KR102256878B1 - Apparatus and method for receiving a signal of hybrid waveform based on m-fsk and ofdm and separating modulated signals using filter - Google Patents

Abstract

According to an embodiment of the present disclosure, a demodulation method of a signal receiving device relates to a demodulation method in which a processor of a signal receiving device including a rolling camera performs at least a part of each step. The demodulation method includes the steps of: photographing, by the rolling camera, a light source multiple times at different times to generate a plurality of image frames; generating a first signal including an FSK modulated signal and an OFDM modulated signal based on the plurality of image frames; generating the FSK-modulated signal by applying a low-pass filter to the first signal, and generating the OFDM modulated signal by applying a high-pass filter to the first signal; and extracting data based on the generated FSK modulated signal and OFDM modulated signal, respectively. The present invention provides the device and method, which are capable of simultaneously receiving high-speed data and low-speed data.

Description

A device and method that receives a signal of a hybrid waveform based on M-FSK and OFDM and separates a modulated signal using a filter. }

The present invention relates to a hybrid waveform based on M-FSK (M-ary Frequency Shift Keying) and OFDM (Orthogonal Frequency Division Multiplexing), and more particularly, to a pulse wave signal modulated based on FSK and OFDM The present invention relates to a technology for simultaneously receiving different information by using a composite signal of a hybrid waveform in which signals are synthesized.

The content described below is only described for the purpose of providing background information related to an embodiment of the present invention, and the described content does not naturally constitute the prior art.

Recently, Visible Light Communication (VLC) technology, a wireless communication technology in which a communication function is added to visible wavelengths, is being actively researched using an infrastructure in which lighting such as incandescent bulbs and fluorescent lamps are replaced with semiconductor LED (Light Emitting Diode) lighting.

Prior art 1 discloses a technology for communicating by a camera-based M-FSK method based on a rolling-shutter type camera, but the general M-FSK method has difficulty in transmitting high-speed data.

Prior art 2 discloses a digital signal optical transmission technology, but after mapping the information bits based on FSK, the mapped signal is again multiplexed based on OFDM. After FSK modulation of the same information rather than different information There is a limit to multiplexing with OFDM.

Prior Art 1: Korean Patent Publication No. 10-165184 (registered on August 22, 2016) Prior Art 2: Korean Patent Application Publication No. 10-2008-0064804 (published on July 9, 2008)

An embodiment of the present disclosure provides an apparatus and method capable of simultaneously receiving high-speed data and low-speed data in visible light communication.

Another embodiment of the present disclosure provides an apparatus and method capable of simultaneously receiving different data using a pulse wave signal modulated through a visible light communication technology and an OFDM modulated signal.

The object of the present invention is not limited to the problems mentioned above, and other objects and advantages of the present invention that are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. In addition, it will be appreciated that the objects and advantages of the present invention can be realized by means and combinations thereof indicated in the claims.

An embodiment of the present disclosure provides a signal receiving apparatus and method for receiving a signal synthesized on one waveform by modulating two different pieces of information based on M-FSK and OFDM, respectively, based on a rolling camera.

The demodulation method of the signal receiving apparatus according to an embodiment of the present disclosure is a demodulation method in which a processor of a signal receiving apparatus including a rolling camera performs at least a part of each step, wherein the rolling camera photographs a light source multiple times at different times. Generating an image frame, generating a first signal including an FSK modulated signal and an OFDM modulated signal based on the image frame, applying a low pass filter to the first signal to generate an FSK modulated signal, It may include generating an OFDM modulated signal by applying a high pass filter to the signal, and extracting data based on the generated FSK modulated signal and the OFDM modulated signal, respectively.

