CN112737984B - Frequency response estimation and signal transmission method and system for multi-carrier incoherent underwater acoustic communication - Google Patents

Abstract

The invention discloses a frequency response estimation and signal transmission method and system for multi-carrier incoherent underwater acoustic communication. The invention uses the character of code word constant weight after coding the control information to carry out preliminary estimation to the amplitude frequency response of the sub-carrier wave, carries out joint optimization estimation to the amplitude frequency response of all frequency points through a deep neural network, and then carries out posterior probability estimation to each symbol according to the amplitude frequency response amplitude of each frequency point to obtain a bit log likelihood sequence for decoding the channel error correcting code. The invention improves the transmission rate of the incoherent underwater acoustic communication and reduces the requirement on the energy consumption of each bit.

Description

Frequency response estimation and signal transmission method and system for multi-carrier incoherent underwater acoustic communication

technical field

The invention belongs to the field of underwater acoustic communication, in particular, aiming at frequency allocation, amplitude-frequency response estimation and high-order modulation of multi-carrier incoherent underwater acoustic communication, and relates to frequency response estimation and signal transmission method of multi-carrier incoherent underwater acoustic communication, system.

Background technique

In the submarine observation wireless network, the underwater acoustic communication is used to realize the data and instruction transmission between fixed observation submersibles, mobile observation submersibles, wireless relay submersibles and wireless gateways. Among them, the non-coherent communication adopts a simple energy detection method, does not need to track the rapidly changing phase, and has the advantages of no pilot overhead and little Doppler effect. Due to the multi-carrier parallel transmission mode, it has strong anti-multipath ability. Incoherent communication is the most commonly used transmission system in wireless expansion systems, which is responsible for the transmission of network control commands and the return of a large amount of sensor data. Technical indicators such as the error rate, transmission rate and energy consumption per bit of non-coherent communication directly determine the working performance and life cycle of the entire wireless expansion network. Due to the serious multipath of the underwater acoustic channel, the channel has serious frequency selectivity. The existing algorithm usually avoids the estimation of the amplitude response of each frequency point, and uses constant weight codewords and on-off keying (OOK, On) at the transmitting end. The information sequence is modulated onto multiple subcarriers by means of -offkeying), and the receiving end adopts the detection method of combining energy.

In the existing incoherent underwater acoustic communication scheme, each sub-carrier can only carry at most 1 bit after encoding. At the same time, the use of constant weight code further reduces the communication rate, and because there is no difference in the frequency response of different carriers, resulting in low signal-to-noise The decoding error rate is higher than the time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to improve the transmission rate of non-coherent underwater acoustic communication and reduce its requirement for energy consumption per bit.

In order to achieve the above purpose, the present invention provides a frequency response estimation and signal transmission method for multi-carrier incoherent underwater acoustic communication. Each data packet transmitted includes control information and data information, and the method includes the steps:

The steps of transmitting end control information coding and modulation:

The control information sequence representing the control information is subjected to dual K code and constant weight code two-level concatenated encoding, the code word encoded by the constant weight code is then subjected to on-off keying OOK modulation, and the control information bits are encoded and modulated for multi-carrier transmission;

The steps of coding and modulation of data information at the transmitting end:

The data information sequence representing the data information is subjected to turbo code encoding and interleaving, the interleaved bit stream is subjected to multi-digit conversion and amplitude shift keying ASK modulation, and the data information bits are coded and modulated for multi-carrier transmission;

The steps of the transmitter group package:

The coded and modulated control information and data information are transmitted in parallel by using the inverse Fourier transform (IFFT) to realize multi-carrier parallel transmission. The signal obtained after the same constant weight code word is modulated by on-off keying OOK is transmitted by the same sub-carrier to ensure that the sub-carrier is in the whole control system. The energy allocated in the information transmission is equal; the time-domain waveform after inverse Fourier transform IFFT includes control information blocks and data information blocks; in order to improve the anti-multipath capability, a cyclic prefix is inserted into the time-domain waveform after inverse Fourier transform IFFT, framing And insert a synchronization signal before and after each frame, the synchronization signal adopts a linear frequency modulation signal, and there is an interval before and after each synchronization signal, and multiple frames form a data packet, thereby completing the generation of the transmission signal;

