KR20160020170A - Method for Ultrasonic wave Signal Transmission and Reception - Google Patents

Abstract

Disclosed is a method for transmitting and receiving an ultrasonic wave signal. According to an embodiment of the present invention, the method for transmitting and receiving an ultrasonic wave signal by a sound output apparatus comprises the following steps of: receiving C (=N/M) data symbols and generating N data symbols by repeating the C data symbols on a C cycle; carrying the C data symbols on C subcarrier groups which are spaced apart from each other at predetermined M intervals among the N subcarriers of the non-audible band, as the N data symbols are carried on N subcarriers of a non-audible band by performing a predetermined phase rotation for each of the N data symbols; and outputting, as sound, a result signal obtained by converting a signal, in which an ultrasound wave signal carrying the C data symbols and an audio signal of an audible band are combined, into an analog signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for transmitting and receiving ultrasound waves,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to information transmission technology, and more particularly, to a method of transmitting and receiving an ultrasonic signal through an audio frequency band using a speaker and a microphone as a transceiver.

As shown in FIG. 1, the ultrasonic signal transmission system is a system in which an information signal is transmitted using a non-audible frequency band (usually a band of 18 kHz to 22 kHz), which is difficult for the general public to hear. Generally, a system using an ultrasonic signal transmission system uses a speaker as a transmitter and a microphone as a receiver without a separate transceiver and an additional circuit / apparatus. Therefore, the communication system of the ultrasonic signal transmission system can be simply implemented in various apparatuses having a speaker or a microphone, such as a digital television, a smart phone or the like.

However, the speaker and microphone system is a system for reproducing and acquiring audio / sound signals of an audio frequency band. Therefore, in order to apply the ultrasonic signal transmission system to a conventional speaker and microphone system, a signal is generated so that ultrasonic signals exist only in the non-audible frequency band without affecting the audible frequency band, Multiplexing with a signal is required.

A conventional method of generating and transmitting a signal in the non-audible frequency band is basically a baseband transmission method and a passband transmission method.

In the former baseband transmission method, a signal is transmitted on the basis of DC (direct current) without using a carrier wave. Since the carrier wave is not used, there is an advantage that sensitivity to carrier frequency synchronization is low. However, basic synchronization such as time synchronization and DC offset must be performed, and it is disadvantageous to process a wider band than the actual band used.

On the other hand, the latter passband transmission scheme has a disadvantage in that the reference for synchronization is strictly more strict than the baseband transmission scheme, but there is an advantage that the signal can be easily limited to exist only in the non-audible frequency band. Further, when a signal having a large computation amount is generated, it is processed at a frequency lower than the audio sampling frequency F _S , and thereafter, upsampling can be performed before upconverting and multiplexing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic signal transmission / reception method capable of transmitting data using an invisible frequency band in an audio frequency band.

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

A method of transmitting ultrasound signals by a speech output apparatus according to an embodiment of the present invention includes generating N data symbols by receiving C (= N / M) data symbols and repeating the C data symbols in C cycles ; And performing a predetermined phase rotation on each of the N data symbols to transmit the N data symbols to N non-audible subcarriers, Loading the C data symbols into a subcarrier group; And outputting a signal obtained by analog-converting a signal obtained by adding an audio signal of an audible band to an ultrasound signal of the C data symbols.

According to another aspect of the present invention, there is provided a method of receiving an ultrasonic signal by a voice sensing apparatus, comprising: detecting a signal of a non-audible range from a signal obtained by digitally converting an output signal of a microphone; Generating a first signal by performing Fast Fourier Transform (NRF) on the signal of the non-audible frequency band; Performing C-size inverse discrete Fourier transform on C subcarriers carrying transmission information using the offset of the subcarrier if a predetermined carrier offset is present; And detecting the transmission information from the inverse discrete Fourier transformed signal.

According to the present invention, data can be transmitted using the non-audible frequency band among audio frequency bands.

1 shows a frequency spectrum of an audio transmission frequency band;
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an ultrasonic transmission system.
3 is a block diagram illustrating an ultrasonic transmission system according to another embodiment of the present invention.
FIG. 4A is a block diagram illustrating the function of an ultrasonic modulator according to another embodiment of the present invention; FIG.
FIG. 4B is a block diagram illustrating an ultrasonic wave modulating unit according to another embodiment of the present invention. FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms " comprises, " and / or "comprising" refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 2 is a block diagram illustrating an ultrasonic transmission system according to an embodiment of the present invention.