A signal receiving apparatus according to an exemplary embodiment of the present disclosure is a signal receiving apparatus using a hybrid waveform, and is electrically connected to a camera generating an image in a rolling-shutter method receiving an optical signal, at least one processor, and a processor. It is connected and includes a memory in which at least one code executed by the processor is stored, and when the memory is executed through the processor, the processor generates an image frame by photographing the light source a plurality of times at different times by the camera and the light source, A first signal including an FSK modulated signal and an OFDM modulated signal is generated based on the image frame, a low pass filter is applied to the first signal to generate an FSK modulated signal, and a high pass filter is applied to the first signal to generate OFDM. It is possible to store a code that generates a modulated signal and causes the data to be extracted respectively based on the generated FSK modulated signal and OFDM modulated signal.

The apparatus and method for receiving signals according to an exemplary embodiment of the present disclosure can simultaneously receive different data using a modulated pulse wave signal and an OFDM modulated signal, thereby improving a data transmission speed in visible light communication.

A signal receiving apparatus and method according to an embodiment of the present disclosure provides an apparatus and method for receiving a signal of a hybrid waveform in which a modulated pulse wave signal and an OFDM modulated signal are synthesized into one waveform. It can be received at the same time.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a diagram schematically illustrating communication between a signal transmission device and a signal reception device according to an embodiment of the present disclosure.
2 is a block diagram showing the configuration of a signal transmission apparatus according to an embodiment of the present disclosure.
3 is a diagram illustrating a frequency used for FSK modulation and an OFDM symbol synthesized at each frequency of FSK according to an embodiment of the present disclosure.
4 is a diagram illustrating a data packet structure for transmitting an OFDM symbol according to an embodiment of the present disclosure.
5 is a diagram illustrating a hybrid waveform generated by mixing a pulse wave generated by M-FSK modulation and an OFDM signal generated by OFDM modulation by a signal transmission apparatus according to an embodiment of the present disclosure.
6 is a flowchart illustrating a signal transmission method according to an embodiment of the present disclosure.
7 is a block diagram illustrating a configuration of a signal receiving apparatus according to an embodiment of the present disclosure.
8 is a flowchart illustrating a method of receiving a signal according to an embodiment of the present disclosure.
9 illustrates a result of applying a received signal and a low pass filter according to an embodiment of the present disclosure.
10 illustrates a result of applying a received signal and a high pass filter according to an embodiment of the present disclosure.

Hereinafter, exemplary embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, but identical or similar elements are denoted by the same reference numerals regardless of reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and "unit" for constituent elements used in the following description are given or used interchangeably in consideration of only the ease of preparation of the specification, and do not have meanings or roles that are distinguished from each other by themselves. In addition, in describing the embodiments disclosed in the present specification, when it is determined that a detailed description of related known technologies may obscure the subject matter of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are for easy understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited by the accompanying drawings, and all changes included in the spirit and scope of the present invention It should be understood to include equivalents or substitutes.

Terms including ordinal numbers such as first and second may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another component.

When a component is referred to as being "connected" or "connected" to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. It should be. On the other hand, when a component is referred to as being "directly connected" or "directly connected" to another component, it should be understood that there is no other component in the middle.

Communication between a signal transmission device and a signal reception device according to an embodiment of the present disclosure will be described with reference to FIG. 1.

Referring to FIG. 1, the signal transmission apparatus 100 modulates two different data based on M-FSK and OFDM, respectively, and synthesizes them into one waveform in the synthesizer 130 to generate a final transmission signal, It may be configured to transmit the resulting final transmission signal to the same communication channel 140 including the LED light source.

In an embodiment of the present disclosure, the hybrid waveform of the final transmission signal is a signal obtained by synthesizing an OFDM signal with a pulse wave signal generated by an M-FSK method based on an optical camera communication (OCC) technology.

A pulse wave signal generated by a conventional FSK method or for an OOK (On-Off Keying) method has an amplitude of a low signal of 0, whereas a hybrid waveform according to an embodiment of the present disclosure has a high amplitude value. It is a signal obtained by synthesizing an OFDM signal with a pulse wave composed of high and low amplitude values of.

Accordingly, the signal transmission apparatus according to an embodiment of the present disclosure synthesizes OFDM signals not only at high duty of pulsed waves (in this specification, any one high or low portion of the pulsed wave is referred to as duty) but also at low duty. Can be done, and the overall data transfer rate can be improved.