The steps of receiving end synchronization, frequency point amplitude acquisition and control information decoding:

The receiving end receives the signal transmitted through the underwater acoustic channel, completes time synchronization and average Doppler compensation by detecting the linear frequency modulation signal, and obtains the carrier amplitude. The carrier amplitude includes two parts: the control information carrier amplitude and the data information carrier amplitude. Then perform Fourier transform FFT and modulo to obtain the control information carrier amplitude sequence and data information carrier amplitude sequence. Then, for the obtained control information carrier amplitude sequence, first perform constant weight code square rate soft decision detection, and then perform dual K code multi-input. Make Viterbi decoding, obtain the control information sequence after decoding, then carry out the same dual K code and constant weight code concatenated encoding of the transmitting end to the control information sequence obtained by decoding, and obtain the control information transmission amplitude estimation sequence;

Steps of Amplitude Frequency Response Estimation:

According to the received control information carrier amplitude sequence and the recovered control information transmission amplitude estimation sequence, first, the energy of all received control information subcarrier symbols with zero transmission amplitude is averaged to obtain a noise variance estimate, and then the received The energy average of the control information sub-carrier symbols of the same sub-carrier with non-zero transmission amplitude is performed, and the noise variance estimation is subtracted to obtain the channel amplitude-frequency response estimate of each sub-carrier. response vector;

The steps of ASK detection and turbo decoding based on amplitude-frequency response estimation:

For the data information carrier amplitude sequence, the log-likelihood ratio of each bit carried by the ASK symbol is obtained based on the channel amplitude-frequency response estimation, and the log-likelihood ratio of each bit of each ASK symbol is deinterleaved as the turbo decoder. Input, after iteration and hard decision, the data information sequence is restored and the transmission is completed.

Further, the amplitude shift keying ASK modulation adopts Gray code mapping and average energy normalization, and adopts the corresponding amplitude shift keying ASK amplitude modulation mapping table according to the ASK order.

Further, in the step of estimating the amplitude-frequency response, after the amplitude-frequency response vector is obtained, the amplitude-frequency response vector is optimized and adjusted by the deep neural network DNN.

Further, the deep neural network DNN contains two levels of hidden layers, the activation function of the hidden layer selects the Relu function, and the mean square error is used as the performance loss function during optimization.

The present invention also provides a multi-carrier incoherent underwater acoustic communication sending device, comprising:

Control information coding and modulation module, this module performs dual K code and constant weight code two-level cascade encoding on the control information sequence representing the control information, the code word encoded by the constant weight code is then subjected to on-off keying OOK modulation, and the control information bits are coded and modulated and then used for multi-carrier transmission;

Data information coding and modulation module, this module performs turbo code coding and interleaving on the data information sequence representing data information, the interleaved bit stream is subjected to multi-digit conversion and amplitude shift keying ASK modulation, and the data information bits are coded and modulated for use. multi-carrier transmission;

Packing module, this module realizes multi-carrier parallel transmission through inverse Fourier transform IFFT of coded and modulated control information and data information, wherein the signal obtained by the same constant-weight code word modulated by on-off keying OOK is transmitted by the same sub-carrier, In order to ensure that the energy allocated by the subcarriers in the entire control information transmission is equal; the time domain waveform after the inverse Fourier transform IFFT includes the control information block and the data information block; in order to improve the anti-multipath ability, the time domain waveform after the inverse Fourier transform IFFT A cyclic prefix is inserted into the frame, and a synchronization signal is inserted before and after each frame. The synchronization signal adopts a linear frequency modulation signal, and there is an interval before and after each synchronization signal. Multiple frames form a data packet, and then complete the generation of the transmitted signal.

