KR20120036254A - Apparatus and method for transmitting and receiving, for visible light communication - Google Patents

Abstract

The visible light wireless communication transmitter sets a pulse width adjustment step of pulse width modulation (PWM) within a unit time period, divides and transmits the input data according to the pulse width adjustment step into a PWM signal. It modulates and controls the lighting of a plurality of light emitting diodes (LEDs) according to the PWM signal, and transmits transmission data using a visible light modulation signal generated from the plurality of LEDs.

Description

Apparatus and method for transmitting and receiving visible light wireless communication {APPARATUS AND METHOD FOR TRANSMITTING AND RECEIVING, FOR VISIBLE LIGHT COMMUNICATION}

The present invention relates to an apparatus and method for transmitting and receiving visible light wireless communication, and to an apparatus and method for transmitting and receiving visible light wireless communication which can reduce brightness of a light source and reduce flicker of a light source.

Recently, with the expansion of lighting devices using light emitting diodes (LEDs) as light sources, visible light communication (VLC) technology that can communicate with LED lighting devices has been introduced. .

VLC technology is a communication technology that delivers data wirelessly in the light of the visible wavelength band that humans can recognize. VLC technology is distinguished from conventional wired optical communication technology and infrared wireless communication technology in terms of using light in the visible wavelength band. In addition, unlike radio frequency communication, VLC technology has the convenience of freely using without restriction or permission in terms of frequency use, excellent physical security, and distinction of visually identifying a communication link. .

In the VLC system using the LED light source, since the information on the phase of the transmission signal is difficult to detect at the receiver and relatively simple in configuration, the transmitter modulates the electrical data "0" and "1" by changing the intensity of the visible light signal. On-Off Keying (OOK) modulation is commonly used. In addition, the transmitting end of the VLC system using the LED light source includes a coding block for mapping data "0" and "1" into signal waveforms of "0" and "1" defined in the system as in the transmitting end of a general digital communication system. Depending on the system, coding methods such as Non-Return to Zero (NRZ), Return-to-Zero, and Manchester are mainly used.

By the way, the OOK modulation method basically has a disadvantage of significantly reducing the average light output of the light source. In other words, when the number of data "1" and "0" is stochastic, the average output of the visible light signal of the transmitting end output through the NRZ-OOK and Manchester-OOK coding and modulation methods is the data "1" signal. It is the same as the light output when a signal of a magnitude corresponding to half of the magnitude is constantly applied. In addition, the average light output through the RZ-OOK coding and modulation method is smaller than that of the NRZ-OOK and Manchester-OOK coding and modulation methods.

Therefore, when the OOK modulation method is applied to the transmitting end of the VLC system using the LED light source, only half or less of the light output that the actual LED light source can provide is radiated in a size range where the light source is not damaged. In terms of the brightness of the light source will not provide sufficient brightness. In this case, the OOK modulation method can increase the average light output of the light source by greatly increasing the amplitude of the modulated signal or adding a DC component. However, these methods may cause the LED light source to exceed its driving allowance, thereby greatly shortening the life of the light source. Can be.

In addition, lighting-based VLC must avoid flicker, or flicker, for eye-safety. Here, flicker refers to a change in brightness of a light source that the human eye can detect. However, the NRZ-OOK and RZ-OOK coding and modulation methods except for the Manchester-OOK coding and modulation method have different brightnesses of the visible light sources representing "1" and "0", and the "1" and "1" in any data transmission interval. The pattern ratio of "0" varies depending on the data combination and flicker may occur.

Meanwhile, PPM (Pulse Position Modulation) modulation method, which has been actively used in the field of infrared wireless communication among the conventional techniques, prevents flicker because the average brightness of the light source representing the unit symbol is always the same, similar to the Manchester-OOK coding and modulation method. It is known to have an effect. However, the maximum average brightness of the light source that can be provided by the PPM modulation method is the highest as 50% in 2-PPM that can represent two symbols, and has a disadvantage that the number of symbols that can be represented decreases as the number of symbols that can be expressed increases.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a transmission and reception apparatus and method using visible light wireless communication that may reduce brightness of a light source and reduce flicker of a light source.

According to an embodiment of the present invention, a method of transmitting a visible light wireless communication (VLC) transmitting apparatus is provided. The transmission method may include setting a pulse width adjustment step of pulse width modulation (PWM) in a unit time period, and modulating each symbol of VLC source data input according to the pulse width adjustment step into a PWM signal. And controlling the lighting of a plurality of light emitting diodes (LEDs) according to the PWM signal to generate a visible light modulated signal, and transmitting the visible light modulated signal.

