KR20140093863A - Method for dimming level estimation and method for processing visible light communication signal and apparatus using the methods - Google Patents

Abstract

Disclosed are a method for estimating a dimming level, a method for processing a visible light signal, and an apparatus using the same. The method for processing the visible light signal according to an aspect of the present invention comprises the steps of: receiving the visible light signal including at least one pulse; estimating a pulse width of the visible light signal; estimating the dimming level of the visible light signal using the estimated pulse width; and demodulating the visible light signal using the estimated dimming level.

Description

TECHNICAL FIELD [0001] The present invention relates to a dimming level estimation method, a visible light signal processing method, and an apparatus using the method.

The present invention relates to a visible light communication, and more particularly, to a dimming level estimation method, a visible light signal processing method, and an apparatus using the method.

Recently, lighting devices and display devices using LED (Light Emitting Diode) have been applied to automobiles, traffic lights, billboards, TVs, monitors, portable devices, special lighting and general lighting It is spreading rapidly in everyday life.

In addition, a wireless communication technology has been actively researched to provide a communication function to the LED lighting apparatus and display devices to simultaneously achieve the intrinsic purpose of the LED light source and the purpose of the communication means.

This is because the LED light source has a longer lifetime than the conventional light sources, has excellent power efficiency, can realize various colors, and has digital control capability. In addition, due to the Kyoto Protocol of the United Nations (UN) Climate Change Convention, realistic situations in which energy savings and greenhouse gas reductions have to be mandatory are also one of the reasons for rapidly replacing existing light sources with LED light sources in many countries around the world .

Visible light wireless communication technology is a wireless communication technology that wirelessly transmits information by using light of a visible light wavelength band (380n ~ 780nm area) that can be recognized by human eyes.

The visible light wireless communication technology is distinguished from the existing wired optical communication technology in that it uses light in the visible light wavelength band. Unlike RF (Radio Frequency) wireless communication, which is currently widely used, visible light wireless communication technology is excellent in convenience and physical security that can be freely used without being regulated or licensed in terms of frequency utilization, It has the distinguishing feature that it can be confirmed, and among other things, it has a characteristic as a fusion technology that can obtain the intrinsic purpose of the light source and the communication function in a straightforward manner.

Since the visible light wireless communication system is a system for transmitting and receiving information based on visible light illumination, wireless communication must be performed with the basic functions of illumination satisfied. Since one of the important basic functions of illumination is the brightness control or dimming function of the illumination, the visible light wireless communication system should have wireless communication function through visible light and also support dimming function.

Methods such as 'Amplitude dimming' and 'Variable-PPM' have been introduced as lighting brightness control technologies that support visible light wireless communication. However, in the case of amplitude dimming, there is a risk that the LED light source may be damaged and the color variation may occur. Also, in the case of the variable-PPM scheme, the pulse width is changed and the bit error rate (BER) performance is not guaranteed at the time of demodulation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dimming level estimation method for visible light communication.

Another object of the present invention is to provide a visible light signal processing method.

It is still another object of the present invention to provide a visible light signal processing apparatus using the above methods.

According to another aspect of the present invention, there is provided a method of processing a visible light signal, the method comprising: receiving a visible light signal including at least one pulse; estimating a pulse width of the visible light signal; Estimating the dimming level of the visible light signal using the estimated pulse width, and demodulating the visible light signal using the estimated dimming level.

The visible light signal processing method may further include suppressing noise in the estimated pulse width by performing an average operation on the estimated pulse width.

The type of the pulse may comprise a pulse having a first pulse width or a pulse having a second pulse width.

Here, the second pulse width may be twice the first pulse width.

Wherein calculating the dimming level comprises: performing an average operation on each of the pulse width of the at least one first type pulse and the pulse width of the at least one second type pulse; / 2, and summing it with the average value of the first type pulse, and multiplying the summed value by 1/2 to determine the dimming level.

The step of demodulating the visible light signal may include obtaining information included in the visible light signal according to the position of the pulse in the visible light signal period.

The step of estimating the pulse width of the visible light signal may include periodically sampling the pulses, calculating the number of consecutive samples having a value greater than or equal to a preset threshold value, And determining the pulse width according to the number of samples to be processed.

