Multi-dimensional channel parameter joint adaptive underwater acoustic single carrier communication method

Abstract

The application belongs to the field of underwater acoustic communication, and particularly relates to an underwater acoustic single-carrier communication method. The application aims to solve the problems of high bit error rate, low spectrum utilization rate, communication interruption and large channel communication overhead caused by the existing adaptive communication method which only focuses on a single channel parameter in the data backhaul scene. The application embeds feedback information into data frames, compresses the interaction period, and keeps the channel information stable within a transceiving period. The application effectively avoids the high-order modulation constellation rotation and aliasing caused by the Doppler effect, greatly reduces the bit error rate, and effectively solves the problems of low spectrum utilization rate and communication interruption caused by incomplete channel cognition. In the subsequent communication process, the application tracks the subsequent channel changes by using the communication signal, thereby reducing the channel communication overhead. The application is used in the field of underwater acoustic single-carrier communication.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic communication, specifically relating to an underwater acoustic single-carrier communication method. Background Technology

[0002] Underwater acoustic channels are considered the most complex and challenging communication channels. They are characterized by extremely low sound propagation speeds (approximately 1500 m / s), severe multipath effects, and Doppler effects. Furthermore, in underwater data transmission scenarios, two different types of ocean nodes—mobile underwater nodes capable of covert data exchange (such as unmanned underwater vehicles) and floating surface nodes with long-term continuous relay capabilities (such as buoys and WGs)—face different channel environments. When the node is mobile, it is significantly affected by reflections from the sea surface and seabed boundaries, resulting in severe multipath spread. Additionally, the signal-to-noise ratio at the receiver exhibits significant dynamic fluctuations as the relative distance between the UUV and the communication target changes. Although the high mobility of the UUV introduces a large Doppler frequency shift, the Doppler factor can be approximated as quasi-static within a single signal frame. When the buoy is a floating node, the channel is generally considered vertical, and signal transmission is mainly dominated by direct waves. Compared to UUVs as ocean nodes, its multipath structure is sparser and more stable, with less multipath spread. However, the buoy is affected by wave undulations, resulting in vertical displacement and a rapidly changing Doppler frequency shift in the received signal. Therefore, designing an adaptive underwater acoustic communication technology that can adapt to both complex channel environments, enabling real-time perception of the channel environment and dynamic adjustment of communication system transmission parameters (modulation method, coding rate, and training sequence length) and signal processing parameters (equalizer feedforward length and phase-locked loop bandwidth), is of significant theoretical and practical value for improving the spectral efficiency of the communication system, reducing the energy consumption of the underwater buoy system, and achieving efficient and robust data transmission from the underwater buoy. Summary of the Invention

[0003] The purpose of this invention is to address the problems of high bit error rate, low spectrum utilization, communication interruption, and large channel communication overhead caused by existing adaptive communication methods that only focus on a single channel parameter in data backhaul scenarios. Therefore, this invention proposes a multi-dimensional channel parameter joint adaptive underwater acoustic single-carrier communication method.

[0004] The specific process of the multi-dimensional channel parameter joint adaptive underwater acoustic single-carrier communication method is as follows:

[0005] Step 1: The receiving end sends a handshake signal to the transmitting end;

[0006] The handshake signal includes the receiver's identity ID, the current receiving status, and initial communication parameters;

[0007] Initial communication parameters include initial modulation order, initial training sequence length, and initial coding rate;

[0008] Step 2: After receiving the handshake signal, the transmitting end sends an acknowledgment signal to the receiving end;

[0009] The response signal carries the transmitter's identity ID information and the bit length information of the data to be transmitted by the transmitter.

[0010] Step 3: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception to obtain the current underwater acoustic channel's signal-to-noise ratio, multipath spread information, and Doppler information.

[0011] Step 4: The receiver determines the error frame number of the current frame data and the communication parameters and receiver signal processing parameters of the next frame signal based on the signal-to-noise ratio information, multiple path spread information and Doppler information of the current underwater acoustic channel.

[0012] The communication parameters include modulation order, training sequence length, and coding rate;

[0013] The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters.

[0014] Step 5: The receiving end feeds back the error frame number of the current frame data determined in Step 4 and the communication parameters of the next frame signal to the transmitting end through an interrogation signal;

[0015] Step 6: The transmitting end extracts communication parameters and error frame bits, encodes and modulates the error frame data and the data to be transmitted according to the communication parameters, and then feeds it back to the receiving end;

[0016] Step 7: The receiver receives the data signal sent by the transmitter, processes the data signal sent by the transmitter, and obtains the current underwater acoustic channel parameters and whether the current frame is erroneous.

[0017] Step 8: Repeat steps 4 to 7 until the transmitting end has completed sending the data to be transmitted.