The transmitting method may further include converting a bit of each symbol of the transmission data input according to the pulse width adjusting step before the modulating step.

The converting may include dividing the transmission data into m-bit symbols when the pulse width adjusting step is 2 ^m , and converting the m bits into 2 m bits. In this case, m may be an integer of 2 or more.

The modulating may include mapping the 2m-bit symbol into a PWM signal having two unit time periods.

The step of converting the m bits into 2m bits may include 2 ^m symbols representing 2 ^m symbols having the same average brightness in the two unit time periods of the 2 2 ^m symbols that can be represented by 2 ^m bits, and 1 ^m each, respectively. And converting the m bits into 2m bits with reference to a bit conversion table stored correspondingly.

According to another embodiment of the present invention, a method of receiving a visible light wireless communication receiver is provided. The receiving method includes receiving a visible light modulated signal from a visible light wireless communication transmitter, extracting a pulse width modulated (PWM) signal from the visible light modulated signal, mapping the PWM signal to a symbol, and Generating demodulated data from the symbol.

The generating may include converting a bit of the symbol.

When the pulse width control step of the PWM signal is set to 2 ^m steps in the visible light wireless communication transmitter, the symbol may be 2 m bits, and the converting may include converting the 2 m bit symbols into m bit symbols. And converting. In this case, m may be an integer of 2 or more.

The converting into m-bit symbols may include 2 ^m symbols representing the same average brightness in the two unit time periods of the 2 2 ^m symbols that may be represented by 2 ^m bits and 2 ^m symbols that may represent m bits, respectively, 1: 1. And converting the 2m-bit symbol into an m-bit symbol with reference to a bit conversion table stored correspondingly.

According to still another embodiment of the present invention, there is provided a visible light wireless communication transmission apparatus including a setting unit, a bit converter, a modulator, and a light source light emitter. The setting unit sets a pulse width adjustment step of pulse width modulation (PWM) in a unit time period. The bit converter converts the bits of the plurality of symbols corresponding to the transmission data according to the pulse width adjusting step. The modulator maps the bit-converted symbols to corresponding PWM signals. The light source light emitting unit includes a plurality of light emitting diodes (LEDs), and generates a visible light modulated signal by controlling lighting of the plurality of LEDs according to the PWM signal, and transmits the visible light modulated signal.

When the pulse width adjusting step is set to 2 ^m , the bit converter may convert the transmission data into m-bit symbols and then convert the m-bit symbols into 2 m-bit symbols. In this case, m may be an integer of 2 or more.

The bit conversion unit, 2m bits, the 2 ^2m symbols of the two average brightness of the same 2 ^m symbols in the unit time period of which can be expressed m bits 2 ^m symbols and each one can be expressed: that is stored in correspondence to the first A bit conversion table may be included, and the m bit symbol may be converted into a 2 m bit symbol by referring to the bit conversion table.

According to another embodiment of the present invention, there is provided a visible light wireless communication receiver including a receiver, a demodulator, and a bit inverse converter. The receiver receives the visible light modulated signal from the visible light wireless communication transmission device. The demodulator demodulates the visible light modulated signal and maps each pulse width modulated (PWM) signal to a corresponding symbol. The bit inverse converter converts the bits of the symbol to generate decoded data.

The demodulator may map the PWM signal to a 2 m-bit symbol when the pulse width control step of the PWM signal is set to 2 ^m in the visible light wireless communication transmitter. In this case, m may be an integer of 2 or more.

The bit inverse converter may convert the 2m-bit symbol into an m-bit symbol.

According to an embodiment of the present invention, when a visible light wireless communication transmission function is added to a lighting device or a visible light source that emits visible light, it is currently widely used for controlling brightness of a light source in pure LED lighting without visible light wireless communication function. The PWM modulation method can be used, and the brightness reduction of the lighting device or the visible light generated by the modulation function can be reduced compared to the OOK modulation method or the PPM modulation method.

In addition, it is possible to provide an effect of reducing the generation of flicker of the visible light source.

