KR101219663B1 - System for visible light communications with multi-carrier modulation and method thereof - Google Patents

Abstract

The visible light transmitting apparatus of the present invention is a visible light transmitting apparatus that transmits data by using visible light, receives symbol data, performs symbol-mapping, converts symbols into parallel data, performs IFFT, and converts IFFT result values. A modulator separating the real data and the imaginary data; A digital / analog converter for converting real part data and imaginary part data into analog signals; And a transmission unit for transmitting the real part data and the imaginary part data converted into analog signals using visible light. According to the present invention, by using a multi-carrier technique capable of higher-order modulation, it is possible to overcome the limitation of the transmission rate of the existing strength modulation scheme in visible light communication and to improve the transmission rate.

Visible light, higher order modulation, IFFT, FFT, multicarrier, VLC

Description

System for visible light communications with multi-carrier and method thereof

The present invention relates to a visible light wireless communication system and a method thereof. More particularly, the present invention relates to a visible light wireless communication system using a multi-carrier and a method thereof.

The present invention is derived from a study conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Telecommunication Research and Development. Meter Visible Light RGB Screening Wireless Communication Research].

Communication technologies using light in the communication area include infrared data wireless communication using an infrared region, visible light wireless communication using visible light, and optical communication using optical fibers.

Visible light is a light ray that has a wavelength in the visible range among the electromagnetic waves, and corresponds to a wavelength range of 380 nm to 780 nm. In visible light, the change of properties according to the wavelength appears in color, and the wavelength becomes shorter from red to purple. Light with a longer wavelength than red is called infrared, and light with a shorter wavelength than purple is called ultraviolet. For monochromatic light, 610nm to 700nm is red, 590nm to 610nm is yellow, 500nm to 570nm is green, 450nm to 500nm is blue, and 400nm to 450nm is purple.

The Infrared Data Association (IrDA) was founded in 1993 as an industry-sponsored nonprofit organization that sets international standards for the hardware and software used in infrared data communication links. IrDA is a private standardization organization established to support and collaborate on the hardware and software needed to transfer data using infrared light between desktops, laptops and personal digital assistants. In 1994, IrDA 1.0 (Serial Infrared) was adopted. The IrDA 1.0 concept replaces cables, connectors, and serial ports with infrared communication ports, based on RS-232C or serial ports. The transmission speed is 2.4 ~ 115.2Kbps half-duplex communication, the communication distance is 1m, the directivity angle is 30 degrees, and it is installed in Windows 95 as standard, so that the popularity of equipment equipped with infrared communication port conforming to IrDA standard is increasing rapidly To come up with. In 1995, up to 4Mps of IrDA 1.1 standard proposed by HP, IBM, and SHARP 3 was set up to improve the existing IrDA 1.0, and laid the foundation for transmitting image information. As a result, IR communication devices, modules corresponding to IrDA 1.1 standards, and mobile information devices such as desktops, notebooks, PDAs, and electronic notebooks equipped with IrDA 1.1 standards ports, digital cameras, and printers have been manufactured. In 1997, a power saving standard with a communication distance of 20m was added. In 1998, a standard was established to connect PCs, peripheral devices such as keyboards, mice, and game packs by standardizing IrDA Control, an infrared standard that can communicate with one host and multiple terminals.

On the other hand, IEEE 802.11 is a wireless network technology supporting a maximum speed of 2Mbps, using infrared (850nm ~ 950nm) or 2.4GHz Industrial, Scientific and Medical (ISM) band propagation. Recently, a study group of wireless communication using visible light, that is, visible light communications (VLC), has been created in the IEEE 802.15 Wireless Personal Area Network (WPAN), and work for international standards is in progress. Visible light wireless communication is a communication technology that transmits information by using visible light (wavelength in the 380 nm to 780 nm region), and transmits information by blinking visible light of a light emitting diode (LED) used in a display device at an invisible speed. Communication technology. Visible light wireless communication widely uses an intensity modulation (IM) using a light source intensity and a direct detection (DD) method using a light detector.