Further, the amplitude shift keying ASK modulation adopts Gray code mapping and average energy normalization, and adopts the corresponding ASK amplitude modulation mapping table according to the ASK order.

The present invention also provides a multi-carrier incoherent underwater acoustic communication receiving device, comprising:

Synchronization, frequency point amplitude and control information decoding module, this module receives the signal transmitted through the underwater acoustic channel, completes time synchronization and average Doppler compensation by detecting the chirp signal, and obtains the carrier amplitude. The carrier amplitude includes The control information carrier amplitude and the data information carrier amplitude are two parts, and then Fourier transform FFT and modulo are performed to obtain the control information carrier amplitude sequence and the data information carrier amplitude sequence, and then for the obtained control information carrier amplitude sequence, the constant weight code square rate is first Soft decision detection, then perform multi-ary Viterbi decoding of the dual K code to obtain the decoded control information sequence, and then perform the same dual K code and constant weight code concatenated encoding at the transmitter on the control information sequence obtained by decoding, Obtain the control information transmission amplitude estimation sequence;

Amplitude-frequency response estimation module, this module firstly averages the energy of all received control information sub-carrier symbols with zero transmission amplitude to obtain noise variance estimation, and then receives control information for the same sub-carrier with non-zero transmission amplitude The sub-carrier symbols are energy averaged, and the noise variance estimation is subtracted to obtain the channel amplitude-frequency response estimation of each sub-carrier, and the amplitude-frequency response vector is obtained according to the channel amplitude-frequency response estimation of all sub-carriers;

ASK detection and turbo decoding module based on amplitude-frequency response estimation, this module obtains the log-likelihood ratio of each bit carried by the ASK symbol based on the channel amplitude-frequency response estimation for the data information carrier amplitude sequence. The bit log-likelihood ratio is deinterleaved and used as the input of the turbo decoder. After iteration and hard decision, the data information sequence is recovered and the transmission is completed.

Further, the receiving device further includes an amplitude-frequency response optimization module, which optimizes and adjusts the amplitude-frequency response vector obtained by the amplitude-frequency response estimation module through a deep neural network DNN.

Further, the deep neural network DNN contains two levels of hidden layers, the activation function of the hidden layer selects the Relu function, and the mean square error is used as the performance loss function during optimization.

The present invention also provides a frequency response estimation and signal transmission system for multi-carrier non-coherent underwater acoustic communication, which is characterized by comprising a sending device and a receiving device, wherein the sending device adopts the sending device as claimed in the claims, and the receiving device adopts the above-mentioned receiving device. equipment.

beneficial effect

The present invention improves the transmission rate of non-coherent underwater acoustic communication and reduces its requirements for energy consumption per bit, specifically:

(1) The present invention uses the waveform of the control frame to estimate the amplitude-frequency response, and does not need to set up a dedicated training pilot, which can avoid pilot overhead.

(2) The traditional linear minimum mean square error channel estimation algorithm is not suitable for incoherent underwater acoustic communication due to the nonlinear influence of the calculation of the modulo value. Computational complexity Combines the amplitude-frequency estimates of multiple symbol times, and further optimizes them by using a deep neural network. The nonlinear correlation between the amplitude-frequency responses of each frequency point is used to improve the accuracy of the frequency response estimation, and it does not depend on the channel. Model.

(3) After the present invention obtains the amplitude-frequency response of each frequency point, the modulation information detection of each frequency point is more accurate, and the modulation mode of high-order amplitude shift keying (ASK, amplitude shift keying) can be used to improve the channel utilization rate, and No pilot overhead is required.

(4) The detection form of the modulation information on each carrier in the present invention is based on the log-likelihood ratio of a posteriori probability. Compared with the traditional energy detection, it is more suitable for the requirements of the turbo decoder for the form of bit information.

