tracking system, the position tracking device detects the position of the light spot by using the light identifier information included in the response signal, The location information of the corresponding user device can be obtained by using the combination. The database of the location tracking system stores data for acquiring location information of the user device using the illumination identifier information and other information according to the setting status.

According to an embodiment of the present invention, a location tracking device that obtains location information of a user device can beam-form a visible light signal to the user device and transmit the beam. The location tracking device determines whether the acquired location information of the user device coincides with the location information indicated by the illumination identifier of the optical signal output by the location tracking device. If the location information matches, the location tracking device transmits the visible light signal to the area corresponding to the corresponding illumination identifier, and transmits the visible light signal efficiently to the user device.

However, the present invention is not limited to this, and optical communication in various frequency bands, such as infrared communication, which are out of the visible light region, may be performed in the same manner Method can be used.

While the present invention has been described with reference to the particular embodiments, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention. Therefore, it is to be understood that those skilled in the art can easily deduce from the detailed description and the embodiments of the present invention that they fall within the scope of the present invention.

1000: Location tracking system
1200: location tracking device
1210: Controller
1220:
1230:
1240: Memory
1250:
1400: User device
1600: Database

Claims (9)

A user device for transmitting and receiving an optical signal;
A position tracking device for transmitting an optical signal to the user device and determining a position of the user device based on the optical signal transmitted from the user device; And
A database for storing position information corresponding to the optical signal; Lt; / RTI >
Wherein the optical signal emission range of the position tracking device is divided into a plurality of regions,
The position tracking device includes:
And outputting an optical signal including identifier information for individually identifying the divided regions, wherein the different regions correspond to the different identifier information, and the different identifier information is different from a position Information,
Receiving a response signal of the user device with respect to the optical signal, extracting the identifier information from the response signal,
Obtains positional information of the user device in the optical signal emission range corresponding to the extracted identifier information with reference to the database,
And the optical signal is beamformed into an area corresponding to the acquired position information of the user device.
An optical transmitter for outputting an optical signal based on a control command of the controller;
A light receiving unit for receiving an optical signal from the outside and transmitting the optical signal to the controller; And
And a controller for controlling operations of the optical transmitter and the light receiver,
Wherein the optical signal emission range of the optical transmitter is divided into a plurality of regions,
The controller comprising:
And outputs the optical signal including the identifier information that individually identifies the divided regions through the optical transmission unit, wherein the different regions correspond to the different identifier information, and the different identifier information includes the optical signal emission range Lt; RTI ID = 0.0 > location information,
Receiving a response signal of the user device with respect to the optical signal through the light receiving unit, extracting the identifier information from the response signal,
Acquiring location information of the user device in the optical signal emission range based on the extracted identifier information,
And performs beamforming of the optical signal to an area corresponding to the acquired position information of the user device.
3. The method of claim 2,
Wherein the controller controls each of the optical signals corresponding to the plurality of regions to be alternately output at a predetermined cycle.
The method of claim 3,
Wherein the period is 5 ms or less.
3. The method of claim 2,
The controller controls the optical signal to be beamformed and transmitted to an area corresponding to the identifier information when the acquired position information of the user device coincides with the position information indicated by the identifier information of the optical signal transmitted by the optical transmitter And the position of the user device.
3. The method of claim 2,
Wherein the optical signal is a visible light signal and the optical transmitter is an LED module.
delete 3. The method of claim 2,
Wherein the location tracking device is an access point for wireless communication of the user device.
The method comprising the steps of: transmitting an optical signal including identifier information, the identifier information being information for individually identifying each region of the plurality of divided optical signal emission ranges, the different regions corresponding to different identifier information, Wherein the different identifier information indicates different position information within the optical signal emission range;
Receiving a response signal of the user device to the optical signal;
Extracting the identifier information from the response signal;
Obtaining location information of the user device in the optical signal emission range based on the extracted identifier information; And
Beamforming an optical signal into an area corresponding to the acquired position information of the user device; And controlling the position of the user device based on the position information.

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