A long-distance ultrasonic communication method and a consumer electronic device

Abstract

The present application provides a long-distance ultrasonic communication method and a consumer electronic device. The method includes: the transmitting end uses a frequency-swept signal as a pulse signal, loads binary data into the pulse signal, generates a baseband signal and modulates it into an ultrasonic signal; the receiving end collects the signal through a microphone, performs demodulation and matched filtering, and through dual-channel channel equalization, phase compensation and symbol judgment, and finally converts the symbol into binary data. This method uses a frequency-swept signal as a symbol function, and utilizes the autocorrelation characteristic of the frequency-swept signal to complete communication transmission under extremely low signal-to-noise ratio conditions. It is preferably to use a dual microphone array to complete ultrasonic signal sampling, and use a dual-channel CMA equalizer to complete channel equalization, which can eliminate the inter-symbol interference caused by room reverberation. In addition, a phase estimation algorithm can be used to compensate for the phase shift that occurs during transmission. By combining the above technical means, stable ultrasonic signal transmission over a distance of more than 5 meters can be achieved.

Description

Technical Field

[0001] The present invention relates to ultrasonic communication technology, and in particular to a long-distance ultrasonic communication method and consumer electronic equipment. Background Art

[0002] Communication transmission between consumer electronic devices usually uses wireless communication and WIFI technology. Both WIFI and Bluetooth technologies require consumer electronic devices to first turn on WIFI and Bluetooth devices and start establishing a connection. This process requires users to wait for several seconds. In addition, WIFI signals have strong penetration and can be detected by outdoor devices, posing a risk of user data leakage. Using ultrasound for communication transmission, the speaker and microphone are turned on in less than 1ms, allowing users to transmit or receive signals without waiting. At the same time, due to the weak penetration ability of ultrasound, ultrasonic signals can only be detected by indoor devices, greatly improving the security of communication data. Due to the low latency and data security of ultrasonic communication, the market demand for ultrasonic communication transmission based on consumer electronic devices has become increasingly strong in recent years.

[0003] Because ultrasonic waves are highly attenuated when propagating through air, and the ultrasonic power emitted by consumer electronics speakers is generally weak, the energy of ultrasonic signals rapidly decays after propagating through air. At transmission distances exceeding five meters, the ultrasonic communication signal is drowned out by the device noise floor and ambient noise, significantly degrading the signal-to-noise ratio. In addition to the deteriorating signal-to-noise ratio, as communication distance increases, the multipath effect caused by room reverberation significantly increases inter-symbol interference between communication signals, further limiting the transmission distance of ultrasonic communication systems. Summary of the Invention

[0004] The object of the present invention is to provide a long-distance ultrasonic communication method and a consumer electronic device for implementing the method, which can achieve stable ultrasonic communication at a distance of more than 5 meters.

[0005] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0006] According to a first aspect of the present invention, there is provided a long-distance ultrasonic communication method, which is performed by a transmitting device and includes:

[0007] Step 101: Modulate the binary data to be transmitted into a symbol sequence o(k);

[0008] Step 102: Use the frequency sweep signal g(t) as the pulse signal.

[0009]

[0010] Where T represents the symbol time length, f1 represents half the spectrum width of the swept frequency signal, t represents time, and j represents the imaginary number symbol;

[0011] Step 103: Upsample the symbol sequence to the same number of sampling points as the swept frequency signal, then convolve it with the pulse signal, and add the symbol signal to the pulse signal to obtain a baseband signal. The baseband signal is expressed as follows:

[0012] s(t)=∑ k o(k)g(t-kT)

[0013] Wherein, k represents the code element number;

[0014] Step 104: frequency modulate the baseband signal to obtain an ultrasonic communication signal u(t) ultimately used for transmission;

[0015] Step 105: Store the ultrasonic communication signal u(t) in an audio format, and use a speaker built into the consumer electronic device to play the ultrasonic communication signal.

[0016] In one embodiment, step 101 includes:

[0017] The binary data of length N to be transmitted is decomposed into N / 2 basic units with two bits as the basic unit. The basic units are divided into four categories: (00, 01, 10, 11). These four categories of basic units are represented by orthogonal phase shift keying and encoded into four categories of complex signals: (1+1j, -1+1j, -1-1j, 1-1j), respectively, to obtain a complex symbol sequence o(k) of length N / 2.