According to another aspect of the present invention, there is provided a method of estimating a dimming level, comprising: receiving a visible light signal including at least one pulse; estimating a pulse width of the visible light signal; And determining a dimming level of the visible light signal using the determined pulse width.

The step of estimating the dimming level of the visible light signal may include comparing a current pulse width with an average pulse width of a plurality of symbol intervals, determining whether the current pulse width is greater than or equal to the average pulse width And calculating the dimming level according to the type of the pulse.

Wherein calculating the dimming level comprises: performing an average operation on each of the pulse width of the at least one first type pulse and the pulse width of the at least one second type pulse; / 2 and summing it with the average value of the first type pulses, and multiplying the summed value by 1/2 to determine the dimming level.

According to another aspect of the present invention, there is provided an apparatus for processing a visible light signal according to an aspect of the present invention, the apparatus including: a visible light signal including at least one pulse; estimating a pulse width of the received visible light signal; A dimming level estimation module for estimating a dimming level of the visible light signal using a pulse width, and a demodulation module for demodulating the visible light signal using the estimated dimming level.

Wherein the dimming level estimation module performs periodic sampling on the pulse, calculates a number of consecutive samples having a value equal to or larger than a predetermined threshold value, and adjusts the visible light signal according to the number of consecutive samples having a value equal to or larger than the threshold value. And a pulse width estimator for estimating a pulse width of the pulse width.

Wherein the dimming level calculating module comprises a first average calculator for calculating an average pulse width for a plurality of symbol periods, a comparator for comparing an output of the first average calculator with a current pulse width, A pulse type determination unit for determining the type of the current pulse according to whether the width is greater than or equal to the width, and a dimming level calculation unit for calculating the dimming level according to the type of the pulse.

Here, the type of the pulse may include a pulse having a first pulse width or a pulse having a second pulse width.

Wherein the second pulse width may be twice the first pulse width, wherein the dimming level arithmetic unit calculates the average of the pulse width of at least one first type pulse and the pulse width of at least one second type pulse, Operation may be performed, the average value of the second type pulse may be multiplied by 1/2 to sum with the average value of the first type pulse, and the summed value may be multiplied by 1/2 to determine the dimming level.

The demodulation module may obtain information included in the visible light signal according to the position of the pulse in the visible light signal period.

The visible light signal is characterized in that the dimming level with respect to the brightness of the illumination is controlled according to the width of the pulse within the period.

According to the present invention as described above, improved reception performance of visible light wireless communication can be obtained by interworking with the VPPM demodulation module based on the cumulative area setting function.

In addition, a visible light communication system having a brightness control function or a dimming function can be easily implemented.

1 shows an example of a visible light signal according to the amplitude dimming technique.
2 shows another example of a visible light signal according to the amplitude dimming technique.
3 shows another example of a visible light signal according to the amplitude dimming technique.
4 is a conceptual diagram illustrating the principle of the VPPM modulation scheme.
5 shows a VPPM modulation waveform having various pulse widths applied to the present invention.
6 is a conceptual diagram showing the relationship between the dimming control and the modulated signal for the VPPM modulated waveform having various dimming levels.
7 is a conceptual diagram illustrating demodulation of a VPPM waveform according to an embodiment of the present invention.
8 is a conceptual diagram of VPPM demodulation using a signal accumulation region for interference mitigation.
9 is a graph showing signal-to-noise ratio variation according to the size of a signal accumulation region for demodulation.
10 is a block diagram of a visible light signal processing apparatus according to a preferred embodiment of the present invention.
11 shows an example of the relationship between the VPPM received signal waveform and demodulated data.
12 shows various examples of the VPPM signal waveform according to the transmission data pattern.
13 shows the relationship between the sampling and the signal pulse width.
14 is a flowchart illustrating an operation of the VPPM signal demodulation method according to an embodiment of the present invention.
15 is a detailed block diagram of a dimming level estimation module based on pulse width estimation and averaging.
16 is an operational flowchart of a visible light signal processing method according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

One of the proposed techniques for adjusting the brightness of illumination related to visible light wireless communication is the amplitude dimming method and the variable-PPM dimming method.

The amplitude dimming method is a method of adjusting the brightness of the light source by changing the amplitude of the signal in the OOK (On-Off Keying) modulation method, and the variable-PPM decoding method is a method of changing the amplitude of the light source by using a modulation method called 'Variable-PPM' This is a method of providing brightness control function.