2, the ultrasonic transmission system 20 according to an embodiment of the present invention includes a first transmission device 2100 and a first reception device 2200. [

The first transmitting apparatus 2100 divides the non-audible frequency band B _u into N small sub-bands, and transmits transmission data (information to be transmitted) by transmitting them to each sub-band. Here, the interval? F between subcarriers in the baseband (digital domain) may be B _u / N. As described above, the first transmitting apparatus 2100 may be an apparatus for outputting an audio signal through a speaker or the like.

The first transmitter 2100 includes an ultrasound signal modulator 2110, a guard interval and window function block 2120, an up-sampler 2130, an up-converter 2140, a summation unit 2160, an audio decoder 2150 ), A DAC 2170, and a speaker 2180. Hereinafter, each block of the first transmitting apparatus 2100 will be described.

The ultrasonic signal modulator 2110 modulates the transmission data by Inverse Fast Fourier Transform (IFFT), and transmits the transmission data to the sub-carrier of the non-audible frequency band B _u . Here, the transmission data may be generated in the frequency domain.

At this time, the non-audible frequency bandwidth B _u may be F _s / 2. Specifically, the audio sampling frequency F _s of a sound source is usually 48 kHz, 96 kHz, etc., and the actual usable audio frequency bandwidth is a positive frequency band B = F _s / 2. However, since the transmission data is combined with the audio signal, the bandwidth (non-audible frequency bandwidth B _u ) of the ultrasonic signal may be F _s / 2 corresponding to the bandwidth of the audio signal.

If the transmission signal in the frequency domain where the number of subcarriers is N is defined as X _l (k) according to the frequency index k, the 1 st ultrasound signal in the IFFT time domain output from the ultrasound signal modulating unit 2110 is expressed by Equation Can be expressed as: Here, the subcarrier interval? F in the baseband (digital domain) may be B _u / N.

At this time, X ₁ (k) may be a signal encoded with a channel error correction code, or may be a binary signal composed of {0, 1}. When X _l (k) is a binary signal, detection by the receiving apparatus can be facilitated.

The guard interval and window function block 2120 applies a time domain window function to the time domain ultrasound signal x _l (n). Therefore, generation of high frequency components between the ultrasonic signal x _l (n) in the time domain and the ultrasonic signal x _{l -1} (n) in the previous time domain can be suppressed.

In addition, the guard interval and window function block 2120 may insert a guard interval into the time domain ultrasound signal, thereby reducing interference with the time domain ultrasound signal transmitted before or after. Herein, the guard interval and window function block 2120 may insert a guard interval in a form in which no signal is output for a certain period of time, and may insert a CP (Cyclic Prefix). The latter case may be advantageous in terms of synchronization. At this time, the guard interval and window function block 2120 may be omitted.

를 출력한다.The up-sampler 2130 applies the up-sampling factor F _s / F _u before the digital modulation DAC to match the sampling frequency F _u of the ultrasonic signal to the sampling frequency F _s of the audio signal, Up-sampling, and as a result, the up-sampled ultrasonic signal

.

The up-converter 2140 applies frequency up-conversion to the up-sampled ultrasonic signal by applying a gain factor g. Here, the gain element g may be a constant or a variable that adjusts the gain of the ultrasonic signal upward or downward to match the audio signal.

The summing unit 2160 outputs a sum signal which is a sum of the frequency up-converted ultrasonic signal and the audio signal. Here, the audio signal may be an audio sample encoded by the audio decoder 2150.

를 출력한다.The DAC 2170 performs digital-analog conversion on the sum signal,

.

은 F_s로 샘플링된 신호의 시간영역 인덱스이며,

은 대역폭이 B_a인 가청주파수 대역의 오디오 신호이며, f_c는 초음파 신호의 중심주파수(즉, 반송파주파수)이며,

은 복소수의 실수부를 의미한다.here,

Is the time domain index of the signal sampled at F _s ,

Is the audio signal in the audio frequency band B is _a bandwidth, f _c is a center frequency (i.e., carrier frequency) of the ultrasonic signal,

Means the real part of a complex number.