[0018] The beneficial effects of this invention are as follows:

[0019] 1) Combining the Automatic Repeat Request (ARQ) mechanism with piggyback acknowledgment, and considering the large propagation delay of underwater acoustic channels, we study the mechanism of downlink data signals carrying error information and uplink data signals carrying acknowledgment information. By embedding feedback information into data frames and compressing the interaction period, the channel information remains stable within a transmission and reception cycle.

[0020] 2) This invention incorporates relative motion speed into the decision logic for modulation order. In scenarios where high speed leads to shorter channel coherence time, even with a high signal-to-noise ratio, lower-order modulation (such as QPSK) is preferentially used. This effectively avoids high-order modulation constellation diagram rotation and aliasing caused by the Doppler effect, greatly reducing the bit error rate.

[0021] 3) This invention not only adjusts the coding and modulation parameters at the transmitting end, but also simultaneously adjusts the signal processing parameters at the receiving end (such as the phase-locked loop tracking bandwidth and equalizer length). The feedback link established through the handshake signal enables both the transmitting and receiving parties to collaboratively cope with the complex and ever-changing underwater acoustic channel, effectively solving the problems of low spectrum utilization and communication interruptions caused by incomplete channel awareness.

[0022] 4) In subsequent communication processes, the present invention uses communication signals to track subsequent channel changes, thereby reducing channel communication overhead. Attached Figure Description

[0023] Figure 1 This is a flowchart of the multi-dimensional channel parameter joint adaptive underwater acoustic single-carrier communication method of the present invention;

[0024] Figure 2 This is a timing diagram of the single-carrier communication protocol of the present invention;

[0025] Figure 3 This is a frame structure diagram of the transmitted signal of the present invention;

[0026] Figure 4 This is a graph showing the velocity estimation results in the simulation scenario of this invention;

[0027] Figure 5 This is a graph showing the bit error rate before and after adjusting the processing parameters in a simulation scenario, based on the present invention.

[0028] Figure 6 This is a comparison chart of the throughput of different modulation methods in a simulation scenario. Detailed Implementation

[0029] Specific implementation method one: Combining Figure 1 , Figure 2 , Figure 3 This embodiment describes the specific process of the multi-dimensional channel parameter joint adaptive underwater acoustic single-carrier communication method as follows:

[0030] Step 1: The receiving end (surface end) sends a handshake signal to the transmitting end;

[0031] The handshake signal includes the receiver's identity ID, the current receiving status (initial stage 00 (steps 1, 2, 3, 4), information transmission 01 (steps 5, 6, 7), and end stage 11) and initial communication parameters.

[0032] Initial communication parameters include initial modulation order, initial training sequence length, and initial coding rate;

[0033] Step 2: After receiving the handshake signal, the transmitting end sends an acknowledgment signal to the receiving end;

[0034] The response signal carries the transmitter's identity ID information and the bit length information of the data to be transmitted by the transmitter.

[0035] Step 3: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception to obtain the current underwater acoustic channel's signal-to-noise ratio, multipath spread information, and Doppler information.

[0036] Step 4: The receiver determines the error frame number of the current frame data and the communication parameters and receiver signal processing parameters of the next frame signal based on the signal-to-noise ratio information, multiple path spread information and Doppler information of the current underwater acoustic channel.

[0037] The communication parameters include modulation order, training sequence length, and coding rate;

[0038] The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters.

[0039] Step 5: The receiving end feeds back the error frame number of the current frame data determined in Step 4 and the communication parameters of the next frame signal to the transmitting end through an interrogation signal;

[0040] Step 6: The transmitting end extracts communication parameters and error frame bits, encodes and modulates the error frame data and the data to be transmitted according to the communication parameters, and then feeds it back to the receiving end;

[0041] Step 7: The receiver receives the data signal sent by the transmitter, processes the data signal sent by the transmitter, and obtains the current underwater acoustic channel parameters and whether the current frame is erroneous.

[0042] Step 8: Repeat steps 4 through 7 until the transmitting end has completed sending the data to be transmitted.

[0043] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the response signal in step two is a direct-sequence response signal.

[0044] The other steps and parameters are the same as in Specific Implementation Method 1.

[0045] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that, in step three, the receiving end receives the response signal transmitted by the transmitting end. Based on the response signal, the receiving end performs channel state perception to obtain the current underwater acoustic channel's signal-to-noise ratio information, multipath spread information, and Doppler information. The specific process is as follows:

[0046] Step 3: 1. The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the signal-to-noise ratio information of the current underwater acoustic channel.

[0047] The specific process is as follows:

[0048] Step 3.11: Assuming that the underwater acoustic signal and noise are statistically independent, based on the effective signal power in the direct-sequence response signal... Noise power segment in direct-sequence response signal The total statistical variance of the direct-sequence response signal segment was obtained. The specific process is as follows:

[0049]

[0050] Step 3.1.2: Based on the noise power segment in the direct-sequence response signal Total statistical variance of direct-sequence response signal segment The effective output signal-to-noise ratio of the underwater acoustic channel is derived. The specific process is as follows:

[0051]

[0052] In the formula, The statistical variance of the direct-sequence response signal segment. This represents the variance of the blank noise signal segment in the direct-sequence response signal; this indicator will accurately reflect the interference level of the current underwater acoustic channel.