1 is a view showing a visible light wireless communication transmission apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a method of transmitting a visible light wireless communication transmitter according to an exemplary embodiment of the present invention.
3 is a diagram illustrating an example of a pulse width adjusting step of PWM according to an embodiment of the present invention.
4 is a diagram illustrating an example of symbol waveforms mapped to a PWM signal having the pulse width adjusting step of FIG. 3.
FIG. 5 is a diagram illustrating an example of a bit conversion table for mapping a PWM signal having the pulse width adjusting step of FIG. 3.
6 and 7 are diagrams illustrating another example of a bit conversion table for mapping a PWM signal having the pulse width adjusting step of FIG. 3, respectively.
8 is a diagram illustrating an example of a method of mapping a 4-bit converted symbol and a PWM signal according to an exemplary embodiment of the present invention.
9 is a view showing a visible light signal and its average brightness according to a conventional Manchester-OOK coding and modulation method.
10 is a view showing another example of the pulse width adjustment step of the PWM according to an embodiment of the present invention.
FIG. 11 is a diagram illustrating an example of symbol waveforms mapped to a PWM signal having the pulse width adjusting step of FIG. 10.
FIG. 12 is a diagram illustrating an example of a bit conversion table for mapping a PWM signal having the pulse width adjusting step of FIG. 10.
13 is a view showing a visible light wireless communication receiving apparatus according to an embodiment of the present invention.
14 is a flowchart illustrating a receiving method of a visible light wireless communication receiving apparatus according to an exemplary embodiment of the present invention.

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

Throughout the specification and claims, when a section is referred to as "including " an element, it is understood that it does not exclude other elements, but may include other elements, unless specifically stated otherwise.

Now, a visible light wireless communication apparatus and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a visible light wireless communication transmission apparatus according to an embodiment of the present invention, Figure 2 is a flow chart showing a transmission method of a visible light wireless communication transmission apparatus according to an embodiment of the present invention. 3 is a diagram illustrating an example of a pulse width adjustment step of PWM according to an embodiment of the present invention.

Referring to FIG. 1, the apparatus for transmitting visible light wireless communication 100 includes a setting unit 110, a bit converter 120, a modulator 130, and a light source light emitter 140.

Referring to FIG. 2, the Visible Light Communication (VLC) source data is input to the bit converter 120.

The bit converter 120 receives VLC source data (S210).

In addition, the setting unit 110 sets a pulse width adjusting step (x) of pulse width modulation (PWM) within a unit time period (S220), and sets the pulse width adjusting step (x) as a bit converting unit ( 120 and the modulator 130. For example, the setting unit 110 may set the pulse width adjusting step x in four steps within the unit time period T. At this time, the visible light modulation signal according to the pulse width of each step of the PWM may be shown as shown in FIG. That is, PWM is a modulation method that basically controls the brightness of the light source by changing the width of the pulse applied to the light source. When a PWM signal having a pulse width of W is input to the light source light emitting unit 140, the light source light emitting unit 140 is used. The waveform of the visible light modulated signal output from is a waveform having a pulse width of W at time T.

When the bit converter 120 receives the VLC source data (S210), the bit converter 120 divides the VLC source data into m-bit symbols, and divides the m-bit symbols according to the bit conversion table 122 to reduce the generation of flicker due to VLC modulation. The symbol is converted into a 2m bit symbol (S230). Here, m means x = 2 ^m and m is an integer of 2 or more.

The bit converter 120 includes a bit conversion table 122 that converts 2 ^m symbols that can be represented by m bits into transforms of 2 ^m bits. For example, when the pulse width adjusting step is four steps, the bit converter 120 may divide the VLC source data by two bits and convert two symbols into four bits. On the contrary, when the pulse width adjustment step is 16, the bit converter 120 may divide the VLC source data by 4 bits and convert the 4 bit symbols into 8 bit symbols.

 The modulator 130 generates a PWM signal by mapping the bit-converted 2m-bit symbols with one of the x PWM signals using the PWM method (S240), and outputs the PWM signal to the light source emitter 140. When the pulse width adjusting step is four steps, four symbols of two bits may be mapped 1: 1 with four PWM signals. In contrast, when the pulse width adjusting step is 16 steps, 16 symbols of 4 bits may be mapped 1: 1 with 16 PWM signals.

The light source emitter 140 includes a light source driver 142 and a light emitting module (LED) light source module 144. The light source driver 142 drives the LED light source module 144. The LED light source module 144 may include a plurality of LEDs. The light source driver 142 generates a driving signal for controlling the on and off states of the plurality of LEDs according to the PWM signal and outputs the driving signal to the LED light source module 144. The LED light source module 144 is turned on in accordance with the drive signal of the light source driver 142 to generate and transmit a visible light modulated signal corresponding to the light emitted from the plurality of LEDs (S250 to S260).