The amplitude dimming method is a method of adjusting the brightness of the light source by changing the amplitude of the signal in the OOK modulation method. Figs. 1 to 3 show various embodiments of a signal according to the amplitude diving technique when Manchester code and OOK modulation method are applied.

1 shows an example of a signal according to the amplitude dimming technique.

FIG. 1 is a graphical representation of the optical waveform output from the LED illumination and the corresponding average light output when the Manchester-OOK technique is applied to the transmitter. In particular, FIG. 1 expresses that the average light output is equal to the light output when a DC signal having a half size of the Manchester-OOK signal amplitude (PM) is applied.

2 shows another example of a signal according to the amplitude dimming technique.

Fig. 2 shows that the average PMO of the LED light source can be increased by driving the amplitude PM1 of the Manchester-OOK signal larger than the signal amplitude PM of Fig. Similarly in the example shown in Fig. 2, when the amplitude of the signal is driven small, the average light output can be reduced.

3 shows another example of a signal according to the amplitude dimming technique.

The signal according to Fig. 3 shows that the amplitude PM2 of the Manchester-OOK signal is equal to the signal amplitude PM in Fig. 1, but the average light output can be consequently increased by applying a DC offset.

It should be noted, however, that the amplitude dimming technique described with reference to Figs. 1 to 3 is practically difficult to meet the maximum brightness level provided by the same specification LED illumination without visible light wireless communication capability. Because, for amplitude dimming, the signal must be applied with an amplitude greatly exceeding the allowable range of the LED light source, the instantaneous signal amplitudes can damage the LED light source and, in the long term, significantly reduce the lifetime of the LED light source It is because.

In addition, adjusting the brightness by changing the amplitude of the signal means that the intensity of the current supplied to the LED light source changes according to the brightness control, and as a result, the amplitude dimming may also cause the color variation of the LED light source.

A VPPM (Variable PPM) modulation scheme has been proposed by combining the 2-PPM modulation method and the PWM (Pulse Width Modulation) modulation method in order to block the occurrence of flicker in the frame and to control the brightness of the light source. The VPPM modulation scheme is one of the modulation schemes for visible light wireless communication adopted in the IEEE 802.15.7 international standard.

4 is a conceptual diagram illustrating the principle of the VPPM modulation scheme.

As shown in FIG. 4, the VPPM modulation scheme is a scheme designed by combining a 2-PPM modulation scheme and a PWM modulation scheme.

The 2-PPM modulation method is a method of expressing bits "0" and "1" according to the position of the pulse as shown on the left side of FIG. For example, as shown in FIG. 4, when one pulse is divided into two halves, "0" is assigned to the former half, and "1" is assigned to the latter half of the pulse . The 2-PPM modulation method provides the same average brightness at bits "1" and "0", similar to the light output of the Manchester code. Therefore, if the 2-PPM modulation scheme is used, flicker generation inside the frame can be prevented.

On the other hand, the PWM modulation method is a modulation technique for adjusting the brightness of the light source by changing the width of the pulse as shown in the right side of FIG. 4, and is a technique mostly used in current LED illumination.

The VPPM modulation method designed by combining the 2-PPM modulation method and the PWM modulation method is similar to the 2-PPM feature in that bits "0" and "1" are represented according to the position of the pulse, The PWM modulation method is similar in that the pulse width can be varied.

Therefore, the optical waveform modulated by the variable-PPM technique with a pulse width of 50% can be considered to be the same as the 2-PPM modulated waveform.

5 shows a VPPM modulation waveform having various pulse widths applied to the present invention.

In FIG. 5, a mechanism for adjusting the brightness through the VPPM modulation method can be visually confirmed. When a digital signal of "001" is modulated by a variable-PPM technique, the same data is displayed, As shown in FIG.

5, a total of five signals are shown, all of which represent the same data "001 ". Also, the pulse width of the signal increases from the upper end to the lower end. The uppermost signal has a pulse width of 12.5% with respect to the period T, and the lowermost signal has a pulse width of 87.5%.

The VPPM technique can provide a maximum brightness similar to that provided by LED lighting of the same specification by further subdividing and setting the pulse width varying step than the pulse width varying step illustrated in FIG. This VPPM technique not only does not damage the LED light source, but also causes no color variation of the light source because the brightness adjustment is determined by the pulse width on the time axis rather than the amplitude of the pulse.