[0053] The signal-to-noise ratio (SNR) of the underwater acoustic channel is obtained by comparing the energy statistics of the received response signal segment with the energy statistics of the noise segment before synchronization.

[0054] Step 3.2: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the maximum multipath spread information of the current underwater acoustic channel.

[0055] The specific process is as follows:

[0056] Step 321: The channel impulse response estimation method based on sparse reconstruction is used to process the direct-sequence spread spectrum response signal to obtain the maximum delay of the effective multipath component. ;

[0057] Step 3.2.2: Maximum delay based on effective multipath components Obtain the maximum multipath spread of the underwater acoustic channel ; indicates as:

[0058]

[0059] in, Indicates the communication rate of underwater acoustic signals:

[0060] Step 3: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the Doppler information of the current underwater acoustic channel.

[0061] The specific process is as follows:

[0062] Step 331: Calculate the phase difference between adjacent symbols in the direct-sequence response signal. (A signal contains many symbols, such as 20 symbols. Each symbol has one phase, and the phase difference between adjacent symbols is...) );

[0063] Step 332: Based on the phase difference between two adjacent symbols in the direct-sequence response signal Calculate Doppler information between adjacent symbols ; indicates as:

[0064]

[0065] in, Indicates the speed of sound; Indicates the duration of each symbol; Indicates the carrier frequency; This represents the residual velocity between two adjacent symbols in the direct-sequence response signal; the residual velocity is the Doppler information.

[0066] Doppler dynamics are characterized by estimating the remaining Doppler frequency shift within a signal frame. A phase-tracking method using per survivor processing (PSP) is employed to extract the net phase rotation caused by channel motion after removing modulation effects. This rate can then be used to measure the time-varying characteristics of the channel and adaptively optimize the receiver's phase-locked loop bandwidth.

[0067] Other steps and parameters are the same as in specific implementation method one or two.

[0068] Specific Implementation Method Four: This implementation method differs from one of Specific Implementation Methods One to Three in that, in step four, the receiving end determines the error frame number of the current frame data and the communication parameters and receiving end signal processing parameters of the next frame signal based on the signal-to-noise ratio information, multiple path spread information and Doppler information of the current underwater acoustic channel.

[0069] The communication parameters include modulation order, training sequence length, and coding rate;

[0070] The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters.

[0071] The specific process is as follows:

[0072] Step 41: Determine the length of the training sequence; the specific process is as follows:

[0073] The length of the training sequence is twice the number of symbols corresponding to the maximum multipath expansion plus one;

[0074] Step 42: Set the encoding rate ;

[0075] Step 4.3: Determine the equalizer feedback length; the specific process is as follows:

[0076] The equalizer feedforward length is twice the number of symbols corresponding to the maximum multipath extension plus one;

[0077] The equalizer feedback length is taken as the maximum number of symbols corresponding to the multipath extension;

[0078] Maximum multiple path spread is time. 10 symbols are not enough to form a signal, while 2 maximum multiple path spreads are enough to form a signal.

[0079] Step 4: Determine the modulation order jointly based on the real-time estimated signal-to-noise ratio and Doppler information; the specific process is as follows:

[0080] Step 441: The receiver determines the reference signal-to-noise ratio threshold corresponding to different modulation orders at the target bit error rate; the specific process is as follows:

[0081] The target bit error rate ;

[0082] Different modulation orders are: , , ;

[0083] Indicates BPSK modulation; Indicates QPSK modulation; Indicates 8PSK modulation;

[0084] Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ;

[0085] Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ;

[0086] Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ;

[0087] Step 442: Calculate the equivalent signal-to-noise ratio loss The specific process is as follows:

[0088] In steady state, the phase of a phase-locked loop (PLL) consists mainly of two parts: loop noise and steady-state noise. For a second-order PLL, the loop noise... With signal-to-noise ratio and natural frequency Related to steady-state noise With Doppler angular acceleration and natural frequency related;

[0089] Residual phase error variance Represented as:

[0090]

[0091] in, Indicates loop noise; Indicates steady-state noise;

[0092] Loop noise variance Mainly limited by dimensionless loop bandwidth Compared with input signal-to-noise ratio ;

[0093]

[0094] in, Indicates the variance of loop noise;

[0095] This represents the effective output signal-to-noise ratio of the underwater acoustic channel;

[0096] Indicates the duration of the symbol; Indicates the loop equivalent noise bandwidth (unknown);