Looking at the prior art related to the conventional visible light wireless communication, the OFDM symbol structure is changed for intensity modulation (eg, OOK, PPM, etc.) / Direct detection so that only real values are output after OFDM modulation (IFFT). However, this method has a disadvantage of only half of the conventional OFDM scheme in terms of transmission speed.

The present invention has been proposed to solve the above problems,

Real-time signal and imaginary part to perform modulation using multi-carrier modulation technique for high speed transmission and to be suitable for the strength modulation / direct detection (IM / DD) method that uses complex modulated signals in optical wireless communication. By dividing the signal and transmitting it by using light sources of different wavelengths (λ) bands, the receiving unit allows the optical filter to selectively receive optical signals transmitted in different wavelength bands using a device. The purpose.

In particular, it is an object of the present invention to provide a visible light wireless communication system and method that overcomes limitations of the transmission speed of the existing strength modulation scheme and improves the transmission speed by using a multicarrier modulation technique capable of higher order modulation.

The visible light transmitting apparatus of the present invention is a visible light transmitting apparatus which transmits data using visible light, receives symbol data, performs symbol-mapping, converts the symbols into parallel data, and performs IFFT, and the IFFT result value. A modulator separating the real data and the imaginary data; A digital / analog converter for converting the real part data and the imaginary part data into analog signals; And a transmitter for transmitting the real part data and the imaginary part data converted into analog signals using visible light.

In particular, the modulator may symbol-map the data to be transmitted according to any one of QPSK, 16-QAM, 64-QAM, and 256-QAM.

The transmitter may include: a first light emitting diode for transmitting the real part data; And a second light emitting diode for transmitting the imaginary part data.

In addition, the first light emitting diode and the second light emitting diode are characterized in that the visible light of different wavelength bands are emitted.

On the other hand, the visible light receiving apparatus of the present invention is a visible light receiving apparatus for receiving data transmitted by using visible light, and collects the optical signal transmitted from the free space to pass the optical signal of a specific wavelength band, An optical detector converting an optical signal into an electrical signal; An analog / digital converter configured to receive an electrical signal from the light detector and convert the electrical signal into a digital signal; And receiving a digital signal from the analog / digital converter, combining the complex data into complex data, converting the complex data into parallel data, performing an FFT operation, and converting the result value according to the FFT operation into serial data. And a demodulator for symbol-demapping.

In particular, the demodulator may symbol-demap the serial data according to any one of QPSK, 16-QAM, 64-QAM, and 256-QAM.

The light detector may further include a first light detector configured to detect real part data from the transmitted optical signal; And a second light detector for detecting imaginary data from the transmitted optical signal.

The first light detector may further include a condenser lens for condensing the transmitted optical signal; And a condenser filter configured to pass an optical signal having a specific wavelength band among the optical signals collected through the condenser lens.

On the other hand, the visible light transmission method of the present invention, a method for transmitting data using the visible light, comprising the steps of: receiving symbol data to perform symbol-mapping; Converting the symbols into parallel data to perform an IFFT operation; Dividing the result value according to the IFFT operation into real data and imaginary data; And converting the real part data and the imaginary part data into an analog signal and transmitting the visible data having different wavelength bands.

On the other hand, the receiving method of the present invention, a method for receiving data transmitted using visible light, comprising: condensing an optical signal transmitted from free space; Passing an optical signal having a specific wavelength band among the collected optical signals; Converting the passed optical signal into an electrical signal; Converting an optical signal converted into an electrical signal into a digital signal and combining the data into a complex form; Converting the complex data into parallel data and performing an FFT operation; And converting the resultant value according to the FFT operation into serial data and performing symbol-demapping.

The present invention has the following effects.

By using a multi-carrier modulation technique capable of higher-order modulation, it is effective in overcoming the limitation of the transmission speed of the existing strength modulation scheme and improving the transmission speed.

The present invention will now be described in detail with reference to the accompanying drawings. Hereinafter, a repeated description, a known function that may obscure the gist of the present invention, and a detailed description of the configuration will be omitted. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Accordingly, the shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity.