6 is a conceptual diagram showing the relationship between the dimming control and the modulated signal for the VPPM modulated waveform having various dimming levels.

In order to implement a VPPM receiver using a sampling-based digital circuit, the signal characteristics considering the VPPM modulation waveform should be derived. FIG. 6 shows the relationship between the sampling level and the modulation signal for the dimming level and the transmission signal from the VPPM modulation waveform.

A digital circuit that processes a digital signal belonging to a discrete-time region is triggered by a clock of a specific frequency. This means that the signal sampled at a specific frequency is signaled through the digital circuitry. In order to implement a VPPM transceiver as a digital circuit, sampling of the VPPM signal must be considered.

In FIG. 6, D _TX represents bit information transmitted through one VPPM-modulated symbol. Further, T represents a symbol time, and T _D represents a dimming level or VPPM pulse width which varies according to the dimming control signal. At this time, the VPPM symbol frequency becomes 1 / T Hz. If the dimming percentage value to be set is Dim _per [%], the dimming level or VPPM pulse width T _D = T * Dim _per / 100 is obtained.

When a VPPM symbol is sampled on a clock with a frequency N _T / T Hz that is N _T times higher than one VPPM symbol frequency 1 / T Hz, one symbol of VPPM is composed of N _T samples. Therefore, the number N _D of samples of the VPPM pulse width associated with brightness is round (T _D / T * N _T ). Where round is the rounding operation. If the number of dimming resolutions in one symbol, i.e., the degree of brightness adjustment, is a divisor of N _T , N _D = T _D / T * N _T without rounding operation.

7 is a conceptual diagram illustrating demodulation of a VPPM waveform according to an embodiment of the present invention.

Since the VPPM modulation basically transmits the transmission data in the position of the pulse symbol, it is possible to detect the data transmitted from the transmitter by discriminating whether the reception pulse energy is detected at the front portion of the received symbol or at the rear portion thereof.

That is, when one period T is divided into half, a front section is referred to as a first time section and a rear section is referred to as a second time section, whether the received pulse energy is detected in the first time interval or in the second time interval Accordingly, it is possible to determine which data represents the received symbol.

Since the detection of the pulse in the corresponding time interval is the same as the detection of the pulse energy, the reception signal accumulator for the first part, that is, the accumulator for the second time section, Lt; / RTI > The detection data D _{VPPM_RX} of the received transmission signal can then be determined by comparing the energy values accumulated in the two signal accumulators.

That is, the value of the first signal accumulator accumulating the received signal in the first time interval and the value of the second signal accumulator accumulating the received signal in the second time interval are compared. If the value of the first signal accumulator is large It is determined that the data of the corresponding symbol is "0 ", and when the value of the second signal accumulator is large, it is determined that the data of the corresponding symbol is" 1 ".

The demodulation method shown in FIG. 7 is a method capable of demodulating a 2-PPM modulated signal that transmits information at the position of a pulse by detecting the position of energy corresponding to the pulse signal and detecting received data.

However, unlike the 2-PPM modulated signal, the VPPM modulated signal has a variable pulse width according to the dimming control signal. As a result, reception performance deterioration that does not occur in 2-PPM transmission and reception occurs.

That is, as can be seen from FIG. 7, in the case of the symbol indicating "0" in the dimming control signal corresponding to 50% or more of the symbol length, the pulse affects not only the beginning part of the symbol but also the rear part of the symbol. Conversely, in the case of a symbol representing "1 ", the pulse affects not only the rear part of the symbol but also the front part of the symbol. In other words, the energy of the pulse containing the transmission data at the symbol position not corresponding to the transmission data may be received and cause interference. In order to prevent such an interference phenomenon, it is necessary to exclude a pulse signal at a portion where interference may occur in the detection process.

8 is a conceptual diagram of VPPM demodulation using a signal accumulation region for interference mitigation.

Fig. 8 shows an example in which the part where interference is generated is excluded in the detection process. In the embodiment shown in FIG. 8, pulse energy detection is not performed in all of the first and second portions of the symbol, that is, the first time interval and the second time interval, but only in a specific first portion of the first time interval, The occurrence of the interference can be excluded by performing the pulse energy detection only in a specific rear part of the time interval.