[0097] steady-state noise Depending on the dynamic characteristics of the Doppler, the steady-state noise resulting from either monotonically changing residual acceleration or periodic phase jitter caused by ocean waves... It can be described by a unified generalized acceleration model;

[0098]

[0099] in, Indicates the natural frequency (unknown); Indicates the carrier frequency; Indicates the speed of sound;

[0100] This represents Doppler angular acceleration. Represents residual velocity The first derivative; Indicates time;

[0101] Natural frequency and loop equivalent noise bandwidth The relationship representing (unknown) is as follows:

[0102]

[0103] in, This represents the damping coefficient, which is usually taken as... ;

[0104] Obtain the residual phase error variance The root mean square value is ; indicates as:

[0105]

[0106] In the formula, This refers to dynamic phase error;

[0107] based on Obtain the equivalent signal-to-noise ratio loss ; indicates as:

[0108]

[0109] In the formula, The modulation order; To take the absolute value;

[0110] when An increase in the threshold indicates a larger phase tracking error caused by Doppler variation, and the system should increase the dynamic modulation switching threshold. Alternatively, a lower-order modulation scheme may be preferred to ensure that the bit error rate meets the requirements.

[0111] Step 443: Utilizing the equivalent signal-to-noise ratio loss Correcting the reference signal-to-noise ratio thresholds for different modulation orders at the target bit error rate. The dynamic modulation switching thresholds for different modulation orders under the target bit error rate are obtained. ; indicates as:

[0112]

[0113] in, Indicates the target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is or target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is or target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ;

[0114] Indicates modulation order or or ; Indicates the signal-to-noise ratio protection margin (taken as 5dB);

[0115] Step 444: When the effective output signal-to-noise ratio is estimated in real time The dynamic modulation switching threshold is higher than a certain modulation order. At this time, the receiver selects the highest modulation order that meets the target bit error rate requirement; the specific process is as follows:

[0116] If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Modulation order less than the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ;

[0117] If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Modulation order less than the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ;

[0118] If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ;

[0119] Steps four and five: Based on the real-time estimated effective output signal-to-noise ratio And Doppler information Jointly determine the phase-locked loop parameters;

[0120] For phase-locked loop (PLL) parameters, there are two criteria for selection. The first criterion is the minimum mean square error criterion, which defines the mean square error cost function of the steady-state residual phase error of the PLL. The second criterion is the minimum bit error rate criterion, which can be further derived for the bit error rate under these parameters.

[0121] The specific process is as follows:

[0122] I. Obtaining the phase-locked loop parameters under the criterion of minimizing mean square error;

[0123] II. Obtain the phase-locked loop parameters under the minimum bit error rate criterion.

[0124] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0125] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that, in Specific Implementation Method One, the phase-locked loop parameters are obtained under the minimum mean square error criterion; the specific process is as follows:

[0126] The mean square error cost function for the steady-state residual phase error of a phase-locked loop is defined as follows:

[0127]

[0128] in, The mean square error cost function represents the steady-state residual phase error of the phase-locked loop; This represents the variance of the residual phase error; Indicates the natural frequency (unknown); This represents the damping coefficient, which is usually taken as... ; Indicates the duration of the symbol; This represents Doppler angular acceleration. Represents residual velocity The first derivative; Indicates time;

[0129] right Differentiate and let The first derivative is zero, yielding the phase-locked loop parameters with the minimum mean square error; expressed as:

[0130]

[0131] in, This represents the optimal natural frequency obtained under the criterion of minimizing mean square error. The optimal natural frequency is the phase-locked loop parameter.

[0132] As shown in the above equation, when the Doppler angular frequency acceleration is large, it indicates that the channel phase changes rapidly. In this case, the inherent angular frequency of the phase-locked loop (PLL) should be increased to improve the PLL's ability to track phase changes. When the input signal-to-noise ratio (SNR) is low, the impact of loop noise on phase tracking is enhanced. In this case, the inherent angular frequency of the PLL should be appropriately reduced to decrease phase jitter caused by noise. Therefore, the receiver can adaptively select PLL parameters based on the current SNR and relative motion state.

[0133] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0134] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One through Five in that, in step two, the phase-locked loop parameters are obtained under the minimum bit error rate criterion; the specific process is as follows:

[0135] Assuming residual phase error If the phase-locked loop (PLL) follows a Gaussian distribution, then the probability of the residual phase error satisfies:

[0136]

[0137] in, Indicates the residual phase error of the phase-locked loop The probability of; This represents the residual phase error of a phase-locked loop that follows a Gaussian distribution. Indicates loop noise; Indicates the variance of loop noise; Indicates steady-state noise;

[0138] For MPSK modulated signals using Gray code mapping (modulation order) MPSK is BPSK modulation. MPSK is QPSK modulated. When the MPSK is 8PSK modulated, consider the residual phase error of the phase-locked loop. Theoretical bit error rate affected Expressed as:

[0139]

[0140] in, Indicates the residual phase error of the phase-locked loop Bit error rate of MPSK under certain conditions; modulation order MPSK is BPSK modulation. MPSK is QPSK modulated. MPSK is 8PSK modulated;

[0141] express function;

[0142] Iterate through different natural frequencies using Python software. The corresponding theoretical bit error rate Select theoretical bit error rate Less than All natural frequencies of time The range is used as the parameters of the phase-locked loop.