1 is a block diagram showing a schematic configuration of a visible light wireless communication system using multiple carriers according to an embodiment of the present invention.

The visible light wireless communication system according to the present invention includes a visible light transmitting apparatus 100 and a visible light receiving apparatus 200.

The visible light transmitting apparatus 100 receives transmission data and transmits the visible data using visible light in the 380 nm to 780 nm wavelength band or infrared light in the 850 nm to 950 nm wavelength band. The visible light receiver 200 receives the transmission data transmitted by the visible light transmitter 100 using visible light in the 380 nm to 780 nm wavelength band or infrared light in the 850 nm to 950 nm wavelength band, and then passes through a predetermined process to be described later. Extract

2 is a block diagram for explaining in detail the configuration of a visible light transmitting apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating the configuration of the multi-carrier-visible light communication (MC-VLC) modulator 110 of FIG. 2 in more detail.

The visible light transmitting apparatus 100 according to the present invention includes an MC-VLC modulator 110, a digital / analog converter 130, and a transmitter 150.

The MC-VLC modulator 110 receives data to be transmitted, divides the data into data streams having a low data rate, divides the data into multiple carriers, and modulates the data to be transmitted at the same time.

For this purpose, the MC-VLC modulator 110 may include a mapping unit 112, a serial / parallel converter 114, an IFFT operator 116, a parallel / serial converter 117, and a real / imaginary separator 119. It is provided. Here, the configuration (for example, convolutional channel coding, scrambling, interleaving) regarding forward error correction (FEC) is omitted. Forward error correction is a method of encoding an error so that not only the detection of the error occurring in the transmission data can be corrected but also the correction at the receiving end. In general, when an error occurs, retransmission is required, but when retransmission is inappropriate, such as unidirectional broadcasting, a forward error correction method is used.

The mapping unit 112 performs symbol-mapping for higher order modulation. More specifically, the mapping unit 112 generates one symbol by grouping transmission data by a predetermined unit bit for higher order modulation. For example, in quadrature phase shift keying (QPSK) mapping, one symbol is generated by combining two bits of transmission data, and in the case of 16-quadrature amplitude modulation (QAM) mapping, one symbol is generated by combining four bits of transmission data. . In case of 64-QAM mapping, one symbol is generated by grouping transmission data by 6 bits, and in case of 256-QAM mapping, one symbol is generated by grouping transmission data by 8 bits. QPSK collects two bits of digital signals 0 and 1 and transmits them in correspondence with four phases of a carrier. QAM classifies digital signals by a predetermined amount and modulates them by changing a carrier signal and a phase. For example, in the case of 16-QAM, a binary digital signal of 4 bits per coordinate can be transmitted through 16 signal spaces having different phases and magnitudes.

The serial / parallel converter 114 converts an input serial data signal (hereinafter referred to as serial data) into a parallel data signal (hereinafter referred to as parallel data) to perform an IFFT operation.

The IFFT operator 116 performs an inverse fast fourier transform (IFFT) operation on the parallel data, which is transformed into a parallel structure through the serial / parallel converter 114, to be divided and transmitted to multiple carriers at the same time and outputs the result value. do.

The parallel / serial converter 117 receives complex IFFT calculation result values simultaneously output in parallel from the IFFT calculator 116 and converts them into serial data.

The real / imaginary separation unit 119 sequentially receives the values output from the parallel / serial conversion unit 117, and converts the result value of the complex IFFT operation into a real value (real data) and an imaginary value (imaginary data). ) And outputs it to the digital / analog converter 130.

The digital / analog converter 130 receives discrete values (real and imaginary values) output from the real / imaginary separator 119 of the MC-VLC modulator 110 and converts them into analog signals. To this end, the digital / analog converter 130 includes a first digital / analog converter 132 and a second digital / analog converter 134. That is, the first digital / analog converter 132 receives the real value output through the real / imaginary separator 119, converts the real value into an analog signal, and outputs the converted analog signal. The second digital / analog converter 134 The imaginary value output through the real / imaginary separation unit 119 is input and converted into an analog signal and output.