In an embodiment, when two different pieces of data are analog data, the signal transmission apparatus 100 may digitally modulate the data and then input them to the FSK encoder 110 and the OFDM encoder 120, respectively.

In an embodiment, two different pieces of data may be low-speed data and high-speed data, respectively.

In one embodiment, the LED light source included in the communication channel 140 may include at least one LED light source.

The signal reception device 200 receives the final transmission signal transmitted by the signal transmission device 100 by a rolling-shutter camera 210, and rolls the signals generated in each column or row of the image sensor of the camera. After decoding based on the shutter, original different data may be extracted by demodulating in the FSK decoder 230 and the OFDM decoder 240, respectively.

A configuration of the signal transmission apparatus 100 according to an embodiment of the present disclosure will be described with reference to FIG. 2.

The signal transmission device 100 may include an FSK encoder 110, a rolling OFDM encoder 120, a synthesizer 130, and a communication channel 140 including an LED light source, and a clock for generating a clock signal It may include a generator.

The FSK encoder 110 may modulate the acquired first information into a pulse wave based on the M-ary FSK, and the pulse wave is composed of high duty and low duty, and both high duty and low duty modes may have positive amplitude values. have.

The FSK encoder 110 determines a frequency corresponding to each information bit using a forward error correction (FEC) encoder, an asynchronous bit insertion unit, and an information bit included in the first information using a preset M-FSK frequency table. It may include a bit frequency mapping unit (bits-frequency mapping) to be allocated. In the preset M-FSK frequency table, a plurality of frequencies corresponding to each information bit value is set.

The OFDM encoder 120 includes a serial to parallel converter (serial to parallel) for converting the acquired second information in parallel, a quadrature amplitude modulation (QAM) modulator for QAM modulation according to each information bit, and an Inverse Discrete Fourier Transform (IDFT). It may include a Hermitian mapping unit, an IDFT transform unit, and a cyclic prefix insertion unit to allow OFDM symbols to have non-imaginary values after transformation.

A frequency mapping of information bits included in packets obtained by transforming first information of the M-FSK encoder 110 according to an embodiment of the present disclosure will be described with reference to FIG. 3.

When the M-FSK encoder 110 allocates a pulse wave having a specific frequency to each information bit corresponding to the first information, the frequency of each pulse wave is based on the number of OFDM symbols of the OFDM signal to be included in the pulse wave. Can be set to

) 및 롤링 OFDM 심볼의 주파수(

)는 <수학식 1> 및 <수학식 2>를 만족하도록 설정할 수 있다. 여기에서, n은 펄스파의 한 듀티에 합성되는 OFDM 프레임의 개수이고,

은 OFDM 심볼인 OFDM 프레임의 길이이다.In order to consider the rolling speed of the rolling shutter camera used in the OCC technology and synthesize the OFDM signal with the pulse wave generated based on M-FSK, the M-FSK encoder 110 uses the pulse wave generated based on the M-FSK. Frequency of (

) And the frequency of the rolling OFDM symbol (

) Can be set to satisfy <Equation 1> and <Equation 2>. Here, n is the number of OFDM frames synthesized for one duty of a pulse wave,

Is the length of an OFDM frame, which is an OFDM symbol.

Accordingly, the preset M-FSK frequency table may be as shown in Table 1 below.

According to the table of <Table 1>, which is a preset M-FSK frequency table, the M-FSK encoder 110 generates an asynchronous symbol constituting packets obtained by transforming the first information and a pulse wave having a frequency according to the bit value of the data packet. To allocate. In this case, both the high-duty and low-duty amplitudes of the pulsed wave may have positive values.

The pulse frequency difference between any two pulse signals having adjacent pulse frequencies among a plurality of pulse signals included in the table of <Table 1>, which is the M-FSK frequency table, may be set to be different from each other.

For example, the difference in pulse frequency between f1 and f2 may be different from the difference in pulse frequency between f2 and f3.