[0018] In one embodiment, step 104 includes:

[0019] Take the real and imaginary parts of the baseband signal s(t) to obtain the real signal a(t) and the imaginary signal b(t);

[0020] The real signal a(t) is compared with cos(2πf c t), the imaginary signal b(t) is multiplied by sin(2πf c t) multiplied, where f c is the modulation frequency;

[0021] The two signals are added together to obtain the final ultrasonic communication signal u(t) for transmission. The mathematical expression of the above process is as follows:

[0022] u(t)=real(s(t))×cos(2πfc t) + imag(s(t)) × sin(2πf c t)

[0023] where real() and imag() represent the operations of taking the real part and the imaginary part respectively.

[0024] According to the second aspect of the present invention, a long - distance ultrasonic communication receiving method based on a consumer electronic device is provided, which is executed by a receiving device and includes:

[0025] Step 201: Collect the ultrasonic communication signal through a microphone to obtain a received signal v c (t);

[0026] Step 202: Demodulate v c (t) into two paths of I / Q signals to obtain signals a′ c (t), b′ c (t);

[0027] Step 203: Use the conjugate inverse sequence g * (-t) of the swept - frequency signal g(t) as a matched filter to convolve the demodulated two - path I / Q signals a′ c (t), b′ c (t) to obtain signals a″ c (t), b″ c (t), where

[0028]

[0029] Step 204: Perform serial - to - parallel conversion on signals a″ c (t), b″ c (t) to obtain a signal r c (t), and perform down - sampling on the signal r c (t) to obtain a signal p c (n);

[0030] Step 205: Send the down - sampled signal p c (n) into a CMA equalizer for channel equalization to obtain a signal x(n);

[0031] Step 206: Perform phase - shift compensation on the signal x(n) to obtain a signal x″(n);

[0032] Step 207: Perform symbol decision on the signal x″(n) to obtain z(n) and convert it into a binary signal o′(n).

[0033] In one embodiment, the step 202 includes:

[0034] Multiply v(t) with cos(2πfc t) and sin(2πf c Multiply with t), to obtain two signals a' c (t), b' c (t), where f c is the modulation frequency.

[0035] In one embodiment, the microphone includes a dual microphone array, and the received signal v c (t) collected contains a first-channel received signal v1(t) and a second-channel received signal v2(t); the expression of the signal x(n) output by the CMA equalizer in step 205 is as follows:

[0036]

[0037] where w c (k) is the weight of the dual-channel CMA equalizer, n represents the signal sampling point subscript, k represents the equalizer tap subscript, and C represents the channel number;

[0038] At the initial moment, let w c (0) be 1, and at other moments w c (0) be 0. The parameter update formula of w c (k) is:

[0039]

[0040] e(n) = |x(n)| 2 -1

[0041] where μ represents the learning rate.

[0042] In one embodiment, step 206 specifically includes:

[0043] Calculate the phase offset values under different phase estimation values:

[0044] [[ID=5I]]

[0045] Through the symbol decision function, judge the positive and negative of the real part and the imaginary part,

[0046] d(n, m) = f(x'(n, m)) I

[0047]

[0048] Select the phase estimation with the minimum error to perform phase compensation on the signal

[0049] i = argmin(e(m))

[0050]

[0051] In one embodiment, step 207 includes: by means of a symbol decision function, converting the signal p c (n) into a complex signal z(n), and converting z(n) into a binary signal o′(n) according to the conversion relationship between the complex signal z(n) and binary data.

[0052] In one embodiment, in step 204, downsampling is performed at the moment of t = kT / 2.

[0053] According to the third aspect of the present invention, there is provided a consumer electronic device, including:

[0054] A speaker for playing an ultrasonic communication signal;

[0055] A memory for storing software programs and data;

[0056] A processor for, when executing the software program, implementing the long-distance ultrasonic communication method according to any one of the first aspect.

[0057] According to the fourth aspect of the present invention, a consumer electronic device includes:

[0058] A microphone for collecting ultrasonic signals;

[0059] A memory for storing software programs and data;

[0060] A processor for, when executing the software program, implementing the long-distance ultrasonic communication method according to any one of the second aspect.