Next, symbol mapping to a PWM signal according to an embodiment of the present invention will be described with reference to FIG. 4.

4 is a diagram illustrating an example of symbol waveforms mapped to a PWM signal having the pulse width adjusting step of FIG. 3.

When the pulse width adjusting step x is set in four steps within the unit time period T, the number of symbols that can be represented by the four-step PWM signal is four of 00, 01, 10, and 11. Can be.

If these four symbols are represented by the waveform of the visible light modulation signal of the LED light source may be as shown in FIG. Accordingly, the VLC source data is divided by two bits, and a total of four symbols represented by two bits may be 1: 1 mapped to PWM signals corresponding to A to D visible light modulation signals.

FIG. 4 is a diagram illustrating an example of symbol waveforms mapped to a PWM signal having the pulse width adjusting step of FIG. 3, and symbols mapped to each PWM signal may be different from FIG. 4. For example, the PWM signals corresponding to the visible light modulation signals of A to D in FIG. 4 are sequentially "01", "10", "11" and "00" or "10", "11", "01" and May be mapped to "00".

Here, since the four symbol-mapped PWM signals have different average brightness in the unit time period T, and the data divided by 2 bits are actually input at random, the visible light modulated signal from this shows the possibility of generating flicker. Have. Therefore, according to an embodiment of the present invention, in order to block the generation of flicker of the visible light modulated signal, the bit converter 120 performs the bit conversion using the bit conversion table 122.

FIG. 5 is a diagram illustrating an example of a bit conversion table for mapping a PWM signal having the pulse width adjusting step of FIG. 3. That is, FIG. 5 is a bit conversion table when four symbols (00, 01, 10, 11) represented by 2 bits are mapped 1: 1 to PWM signals corresponding to the visible light modulated signals of A to D of FIG. to be.

Referring to FIG. 5, the bit conversion table 122 includes four bits 4B (0011, 0110, 1001) corresponding to the two bits 2B (00, 01, 10, 11) in a 1: 1 manner. , 1100). In this case, when a total of four symbols (00, 01, 10, 11) represented by 2 bits are 1: 1 mapped to the PWM signals corresponding to the visible light signals of A to D of FIG. 4, the symbol of 4 bits (4B) (0011, 0110, 1001, 1100) are four symbols having the same average brightness within a two unit time period (2T) of 16 symbols that can be represented by four bits, and symbols of two bits (2B) (00, 01, 10, 11) and 1: 1.

Accordingly, the bit converter 120 may convert the 2-bit symbols (00, 01, 10, 00) into 4-bit symbols (0011, 0110, 1001, 1100) with reference to the bit conversion table 122. have.

In this case, even when data divided into two bits is randomly inputted, since the average brightness is the same through bit conversion in the bit converter 120, flicker can be reduced.

6 and 7 illustrate another example of a bit conversion table for mapping a PWM signal having the pulse width adjusting step of FIG. 3.

FIG. 6 is a bit conversion table when four symbols (01, 10, 11, 00) represented by two bits are mapped 1: 1 to PWM signals corresponding to the visible light modulated signals of FIGS. FIG. 7 is a bit conversion table in a case where a total of four symbols 10, 11, 01, and 00 represented by two bits are mapped 1: 1 to PWM signals corresponding to the visible light modulated signals of FIGS.

The bit conversion tables 122a and 122b shown in Figs. 6 and 7 correspond to 1: 1 corresponding to the symbols 01, 10, 11, 00/10, 11, 01, 00 of 2 bits 2B, respectively. The symbols 0001, 0100, 1011, 1110/0010, 0111, 1000, and 1101 of the bit 4B are stored. In this case, the symbols 0001, 0100, 1011, 1110/0010, 0111, 1000, and 1101 of the 4 bits 4B have 4 equal average brightness within 2 unit time periods 2T of 16 symbols that can be represented by 4 bits. Symbol.

The result of mapping the 4-bit symbol bit-converted by the bit conversion table 122 of FIG. 5 to the PWM signal by the modulator 130 may be the same as that of FIG. 8.

8 is a diagram illustrating an example of a method of mapping a 4-bit converted symbol and a PWM signal according to an exemplary embodiment of the present invention.

The modulator 130 maps the bit-converted 4-bit symbols (0011, 0110, 1001, 1100) to PWM signals corresponding to the four visible light modulation signals shown in FIG. 142).