That is, by setting the signal accumulation regions having the same width in the front and rear sections of the symbol with respect to the pulse, it is possible to obtain an interference elimination effect in signal demodulation.

9 is a graph showing signal-to-noise ratio variation according to the size of a signal accumulation region for demodulation.

FIG. 9 shows a simulation result of bit error rate (BER) performance for VPPM demodulation in which a cumulative area is set in a signal-to-noise ratio (SNR) of 8 dB for a sample signal.

9, N _s is the number of received signal samples accumulated for pulse energy detection. Therefore, when N _s is half of the number of samples N _T per symbol (N _s = N _T / 2), the basic demodulation method shown in Fig. 7 is obtained.

In the graph of FIG. 9, in the case of a general demodulation method (N _s = N _T / 2), the BER performance decreases at a dimming control value of less than 50% because the pulse width is small and the transmission signal energy is small. However, the BER performance is degraded at a dimming control value of 50% or more because the pulse width is wide and the energy of the transmission signal is relatively large. This is because pulse interference occurs before and after the symbol.

It can be seen from FIG. 9 that as the dimming control value increases, the pulse interference further increases and the performance further degrades. Also, for the intermediate dimming control values around 50%, the general demodulation method shows good reception performance, and for smaller or larger dimming control values, the demodulation method that sets the specific accumulation area has good reception performance.

Therefore, it can be concluded that the best VPPM demodulation performance can be obtained through a demodulation method (N _s = N _D ) in which the cumulative area varies depending on the pulse width and the dimming level of the received signal.

In summary, in order to perform the enhanced demodulation of the VPPM signal with respect to the channel noise through the simulation shown in the graph of FIG. 9, it can be confirmed that the pulse width of the received signal, that is, the dimming level value must be estimated first.

10 is a block diagram of a visible light signal processing apparatus according to a preferred embodiment of the present invention.

The visible light signal processing apparatus shown in FIG. 10 may include a dimming level estimation module 100 and a VPPM demodulation module 200, thereby improving the performance of the VPPM signal with respect to channel noise.

The dimming level estimation module 100 transmits the estimated dimming level value from the VPPM reception signal to the VPPM demodulation module 200. The VPPM demodulation module 200 demodulates the VPPM signal by setting the accumulation area in the manner shown in FIG. 8 based on the estimated dimming level.

In the visible light signal processing apparatus shown in Fig. 10, the estimation of the dimming level precedes the VPPM demodulation step. For this dimming level estimation, the present invention derives the relationship between the dimming level and the signal waveform in the VPPM communication system.

7 and 8, the dimming level in the VPPM modulation / demodulation scheme is related to the pulse width of the transmission / reception signal. However, the dimming level and the VPPM signal pulse width do not always correspond one-to-one. 11 and 12, the relationship between the dimming level and the VPPM signal pulse width will be described in more detail.

11 shows an example of the relationship between the VPPM received signal waveform and demodulated data.

11 shows waveforms of VPPM received signal waveforms at 50% dimming and demodulated VPPM demodulated data therefrom. It can be seen from Fig. 11 that there are two types of pulse widths of the VPPM reception signal.

12 shows various examples of the VPPM signal waveform according to the transmission data pattern.

The dimming level can be expressed by the number of pulse samples N _D as described above with reference to FIG. 6, and FIGS. 12A, 12B, 12C and 12D show transmission data "00"Quot;,"10"," 11 "

12 (a), 12 (b) and 12 (d), the dimming level becomes N _D in proportion to the signal pulse width. However, in the case of (c) of FIG. 12, pulses are connected at the point where the period is changed, and two pulse of the symbol are consecutively output, resulting in the signal pulse width being twice the dimming level N _D. In the present invention, it is possible to derive the dimming level from the VPPM signal pulse width by taking advantage of the fact that there are two cases of the VPPM signal pulse widths N _D and 2N _D.

The present invention includes a method of estimating the width of consecutive signal pulses in order to estimate the VPPM dimming level from the pulse width of the VPPM received signal. A relationship between the sampling and the signal pulse width and a method of estimating the signal pulse width will be described with reference to FIG. 13 and FIG.

13 shows the relationship between the sampling and the signal pulse width.