[0061] The beneficial effects of the embodiments of the present invention are as follows: A frequency-swept signal is used as the symbol function, and the signal-to-noise ratio of the communication signal is improved by using the autocorrelation characteristic of the frequency-swept signal, thereby improving the transmission distance of the communication system. Preferably, a dual-microphone array is used to sample the ultrasonic signal, and a two-channel communication signal can be obtained. After passing through a two-channel CMA equalizer, it can not only compensate for the inter-symbol interference caused by the multi-path effect of the room, but also further enhance the signal-to-noise ratio of the communication signal, and further improve the transmission distance of the communication system. The phase estimation algorithm is used to compensate for the phase shift that occurs during the transmission process. In addition, the QPSK modulation method is used in the embodiments of the present invention, and 2-bit data can be loaded onto one symbol, improving the transmission rate of long-distance communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0063] After reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings, the above features and advantages of the present invention can be better understood. In the drawings, the components are not necessarily drawn to scale, and components with similar relevant characteristics or features may have the same or similar reference numerals.

[0064] Figure 1 is a schematic diagram of steps in the method embodiment of the present application;

[0065] Figure 2 is a comparison diagram of swept-frequency signal spectra;

[0066] Figure 3 is a comparison diagram of the effects before and after CMA equalization;

[0067] Figure 4 is a comparison diagram of the effects before and after phase compensation;

[0068] Among them, Figure 3 and Figure 4 use two-dimensional coordinates to represent complex signals. In the figure, the abscissa In-phase represents the real part of the signal, and the ordinate Quad rature represents the imaginary part of the signal. Detailed implementation manners

[0069] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. Note that the aspects described below in conjunction with the drawings and specific embodiments are merely exemplary and should not be construed as imposing any limitation on the protection scope of the present invention.

[0070] The embodiment of the present application provides a long-distance ultrasonic communication method, including a signal generation and transmission step and a signal reception and processing step.

[0071] Among them, the signal generation and transmission step is as shown in Figure 1 a in, and includes:

[0072] Step 101, modulating the binary data to be transmitted into a symbol sequence o(k);

[0073] The modulation method can be BPSK (binary phase shift keying) modulation, QSPK (quadrature phase shift keying) modulation, 16QAM (quadrature amplitude modulation), 32QAM, 128QAM, 1024QAM, etc. Different modulation methods affect the expression form of the symbol sequence o(k). For example, if it is BPSK modulation, there are only 2 possible representations, namely (1, -1); if it is 16QAM modulation, there are 16 possible representations (1 + 1j, 1 - 1j, -1 - 1j, -1 + 1j, 1 + 3j, 1 - 3j, -1 - 3j, -1 + 3j, 3 + 1j, 3 - 1j, -3 - 1j, -3 + 1j, 3 + 3j, 3 - 3j, -3 - 3j, -3 + 3j).

[0074] In this embodiment, a QSPK (Quadrature Phase Shift Keying) modulation signal is adopted, enabling one symbol to transmit 2-bit data and improving the communication rate of the system. First, the binary data with a length of N to be transmitted is disassembled into N / 2 basic units with two bits as the basic unit. The basic units are of four types: (00, 01, 10, 11); these four types of basic units are represented by quadrature phase shift keying and encoded into four types of complex signals: (1 + 1j, -1 + 1j, -1 - 1j, 1 - 1j) respectively, obtaining a complex symbol sequence o(k) with a length of N / 2.

[0075] Step 102: Use a frequency-swept signal g(t) as the pulse signal.

[0076]

[0077] Where T represents the symbol time length, f1 represents half of the frequency spectrum width of the frequency-swept signal, t represents time, and j represents the imaginary symbol;

[0078] In this embodiment, the initial frequency and the termination frequency of the frequency-swept signal are -1.5 kHz and 1.5 kHz respectively, the duration of the frequency-swept signal is 5 ms, and the sampling frequency is 48 kHz.

[0079] This frequency-swept signal has very strong autocorrelation characteristics, and the signal expression after its autocorrelation is as follows:

[0080]

[0081] Where g * (-t) is the conjugate inverse sequence of g(t), and * represents the convolution operation. The autocorrelation of the signal g(t) can be equivalent to the convolution of g(t) and g * (-t). Taking f1 = 1.5 kHz, T = 5 ms, and the sampling frequency f s = 48 kHz, substituting the parameters into formula 1 can obtain a digital frequency-swept signal with a sampling point number of f s ×T = 240.