The speaker 2180 outputs a sound signal of a transmission signal combined with an audio signal and an ultrasonic signal and propagates it into the air. Then, the transmission signal is input to the first receiving device 2200 through the microphone 2210. [

The first receiver 2200 includes a microphone 2210, an ADC 2220, a high pass filter (HPF) 2230, a sample rate converter 2240, an ultrasound signal demodulator 2250, (2260). The first receiver 2200 may be a device having a microphone for sensing sounds. Hereinafter, each block of the first receiving apparatus 2200 will be described.

The combined signal of the digital domain (the combined signal of the audio signal and the ultrasonic signal), which is sensed and received by the microphone 2210 and sampled at f _s through the ADC 2220, can be expressed as Equation 3 below .

는 스피커(2180)와 마이크로폰(2210) 사이의 p번째 다중경로 채널을 의미하며,

은 잡음전력이

이며 평균이 0인 가산성백색잡음(AWGN: Additive White Gaussian Noise)을 의미한다.here,

Means a pth multipath channel between the speaker 2180 and the microphone 2210,

Noise power

And an additive white Gaussian noise (AWGN) with an average of 0.

The high-pass filter 2230 removes the audio signal from the combined signal in the digital domain through high-frequency filtering.

Then, the high-frequency filtered ultrasonic signal is down-converted, and then the transmitted data can be detected from the baseband. However, this scheme may be sensitive to frequency synchronization. In order to prevent such a problem, according to the present invention, a signal can be detected using a baseband direct reception system. In the following description, the case where the first receiving apparatus 2200 according to the embodiment of the present invention uses the baseband direct receiving method will be described as an example.

When the baseband direct reception system is applied, the received ultrasound signals are demodulated by the ultrasound signal demodulator 2250 into N _R FFT (Fast Fourier Transform), and is converted into a frequency domain signal Y (k). Hereinafter, this process will be described in more detail.

로 샘플링 주파수를 변경한다. 이와 같이, 본 발명의 일 실시예는 샘플링 주파수를 FFT 크기에 대응하도록 변경하여 제1 송신 장치(2100)와 제1 수신 장치(2200) 사이에 부반송파 간격을 일정하게 유지할 수 있다.The sample rate converter 2240 converts the received ultrasound signal into an analog signal,

To change the sampling frequency. As such, an embodiment of the present invention can maintain the subcarrier interval constant between the first transmission device 2100 and the first reception device 2200 by changing the sampling frequency to correspond to the FFT size.

The ultrasound signal demodulator 2250 performs FFT processing on the ultrasound signal whose sampling frequency is changed and outputs an ultrasound signal Y (k) in a frequency domain defined by Equation (4).

로 계산되며,

는 x보다 크면서, 2의 지수 형태

로 표기될 수 있는 최소의 양의 정수일 수 있다.Here, FFT size, according to the audio sampling frequency F _s

Lt; / RTI >

Is greater than x and has an exponential form of 2

Lt; / RTI > may be the smallest positive integer that can be represented by < RTI ID = 0.0 >

The information detector 2260 detects the transmission data X _l (k) from the N subcarriers of the B _u band, which is the bandwidth of the non-audible frequency of the reception signal converted into the frequency domain signal.

이므로, 비가청대역의 부반송파 인덱스는

로 계산될 수 있다.At this time, the transmission signal X _l (k) is a binary signal, and the carrier frequency is

, The subcarrier index of the non-audible frequency is

Lt; / RTI >

For example, the information detector 2260 may include an energy detector to detect the energy of a subcarrier having a subcarrier index of a predetermined non-audible frequency band to detect a transmission signal as shown in Equation (5) have. Here, the threshold value T may be determined based on the average noise power of the subcarriers carrying the transmission data according to an experiment.

As described above, the ultrasonic transmission system according to an embodiment of the present invention generates signals in the frequency domain to reduce transmission data affected by the audio signals, and converts the signals into time domain through IFFT.

In order to efficiently transmit ultrasound signals, it is preferable that the first transmitting apparatus 2100 generates ultrasound signals only in a non-audible band that can not be heard by ordinary people as in Equation (1).

Also, in order to reduce synchronization problems such as frequency offset, it is effective to use a baseband direct reception method in which IFFT modulation is performed by putting a signal in only a desired subcarrier among subcarriers of an unvoiced band. However, when the baseband transmission method is used, since data is transmitted using only a few sub-carriers among sub-carriers of the non-audible band, the number of usable sub-carriers is smaller and data transmission is difficult.