[0143] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0144] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that, in step six, the transmitting end extracts communication parameters and error frame bits, encodes and modulates the error frame data and the data to be transmitted according to the communication parameters, and then feeds it back to the receiving end; the specific process is as follows:

[0145] After receiving an interrogation signal carrying communication parameters and an error frame number, the transmitting end parses the modulation order and training sequence length, and adjusts the waveform structure of the next frame of the transmitted signal according to the modulation order and sequence length in the communication parameters; the process is as follows:

[0146] Modulation order in communication parameters The current transmitted signal is BPSK, and the modulation order is... The transmitted signal in the next frame is QPSK modulated; modulation order The current frame transmits a signal of 8PSK;

[0147] Determine whether the next frame's transmitted signal is an incorrect frame number;

[0148] If the next frame of the transmitted signal is not an erroneous frame number, then the transmitted signal is transmitted directly according to the waveform structure of the next frame of the transmitted signal.

[0149] If the next frame of transmitted signal is an erroneous frame number, the bits of the next frame of transmitted signal are encoded, and the encoded erroneous frame number is modulated according to the modulation order in the waveform structure of the next frame of transmitted signal. After modulation, it is retransmitted to the receiving end.

[0150] The process of modulating the encoded error frame number according to the modulation order in the waveform structure of the next frame transmitted signal is as follows:

[0151] Modulation order The time error frame number is modulated as BPSK, and the modulation order is... The frame number is modulated using QPSK modulation; modulation order. The error frame number is modulated to 8PSK.

[0152] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0153] Specific Implementation Method Eight: This implementation method differs from one of Specific Implementation Methods One to Seven in that when the error frame number is empty, it indicates that the previous frame of data did not have an error frame number or that the current time is the first time to send an inquiry signal.

[0154] When the error frame number is not empty, the transmitting end extracts the corresponding frame data according to the error frame number and retransmits it (when the error frame number is not empty, the bits of the next frame of transmitted signal are encoded, and the encoded error frame number is modulated according to the modulation order in the waveform structure of the next frame of transmitted signal, and then retransmitted to the receiving end).

[0155] The other steps and parameters are the same as those in any of the specific implementation methods one to seven.

[0156] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that, in step seven, the receiving end receives the data signal sent by the transmitting end, processes the data signal sent by the transmitting end, and obtains the current underwater acoustic channel parameters and whether the current frame is erroneous; the specific process is as follows:

[0157] The receiving end receives the data signal sent by the transmitting end and determines whether the waveform characteristics of the received data signal are consistent with the communication parameters determined in step four; the waveform characteristics include the modulation order and the sequence length.

[0158] If they match, the received data signal is demodulated, equalized, decoded, and channel tracked sequentially using the signal processing parameters determined in step four. If no erroneous frame number is identified after decoding, the communication parameters obtained from channel tracking are fed back to the transmitter. If an erroneous frame number is identified after decoding, the erroneous frame number and the communication parameters obtained from channel tracking are fed back to the transmitter.

[0159] If they are inconsistent, the parameter downlink is determined to have failed. The receiver determines the communication parameters and receiver signal processing parameters of the next frame signal based on the current underwater acoustic channel's signal-to-noise ratio, multiple path spread information, and Doppler information. The re-determined communication parameters of the next frame signal are fed back to the transmitter, and all frame numbers corresponding to the current frame data are fed back to the transmitter as error frame numbers.

[0160] The communication parameters include modulation order, training sequence length, and coding rate;

[0161] The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters.

[0162] The channel tracking employs channel estimation equalization tracking.

[0163] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0164] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the receiving end receives the data signal sent by the transmitting end and determines whether the waveform characteristics of the received data signal are consistent with the communication parameters determined in step four; the specific process is as follows:

[0165] The data signal received by the receiver and transmitted by the transmitter is correlated with the local training sequence copy. The data signal transmitted by the transmitter corresponding to the maximum value of the correlation detection is selected as the selected data signal.

[0166] Compare the selected data signal with the communication parameters determined in step four;

[0167] If the modulation order and training sequence length in the selected data signal are the same as the modulation order and training sequence length in the communication parameters determined in step four, then it is determined that the training sequence length and modulation method in the received signal are consistent with the communication parameters determined in step four.

[0168] Otherwise, it is determined that the length of the training sequence and the modulation scheme in the received signal are inconsistent with the communication parameters determined in step four.

[0169] The other steps and parameters are the same as those in any of the specific implementation methods one to nine.