The transmitter 150 receives a real value and an imaginary value converted into an analog signal through the digital / analog converter 130 and transmits a signal using visible light having different wavelength bands λ1 and λ2. do.

To this end, the transmitter 150 includes a first light emitting diode 152 and a second light emitting diode 154. For example, when the first light emitting diode 152 emits light in the λ1 wavelength band, the second light emitting diode 154 emits light in the λ2 wavelength band. λ1 and λ2 may be configured to have different wavelengths in the 380 nm to 780 nm wavelength band (visible light), or may have different wavelengths in the 850 nm to 950 nm (infrared) wavelength band.

For example, the transmitter 150 may be configured such that the first light emitting diode 152 emits a red light source in the visible light wavelength band and the second light emitting diode 154 emits a blue light source in the visible light band. Alternatively, a white light emitting diode for indoor lighting may be used as the first light emitting diode 152, and an infrared light emitting diode may be used as the second light emitting diode 154.

Meanwhile, when data is transmitted using two light emitting diodes having different wavelengths in the 850 nm to 950 nm infrared wavelength band, data is transmitted using two light emitting diodes having different wavelengths in the 380 nm to 780 nm visible light wavelength band. In this case, there is an advantage that the available frequency band can be effectively used and the production cost of building a communication system is low. This is because communication using infrared rays is commercially available, and thus it is possible to receive the optical signal transmitted from the transmitting end and receive the optical signal in detail.

4 is a block diagram for explaining in detail the configuration of the visible light receiving apparatus 200 according to an embodiment of the present invention. FIG. 5 is a block diagram illustrating in detail the configuration of the first light detector 212 of FIG. 4. FIG. 6 is a block diagram illustrating the configuration of the MC-VLC demodulator 250 of FIG. 4 in detail. .

First, referring to FIG. 4, the visible light receiver 200 according to the present invention includes a light detector 212, an analog / digital converter 230, and an MC-VLC demodulator 250.

The light detector 210 electrically converts the optical signals transmitted from the visible light transmitting apparatus 100 of FIG. 2 through light sources having different wavelength bands λ1 and λ2. To this end, the light detector 210 includes a first light detector 212 and a second light detector 214. Since the first light detector 212 and the second light detector 214 are configured in the same configuration, only the first light detector 212 will be described as an example in order to avoid overlapping descriptions below.

The first light detector 212 includes a condenser lens 10, an optical filter 20, and a photoelectric element 30.

The condenser lens 10 collects the light signals emitted in the free space and collects light in the optical filter 20.

The optical filter 20 is a device for selectively passing light of a specific wavelength λ1. That is, the optical filter 20 of the first light detector 212 selectively passes an optical signal having a wavelength of λ 1 emitted through the first light emitting diode 152 described above, and the optical filter of the second light detector 214. (Not shown) selectively passes only an optical signal having a wavelength? 2 of light emitted through the above-described second light emitting diode 154.

The optoelectronic device 30 converts an optical signal passing through the optical filter 20 into an electrical signal. The optical signal converted into an electrical signal is input to the analog / digital converter 230.

The analog / digital converter 230 receives each electrical signal input from the light detector 210 and converts the electrical signal into a digital signal. That is, the analog / digital converter 230 includes a first analog / digital converter 232 and a second analog / digital converter 234, and each of the electrical signals input from the light detector 210 is provided. Convert to a digital signal.

Each digital signal output from the analog / digital converter 230 is input to the MC-VLC demodulator 250.

The MC-VLC demodulator 250 receives each digital signal output from the analog / digital converter 230 and restores the received data.

To this end, the MC-VLC demodulator 250 includes a real / imaginary combination unit 252, a serial / parallel converter 254, an FFT calculator 256, a parallel / serial converter 257, and a demapping unit 259. ). Here, the structure regarding forward error correction (FEC) is omitted. Forward error correction is a method of encoding an error so that not only the detection of the error occurring in the transmission data can be corrected but also the correction at the receiving end.