Description of drawings

1 is a schematic block diagram of a frequency response estimation and signal transmission method for multi-carrier incoherent underwater acoustic communication according to the present invention;

Fig. 2 is the composition structure schematic diagram of transmitting packet in the present invention;

Fig. 3 is the simulation comparison diagram of frequency response estimation effect and true value in the present invention;

FIG. 4 is a comparison diagram of the relationship between the number of decoding iterations and the bit error rate under different frequency response estimation and detection methods.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The invention proposes a multi-carrier incoherent underwater acoustic communication method based on a transmit waveform generation scheme that can be used for sub-carrier amplitude detection, accurate amplitude response estimation of each sub-carrier at the receiving end, and a posteriori probability detection of information on each carrier. Frequency response estimation and signal transmission method, system and its transmitting device and receiving device.

The present invention utilizes the characteristic of constant weight of the code word after encoding the control information to perform preliminary estimation on the amplitude and frequency response of the sub-carrier, and jointly optimizes and estimates the amplitude and frequency responses of all frequency points through a deep neural network, and then conducts a joint optimization estimation according to each The amplitude-frequency response amplitude of the frequency point is used to estimate the posterior probability of each symbol to obtain a bit log-likelihood sequence, which is used for channel error correction code decoding.

The frequency response estimation and signal transmission method of multi-carrier incoherent underwater acoustic communication of the present invention, including:

The steps of transmitting end control information coding and modulation:

经过对偶K码编码后，得到编码的多进制序列为

其中

R_Dual为对偶K码的码率，N_CWI为后级恒重码编码每个分组的输入比特数目。N_CWO为恒重码编码分组的输出比特数目。恒重码映射矩阵记为

即当恒重码映射输入的多进制取值为i时，映射输出的二进制序列的第j位结果为

矩阵采用Hadamard矩阵生成，恒重码出现1的概率为

恒重码编码码率为

控制信息比特经过对偶K和恒重码级联编码，在OOK调制后，采用多载波传输的方式，N_Carrier为并行的多载波个数。同一恒重码码字由同一子载波传输，以保证子载波在整个控制信息传输中分配的能量相等。第i个子载波的第j个多载波符号的幅度为：The process of transmitting the signal is shown in Figure 1. Each transmission packet needs to transmit control information and data information in two parts. The number of control information bits is N _Ctrl , and all control information bits are denoted as

After dual K code encoding, the encoded multi-ary sequence is obtained as

in

R _Dual is the code rate of the dual K code, and N _CWI is the number of input bits of each packet encoded by the latter-stage constant weight code. N _CWO is the number of output bits of the constant weight code coded packet. The constant weight code mapping matrix is denoted as

That is, when the multi-binary value of the constant weight code mapping input is i, the result of the jth bit of the binary sequence output by the mapping is:

The matrix is generated by the Hadamard matrix, and the probability of the constant weight code appearing 1 is

Constant weight code encoding rate

The control information bits are coded by dual K and constant weight code concatenated, and after OOK modulation, multi-carrier transmission is adopted, and N _Carrier is the number of parallel multi-carriers. The same constant-weight code word is transmitted by the same sub-carrier to ensure that the sub-carriers are allocated equal energy in the entire control information transmission. The amplitude of the jth multicarrier symbol of the ith subcarrier is:

为向下取整函数，且控制信息传输使用的多载波符号个数为

Among them, 0≤i＜N _Carrier , 0≤j＜N _CtrlSymb ,

is a round-down function, and the number of multi-carrier symbols used for control information transmission is

The steps of coding and modulation of data information at the transmitting end:

其中N_Data为数据信息比特的个数。经turbo码编码及交织后，获得的比特矢量为

其中

为turbo编码输出比特数，R_Turbo为turbo编码的码率。The data information bits to be transmitted are recorded as

Wherein N _Data is the number of data information bits. After turbo coding and interleaving, the obtained bit vector is

in

is the number of output bits for turbo coding, and R _Turbo is the bit rate of turbo coding.