[0082] Figure 2 The left side shows the frequency-swept signal and the signal after its autocorrelation. It can be seen that only near the 0 moment, the amplitude of the signal has a very high value after the autocorrelation of the frequency-swept signal, while at the other moments, the signal amplitude is almost 0. Using the autocorrelation characteristics of the frequency-swept signal can be used to counteract the interference of strong noise on the signal during long-distance transmission. Figure 2 The right side shows that after adding Gaussian white noise to the frequency-swept signal, the signal-to-noise ratio is 0 dB, using g *(-t) is the result after filtering by the matched filter. It can be seen that due to the strong autocorrelation characteristic of the frequency-swept signal, even under the condition of a signal-to-noise ratio of 0 dB, after passing through the matched filter, the signal still has a very high amplitude value at t = 0.

[0083] Step 103: Upsample the symbol sequence 240 times by padding with zeros until it has the same number of sampling points as the frequency-swept signal, and then convolve it with the pulse signal to load the symbol signal into the pulse signal, obtaining the baseband signal. The expression of the baseband signal is as follows:

[0084] s(t) = ∑ k o(k)g(t - kT) #(3)

[0085] where k represents the symbol number;

[0086] Step 104: Perform frequency modulation on the baseband signal to obtain the final ultrasonic communication signal for transmission;

[0087] In this embodiment, Step 104 includes:

[0088] Take the real part and the imaginary part of the baseband signal s(t) to obtain the real part signal a(t) and the imaginary part signal b(t);

[0089] Multiply the real part signal a(t) by cos(2πf c t), and multiply the imaginary part signal b(t) by sin(2πf c t), where f c is the modulation frequency;

[0090] Add the two signals to obtain the final ultrasonic communication signal u(t) for transmission. The mathematical expression of the above process is as follows:

[0091] u(t) = real(s(t)) × cos(2πf c t) + imag(s(t)) × sin(2πf c t) #(4)

[0092] where real() and imag() respectively represent the operations of taking the real part and the imaginary part. Formula 4 can shift the center of the signal spectrum from 0 Hz to f c , thus turning the baseband signal into an ultrasonic signal. Figure 2 Shows the spectra of the signal before and after carrier modulation.

[0093] Step 105: Store the ultrasonic communication signal u(t) in audio format and play the ultrasonic communication signal using the built-in speaker of the consumer electronic device.

[0094] The signal reception and processing steps are as Figure 1As shown in b, it includes:

[0095] Step 201: Collect the ultrasonic communication signal through a microphone to obtain the received signal v c (t);

[0096] Preferably, in order to compensate for the inter-symbol interference caused by the multi-path effect of the room, a dual-microphone array ultrasonic signal can be used. The received signal v c (t) includes the first-channel received signal v1(t) and the second-channel received signal v2(t);

[0097] Step 202: Demodulate v c (t), which specifically includes:

[0098] Multiply v(t) by cos(2πf c t) and sin(2πf c t) respectively to obtain two signals a′ c (t), b′ c (t), where f c is the modulation frequency;

[0099] Step 203: Use the conjugate inverse sequence g * (-t) of the pulse signal in Step 102 as a matched filter, and convolve it with the two signals respectively to obtain signals a″ c (t), b″ c (t). The matched filter g * (-t) is a low-pass filter, and its spectral width is exactly the same as that of the pulse signal, so it can filter out the interference frequency components outside the spectral width of the pulse signal.