[0170] Example:

[0171] The basic signal parameters of an adaptive underwater acoustic communication method based on velocity estimation using direct-sequence spread spectrum (DSSS) in a time-varying Doppler channel are shown in Table 1.

[0172]

[0173] The simulation depicts the transceiver nodes moving sinusoidally with an amplitude of 0.1m and a period of 1s, simulating a scenario where the transmitting node is anchored on the seabed and the receiving node oscillates on the sea surface due to wave influence. Under these simulation conditions, the velocity variation within a single frame of the signal can be estimated using direct-sequence spread spectrum (DSSS) signal velocity estimation. The estimated velocity is as follows: Figure 4 As shown, the bit error rate curves before and after adjusting the processing parameters are as follows: Figure 5 As shown, the throughput before and after adaptive modulation is simulated, and the results are as follows. Figure 6 As shown in the figure, the results demonstrate that the adaptive underwater acoustic communication method based on velocity estimation using direct-sequence spread spectrum (DSS) signals has a lower bit error rate and higher throughput compared to traditional adaptive communication methods.

[0174] This invention may have other embodiments. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A multi-dimensional channel parameter joint adaptive underwater acoustic single-carrier communication method, characterized in that: The specific process of the method is as follows: Step 1: The receiving end sends a handshake signal to the transmitting end; The handshake signal includes the receiver's identity ID, the current receiving status, and initial communication parameters; Initial communication parameters include initial modulation order, initial training sequence length, and initial coding rate; Step 2: After receiving the handshake signal, the transmitting end sends an acknowledgment signal to the receiving end; The response signal carries the transmitter's identity ID information and the bit length information of the data to be transmitted by the transmitter. Step 3: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception to obtain the current underwater acoustic channel's signal-to-noise ratio, multipath spread information, and Doppler information. Step 4: The receiver determines the error frame number of the current frame data and the communication parameters and receiver signal processing parameters of the next frame signal based on the signal-to-noise ratio information, multiple path spread information and Doppler information of the current underwater acoustic channel. The communication parameters include modulation order, training sequence length, and coding rate; The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters. Step 5: The receiving end feeds back the error frame number of the current frame data determined in Step 4 and the communication parameters of the next frame signal to the transmitting end through an interrogation signal; Step 6: The transmitting end extracts communication parameters and error frame bits, encodes and modulates the error frame data and the data to be transmitted according to the communication parameters, and then feeds it back to the receiving end; Step 7: The receiver receives the data signal sent by the transmitter, processes the data signal sent by the transmitter, and obtains the current underwater acoustic channel parameters and whether the current frame is erroneous. Step 8: Repeat steps 4 to 7 until the transmitting end has completed sending the data to be transmitted.

2. The underwater acoustic single-carrier communication method with multi-dimensional channel parameters jointly adaptive according to claim 1, characterized in that: The response signal in step two is a direct-sequence response signal.

3. The underwater acoustic single-carrier communication method with multi-dimensional channel parameters jointly adaptive according to claim 2, characterized in that: In step three, the receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the signal-to-noise ratio, multiple path spread, and Doppler information of the current underwater acoustic channel. The specific process is as follows: Step 3:

1. The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the signal-to-noise ratio information of the current underwater acoustic channel. The specific process is as follows: Step 3.11: Assuming that the underwater acoustic signal and noise are statistically independent, based on the effective signal power in the direct-sequence response signal... Noise power segment in direct-sequence response signal The total statistical variance of the direct-sequence response signal segment was obtained. The specific process is as follows: Step 3.1.2: Based on the noise power segment in the direct-sequence response signal Total statistical variance of direct-sequence response signal segment The effective output signal-to-noise ratio of the underwater acoustic channel is derived. ; The specific process is as follows: In the formula, The statistical variance of the direct-sequence response signal segment. The variance of the blank noise signal segment in the direct-sequence response signal; Step 3.2: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the maximum multipath spread information of the current underwater acoustic channel. The specific process is as follows: Step 321: The channel impulse response estimation method based on sparse reconstruction is used to process the direct-sequence spread spectrum response signal to obtain the maximum delay of the effective multipath component. ; Step 3.2.2: Maximum delay based on effective multipath components Obtain the maximum multipath spread of the underwater acoustic channel ; indicates as: in, Indicates the communication rate of underwater acoustic signals: Step 3: The receiver receives the response signal transmitted by the transmitter. Based on the response signal, the receiver performs channel state perception and obtains the Doppler information of the current underwater acoustic channel. The specific process is as follows: Step 331: Calculate the phase difference between adjacent symbols in the direct-sequence response signal. ; Step 332: Based on the phase difference between two adjacent symbols in the direct-sequence response signal Calculate Doppler information between adjacent symbols ; indicates as: in, Indicates the speed of sound; Indicates the duration of each symbol; Indicates the carrier frequency; This represents the residual velocity between two adjacent symbols in the direct-sequence response signal; the residual velocity is the Doppler information.