13, S (nT _s ) is a received signal, T _s is a sampling period, and S _TH is a threshold value for discriminating whether a pulse level is a high level or a low level .

In the case of the signal shown in FIG. 13, the pulse is maintained at the low level for a predetermined time from the initial time value, and the pulse is changed to the high level in the samples from 2T _s to 7T _s , and again from the 8T _s . Therefore, the pulse width of the signal shown in FIG. 13 is 6T _s in time, and the number of samples is '6'.

13, in order to estimate the pulse width, the current received signal S (nT _s ) is compared with the boundary value S _TH to determine whether the pulse level S _n in the current sample is High level or Low Level and a step of storing the pulse level S _n-1 in the previous sample are necessary. The current signal level is compared with the boundary value S _TH, and if the pulse level S _n is High level after the discrimination, the temporary pulse width PW _tmp is increased by '1'. This operation corresponds to a sample from 2T _s to 7T _s in the case of the signal of Fig.

If the current signal level is compared with the boundary value S _TH and the pulse level S _n is Low and the pulse level S _n-1 in the previous sample is High level, the temporary pulse width PW _tmp is stored in the estimated pulse width PW _est , The pulse width PW _tmp is reset to '0'. This operation corresponds to a sample of 8T _{s in} the case of the signal of Fig.

If the pulse level S _n in the current sample and the pulse level S _n-1 in the previous sample are both low, the temporary pulse width PW _tmp is reset to '0', and the value of the estimated pulse width PW _est is maintained. This operation corresponds to a sample of 9T _{s in} the case of the signal of Fig.

Through this process, the pulse width PW _est of the continuous signal can be estimated.

14 is a flowchart illustrating an operation of the VPPM signal demodulation method according to an embodiment of the present invention.

Specifically, FIG. 14 is a signal flow diagram for a process of estimating the pulse width PW _est of a continuous signal related to VPPM demodulation.

The received signal at the current sample S (nT _s) in FIG. 14, S ((n-1 ) T s) represents the received signal at the previous sample, S _TH is "0" or "1" for the judgment Lt; / RTI > Also, PW _est is the pulse width of the continuous signal, and PW _tmp is a variable value for pulse width estimation.

Referring to the pulse width estimation method shown in FIG. 14, PW _est and PW _tmp are initially set to zero at the beginning of operation (S 1410).

In order to estimate the pulse width, first, the current received signal S (nT _s ) is compared with the boundary value S _TH to determine whether the pulse level S _n in the current sample is a high level or a low level (S1411).

It is necessary to store the pulse level S _n-1 in the previous sample. If it is determined that the current signal level is compared with the boundary value S _TH and the pulse level S _n is High level, the temporary pulse width PW _tmp is increased by '1' (S1412).

On the other hand, if the current signal level is compared with the threshold S _TH and the pulse level S _n is low, the pulse level S _n-1 in the previous sample is compared with the threshold S _TH (S1420). If the pulse level S _n-1 in the previous sample is at the High level, it means that the continuous pulse is ended. Therefore, the temporary pulse width PW _tmp is stored in the estimated pulse width PW _est and the variable PW _tmp for the temporary pulse width is set to '0 '(S1422).

On the other hand, if the pulse level S _n in the current sample and the pulse level S _n-1 in the previous sample are both low, the temporary pulse width PW _tmp is reset to '0', and the value of the estimated pulse width PW _est is maintained S1430).

The pulse width PW _est of the continuous signal can be estimated through the estimation method of S1410 to S1430 in Fig. If the pulse width of the received signal is estimated through the method shown in FIG. 14, two types of pulse widths, N _D and 2N _D , as shown in FIG. 12 can be measured according to the data pattern.

Thereafter, noise in PW _est is suppressed through an average operation (S1440), and the VPPM signal is demodulated based on the estimated PW _est (S1450). Here, the averaging operation is performed to estimate the dimming level N _D from the two types of pulse width values robustly from the influence of the channel noise.

Finally, it is checked whether the reception of one continuous pulse of the visible light signal is terminated (S1460). If not completed, the process returns to the step 1411 and the above-described procedures of S1411 to S1460 are repeated.

Figure 15 shows a detailed block diagram of a dimming level estimation module based on pulse width estimation and averaging.