[0100] Step 204: Perform serial-to-parallel conversion on the signal v″ c (t) to obtain the signal r c (t), and perform downsampling on the signal r c (t) to obtain the signal p c (n);

[0101] In this embodiment, let r c (t) = a″ c (t) + jb″ c (t), assume that the noise introduced by space propagation is n c (t), and the space reverberation plus the channel transfer function is h c (t), then the relationship between the phase shift φ(t) caused by the space propagation of the signal r c (t) and the transmitting-end signal is as follows:

[0102] r c (t) = (s(t) * h c(t)×exp(jφ(t)) + n c (t)) * g * (-t) #(5)

[0103] Substituting formula (3) into formula (5) gives

[0104]

[0105] It can be seen from formula (6) that the signal r c (t) is represented by the autocorrelation function y(t) of the frequency-swept signal, and y(t) has a high amplitude only near t = 0, and the amplitude values at other times are very low. Therefore, if the signal r(t) is downsampled at t = kT, the noise resistance of the obtained signal will be greatly enhanced, thereby enhancing the transmission distance of the ultrasonic communication system. Considering the synchronization error, here t = nT / 2 is taken to downsample the signal r c (t) to obtain the signal p c (n), that is, two sampling points are collected within one symbol time length T.

[0106] For the dual-channel communication signal, this method further includes step 205 of sending the downsampled signal p c (n) into the dual-channel CMA equalizer. The expression of the output signal x(n) of the dual-channel CMA equalizer is as follows:[[]]

[0107]

[0108] where w c (k) is the weight of the dual-channel CMA equalizer, n represents the signal sampling point subscript, k represents the equalizer tap subscript, and c represents the channel number;

[0109] At the initial moment, let w c (0) be 1, and at other times w c (0) be 0. The parameter update formula of w c (k) is:[[]]

[0110]

[0111] e(n) = |x(n)| 2 -1 #(9)

[0112] where μ represents the learning rate.

[0113] Using the dual-channel CMA equalizer for the dual-channel signal can not only compensate for the inter-symbol interference caused by the multi-path effect of the room, but also further enhance the signal-to-noise ratio of the communication signal, thereby improving the transmission distance of the communication system. This CMA equalizer can compensate for the inter-symbol interference caused by the multi-path effect of the room during the spatial propagation of the ultrasonic communication signal.Figure 3 The constellation diagrams of the input and output of the CMA equalizer are shown. It can be seen that due to inter-symbol interference, the constellation diagram of the input signal is very chaotic. However, since the CMA equalizer compensates for the inter-symbol interference, the constellation diagram of the output presents a shape similar to a circle.

[0114] In one embodiment, the method further includes step 206 of compensating for the phase offset of the signal output by the equalizer. The constant phase offset φ(t) is a slowly changing process. Within a relatively short time (e.g., 100 ms), the phase offset can be considered a fixed value. The following formula is used to complete the phase offset compensation:

[0115] Calculate the phase offset values under different phase estimation values:

[0116]

[0117] Through the symbol decision function, judge the positive and negative of the real part and the imaginary part.

[0118] d(n, m) = f(x′(n, m)) #(11)

[0119]

[0120] Select the phase estimation with the minimum error to perform phase compensation on the signal.

[0121] i = argmin(e(m)) #(13)

[0122]

[0123] It is experimentally found that the phase offsets of 24 consecutive data are approximately the same. Therefore, in this embodiment, x(n) is grouped into sets of 24, and it is considered that the phase offset values of the signals within a set are the same. Each value of m in formula 10 represents an estimation of a phase offset. Taking L = 8, m can take 2L + 1, that is, 17 values, which means 17 different phase estimations.

[0124] Calculate the errors of 17 different phase estimations through formulas 11 and 12. Among them, the function f() is the symbol decision function, which discriminates whether the real part and the imaginary part of the input signal are positive numbers as -1 and 1. For example, if the input signal is 0.5 - 0.5j, the real part of this signal is 0.5 which is a positive number, so the real part is discriminated as 1, and the imaginary part -0.5 is a negative number, so the imaginary part is discriminated as -1. Then the result of this signal passing through the function f() is 1 - 1j.

[0125] Select the phase estimation with the minimum error through formulas 13 and 14, and perform phase compensation on the signal x(n). Figure 4 The constellation diagrams of the signal before and after phase compensation are shown.

[0126] Step 207: Convert the signal p c (n) into a binary signal o′(n). Since the QSPK modulation method is adopted in this embodiment, the signal x″(n) needs to be sent to the function f() first to obtain a complex signal z(n). The data included in z(n) are four types of complex signals (1 + 1j, -1 + 1j, -1 - 1j, 1 - 1j). According to the conversion relationship between the complex signal and the binary data, z(n) can be converted into the final binary signal o′(n).