Looking at the PWM signals corresponding to the four visible light modulation signals shown in FIG. 8, it can be seen that the average brightnesses obtained from the four PWM signals are all the same. It can also be seen that the average brightness exceeds 50% within a two unit time period 2T.

9 illustrates a visible light modulated signal and its average brightness according to a conventional Manchester-OOK coding and modulation method.

Referring to FIG. 9, the average brightness of the visible light modulated signal according to the Manchester-OOK coding and modulation method is equal to the brightness when a DC signal having a size corresponding to half of the data “1” signal is constantly applied. . On the other hand, since the PWM method according to the embodiment of the present invention has an average brightness of more than 50% within a 2 unit time period (2T), the average brightness of the LED light source in visible light wireless communication compared to the OOK modulation method or PPM modulation method Has the effect of improving.

As another embodiment of the present invention, a case in which the pulse width adjusting step is set to eight steps in the unit time period T will be briefly described with reference to FIGS. 10 to 12. FIG. 10 is a diagram illustrating another example of a pulse width adjusting step of PWM according to an embodiment of the present invention, and FIG. 11 is a diagram illustrating an example of symbols mapped to a PWM signal having the pulse width adjusting step of FIG. 10. FIG. 12 is a diagram illustrating an example of a bit conversion table having the pulse width adjusting step of FIG. 10.

As shown in FIG. 10, the setting unit 110 may set the pulse width adjusting step (x) of the PWM in eight steps within the unit time period (T). When the pulse width adjustment step is set to eight steps within the unit time period T, the number of symbols that can be represented by the eight-step PWM signal is 8 of 000, 001, 010, 011, 100, 101, 110, and 111. As shown in FIG. 11, eight symbols (000, 001, 010, 011, 100, 101, 110, and 111) may be mapped 1: 1 with the PWM signal corresponding to the corresponding visible light modulated signal.

In addition, the bit converter 120 divides the VLC source data into 3 bits (= 2 ³ ) and bit converts the 3-bit symbol into 6 (= 2 * 3) bits with reference to the bit conversion table 120c of FIG. 12. can do. Referring to FIG. 12, the bit conversion table 120c may include eight 6-bit symbols having the same average brightness within a two unit time period 2T among the 64 symbols that may be represented by the six bits. 001110, 010101, 011100, 100011, 101010, 110001, 111000 are stored in a 1: 1 correspondence with six 3-bit symbols (000, 001, 010, 011, 100, 101, 110, 111).

That is, eight symbols of six bits of the bit conversion table 122c (000111, 001110, 010101, 011100, 100011, 101010, 110001, 111000) all have the same average brightness within a two unit time period 2T. Therefore, even if the data divided into three bits is randomly input, since the average brightness in the two unit time period 2T can be the same through the bit conversion in the bit converter 120c, it is possible to reduce the flicker generation, It is possible to have an average brightness of 50% or more within the time period 2T.

13 is a view showing a visible light wireless communication receiving apparatus according to an embodiment of the present invention, Figure 14 is a flow chart showing a receiving method of a visible light wireless communication receiving apparatus according to an embodiment of the present invention.

Referring to FIG. 13, the apparatus for receiving visible light wireless communication according to an exemplary embodiment of the present invention includes a receiver 210, a demodulator 220, and a bit inverse converter 230.

Referring to FIG. 14, the receiver 210 receives a visible light modulated signal from the visible light wireless communication transmitter 100 (S1410).

The demodulator 220 performs a reverse process of the modulator 130. The demodulator 220 demodulates the received visible light modulated signal and maps each PWM signal to symbols of corresponding 2m bits. (S1420).

The bit inverse converter 230 performs an inverse process of the bit converter 120. The bit inverse converter 230 generates decoded data by converting 2 m bits of symbols into m bits of symbols (S1430 to S1440). The bit inverse converter 230 converts the 2m bit symbols into mbit symbols through the inverse process of the bit conversion tables 122, 122a, 122b, and 122c.