4. The underwater acoustic single-carrier communication method with multi-dimensional channel parameters jointly adaptive according to claim 3, characterized in that: In step four, the receiver determines the error frame number of the current frame data, as well as the communication parameters and receiver signal processing parameters of the next frame signal, based on the signal-to-noise ratio information, multiple path spread information, and Doppler information of the current underwater acoustic channel. The communication parameters include modulation order, training sequence length, and coding rate; The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters. The specific process is as follows: Step 41: Determine the length of the training sequence; the specific process is as follows: The length of the training sequence is twice the number of symbols corresponding to the maximum multipath expansion plus one; Step 42: Set the encoding rate ; Step 4.3: Determine the equalizer feedback length; the specific process is as follows: The equalizer feedforward length is twice the number of symbols corresponding to the maximum multipath extension plus one; The equalizer feedback length is taken as the maximum number of symbols corresponding to the multipath extension; Step 4: Determine the modulation order jointly based on the real-time estimated signal-to-noise ratio and Doppler information; the specific process is as follows: Step 441: The receiver determines the reference signal-to-noise ratio threshold corresponding to different modulation orders at the target bit error rate; the specific process is as follows: The target bit error rate ; Different modulation orders are: , , ; Indicates BPSK modulation; Indicates QPSK modulation; Indicates 8PSK modulation; Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ; Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ; Target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ; Step 442: Calculate the equivalent signal-to-noise ratio loss The specific process is as follows: Residual phase error variance Represented as: in, Indicates loop noise; Indicates steady-state noise; in, Indicates the variance of loop noise; This represents the effective output signal-to-noise ratio of the underwater acoustic channel; Indicates the duration of the symbol; Indicates the loop equivalent noise bandwidth; in, Indicates the natural frequency; Indicates the carrier frequency; Indicates the speed of sound; This represents Doppler angular acceleration. Represents residual velocity The first derivative; Indicates time; Natural frequency and loop equivalent noise bandwidth The relationships are represented as follows: in, Indicates the damping coefficient; Obtain the residual phase error variance The root mean square value is ; indicates as: In the formula, This refers to dynamic phase error; based on Obtain the equivalent signal-to-noise ratio loss ; indicates as: In the formula, The modulation order; To take the absolute value; Step 443: Utilizing the equivalent signal-to-noise ratio loss Correcting the reference signal-to-noise ratio thresholds for different modulation orders at the target bit error rate. The dynamic modulation switching thresholds for different modulation orders under the target bit error rate are obtained. ; indicates as: in, Indicates the target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is or target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is or target bit error rate down-modulation order The corresponding reference signal-to-noise ratio threshold is ; Indicates modulation order or or ; Indicates the signal-to-noise ratio protection tolerance; Step 444: When the effective output signal-to-noise ratio is estimated in real time The dynamic modulation switching threshold is higher than a certain modulation order. At this time, the receiver selects the highest modulation order that meets the target bit error rate requirement; the specific process is as follows: If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Modulation order less than the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ; If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Modulation order less than the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ; If the effective output signal-to-noise ratio is estimated in real time Modulation order greater than or equal to the target bit error rate Corresponding dynamic modulation switching threshold Select the highest modulation order that meets the target bit error rate requirement. ; Steps four and five: Based on the real-time estimated effective output signal-to-noise ratio And Doppler information The parameters of the phase-locked loop are determined jointly; the specific process is as follows: I. Obtaining the phase-locked loop parameters under the criterion of minimizing mean square error; II. Obtain the phase-locked loop parameters under the minimum bit error rate criterion.

5. The underwater acoustic single-carrier communication method with multi-dimensional channel parameters jointly adaptive according to claim 4, characterized in that: The phase-locked loop parameters are obtained under the criterion of minimizing mean square error; the specific process is as follows: The mean square error cost function for the steady-state residual phase error of a phase-locked loop is defined as follows: in, The mean square error cost function represents the steady-state residual phase error of the phase-locked loop; This represents the variance of the residual phase error; Indicates the natural frequency; This represents the damping coefficient, which is usually taken as... ; Indicates the duration of the symbol; This represents Doppler angular acceleration. Represents residual velocity The first derivative; Indicates time; right Differentiate and let The first derivative is zero, yielding the phase-locked loop parameters with the minimum mean square error; expressed as: in, This represents the optimal natural frequency obtained under the criterion of minimizing mean square error. The optimal natural frequency is the phase-locked loop parameter.