In one embodiment, the M-FSK encoder 110 has a frequency corresponding to the Ab bit for synchronization with the rolling shutter camera 210 of the signal receiving device 200 between pulse waves of a frequency corresponding to each information bit. A pulse wave can be generated by inserting the pulse wave f5.

As described in Table 1 and above, the synthesizer 130 may synthesize an appropriate number of OFDM symbols for each frequency when synthesizing an OFDM signal with a pulse wave having a corresponding frequency.

3 and <Table 1>, the synthesizer 130 synthesizes two OFDM symbols in one period of a pulse wave of frequency f0 (thus, synthesizes one OFDM symbol for each duty), and a pulse of frequency f1 Four OFDM symbols are synthesized in one spar period (thus, two OFDM symbols are synthesized for each duty), and six OFDM symbols are synthesized in one period of a pulse wave of frequency f2 (hence, three OFDM symbols for each duty). Can be synthesized).

That is, the frequency of each pulse wave used for M-FSK modulation may be set to be inversely proportional to the number of OFDM symbols of an OFDM signal synthesized with one duty of the pulse wave.

In an embodiment, when the rolling rate of the rolling shutter camera 210 of the signal receiving device 200 is not constant, the synthesizer 130 may lose some of the transmitted frames, as shown in FIG. 3. The same OFDM frame corresponding to the same OFDM symbol may be repeatedly inserted into a pulse wave.

A data packet for transmitting an OFDM frame according to an embodiment of the present disclosure will be described with reference to FIG. 4. The OFDM frame may be transmitted based on a plurality of data packets i-1, i, i+1.

A plurality of data packets (i-1, i, i+1) each includes a plurality of data sub-packets (i1, i2, i3) (n), and each data sub-packet (i2) is an arbitrary data packet A payload indicating an OFDM symbol corresponding to the portion of the second information allocated to (i2) may be included.

In an embodiment, in order to prevent packet loss due to a variable frame rate of a receiving camera, data subpackets included in one data packet may include the same payload representing the same OFDM symbol.

In one embodiment, a serial number may be assigned to each data packet, and the serial number may be assigned as a contiguous number for consecutive data packets.

In one embodiment, each data sub-packet i2 includes a payload indicating a serial number of the data packet i2 and an OFDM symbol corresponding to a portion of the second information allocated to the data packet i2. I can.

In an embodiment, data subpackets included in one data packet may have the same serial number. Accordingly, even if a part of a specific packet is lost, information loss is prevented by a plurality of data subpackets to which information is copied, thereby preventing an information transmission error. In addition, redundantly received signals through the serial number may be removed, and it may be determined whether there is an omission in the received signal.

A hybrid waveform generated by synthesizing an OFDM signal with a pulse wave generated based on M-FSK generated by the synthesizer 130 according to an embodiment of the present disclosure will be described with reference to FIGS. 3 and 5.

The synthesizer 130 may synthesize an OFDM signal for both the high duty and the low duty of the pulse wave generated by the FSK encoder 110, and in this case, the number of OFDM frames synthesized for the high duty and the low duty may be the same. .

When the pulse wave modulated by the M-FSK method and the OFDM signal modulated by the OFDM method are synthesized through the above-described method, a final transmission signal having a hybrid waveform as shown in FIG. 5 may be generated. The final transmission signal of FIG. 5 shows an example of a final transmission signal obtained by synthesizing an OFDM signal with pulse waves having different frequencies.

Referring to FIG. 5, an OFDM signal is synthesized with both high and low duty of a pulse wave of a final transmission signal, and a final transmission signal may be generated so that both high and low duty have a positive amplitude.

In an embodiment, the OFDM encoder 120 may generate an OFDM signal such that a difference between a minimum value and a maximum value of the OFDM signal is less than half of the difference between the high duty and the low duty of the pulse wave. This is to prevent the OFDM signal from changing significantly in the hybrid waveform synthesized based on M-FSK and OFDM, so that low duty and high duty are not confused at the receiving side. In order to reduce confusion between low duty and high duty in a pulse wave, the amplitude of the OFDM signal may be set to be 1/4, 1/6, 1/8 or 1/10 of the pulse wave amplitude.