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such an implementation can be easily implemented by those skilled in the art to which the present invention pertains based on the description of the above-described embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (17)

In the transmission method of the visible light wireless communication (VLC) transmitting apparatus,
Setting a pulse width adjustment step of pulse width modulation (PWM) in a unit time period,
Modulating each symbol of the VLC source data input according to the pulse width adjusting step into a PWM signal,
Generating a visible light modulated signal by controlling lighting of a plurality of light emitting diodes (LEDs) according to the PWM signal; and
Transmitting the visible light modulated signal
Transmission method comprising a. In claim 1,
Before the modulating step, converting the bits of each symbol of the transmission data input according to the pulse width adjusting step
Transmission method further comprising. In claim 2,
Wherein the converting comprises:
Dividing the transmission data into m-bit symbols when the pulse width adjusting step is 2 ^m , and
Converting the m bits to 2m bits,
M is an integer of 2 or more. 4. The method of claim 3,
The modulating step,
And mapping the 2m bit symbol into a PWM signal having two unit time periods. 5. The method of claim 4,
Converting the m bits to 2m bits,
The of 2m bits, 2 ^2m symbols that can be represented two-unit time period the average brightness is the same 2 ^m symbols m bits 2 ^m symbols and each one can be expressed in: refer to bit conversion table that is stored in correspondence to the 1 Converting the m bits to 2m bits. 5. The method of claim 4,
2 ^m symbols, which can be expressed as m bits, are mapped one-to-one with 2 ^m PWM signals in a unit time period.
The PWM signal having two unit time periods is generated by combining a PWM signal of a unit time period corresponding to each m-bit symbol of the 2 m-bit symbol. In the receiving method of the visible light wireless communication receiving apparatus,
Receiving a visible light modulated signal from a visible light wireless communication transmitter,
Extracting a pulse width modulation (PWM) signal from the visible light modulation signal;
Mapping the PWM signal to a symbol, and
Generating demodulated data from the symbol
Receiving method comprising a. In claim 7,
Wherein the generating comprises:
Converting the bits of the symbol. 9. The method of claim 8,
When the pulse width control step of the PWM signal is set to 2 ^m steps in the visible light wireless communication transmitter, the symbol is 2 m bits, and m is an integer of 2 or more,
Wherein the converting comprises:
And converting the 2 m-bit symbol into an m-bit symbol. In claim 9,
Converting to the m-bit symbol,
The of 2m bits, 2 ^2m symbols that can be represented two-unit time period the average brightness is the same 2 ^m symbols m bits 2 ^m symbols and each one can be expressed in: refer to bit conversion table that is stored in correspondence to the 1 And converting the 2 m bit symbol into an m bit symbol. In the visible light wireless communication transmitter,
Setting unit for setting the pulse width control step of the pulse width modulation (PWM) in the unit time period,
A bit converter for converting bits of a plurality of symbols corresponding to transmission data according to the pulse width adjusting step;
A modulator for mapping the bit-converted symbols to corresponding PWM signals, and
A light source including a plurality of light emitting diodes (LEDs), and generating a visible light modulation signal by controlling the lighting of the plurality of LEDs according to the PWM signal and transmitting the visible light modulation signal.
Visible light wireless communication transmission device comprising a. In claim 11,
The bit converter,
When the pulse width adjusting step is set to 2 ^m , after dividing the transmission data into m bits of symbols, converts to 2 m bits of symbols,
M is an integer of 2 or more. The method of claim 12,
The bit converter,
2 ^m symbols representing the same average brightness in the two unit time periods of 2 2 ^m symbols that can be represented by 2 ^m bits, and 2 ^m symbols that can be represented by m bits, and a bit conversion table that stores 1: 1 correspond to each other. and,
And a visible light wireless communication transmitter for converting the m-bit symbol into a 2m-bit symbol by referring to the bit conversion table. In claim 13,
2 ^m symbols, which can be represented by m bits, are mapped one-to-one with 2 ^m PWM signals of a unit time period, and the PWM signals are PWM of two unit time periods corresponding to symbols of each m bit of the 2 m bit symbol. Visible light wireless communication transmission device is a signal combined signal. In the visible light wireless communication receiver,
A receiver for receiving a visible light modulated signal from a visible light wireless communication transmitter,
A demodulator for demodulating the visible light modulated signal and mapping each pulse width modulated (PWM) signal to a corresponding symbol; and
A bit inverse converter for converting bits of the symbol to generate decoded data
Visible light wireless communication receiving apparatus comprising a. 16. The method of claim 15,
When the pulse width adjustment step of the PWM signal is set to 2 ^m in the visible light wireless communication transmitter,
The demodulator maps the PWM signal into a symbol of 2 m bits,
M is an integer of 2 or more. The method of claim 16,
And the bit inverse converter is configured to convert the 2m bit symbol into an mbit symbol.

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