A dimming level estimation module 100 according to an embodiment of the present invention shown in FIG. 15 includes a pulse width estimator 110, a first average calculator 120 for calculating an average pulse width during a plurality of symbol intervals, A pulse type determination unit 140 for determining the type of the current pulse according to whether the current pulse width is equal to or greater than the average pulse width, And a dimming level calculator 150 for calculating a dimming level according to the type.

The dimming level calculator 150 includes a second average calculator 151 and a third average calculator 152, and may further include an adder, a multiplier, and the like.

)는 평균 연산을 나타낸다. In the embodiment of FIG. 15, a total of three average calculation units are used. In FIG. 15, Avg

) Represents an averaging operation.

Since the operation of the pulse width estimator 110 has been described in detail with reference to FIGS. 13 and 14, a detailed description thereof will be omitted.

A first average calculation unit 120, a pulse width estimation by taking the pulse width PW _est estimated output from the unit 110 to perform an averaging operation on, the pulse width PW _est estimates for multiple symbol periods to detect the dimming level And outputs it. At this time, the average pulse width value Avg (PW _est ) output from the first average operation unit 120 becomes a value between N _D and 2N _D.

The comparator 130 compares the value output by the pulse width estimator 110 with the value output by the first mean calculator 120. That is, the comparator 130 compares the currently estimated pulse width value PW _est with the average pulse width value Avg (PW _est ) averaged over a plurality of symbol periods.

The comparison result of the comparator 130 is input to a demux 140 that determines the type of pulse. The demultiplexer 140 receives the comparison result output from the comparator 130 and the estimated current pulse width output from the pulse width estimator 110 and outputs the estimated pulse width PW _est to the N _D calculation line And selects one of the 2N _D operation lines to transmit the currently estimated pulse width value PW _est .

In other words, when the currently estimated pulse width value PW _est is equal to or greater than the average pulse width value Avg (PW _est ), the demultiplexer 140 determines that the value PW _est for the pulse width of the noise mixed pulse is close to 2N _D Value, and sends PW _est to the line on which the operation on 2N _D is performed. In the opposite case, that is, if the currently estimated pulse width value PW _est is smaller than the average pulse width value Avg (PW _est ), PW _est is sent to the line on which the operation on N _D is performed.

The two output lines of the demux, that is, the N _D operation line and the 2N _D operation line, are input to the second average operation unit 151 and the third average operation unit 152, respectively. That is, an average operation is performed on the N _D operation line and the 2N _D operation line, respectively, to suppress the channel noise effect.

Is multiplied by 1/2 with respect to the output of the third average arithmetic operation unit 152 that performs an average with respect to the 2N _D arithmetic operation line, and is then added to the output of the second average arithmetic operation unit 151. [ The sum of the average value for the N _D computation line and the 1/2 value of the average for the 2N _D computation line is again multiplied by 1/2 to obtain the final estimated dimming level value.

16 shows an operation procedure of a visible light signal processing method according to an embodiment of the present invention.

The method of processing a visible light signal according to an embodiment of the present invention as shown in FIG. 16 includes receiving a visible light signal including at least one pulse (S1610), estimating a pulse width of a visible light signal (S1620) (S1630) suppressing noise in the estimated pulse width by performing an average operation on the pulse width, estimating a dimming level of the visible light signal using the average estimated pulse width (S1640), and estimating the dimming level of the visible light signal (Step S1650).

The step S1620 of estimating the pulse width of the visible light signal includes periodically sampling the pulses, calculating the number of consecutive samples having a value greater than or equal to a preset threshold value, And determining the pulse width according to the number of samples to be processed.

The step (S1640) of estimating the dimming level of the visible light signal using the average estimated pulse width may be performed by performing an average operation on each of the pulse width of at least one first type pulse and the pulse width of at least one second type pulse Multiplying the average value of the second type pulses by one half and summing with the average value of the first type pulses and multiplying the summed value by 1/2 to determine the dimming level can do.

Meanwhile, the step of demodulating the visible light signal (S1650) may include obtaining information included in the visible light signal according to the position of the pulse in the visible light signal period.