A signal transmission method using a hybrid waveform according to an embodiment of the present disclosure will be described with reference to FIG. 6.

Referring to FIG. 6, a method of transmitting a signal using a hybrid waveform according to an embodiment of the present disclosure may be performed by the following steps.

The signal transmission apparatus may modulate the first information and the second information obtained from two different pieces of information by different modulation methods, and in this case, the first information is modulated based on the M-FSK method to generate a pulse wave. And, the second information may generate an OFDM signal based on the OFDM scheme (S110).

The signal transmission apparatus may allocate pulse waves having different pulse frequencies corresponding to the information bits generated from the first information, and the relationship between each information bit and the pulse waves having a specific pulse frequency is shown in Table 1 described above. It can be the same.

The signal transmission apparatus may preset the pulse frequency of the pulse wave corresponding to the information bit generated from the first information based on the number of symbols of the OFDM signal included in the pulse wave. For example, the pulse frequency of the pulse wave is set so that two OFDM symbols can be synthesized in one period of a pulse wave corresponding to a certain information bit, and 3 OFDM symbols are used in one period of a pulse wave corresponding to another information bit. The pulse frequency of the pulse wave can be set so that it can be synthesized individually.

The first information and the second information may be obtained from stream data of different rates, respectively.

The signal transmission device may generate a final transmission signal by synthesizing the generated pulse signal and the OFDM signal (S120). In this case, the pulse signals are all composed of high duty and low duty having a positive amplitude, and each high duty and low OFDM symbols can be synthesized for all of the duties.

The signal transmission device can transmit the final transmission signal, in which different information is modulated by different modulation methods, M-FSK and OFDM, and synthesized into one waveform, through one signal transmission channel. In this case, through an LED light source. The final transmission signal may be transmitted (S130).

A signal receiving apparatus 200 according to an embodiment of the present disclosure will be described with reference to FIG. 7.

The signal receiving device 200 includes a rolling camera 210 that generates an image based on a signal acquired from an image sensor in a rolling-shutter method that receives an optical signal, and the image acquired from the image sensor is a one-dimensional signal. A down sampler for down-sampling, a low pass filter unit 230 that detects an FSK modulated signal using a low pass filter, an FSK decoder that performs decoding based on a preset M-ary FSK frequency table period, and removes the Ab bit. An FSK decoder unit 230 including an Ab bits remover that performs a high pass filter, a high pass filter unit that detects an OFDM modulated signal using a high pass filter, and a Discrete Fourier Transform (DFT) after removing the cyclic prefix. An OFDM decoder unit 240 including a DFT transform unit to perform, an equalizer to reduce amplitude deformation, a Hermitian mapping unit, and a QAM demodulator may be included.

The rolling camera continuously photographs the blinking of the LED light source at different times and stores each photographed signal in one column or row of the image sensor to generate an image frame. The rolling camera sequentially exposes each row or column of the image sensor, so that a signal value corresponding to the brightness of the LED light source may be obtained according to the blinking of the LED light source in one column or row of the image sensor of the rolling camera. The rolling camera can generate a plurality of image frames. In the following description, it is assumed that the rolling camera sequentially exposes each row of the image sensor.

The down sampler generates a one-dimensional brightness signal (first signal) based on the amount of electric charge captured by the image sensor according to the brightness value of the light source photographed for each row.

The first signal generated by the down sampler based on the plurality of image frames may be the signal 1010 of FIG. 10. A value in consideration of the order of each row and the rolling-rate of the camera may be set as the time axis of the first signal.

The first signal is generated by the rolling camera receiving the blinking of the LED light source according to the hybrid waveform as shown in FIG. 5 generated by the signal transmission device 100, and the first signal may include an FSK modulated signal and an OFDM modulated signal. have.