To overcome this problem, a larger number of subcarriers may be assigned to the non-audible band for data transmission, which in turn requires a larger IFFT, which further increases the complexity and complexity of the transmitter.

In addition, when the baseband direct reception scheme is utilized as described above, a larger IFFT is required to obtain a real value after IFFT conversion.

Further, when the bandwidth of the non-audible range is further narrowed to increase the detection probability of the first receiving apparatus 2200, the size of the IFFT becomes larger.

Hereinafter, an ultrasonic transmission system according to another embodiment of the present invention, which can reduce the amount of calculation as compared with the above-described method with reference to Figs. 3 to 4B, will be described.

FIG. 3 is a configuration diagram illustrating an ultrasonic transmission system according to another embodiment of the present invention. FIG. 4A is a diagram illustrating a function of an ultrasonic modulator according to another embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an ultrasonic wave modulating unit according to an embodiment.

As shown in FIG. 3, the ultrasonic transmission system 30 according to another embodiment of the present invention includes a second transmission device 3100 and a second reception device 3200.

The second transmitter 3100 includes an ultrasound signal modulator 3110, a window function block 3120, an up-sampler 3130, an up-converter 3140, an audio decoder 3150, a summation unit 3160, a DAC (3170) and a speaker (3180). Here, the window function block 3120 corresponds to the guard interval and window function block 2120 of FIG. 2 and includes an up-sampler 3130, an up-converter 3140, an audio decoder 3150, a summation unit 3160, The DAC 3170, and the speaker 3180 are the same as or similar in function to the ultrasonic transmission system 20 according to the embodiment of the present invention, and a detailed description thereof will be omitted. Hereinafter, the components of the second transmission apparatus 3100 in addition to the conceptual description of the other embodiments of the present invention will be described.

In another embodiment of the present invention, transmission data is carried on only C subcarriers (C = N / M) arranged at M (frequency) intervals among N subcarriers in the non-audible band. At this time, the subcarrier index group used for data transmission can be calculated by Equation (6) below.

Here, q denotes an offset of a subcarrier. At this time, the offset of the subcarrier can be utilized as a code for distinguishing a specific receiver group or transmission data type.

In the latter example, the transmission data may include various information such as control information, user information, and the like. Therefore, the second transmission apparatus 3100 may transmit different q's according to the kind of transmission data. In this case, it is needless to say that the second transmitting apparatus 3100 and the second receiving apparatus 3200 define q.

On the other hand, if the second receiving apparatus 3200 does not know the q information, q can be used as transmission data and the transmission data can not be detected accurately, so that the second receiving apparatus 3200 can transmit q Information needs to be detected first. Accordingly, if the second transmitting apparatus 3100 according to another embodiment of the present invention does not know the q information in the second receiving apparatus 3200, the transmitting apparatus 3100 may transmit q data in Q subcarriers, The modulated information can be transmitted. At this time, the order may be performed simultaneously, or q information may be transmitted first and then transmission data may be transmitted.

The modulation process will be described with reference to FIG. 4A. First, transmission data is converted into a frequency domain signal through a DFT (Discrete Fourier Transform) having a size of C, and then the converted frequency domain signals are transmitted to subcarriers arranged at M equal intervals And performs inverse fast Fourier transform (IFFT) of N size again.

Referring to FIG. 4A, when another embodiment of the present invention is compared with an embodiment of the present invention, the discrete Fourier transform and the inverse fast Fourier transform (DFT-IFFT) Is performed continuously, there is a portion canceled each other on the modification surface, so that the amount of computation can be reduced as a result. Hereinafter, we will prove this mathematically.

이고, l번째 전송 데이터가

이면, 크기 C인 DFT 변환된 C개의 데이터 심볼 x_{l ,u}(k)는 하기의 수학식 7과 같이 표현될 수 있다.The number of elements of the subcarrier index group used for data transmission (cardinality) C

, And the lth transmission data is

, The D data transformed C data symbols x _{l , u} (k) having the size C can be expressed as Equation (7).

The C data symbols subjected to the DFT are mapped again to an N-sized IFFT frequency index. Here, the data symbols mapped by the q-th frequency index group are expressed by Equation (8).

The time domain signal, which is the result of performing an IFFT of size N, can be expressed as: < EMI ID = 9.0 >

이다.here,

to be.

는 위상천이에 대응되며,

는 심볼 반복기의 기능에 대응될 수 있다.In Equation (9)

Corresponds to a phase shift,

May correspond to the function of the symbol repeater.