With the embodiments of the present invention described above, it is possible to estimate the dimming level of the VPPM signal robustly to the channel noise, and the estimated dimming level can be utilized in the VPPM demodulation to improve the performance of the VPPM radio reception.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

100: Dimming level estimation module (100) 110: Pulse width estimation part
120: first average calculating unit 130: comparator
140: pulse type determining unit (Demux) 150: dimming level calculating unit
151: second average operation unit 152: third average operation unit
200: VPPM demodulation module

Claims (20)

Receiving a visible light signal including at least one pulse;
Estimating a pulse width of the visible light signal;
Estimating a dimming level of the visible light signal using the estimated pulse width; And
And demodulating the visible light signal using the estimated dimming level. The method according to claim 1,
And performing an averaging operation on the estimated pulse width to suppress noise in the estimated pulse width. The method according to claim 1,
Wherein the type of pulse comprises a pulse having a first pulse width or a pulse having a second pulse width. The method of claim 3,
Wherein the second pulse width is twice the first pulse width. The method of claim 4,
The step of calculating the dimming level includes:
Performing an average operation on the pulse width of at least one first type pulse and the pulse width of at least one second type pulse, respectively;
Multiplying the average value of the second type pulses by one half, and summing with the average value of the first type pulses; And
And multiplying the summed value by 1/2 to determine a dimming level. The method according to claim 1,
Wherein the step of demodulating the visible light signal comprises:
And acquiring information included in the visible light signal according to a position of the pulse in the visible light signal period. The method according to claim 1,
Wherein the step of estimating the pulse width of the visible light signal comprises:
Performing periodic sampling on the pulse;
Calculating a number of consecutive samples having a value equal to or larger than a preset threshold value; And
And determining a pulse width according to the number of consecutive samples having a value equal to or larger than the threshold value. Receiving a visible light signal including at least one pulse;
Estimating a pulse width of the visible light signal; And
And determining a dimming level of the visible light signal using the estimated pulse width. The method of claim 8,
Wherein the step of estimating the dimming level of the visible light signal comprises:
Comparing the current pulse width to an average pulse width for a plurality of symbol periods;
Determining a type of a current pulse according to whether the current pulse width is equal to or greater than the average pulse width; And
And calculating a dimming level according to the type of the pulse. The method of claim 8,
Wherein the type of pulse comprises a pulse having a first pulse width or a pulse having a second pulse width. The method of claim 10,
Wherein the second pulse width is twice the first pulse width. The method of claim 11,
The step of calculating the dimming level includes:
Performing an average operation on the pulse width of at least one first type pulse and the pulse width of at least one second type pulse, respectively;
Multiplying the average value of the second type pulses by one half, and summing with the average value of the first type pulses; And
And multiplying the summed value by 1/2 to determine a dimming level. A dimming level estimating module that receives a visible light signal including at least one pulse and estimates a pulse width of the received visible light signal and estimates a dimming level of the visible light signal using the estimated pulse width; And
And a demodulation module for demodulating the visible light signal using the estimated dimming level. 14. The method of claim 13,
Wherein the dimming level estimating module comprises:
A pulse for estimating a pulse width of the visible light signal in accordance with the number of consecutive samples having a value equal to or larger than the threshold value, the method comprising the steps of: periodically sampling the pulse, calculating a number of consecutive samples having a value equal to or larger than a predetermined threshold, And a width estimation unit. 14. The method of claim 13,
Wherein the dimming level estimating module comprises:
A first average calculator for calculating an average pulse width for a plurality of symbol periods;
A comparator for comparing an output of the first averaging operator with a current pulse width;
A pulse type determining unit for determining a type of a current pulse according to whether the current pulse width is equal to or greater than the average pulse width; And
And a dimming level calculating section for calculating a dimming level according to the type of the pulse. 16. The method of claim 15,
Wherein the type of pulse comprises a pulse having a first pulse width or a pulse having a second pulse width. 18. The method of claim 16,
Wherein the second pulse width is twice the first pulse width. 18. The method of claim 17,
Wherein the dimming level calculating unit comprises:
An average operation is performed for each of the pulse width of the at least one first type pulse and the pulse width of at least one second type pulse, and an average of the first type pulses is calculated by multiplying the average value of the second type pulses by 1/2, And determines the dimming level by multiplying the summed value by 1/2. 14. The method of claim 13,
The demodulation module comprises:
And acquires information included in the visible light signal according to a position of the pulse in the visible light signal period. 14. The method of claim 13,
Wherein the visible light signal is controlled in dimming level with respect to the brightness of the illumination in accordance with the width of the pulse within the period.

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