[0127] The embodiment of the present application also provides a consumer electronic device to implement the above-mentioned long-distance ultrasonic communication method. The consumer electronic device can either only execute one of the signal generation and transmission step and the signal reception and processing step, or execute both of them.

[0128] When executing the signal generation and transmission step, it is required that the consumer electronic device should at least have a speaker for playing the ultrasonic communication signal, a memory for storing software programs and data, and a processor for executing the software programs.

[0129] When executing the signal reception and processing step, it is required that the consumer electronic device should at least have a microphone for collecting ultrasonic signals, a memory for storing software programs and data, and a processor for executing the software programs.

[0130] When it is necessary to execute both the signal generation and transmission step and the signal reception and processing step, the consumer electronic device should have a microphone, a speaker, a memory, and a processor at the same time.

[0131] For example, in the home use scenario, this method can be used to connect a mobile phone and a TV (which needs to have a microphone). When the mobile phone sends an instruction signal to the TV, the mobile phone executes the signal generation and transmission step, sends the ultrasonic signal through the mobile phone speaker, and the TV microphone collects the ultrasonic signal and executes the signal reception and processing step. When the TV sends audio and video signals to the mobile phone, the TV executes the signal generation and transmission step, sends the ultrasonic signal through the TV speaker, and the mobile phone microphone collects the ultrasonic signal and executes the signal reception and processing step.

[0132] It is easy to understand that the consumer electronic device refers to the electronic products related to radio and television for personal and family use, mainly including televisions, telephones, personal computers, home office equipment, home electronic health care equipment, automotive electronic products, etc. With the development of technology and the emergence of new products and new applications, products such as digital cameras, smart speakers, and smart conference systems are also becoming emerging consumer electronic devices.

[0133] In summary, the beneficial effects of the long-distance ultrasonic communication method provided by the present application include:

[0134] 1. It is possible to generate an ultrasonic communication signal using a consumer electronic device, transmit the ultrasonic communication signal with its built-in speaker, receive the long-distance ultrasonic communication signal with its built-in dual microphones, and complete the decoding of the long-distance ultrasonic communication through signal processing.

[0135] 2. By using a swept-frequency signal as a pulse function, using the conjugate inverse sequence of the swept-frequency signal as a matched filter, and leveraging the autocorrelation characteristics of the swept-frequency signal to improve the signal-to-noise ratio of the signal in a strong noise environment.

[0136] 3. By using a dual-channel CMA equalizer to complete channel equalization and compensate for the inter-symbol interference caused by the multi-path effect of the room during spatial propagation.

[0137] 4. By using a phase estimation algorithm to compensate for the phase shift that occurs during transmission.

[0138] 5. Preferably using the QPSK modulation method, 2 bits of data can be loaded onto one symbol, improving the transmission rate of long-distance communication.

[0139] After testing, this method can use a consumer electronic device to complete signal transmission at 400 bit / s at a distance of more than 5 meters. Compared with existing ultrasonic communication methods, the communication distance has been significantly improved.

[0140] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0141] The foregoing description of the present disclosure is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the examples and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0142] The above are only the preferred examples of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A long-distance ultrasonic communication method, which is executed by a transmitting device, characterized in that, Including: Step 101: Modulate the binary data to be transmitted into a symbol sequence o(k); Step 102: Use a frequency-swept signal g(t) as a pulse signal, where T represents the symbol time length, f1 represents half of the frequency spectrum width of the frequency-swept signal, t represents time, and j represents the imaginary symbol; Step 103: Upsample the symbol sequence to the same number of sampling points as the frequency-swept signal, then perform convolution with the pulse signal to load the symbol signal into the pulse signal to obtain a baseband signal, and the expression of the baseband signal is as follows: where k represents the symbol number; Step 104: Perform frequency modulation on the baseband signal to obtain the final ultrasonic communication signal for transmission; Step 105: Store the ultrasonic communication signal in audio format and play the ultrasonic communication signal using the built-in speaker of the consumer electronic device.

2. The long-distance ultrasonic communication method according to claim 1, wherein The said Step 101 includes: Take the binary data with length N to be transmitted, disassemble it into N / 2 basic units with two bits as the basic unit. The basic units have four categories: (00, 01, 10, 11). Represent these four categories of basic units using quadrature phase shift keying and encode them into four categories of complex signals: (1 + 1j, -1 + 1j, -1 - 1j, 1 - 1j) respectively to obtain a complex symbol sequence o(k) with length N / 2.