Convert the encoded and interleaved bit stream to a multi-sequence sequence to get

Among them, N _ASK is the number of bits carried by each ASK symbol. For different ASK orders, Gray code is used for mapping and the average energy is normalized to obtain the ASK amplitude mapping (modulation) table. The mapping tables for orders 1 to 3 are as follows :

表示输入*时，输出的ASK幅度。in

Indicates the ASK amplitude of the output when * is input.

The amplitude of the j-th multi-carrier symbol of the i-th sub-carrier encoded with the data information is:

Among them, 0≤i<N _Carrier , 0≤jN _CtrlSymb <N _DataSymb , and the number of multi-carrier symbols used for data information transmission is

The steps of the grouping of the transmitting end:

The composition structure of the sending packet is shown in Figure 2. After the control information and data information are encoded and mapped, the parallel transmission in multi-carrier mode is realized by inverse Fast Fourier Transform (IFFT). The lowest and highest sub-carrier frequencies are f _L and f _H , respectively, and the sub-carrier spacing is f _δ . The effective length of a subcarrier is T _δ . The multi-carrier symbols of the former control information block part carry control information, and the multi-carrier symbols of the latter data information blocks carry data information. The same multi-carrier symbol contains multiple sub-carriers that carry the same type of information. To improve the ability to overcome multipath, a cyclic prefix is inserted into the time domain waveform, the length of which is T _g . A frame contains N _SymbPerFrm multi-carrier symbols, and a synchronization signal is inserted before and after each frame to complete the generation of the transmitted signal. The synchronization signal is in the form of a chirp, the lowest and highest frequencies are f ₀ and f ₁ , respectively, and the duration is T _Sync . The length of the space left before and after each synchronization signal is T _Gap . The length of each frame is T _Frm . According to the number of frames and the frame length in the transmitted packet, the transmission length of the packet is obtained as T _packet .

The steps of receiving end synchronization, frequency point amplitude acquisition and control information decoding:

The signal flow at the receiving end is shown in Figure 1. Through the detection of the chirp signal, the time synchronization and the average Doppler synchronization are completed, and the Fourier transform (Fast Fourier Transform, FFT) calculation is performed to obtain the amplitude of the jth symbol of the ith subcarrier in the entire packet as y(i, j), where 0≤i<N _Carrier and 0≤j<N _CtrlSymb +N _DataSymb . Its simulation generation model is expressed as

y(i,j)=|h(i)x(i,j)+w(i,j)|

将译码得到的控制信息序列进行发送端相同的对偶K码和恒重码级联编码，获得控制信息中的第i个子载波第j个符号的幅度的发射幅度估计，即

其中0≤i＜N_Carrier，0≤j＜N_CtrlSymb。Where h(i) is the amplitude-frequency response of the ith subcarrier, which is the quantity to be estimated, and w(i, j) is the additive noise at the corresponding subcarrier. According to the received carrier amplitude carrying the control information, the constant weight code is first subjected to traditional square rate soft decision detection, and then the dual K code is subjected to multi-ary Viterbi decoding to obtain the decoded control information sequence.

The control information sequence obtained by decoding is subjected to the same dual K code and constant weight code concatenated encoding at the transmitting end to obtain the transmission amplitude estimate of the amplitude of the jth symbol of the ith subcarrier in the control information, that is,

Wherein 0≤i<N _Carrier , 0≤j<N _CtrlSymb .

Steps of Amplitude Frequency Response Estimation and Its Improved Estimation Based on Deep Neural Networks

According to the received amplitude sequence of the control information and the estimation of the transmitted amplitude of the control information recovered by the receiver, the energy of the received sub-carrier symbols with the transmitted amplitude of 0 is firstly averaged, and the noise variance estimate is obtained as

Then, for each subcarrier, the energy of the received subcarrier symbols with non-zero transmission amplitude is averaged, and the noise variance is subtracted to obtain the estimated channel amplitude-frequency response of the ith subcarrier as

The amplitude-frequency response vector is adjusted through a deep neural network (DNN), and the input amplitude-frequency response vector and the output amplitude-frequency response vector are respectively recorded as

The DNN contains two levels of hidden layers, and the activation function of the hidden layer selects the ReLu function, denoted as f _ReLu ( ). Therefore, the output vector of DNN can be expressed as:

Among them, {W ₀ , b ₀ , W ₁ , b ₁ , W ₂ , b ₂ } are weighted matrices and bias vectors at all levels. These parameters are obtained through Adam tool training and optimization, and the mean square error is used as the performance loss function during optimization.