9 and 10, a first signal 910 is an FSK modulated signal 920 composed of a high duty and a low duty, and an OFDM modulated signal 930 synthesized with both a high duty 911 and a low duty 913. ), and both the high duty and the low duty may have positive amplitude values.

The low pass filter unit detects the FSK modulated signal included in the first signal based on the result of applying the low pass filter to the first signal, and the high pass filter unit detects the first signal based on the result of applying the high pass filter to the first signal. The OFDM modulated signal included in is detected, and the FSK decoder unit 230 and the OFDM decoder unit 240 may respectively extract different data based on the detected FSK modulated signal and OFDM modulated signal.

A method of receiving a signal by a signal receiving apparatus according to an embodiment of the present disclosure will be described with reference to FIG. 8.

The signal receiving device sequentially exposes each row or column of the image sensor of the rolling camera, thereby obtaining a signal value corresponding to the brightness of the LED light source according to the blinking of the LED light source in one column or row of the image sensor of the rolling camera, A plurality of image frames are generated (S210).

The signal receiving device generates a one-dimensional brightness signal (first signal) based on the amount of electric charge captured by the image sensor according to the brightness value of the light source photographed for each row (S220). The first signal is an FSK modulated signal composed of a high duty and a low duty having positive amplitude values, and an OFDM modulated signal 1011 and 1013 synthesized in both the high duty 1011 and the low duty 1013 of the FSK modulated signal. Can include.

The signal receiving apparatus may generate an FSK modulated signal by applying a low pass filter to the first signal, and may generate an OFDM modulated signal by applying a high pass filter to the first signal (S230).

A step of generating an FSK modulated signal by applying a low pass filter to the first signal will be described with reference to FIG. 9.

In the image frame generated by the image sensor of the rolling camera, the first signal 910 may have a form including a low-frequency pulsed FSK modulated signal and a high-frequency OFDM modulated signal. The FSK modulated signal may be composed of high duty and low duty having positive amplitude values, and high-frequency OFDM modulated signals may be included in both the high duty and low duty.

The signal receiving apparatus extracts a zero crossing point from the result of applying a low pass filter that filters a waveform having a frequency equal to or higher than a preset frequency to the first signal to the first signal, and extracts the frequency period using the time between the extracted zero crossing points or The frequency of the FSK modulated signal may be determined based on various known methods not disclosed in the specification.

In one embodiment, the signal receiving apparatus may determine the amplitude value of the high duty and the amplitude of the low duty of the FSK modulated signal by scanning a result of applying the first signal or the low pass filter to the first signal, and the intermediate value thereof It may be determined as a reference value for determining the high duty and low duty.

After removing the Ab bit, the signal receiving apparatus may detect the bit data based on the determined frequency of the FSK modulated signal and the relationship between each information bit in Table 1 and pulse waves having a specific pulse frequency.

Referring to FIG. 9, as a result of applying the low pass filter to the first signal, frequency interference is removed or reduced, so that data can be easily decoded from the FSK modulated signal.

A step of generating an OFDM modulated signal by applying a high pass filter to the first signal will be described with reference to FIG. 10.

In the image frame generated by the image sensor of the rolling camera, the first signal 910 may have a form including a low-frequency pulsed FSK modulated signal and a high-frequency OFDM modulated signal. The FSK modulated signals may be composed of high duty and low duty having positive amplitude values, and OFDM modulated signals 911 and 913 having high frequencies may be included in both the high duty and the low duty.

Referring to FIG. 10, the signal receiving apparatus applies a high pass filter for filtering a waveform having a frequency higher than a preset frequency to the first signal, and as a result, an OFDM modulated signal 930 from which a low-frequency FSK modulated signal is removed. Can be obtained.

The signal receiving apparatus detects the start frame from the OFDM modulated signal 930, taking into account the data packet structure of FIG. Then, they can be compared with each other, and the payload can be restored based on the front and rear Ab bits.