을 C주기로 반복하고, q만큼 위상회전시킴에 따라 구현될 수 있다. As shown in Equation (9), the continuous operation of the DFT of size C and the IFFT of size N largely compensates for complicated operations. As shown in FIG. 4B, in the time domain,

To the C period, and to phase rotation by q.

Accordingly, the ultrasonic signal modulator 3110 according to another embodiment of the present invention includes a symbol repeater 3111 and a phase rotator 3112 as shown in FIG. 4B. If q is 0, no phase rotation is required, so that the ultrasonic signal modulating unit 3110 may include only the symbol repeater 3111. Hereinafter, components of the ultrasonic signal modulator 3110 will be described with reference to FIG. 4B.

The symbol repeater 3111 repeatedly outputs C transmission symbols in C cycles to output N transmission symbols. Here, the transmission symbol may be information obtained by dividing the transmission information by a predetermined bit unit.

For example, the symbol repeater 3111 receives three data symbols whose values are 0, 1, and 2, and outputs N data symbols as it repeatedly outputs in three cycles.

The phase rotator 3112 performs a predetermined phase rotation on each of the N transmission symbols to output DFT and IFFT ultrasound signals.

For example, the phase rotator 3112 does not perform phase rotation on the 0th transmission symbol, performs phase rotation on the first transmission symbol by the subcarrier offset q, performs phase rotation on the second transmission symbol by 2q, And the phase rotation can be performed by (N-1) q on the Nth transmission symbol.

Next, the second receiving apparatus 3200 includes a microphone 3210, an ADC 3220, an HPF 3230, an M _R -FTFT 3240, a C-IDFT 3250 and an information detecting unit 3260. The microphone 3210, the ADC 3220, and the HPF 3230 are the same as or similar in function to the components according to the embodiment of the present invention, and therefore, detailed description thereof will be omitted. Hereinafter, components of the second receiving apparatus 3200 in addition to the conceptual description of another embodiment of the present invention will be described.

If the received ultrasonic signal is present, the second receiving apparatus 3200 checks whether there is a predetermined q. If q is not defined, the second receiving apparatus 3200 detects the q first and performs demodulation through the IDFT after performing the FFT. Here, q may be preset by an appointment between the second transmission / reception apparatuses 3100 and 3200.

를 검출할 수 있다.For example, the second receiving apparatus 3200 determines the energy of the FFT-processed ultrasonic signal as shown in Equation (10)

Can be detected.

The second receiving apparatus 3200 performs FFT on the ultrasonic signal and performs IDFT (Inverse Discreet Fourier Transform) with the size C on the FFT-processed ultrasonic signal in the frequency domain, It is possible to detect transmission data in the time domain as shown in Equation (11). Specifically, the M _R -FFT 3240 performs an M _R size FFT on the ultrasound signal in the time domain to convert the ultrasound signal into a frequency domain ultrasound signal. In addition, the C-IDFT 3250 can detect transmission data in the time domain as shown in Equation (11) by performing the C-size IDFT on the frequency domain ultrasonic signal.

When the transmission data is a binary signal, the information detection unit 3260 can decode the transmission data by detecting the energy of each subcarrier as shown in Equation (12). If the transmission data is another signal, the information detector 3260 may be in a different form corresponding thereto.

If the second receiver 3200 uses the baseband direct reception method, a problem may arise in which the audio sampling frequency needs to be changed in order to maintain the identity of the subcarrier intervals.

However, in another embodiment of the present invention, by using parameters satisfying the following conditions, it is possible to reduce the amount of computation according to the sampling frequency change of the second transmitter 3100 and the second receiver 3200.

======= Condition of FFT-IFFT, DFT-IDFT parameter ========================

① N _R must be expressible in exponential form of 2 and must be an integer multiple of N (ie, N _R = αN, α is an integer). Also, N _R / 2 = N _a + N is satisfied.

② N should be able to express in exponential form of 2.

(3) The boundary frequency F _u between the ultrasonic signal and the audio signal should be larger than the audio bandwidth B _a .

================================================== =====================

If the audio sampling frequency F _s and the minimum audio frequency band B _a are given, a parameter satisfying the above condition can be calculated by the following equation (13).