6. The underwater acoustic single-carrier communication method with joint adaptive multi-dimensional channel parameters according to claim 5, characterized in that: The second method obtains the phase-locked loop parameters under the minimum bit error rate criterion; the specific process is as follows: Assuming residual phase error If the phase-locked loop (PLL) follows a Gaussian distribution, then the probability of the residual phase error satisfies: in, Indicates the residual phase error of the phase-locked loop The probability of; This represents the residual phase error of a phase-locked loop that follows a Gaussian distribution. Indicates loop noise; Indicates the variance of loop noise; Indicates steady-state noise; Considering the residual phase error of the phase-locked loop Theoretical bit error rate affected Expressed as: in, Indicates the residual phase error of the phase-locked loop Bit error rate of MPSK under certain conditions; modulation order MPSK is BPSK modulation. MPSK is QPSK modulated. MPSK is 8PSK modulated; express function; Iterate through different natural frequencies using Python software. The corresponding theoretical bit error rate Select theoretical bit error rate Less than All natural frequencies of time The range is used as the parameters of the phase-locked loop.

7. The underwater acoustic single-carrier communication method with joint adaptive multi-dimensional channel parameters according to claim 6, characterized in that: In step six, the transmitting end extracts communication parameters and error frame bits, encodes and modulates the error frame data and the data to be sent according to the communication parameters, and then feeds it back to the receiving end. The specific process is as follows: After receiving an interrogation signal carrying communication parameters and an error frame number, the transmitting end parses the modulation order and training sequence length, and adjusts the waveform structure of the next frame of the transmitted signal according to the modulation order and sequence length in the communication parameters; the process is as follows: Modulation order in communication parameters The current transmitted signal is BPSK, and the modulation order is... The transmitted signal in the next frame is QPSK modulated; modulation order The current frame transmits a signal of 8PSK; Determine whether the next frame's transmitted signal is an incorrect frame number; If the next frame of the transmitted signal is not an erroneous frame number, then the transmitted signal is transmitted directly according to the waveform structure of the next frame of the transmitted signal. If the next frame of transmitted signal is an erroneous frame number, the bits of the next frame of transmitted signal are encoded, and the encoded erroneous frame number is modulated according to the modulation order in the waveform structure of the next frame of transmitted signal. After modulation, it is retransmitted to the receiving end. The process of modulating the encoded error frame number according to the modulation order in the waveform structure of the next frame transmitted signal is as follows: Modulation order The time error frame number is modulated as BPSK, and the modulation order is... The frame number is modulated using QPSK modulation; modulation order. The error frame number is modulated to 8PSK.

8. The underwater acoustic single-carrier communication method with joint adaptive multi-dimensional channel parameters according to claim 7, characterized in that: When the error frame number is empty, it indicates that the previous frame of data did not have an error frame number or that this is the first time an inquiry signal has been sent.

9. The underwater acoustic single-carrier communication method with joint adaptive multi-dimensional channel parameters according to claim 8, characterized in that: In step seven, the receiving end receives the data signal sent by the transmitting end, processes the data signal sent by the transmitting end, and obtains the current underwater acoustic channel parameters and whether the current frame is erroneous. The specific process is as follows: The receiving end receives the data signal sent by the transmitting end and determines whether the waveform characteristics of the received data signal are consistent with the communication parameters determined in step four. Waveform characteristics include modulation order and sequence length; If they match, the received data signal is demodulated, equalized, decoded, and channel tracked sequentially using the signal processing parameters determined in step four. If the erroneous frame number is not identified after decoding, the communication parameters obtained from channel tracking are fed back to the transmitter. If an erroneous frame number is identified after decoding, the erroneous frame number and the communication parameters obtained from channel tracing are fed back to the transmitter. If they are inconsistent, the parameter downlink is determined to have failed. The receiver determines the communication parameters and receiver signal processing parameters of the next frame signal based on the current underwater acoustic channel's signal-to-noise ratio, multiple path spread information, and Doppler information. The re-determined communication parameters of the next frame signal are fed back to the transmitter, and all frame numbers corresponding to the current frame data are fed back to the transmitter as error frame numbers. The communication parameters include modulation order, training sequence length, and coding rate; The signal processing parameters include equalizer feedforward length, equalizer feedback length, and phase-locked loop parameters.

10. The underwater acoustic single-carrier communication method with joint adaptive multi-dimensional channel parameters according to claim 9, characterized in that: The receiving end receives the data signal sent by the transmitting end and determines whether the waveform characteristics of the received data signal are consistent with the communication parameters determined in step four. The specific process is as follows: The data signal received by the receiver and transmitted by the transmitter is correlated with the local training sequence copy. The data signal transmitted by the transmitter corresponding to the maximum value of the correlation detection is selected as the selected data signal. Compare the selected data signal with the communication parameters determined in step four; If the modulation order and training sequence length in the selected data signal are the same as the modulation order and training sequence length in the communication parameters determined in step four, then it is determined that the training sequence length and modulation method in the received signal are consistent with the communication parameters determined in step four. Otherwise, it is determined that the length of the training sequence and the modulation scheme in the received signal are inconsistent with the communication parameters determined in step four.

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