The real / imaginary combination unit 252 receives each digital signal output from the analog / digital converter 230 and combines the digital signals into complex data. That is, the first analog / digital converter 232 receives a discrete real value, and the second analog / digital converter 234 receives a discrete imaginary value and combines the data into a complex number.

The serial / parallel converter 254 sequentially receives digital signals combined with complex data through the real / imaginary combination unit 252 and converts them into parallel data.

The FFT calculator 256 receives parallel data from the serial / parallel converter 254 and performs a fast fourier transform (FFT) operation.

The parallel / serial converter 257 receives complex FFT calculation result values simultaneously output in parallel from the FFT calculator 256 and converts the result into serial data.

The demapping unit 259 receives the FFT result of the serial structure and performs symbol-mapping. That is, the reception data is extracted by performing the reverse operation of the operation performed by the mapping unit 112 in the above-described visual tube transmitter 100. For example, QPSK mapped transmission data is restored to 2 bits of received data, and 256-QAM mapped transmission data is restored to 8 bits of received data.

7 is a flowchart illustrating a transmission operation of the visible light transmitting apparatus according to the present invention.

Referring to FIG. 7, data to be transmitted is received, divided into data strings having a low data rate, divided into multiple carriers, and modulated transmission data for simultaneous transmission. Here, description of the forward error correction (FEC) will be omitted.

First, symbol-mapping for higher-order modulation is received by receiving data to be transmitted (S100). More specifically, one symbol is generated by grouping data to be transmitted for a higher order modulation by predetermined unit bits. For example, in quadrature phase shift keying (QPSK) mapping, one symbol is generated by combining two bits of transmission data, and in the case of 16-quadrature amplitude modulation (QAM) mapping, one symbol is generated by combining four bits of transmission data. . In case of 64-QAM mapping, one symbol is generated by grouping transmission data by 6 bits, and in case of 256-QAM mapping, one symbol is generated by grouping transmission data by 8 bits.

Next, in order to perform an IFFT operation, a serial data signal (serial data) converted into a plurality of symbols is converted into a parallel data signal (parallel data) through step S100 (S110 and S120). For example, a data signal having a serial structure converted into N symbols is converted to have one column per symbol, that is, N columns are generated.

In addition, inverse fast fourier transform (IFFT) operation is performed to divide parallel data into multiple carriers and transmit the same at the same time (S130). Since the method of performing the IFFT operation can be easily inferred by those skilled in the art, a detailed description thereof will be omitted. The IFFT operation result value in step S130 is output in a complex form.

Next, the complex IFFT operation result values simultaneously output in parallel are converted into serial data signals (S140).

The IFFT calculation result of the complex form converted into the serial structure is separated into a real value and an imaginary value (S150). Each discrete value (real and imaginary values) is converted into an analog signal for transmission using visible light (S160).

In operation S160, the real and imaginary values converted into analog signals are transmitted using light sources having different wavelength bands λ 1 and λ 2. At this time, λ1 and λ2 may have different wavelengths in the 380 nm to 780 nm wavelength band (visible light) or may have different wavelengths in the 850 nm to 950 nm (infrared) wavelength band. For example, λ1 may be a red visible light wavelength band and λ2 may be a blue visible light band.

As described above, the shortcomings of the prior art related to the field are compensated for by separating the complex IFFT calculation result into real data and imaginary data. In addition, the receiver may selectively receive the optical signals transmitted in different wavelength bands using the optical filter device.

8 is a flowchart illustrating a receiving operation of the visible light receiving apparatus according to the present invention.

Referring to FIG. 8, an optical signal transmitted to a free space using a condenser lens is condensed on the condenser filter (S200). In order to receive the transmission data transmitted from the visible light transmitting apparatus in the received optical signal, only the optical signal of a specific wavelength band λ1 or λ2 is selectively passed (S210 and S220). That is, in order to receive transmission data (real data and imaginary data) transmitted from the visible light transmitting apparatus according to the present invention, only an optical signal of wavelength λ1 and an optical signal of wavelength λ2 are selectively passed.