The steps of ASK detection and turbo decoding based on amplitude-frequency response estimation:

的后验概率正比于非中心化参数为

尺度参数

的莱斯分布概率密度，即For the j-th symbol of the i-th subcarrier carrying data information (0≤i<N _Carrier , N _CtrlSymb ≤j≤N _CtrlSymb +N _DataSymb ), the ASK amplitude is

The posterior probability of is proportional to the decentralization parameter as

scale parameter

The Rice distribution probability density of

The probability density function of the Rice distribution is

And I ₀ (·) is a modified Bessel function of the 0th order of the first kind. The log-likelihood ratio of the nth bit carried by this ASK symbol is

为求ASK符号对应的整数m的第n位比特，求解过程为

为向下取整函数。将各ASK符号的各比特对数似然比经解交织后作为turbo译码器的输入，经过多次迭代及硬判决后，恢复数据信息比特流，即

完成传输过程。in

In order to find the nth bit of the integer m corresponding to the ASK symbol, the solving process is as follows

is the round-down function. The log-likelihood ratio of each bit of each ASK symbol is deinterleaved as the input of the turbo decoder, and after multiple iterations and hard decisions, the data information bit stream is restored, that is,

Complete the transfer process.

Typical parameters used in the present invention and their values are as follows:

According to the above parameters, the performance simulation under the multipath channel is carried out. The channel multipath adopts an independent uncorrelated Rayleigh distribution with a multipath spread length of 0.625ms, and is used to generate frequency response samples for DNN training. Figure 3 presents a comparison of the frequency responses obtained by different methods. Including the real frequency response, the amplitude-frequency response estimation obtained by using the frequency points of the control information to estimate the average energy, and the amplitude-frequency estimation after the DNN adjustment, it can be seen that the DNN adjustment is closer to the real value.

The encoder of the data information adopts a turbo code with a code rate of 1/3, and its component code is a recursive systematic convolutional code whose generator polynomial is [37,21]. Fig. 4 shows the relationship curve between the number of decoding iterations and the bit error rate (BER) under different detection modes of 4th-order ASK. The signal-to-noise ratio used was 10 dB. Among them, the Rayleigh distribution ASK detection method without frequency response estimation in the traditional method increases the number of iterations, and the BER cannot be improved, indicating that the traditional incoherent technology cannot perform reliable transmission of high-order modulation. After the frequency response estimation based on the control information constant weight code proposed by the present invention, the high-order ASK detection based on the Rice distribution assumption becomes credible. For two different frequency response estimation methods, the BER can be improved by multiple iterations. After adjusting the frequency response estimation with DNN, the BER of the system is lower.

Based on the same inventive concept, the specific embodiment of the present invention also provides a frequency response estimation and signal transmission system for multi-carrier incoherent underwater acoustic communication, and a transmitting device and a receiving device in the system. The sending device includes a control information coding and modulation module, a data information coding and modulation module and a package module. The receiving device includes a synchronization, frequency point amplitude and control information decoding module, an amplitude-frequency response estimation module, an amplitude-frequency response optimization module, and an ASK detection and turbo decoding module based on the amplitude-frequency response estimation. These modules and the corresponding equipment formed by them complete the above-mentioned corresponding functions of the frequency response estimation and signal transmission method for multi-carrier incoherent underwater acoustic communication of the present invention.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A method for frequency response estimation and signal transmission in multi-carrier incoherent underwater acoustic communication, wherein each data packet transmitted comprises control information and data information, the method comprising the steps of:

the method comprises the following steps of transmitting end control information coding modulation:

carrying out dual K code and constant weight code two-stage cascade coding on a control information sequence representing control information, carrying out on-off keying (OOK) modulation on a code word coded by the constant weight code, and using a control information bit for multi-carrier transmission after coding modulation;

the method comprises the following steps of transmitting end data information coding modulation:

turbo code coding and interleaving are carried out on a data information sequence representing data information, multi-system conversion and Amplitude Shift Keying (ASK) modulation are carried out on a bit stream after interleaving, and data information bits are used for multi-carrier transmission after being coded and modulated;

and a transmitting end group packaging step:

the coded and modulated control information and data information are subjected to inverse Fourier transform (IFFT) to realize multi-carrier parallel transmission, wherein signals obtained by modulating the same constant-weight code word by on-off keying (OOK) are transmitted by the same subcarrier to ensure that the energy distributed by the subcarrier in the whole control information transmission is equal; the time domain waveform after inverse Fourier transform IFFT comprises a control information block and a data information block; in order to improve the anti-multipath capability, a cyclic prefix is inserted into a time domain waveform after inverse Fourier transform (IFFT), frames are formed, synchronous signals are inserted in front of and behind each frame, the synchronous signals adopt linear frequency modulation signals, an interval is reserved in front of and behind each synchronous signal, a plurality of frames form a data packet, and then the generation of transmitting signals is completed;

the receiving end synchronization, frequency point amplitude acquisition and control information decoding method comprises the following steps:

a receiving end receives a signal transmitted by an underwater acoustic channel, time synchronization and average Doppler compensation are completed through detection of a linear frequency modulation signal to obtain carrier amplitude, the carrier amplitude comprises a control information carrier amplitude and a data information carrier amplitude, then Fourier transform FFT and modulus calculation are carried out to obtain a control information carrier amplitude sequence and a data information carrier amplitude sequence, then constant-weight-code square-rate soft-decision detection is carried out on the obtained control information carrier amplitude sequence, multi-system Viterbi decoding of dual K codes is carried out to obtain a decoded control information sequence, and then dual K codes and constant-weight codes which are the same as a transmitting end are carried out on the decoded control information sequence to obtain a control information transmitting amplitude estimation sequence;

and (3) amplitude-frequency response estimation:

according to the received control information carrier amplitude sequence and the recovered control information transmission amplitude estimation sequence, firstly, carrying out energy averaging on all received control information subcarrier symbols with transmission amplitudes of zero to obtain noise variance estimation, then carrying out energy averaging on received control information subcarrier symbols with transmission amplitudes of non-zero of the same subcarrier, subtracting the noise variance estimation to obtain channel amplitude-frequency response estimation of each subcarrier, and obtaining an amplitude-frequency response vector according to the channel amplitude-frequency response estimation of all subcarriers;

ASK detection and turbo decoding based on amplitude-frequency response estimation:

and for the amplitude sequence of the data information carrier, obtaining the log-likelihood ratio of each bit carried by the ASK symbol based on channel amplitude-frequency response estimation, de-interleaving each bit log-likelihood ratio of each ASK symbol to be used as the input of a turbo decoder, and recovering the data information sequence after iteration and hard decision to finish transmission.

2. The method of claim 1, wherein the Amplitude Shift Keying (ASK) modulation is mapped using Gray code and normalized for average energy, and a corresponding Amplitude Shift Keying (ASK) amplitude modulation mapping table is used according to ASK order.

3. The method of claim 1, wherein in the step of magnitude-frequency response estimation, after the magnitude-frequency response vector is obtained, the magnitude-frequency response vector is optimally adjusted by a Deep Neural Network (DNN).

4. The method of claim 3, wherein the deep neural network DNN comprises two stages of hidden layers, wherein the activation function of the hidden layers is a Relu function, and the mean square error is used as a performance loss function during optimization.