3. The long-distance ultrasonic communication method according to claim 2, characterized in that, The said Step 104 includes: Take the real part and the imaginary part of the baseband signal s(t) to obtain the real part signal a(t) and the imaginary part signal b(t); Multiply the real part signal a(t) by cos(2πf c t), and multiply the imaginary part signal b(t) by sin(2πf c t), where f c is the modulation frequency; Add the two signals to obtain the final ultrasonic communication signal u(t) for transmission. The mathematical expression of the above process is as follows: u(t) = real(s(t)) × cos(2πf c t) + imag(s(t)) × sin(2πf c t) where real() and imag() respectively represent the operations of taking the real part and the imaginary part.

4. A long-distance ultrasonic communication method, performed by a receiving device, characterized in that, Including: Step 201: Collect the ultrasonic communication signal through a microphone to obtain the received signal v c (t); Step 202: Demodulate v c (t) in two paths of I / Q to obtain a′ c (t), b′ c (t); Step 203: Use the conjugate inverse sequence g*(-t) of the frequency-swept signal g(t) as the matched filter to convolve the demodulated I / Q two-channel signals a′ c (t), b′ c (t) to obtain signals a″ c (t), b″ c (t), where T represents the symbol time length, f1 represents half of the frequency spectrum width of the frequency-swept signal, t represents time, and j represents the imaginary symbol; Step 204, perform serial-to-parallel conversion on signals a″ c (t), b″ c (t) to obtain signal r c (t), and perform downsampling on signal r c (t) to obtain signal p c (n); Step 205: Feed the downsampled signal p c (n) into CMA equalization for channel equalization to obtain the signal x(n), where n represents the subscript of the signal sampling point; Step 206: Perform phase offset compensation on the signal x(n) to obtain the signal x″(n); Step 207: Perform symbol decision on the signal x″(n) to obtain the signal z(n) and convert it into a binary signal o′(n).

5. The long-distance ultrasonic communication method according to claim 4, characterized in that, The said Step 202 includes: Multiply v c (t) by cos(2πf c t) and sin(2πf c t) respectively to obtain two signals a′ c (t) and b′ c (t), where f c is the modulation frequency.

6. The long-distance ultrasonic communication method according to claim 4, characterized in that The microphone includes a dual microphone array, and the received signal v c (t) includes a first-channel received signal v1(t) and a second-channel received signal v2(t); In step 205, the downsampled signal p c (n) is fed into a dual-channel CMA equalizer, and the expression of the output signal x(n) of the dual-channel CMA equalizer is as follows: where w c (k) is the weight of the dual-channel CMA equalizer, k represents the subscript of the equalizer tap, and c represents the channel number; At the initial moment, let w c (0) be 1, and at other moments, w c (0) be 0.

7. The long-distance ultrasonic communication method according to claim 6, characterized in that, It also includes that Step 206 specifically includes: Calculate the phase offset values under different phase estimation values: where each value of m represents an estimation of a phase offset, Judge the positive and negative of the real part and the imaginary part through the symbol decision function, d(n, m) = f(x′(n, m)) where the function f() is the symbol decision function, Select the phase estimation with the minimum error to perform phase compensation on the signal i = argm in(e(m)) 8. The long-distance ultrasonic communication method according to claim 4, characterized in that, The step 207 includes: by means of a symbol decision function, converting the signal p c (n) into a complex signal z(n), and converting z(n) into a binary signal o′(n) according to the conversion relationship between the complex signal z(n) and binary data.

9. The long-distance ultrasonic communication method according to claim 4, characterized in that, In Step 204, downsampling is performed at the moment of t = kT / 2.

10. A consumer electronic device, characterized in that, Including: A speaker for playing the ultrasonic communication signal; A memory for storing software programs and data; A processor, which when executing the said software program, implements the long-distance ultrasonic communication method according to any one of claims 1 to 3.

11. A consumer electronic device, characterized in that, Including: A microphone for collecting ultrasonic signals; A memory for storing software programs and data; A processor, which when executing the said software program, implements the long-distance ultrasonic communication method according to any one of claims 4 to 9.

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