The signal receiving apparatus converts the OFDM modulated signal 930 (which may be the payload described above) from which the serial form FSK modulated signal has been removed into a parallel form, and removes the original CP (Cyclic Prefix) inserted into each of the OFDM symbols. Thereafter, a Discrete Fourier Transform (DFT) is performed to convert OFDM symbols in a time domain into OFDM symbols in a frequency domain, and a demapping operation may be performed. The signal receiving apparatus may obtain final data by converting the data including the demapped OFDM symbols into a serial form and decoding the parallel-type OFDM symbols into a serial form.

In this process, the signal receiving apparatus may demodulate the OFDM modulated signal 930 with an OFDM decoder, and perform synchronization of the demodulated OFDM modulated signal by equalizing the demodulated result.

A method of demodulating the OFDM modulated signal by the OFDM decoder is known to those of ordinary skill in the art, and thus a detailed description thereof will be omitted.

In one embodiment, the signal receiving apparatus synchronizes with the FSK modulated signal and considers the determined pulse frequency of the FSK modulated signal and the number of high and low duties of the FSK modulated signal, as shown in FIG. 3. OFDM symbols can be extracted as many as the number of OFDM symbols included in the duty. In this case, the number of OFDM symbols included in the OFDM modulated signal corresponding to the high duty and the low duty of the first signal may be the same.

In an embodiment, the signal receiving apparatus may determine the width of each duty of the FSK modulated signal based on the high duty and the low duty determined from the detected FSK modulated signal, and may determine the high duty by considering the width of the FSK modulated signal. And demodulate the OFDM signal based on the signal obtained at low duty.

As described above in the signal transmission apparatus, data extracted by demodulating the FSK modulated signal and the OFDM modulated signal respectively detected from the first signal are different data and may have different data rates.

Referring to FIG. 10, as a result of applying a high pass filter to the first signal, frequency interference is removed or reduced, so that data can be easily decoded from an OFDM modulated signal.

The above-described present disclosure can be implemented as a computer-readable code on a medium in which a program is recorded. The computer-readable medium includes all types of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable media include hard disk drives (HDDs), solid state disks (SSDs), silicon disk drives (SDDs), ROMs, RAM, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc. There is this. In addition, the computer may include a signal transmission device or a processor of the signal reception device.

Meanwhile, the program may be specially designed and configured for the present disclosure, or may be known and usable to a person skilled in the computer software field. Examples of the program may include not only machine language codes such as those produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like.

In the specification of the present disclosure (especially in the claims), the use of the term "above" and a reference term similar thereto may correspond to both the singular and the plural. In addition, when a range is described in the present disclosure, it includes the invention to which individual values belonging to the range are applied (unless otherwise stated), and each individual value constituting the range is described in the detailed description of the invention. Same as.

The steps constituting the method according to the present disclosure may be performed in an appropriate order unless explicitly stated or contradicted by the order. The present disclosure is not necessarily limited according to the order of description of the steps. In the present disclosure, the use of all examples or illustrative terms (for example, etc.) is merely for describing the present disclosure in detail, and the scope of the present disclosure is limited by the examples or exemplary terms unless limited by the claims. It does not become. In addition, a person of ordinary skill in the art can recognize that various modifications, combinations, and changes may be configured according to design conditions and factors within the scope of the appended claims or their equivalents.

Therefore, the spirit of the present disclosure is limited to the above-described embodiments and should not be defined, and all ranges equivalent to or equivalently changed from the claims to be described later as well as the claims to be described later are the scope of the spirit of the present disclosure. It will be said to belong to.

100: signal transmission device
200: signal receiving device
510, 520: hybrid waveform
910: first signal
920: Result of applying the low pass filter of the first signal
930: Result of applying the high pass filter of the first signal

Claims (14)