5. A multi-carrier incoherent underwater acoustic communication transmission apparatus, characterized by comprising:

the control information coding and modulating module is used for carrying out dual K code and constant weight code two-stage cascade coding on a control information sequence representing control information, carrying out on-off keying (OOK) modulation on a code word coded by the constant weight code, and using a control information bit for multi-carrier transmission after coding modulation;

a data information coding modulation module, which performs turbo code coding and interleaving on a data information sequence representing data information, performs multilevel system conversion and Amplitude Shift Keying (ASK) modulation on an interleaved bit stream, and uses the data information bits for multi-carrier transmission after coding modulation;

the packaging module is used for realizing multi-carrier parallel transmission of the control information and the data information after the coding modulation through inverse Fourier transform (IFFT), wherein signals obtained after the same constant-weight code word is subjected to on-off keying (OOK) modulation are transmitted by the same subcarrier so as to ensure that the energy distributed by the subcarrier in the whole control information transmission is equal; the time domain waveform after inverse Fourier transform IFFT comprises a control information block and a data information block; in order to improve the multipath resistance, a cyclic prefix is inserted into a time domain waveform after inverse Fourier transform (IFFT), frames are formed, synchronous signals are inserted in front of and behind each frame, the synchronous signals adopt linear frequency modulation signals, an interval is reserved in front of and behind each synchronous signal, a plurality of frames form a data packet, and then the generation of transmitting signals is completed.

6. The transmitting device of claim 5, wherein the Amplitude Shift Keying (ASK) modulation employs Gray code mapping and average energy normalization, and a corresponding ASK amplitude modulation mapping table is employed according to an ASK order.

7. A multi-carrier incoherent underwater acoustic communication receiving apparatus for receiving the transmission signal generated by the transmitting apparatus of claim 5 or 6, characterized by comprising:

a synchronization, frequency point amplitude and control information decoding module, which receives signals transmitted through an underwater acoustic channel, completes time synchronization and average Doppler compensation by detecting a linear frequency modulation signal to obtain carrier amplitude, the carrier amplitude comprises two parts of control information carrier amplitude and data information carrier amplitude, then performs Fourier transform FFT and module calculation to obtain a control information carrier amplitude sequence and a data information carrier amplitude sequence, then performs constant repetition rate soft decision detection on the obtained control information carrier amplitude sequence, then performs multi-system Viterbi decoding on dual K codes to obtain a decoded control information sequence, and then performs dual K code and constant repetition code cascade coding on the decoded control information sequence with the same transmitting end to obtain a control information transmitting amplitude estimation sequence;

the module firstly carries out energy averaging on all received control information subcarrier symbols with zero transmission amplitude to obtain noise variance estimation, then carries out energy averaging on the received control information subcarrier symbols with non-zero transmission amplitude of the same subcarrier, subtracts the noise variance estimation to obtain channel amplitude-frequency response estimation of each subcarrier, and obtains an amplitude-frequency response vector according to the channel amplitude-frequency response estimation of all subcarriers;

the ASK detection and turbo decoding module based on amplitude-frequency response estimation obtains the log-likelihood ratio of each bit carried by an ASK symbol for a data information carrier amplitude sequence based on channel amplitude-frequency response estimation, the log-likelihood ratio of each bit of each ASK symbol is used as the input of a turbo decoder after being deinterleaved, and after iteration and hard decision, the data information sequence is recovered to finish transmission.

8. The receiving device of claim 7, further comprising a magnitude-frequency response optimization module that performs optimization adjustment on the magnitude-frequency response vector obtained by the magnitude-frequency response estimation module through a Deep Neural Network (DNN).

9. The receiver apparatus of claim 8, wherein the deep neural network DNN comprises two stages of hidden layers, wherein an activation function of the hidden layers is a Relu function, and a mean square error is used as a performance loss function during optimization.

10. A frequency response estimation and signal transmission system for multi-carrier incoherent underwater acoustic communication, characterized by comprising a transmitting device and a receiving device, wherein the transmitting device adopts the transmitting device as claimed in one of claims 5 to 6, and the receiving device adopts the receiving device as claimed in one of claims 7 to 9.

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