Next, optical signals carried in the wavelength bands λ 1 and λ 2 are converted into electrical signals, respectively (S220). In operation S230, each optical signal converted into an electrical signal is converted into a digital signal (S230).

Each optical signal converted into a digital signal is combined into complex data in order to perform an FFT operation (S240). In other words, real data and imaginary data are combined into complex data.

In operation S240, digital signals combined with complex data are sequentially input (S250) and converted into parallel data to perform an FFT operation (S260).

Next, the parallel data passing through the step S260 is input to perform a fast fourier transform (FFT) operation (S270).

In S270, the result of performing the FFT operation is simultaneously output in parallel. Therefore, the complex-type FFT calculation result is converted into serial data to perform symbol-demapping (S280).

Finally, the result of receiving the FFT operation result of the serial structure is performed symbol-demapping (S290). For example, QPSK mapped transmission data is restored to 2 bits of received data, and 256-QAM mapped transmission data is restored to 8 bits of received data.

The present invention can be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of computer-readable recording media may include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage. Also included are those implemented in the form of carrier waves (eg, transmission over the Internet). The computer readable recording medium can also be distributed over network coupled systems so that the computer readable code is stored and executed in a distributed fashion.

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a block diagram showing a schematic configuration of a visible light wireless communication system using multiple carriers according to an embodiment of the present invention.

2 is a block diagram for explaining in detail the configuration of a visible light transmitting apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating in detail the configuration of the MC-VLC modulator of FIG. 2.

4 is a block diagram for explaining in detail the configuration of a visible light receiving apparatus according to an embodiment of the present invention.

FIG. 5 is a block diagram for describing in detail the configuration of the first light detector of FIG. 4, and FIG. 6 is a block diagram for describing the configuration of the MC-VLC demodulator of FIG. 4 in detail.

7 is a flowchart illustrating a transmission operation of the visible light transmitting apparatus according to the present invention.

8 is a flowchart illustrating a receiving operation of the visible light receiving apparatus according to the present invention.

Claims (10)