A demodulation method in which a processor of a signal receiving device including a rolling camera performs at least a part of each step,
Generating an image frame by photographing the light source a plurality of times at different times by the rolling camera;
Generating a first signal including an FSK modulated signal and an OFDM modulated signal based on the image frame;
Generating the FSK modulated signal by applying a low pass filter to the first signal, and generating the OFDM modulated signal by applying a high pass filter to the first signal; And
Comprising the step of extracting data respectively based on the generated FSK modulated signal and the OFDM modulated signal,
Demodulation method of a signal receiving device. The method of claim 1,
The first signal includes an FSK modulated signal composed of a high duty and a low duty and the OFDM modulated signal synthesized for both the high and low duty,
Both the high duty and the low duty have positive amplitude values.
Demodulation method of a signal receiving device. The method of claim 1,
Demodulating the FSK modulated signal and the OFDM modulated signal to generate an FSK demodulated signal and an OFDM demodulated signal, respectively; And
Extracting data from the FSK demodulated signal and the OFDM demodulated signal, respectively,
Data extracted from the FSK demodulation signal and the OFDM demodulation signal are different data,
Demodulation method of a signal receiving device. The method of claim 3,
Extracting data from the OFDM demodulated signal,
Including the step of extracting a number of OFDM symbols corresponding to the number of the high duty and the low duty of the FSK modulation signal,
Demodulation method of a signal receiving device. The method of claim 1,
Extracting data based on the FSK modulated signal,
Including the step of determining a frequency of the FSK modulated signal corresponding to a result of applying the low pass filter by using a M-ary Frequency Shift Keying (M-FSK) frequency table preset in the result of applying the low pass filter,
Demodulation method of a signal receiving device. The method of claim 5,
Extracting data based on the OFDM modulated signal,
Including the step of extracting the number of OFDM symbols corresponding to the frequency of the OFDM modulated signal,
The number of OFDM symbols corresponds to both high duty and low duty of the FSK modulation signal,
Demodulation method of a signal receiving device. The method of claim 6,
The number of OFDM symbols corresponding to the high duty of the FSK modulated signal and the number of OFDM symbols corresponding to the low duty are the same,
Demodulation method of a signal receiving device. As a signal receiving device using a hybrid waveform,
A camera that generates an image in a rolling-shutter method that receives an optical signal;
At least one processor; And
A memory electrically connected to the processor and storing at least one code executed by the processor,
When the memory is executed through the processor, the processor,
The camera generates an image frame by photographing the light source multiple times at different times,
Generates a first signal including an FSK modulated signal and an OFDM modulated signal based on the image frame,
Applying a low pass filter to the first signal to generate the FSK modulated signal, applying a high pass filter to the first signal to generate the OFDM modulated signal,
Storing a code that causes each data to be extracted based on the generated FSK modulated signal and the OFDM modulated signal,
Signal receiving device. The method of claim 8,
The first signal includes an FSK modulated signal composed of a high duty and a low duty and the OFDM modulated signal synthesized for both the high and low duty,
Both the high duty and the low duty have positive amplitude values.
Signal receiving device. The method of claim 8,
The memory causes the processor,
Demodulate the FSK modulated signal and the OFDM modulated signal to generate an FSK demodulated signal and an OFDM demodulated signal, respectively,
Further storing a code that causes data to be extracted from the FSK demodulated signal and the OFDM demodulated signal, respectively,
Data extracted from the FSK demodulation signal and the OFDM demodulation signal are different data,
Signal receiving device. The method of claim 10,
The memory causes the processor,
Further storing a code causing to extract a number of OFDM symbols corresponding to the number of the high duty and the low duty of the FSK modulated signal,
Signal receiving device. The method of claim 8,
The memory causes the processor,
A code that causes the frequency of the FSK modulated signal corresponding to the result of applying the low pass filter to be determined using a preset M-FSK (M-ary Frequency Shift Keying) frequency table in the result of applying the low pass filter is further added. Saved,
Signal receiving device. The method of claim 12,
The memory causes the processor,
Further storing a code causing to extract the number of OFDM symbols corresponding to the frequency of the OFDM modulated signal,
The number of OFDM symbols corresponds to both high duty and low duty of the FSK modulation signal,
Signal receiving device. The method of claim 13,
The number of OFDM symbols corresponding to the high duty of the FSK modulated signal and the number of OFDM symbols corresponding to the low duty are the same,
Signal receiving device.

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