함수는 x를 넘지 않으면서 2의 지수형태로 표현될 수 있는 최소 양의 정수를 의미한다. here,

Function is the smallest positive integer that can be expressed in exponential form of 2 without exceeding x.

At the time of designing the second transmitting apparatus 3100 and the second receiving apparatus 3200, N _R is determined and Δf is calculated. Based on the calculated sub-carrier spacing Δf, N, which can be expressed in the exponential form of "

Since the second receiving apparatus 3200 according to another embodiment of the present invention uses parameters designed as shown in Equation (13), there is no need to provide a component for changing the sampling frequency.

)를 사용할 수 있어, 종래의 소수배 업샘플링 요소를 사용하는 송수신 장치에 비해 샘플링 주파수 변경에 따른 연산량을 줄일 수 있다.As described above, in another embodiment of the present invention, an integer multiple of the up-sampling element g (

) Can be used, so that the amount of computation according to the sampling frequency change can be reduced as compared with a conventional transceiver using a small number of back-up sampling elements.

In addition, other embodiments of the present invention may be suitable for applications where a transmitter needs to be implemented with low power, such as a portable terminal. Specifically, since the receiving unit of the portable terminal does not have to be the same as the uplink transmission method, a method with a small amount of calculation can be separately applied to the receiving unit. Thus, another embodiment of the present invention may be more suitable for applications where the transmitter must be implemented with low power, such as a portable terminal.

In addition, another embodiment of the present invention can efficiently transmit ultrasonic signals in a system in which audio signals of an audible band and ultrasonic signals of a non-audible band are mixed using a relatively low-complexity transmission / reception scheme and structure.

In addition, according to another embodiment of the present invention, the use of the transmission parameter satisfying the criterion can reduce the amount of operation of the sampling frequency converter according to the sampling frequency mismatch between the ultrasonic signal and the audio signal.

While the present invention has been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to the above-described embodiments. Those skilled in the art will appreciate that various modifications, Of course, this is possible. Accordingly, the scope of protection of the present invention should not be limited to the above-described embodiments, but should be determined by the description of the following claims.

Claims (6)

A method of transmitting an ultrasonic signal by a sound output apparatus,
Generating N data symbols by receiving C (= N / M) data symbols and repeating the C data symbols in C cycles;
And performing a predetermined phase rotation on each of the N data symbols to transmit the N data symbols to N non-audible subcarriers, Loading the C data symbols into a subcarrier group; And
A step of outputting a signal obtained by analog-converting a signal obtained by summing the ultrasound signal of the C data symbols and the audio signal of the audible band by a sound
And transmitting the ultrasonic signal. 2. The method of claim 1, wherein generating the data symbol and generating the ultrasound signal comprise:
Generating C first signals by performing Discrete Fourier Transform (DFT) on the C data symbols having a size of C; And
Performing N-order inverse fast Fourier transform on the C first signals, if the frequency index of the inverse fast Fourier transform is included in the C subcarrier groups, loading the C first signals, Wherein if the frequency index of the inverse fast Fourier transform is not included in the C subcarrier groups, the step of not including the C first signals is performed. 2. The method of claim 1, wherein the number N of sub-
Which is obtained by subtracting a bandwidth minimum value of the non-audible frequency band required for carrying out the C data symbols at a sampling frequency of the audio signal by a first frequency value, Wherein the first frequency value is a value obtained by dividing the sampling frequency by a size of a fast Fourier transform of a receiving side that receives the sound and decodes the data symbol. The method of claim 1, wherein the first frequency index Na of the non-
Wherein a value obtained by dividing the size of the fast Fourier transform on the receiving side, which receives the sound and decodes the data symbol, by 2 is a value obtained by subtracting N from the result. A method of receiving an ultrasonic signal by a voice sensing device,
Detecting a signal of a non-audible range from a signal obtained by digitally converting an output signal of the microphone that senses sound;
Generating a first signal by performing Fast Fourier Transform (NRF) on the signal of the non-audible frequency band;
Performing C-size inverse discrete Fourier transform on C subcarriers carrying transmission information using the offset of the subcarrier if a predetermined carrier offset is present; And
Detecting the transmission information from the inverse discrete Fourier transformed signal
And transmitting the ultrasonic signal to the ultrasonic probe. 6. The method of claim 5,
Detecting the subcarrier offset using the energy of the first signal if the predetermined carrier offset is not present
Wherein the ultrasonic signal is received by the ultrasonic transducer.

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