A visible light transmitting device for transmitting data by using visible light, A modulator configured to receive data to be transmitted, perform symbol-mapping, convert the mapped symbols into parallel data, perform an IFFT operation, and separate a result value of the IFFT operation into real and imaginary data; A digital / analog converter for converting the real part data and the imaginary part data into analog signals; And And a transmitter configured to transmit the real part data and the imaginary part data, which are converted into the analog signals, by using visible rays having different wavelength bands. The modulator may include: QPSK mapping that combines the data to be transmitted by 2 bits to generate one symbol; 16-QAM mapping that generates 4 symbols by combining the data to be transmitted by 4 bits; A mapping unit configured to perform the symbol-mapping according to any one of 64-QAM mapping for generating a symbol and 256-QAM mapping for generating one symbol by binding the data to be transmitted by 8 bits; A serial / parallel converter for converting data of the serial structure from the mapping unit into data of a parallel structure to perform an IFFT operation; An IFFT calculator which performs an IFFT operation on the parallel data from the serial / parallel converter; A parallel / serial conversion unit which receives complex IFFT result values from the IFFT operation unit and converts the result values into serial data; And a real / imaginary separator configured to separate the complex-type IFFT calculation result value converted and converted into serial data by the parallel / serial converter into the real part data and the imaginary part data. Transmitter. delete The method according to claim 1, The transmission unit, A first light emitting diode for transmitting the real part data; And And a second light emitting diode for transmitting the imaginary part data. delete A visible light receiver for receiving data transmitted by using visible light, The first optical signal of the first wavelength band in which the real part data by the IFFT operation is carried in the data and the second optical signal of the second wavelength band in which the imaginary part data is carried by the IFFT operation is collected from the data, thereby converging the respective optical signals. An optical detector for passing an optical signal of a corresponding wavelength band through a filter, and converting each of the transmitted optical signals into corresponding electrical signals; An analog / digital converter which receives each electric signal from the light detector and converts each electric signal into a corresponding digital signal; And And a demodulator configured to receive each digital signal from the analog / digital converter and restore received data. The demodulator includes a real / imaginary combination unit that receives each digital signal from the analog / digital converter and combines the digital signals into complex data, and parallels the digital signals that are combined with complex data from the real / imaginary combination unit. Serial / parallel converter for converting data into the data, FFT operator for performing FFT operation by receiving parallel data from the serial / parallel converter, and receiving complex FFT calculation result output from the FFT operator And a symbol-demapping operation using the parallel / serial conversion unit and the FFT operation result of the serial data structure from the parallel / serial conversion unit, and when the received data is mapped to QPSK, the FFT of the serial data structure. If the result of the operation is restored to 2-bit received data and the received data is mapped to 16-QAM, the serial When the FFT calculation result of the data structure is restored to 4-bit received data and the received data is mapped to 64-QAM, the FFT calculation result of the serial data structure is restored to 6-bit received data and the received data is received. And a demapping unit for reconstructing the FFT calculation result of the serial data structure into 8-bit received data when the data is mapped to 256-QAM. delete The method of claim 5, The light detector, A first light detector for detecting the first optical signal among the transmitted first optical signal and the second optical signal; And And a second light detector for detecting the second optical signal among the first and second optical signals transmitted. The method of claim 7, The first light detector, A condenser lens for condensing the transmitted first and second optical signals; And And an optical filter configured to pass the first optical signal among the first optical signal and the second optical signal collected through the condenser lens. As a method of transmitting data using visible light, QPSK mapping that combines two bits of data to generate one symbol, 16-QAM mapping that generates one symbol by four bits of the data to be transmitted, and 64 symbols to generate one symbol by six bits of the data to be transmitted. Performing symbol-mapping according to any one of a QAM mapping and a 256-QAM mapping that combines the data to be transmitted by 8 bits to generate one symbol; Converting data of a serial structure by performing the symbol-mapping into data of a parallel structure to perform an IFFT operation; Performing an IFFT operation on the parallel data by converting the data into the parallel structure; Converting a complex IFFT operation result value into serial data by performing the IFFT operation; Dividing the complex-valued IFFT operation result value converted into serial data into real and imaginary data by converting the serial data into serial data; And And converting the real part data and the imaginary part data by separating the real part data and the imaginary part data into analog signals, respectively, and transmitting them by using visible light having different wavelength bands. Visible light transmission method. A method of receiving data transmitted using visible light, Condensing a first optical signal of a first wavelength band in which real part data by an IFFT operation is carried in the data and a second optical signal in an imaginary part data by the IFFT operation in the data; Passing the first optical signal and the second optical signal collected by condensing the first optical signal and the second optical signal through respective optical filters; Converting each optical signal by passing through each optical filter into a respective electrical signal corresponding thereto; Converting each electrical signal into a respective digital signal corresponding to each electrical signal; Restoring the received data based on each digital signal by converting the respective digital signals; The recovering of the received data may include: combining the digital signal by the conversion into the respective digital signals into complex data; Converting the digital signal combined into complex data into parallel data by combining the complex data into data; Performing an FFT operation on the parallel data by converting the parallel data into the parallel data; Converting a complex-valued FFT operation result value into serial data by performing the FFT operation; And performing symbol-demapping of the FFT operation result of the serial data structure by converting the serial data, and if the received data is mapped to QPSK, 2 bits of the FFT operation result of the serial data structure. When the received data is mapped to 16-QAM, the FFT calculation result of the serial data structure is restored to 4-bit received data, and the received data is mapped to 64-QAM. In this case, the FFT operation result of the serial data structure is restored to 6-bit received data. If the received data is mapped to 256-QAM, the FFT operation result of the serial data structure is 8-bit received data. Receiving; Visible light receiving method comprising a.

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