A signal recovery method of combining weighted channel equalization and carrier synchronization

Abstract

The application discloses a signal recovery method of weighted channel equalization and carrier synchronization combination, and belongs to the field of high-frequency wireless communication.The application realizes the method as follows: a constant modulus blind equalization algorithm is used to quickly estimate a channel, signal amplitude is quickly converged, and a carrier offset is preliminarily obtained, and the interference of channel characteristics on carrier offset estimation and compensation is weakened; a feedback mechanism is used to feed back residual errors of a signal compensated with a carrier parameter after carrier synchronization to an equalization module to participate in the estimation of inter-symbol interference and channel characteristics; the equalization errors of different equalization algorithms are calculated according to the signal residual errors obtained by using a decision-directed algorithm, the weights of the equalization errors in the joint errors are calculated, the joint errors are dynamically adjusted, the signal residual error weights are gradually improved, the complex channel environment is accurately estimated, the tap coefficients are updated and compensated according to the joint errors, the accuracy of the recovery of new symbols coming at the next moment is improved, and the robustness and accuracy of the demodulation and recovery of high-frequency signals are improved.

Description

Technical Field

[0001] This invention relates to a signal recovery method combining weighted channel equalization and carrier synchronization, used for demodulation in terahertz high-frequency wireless communication, and belongs to the field of high-frequency wireless communication. Background Technology

[0002] Channel equalization and carrier synchronization are key technologies in the field of high-frequency wireless communication, which directly affect the signal quality received by high-frequency communication systems.

[0003] In practical communication, the channel characteristics of the terahertz band are complex. The signal received by the communication system's receiver suffers from inter-symbol interference (ISI) caused by multipath effects and nonlinear fading, affecting normal signal demodulation. Channel equalization techniques improve signal quality by estimating non-ideal channel characteristics and ISI, and compensating for equalization errors, thereby recovering the original signal. Furthermore, excessively high carrier frequencies in the terahertz band can lead to carrier mismatch between the receiver and transmitter, causing carrier offset between them and severely impacting communication performance. Carrier synchronization techniques compensate for the frequency and phase offsets caused by carrier mismatch, recovering the signal after carrier offset compensation.

[0004] To achieve reliable and efficient communication in the terahertz band, the current conventional method is to cascade channel equalization and carrier synchronization for signal demodulation, thereby compensating for terahertz channel characteristics and carrier offset. However, several problems exist. Actual receiver signals often exhibit both intersymbol interference (ISI) and carrier offset, and the cascaded channel equalization and carrier synchronization introduces interference between modules. The performance of commonly used channel equalization algorithms degrades significantly during signal processing; theoretically superior time-domain equalization methods fail when carrier frequency and phase offsets exist. Common carrier synchronization methods require signal amplitude recovery as a prerequisite, and in complex channel environments, carrier synchronization performance degrades drastically due to the superposition of phase distortion. Summary of the Invention

[0005] To address the shortcomings of current terahertz high-frequency demodulation technologies, the main objective of this invention is to provide a signal recovery method combining weighted channel equalization and carrier synchronization. This method utilizes a constant-mode blind equalization algorithm to rapidly estimate channel characteristics, achieving rapid signal amplitude convergence and initial carrier offset acquisition, ensuring the robustness of the combined approach and reducing interference from channel characteristics on carrier offset estimation and compensation. A feedback mechanism is used to feed back the residual error of the signal after carrier synchronization and carrier parameter compensation to the equalization module to participate in the estimation of inter-symbol interference and channel characteristics, thereby eliminating interference from carrier offset on decision-guided channel equalization. The residual error obtained from the decision-guided algorithm is used to calculate different average signals... The weight of the equalization error in the joint error is dynamically adjusted. When the channel characteristics of the terahertz high-frequency band are difficult to estimate, the robustness of constant modulus equalization is used to keep the receiver stable. The weight of the residual error of the signal is gradually increased to complete the accurate estimation of complex channel environments. The joint error is used to update and compensate the tap coefficients, which improves the accuracy of the recovery of the new symbol arriving at the next time moment, thereby improving the quality of the received signal. This solves the problem of the performance degradation of decision-guided equalization caused by carrier parameter offset, reduces the demodulation loss at the receiver of the communication system, improves the performance of the equalizer, and enhances the robustness and accuracy of high-frequency signal demodulation recovery.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention discloses a signal recovery method combining weighted channel equalization and carrier synchronization. By introducing a residual signal error feedback mechanism after carrier synchronization into the equalization module, replacing the previous architecture of cascaded equalization and carrier synchronization modules, this method eliminates demodulation interference between modules caused by the simultaneous presence of inter-symbol interference and carrier parameter offset, improving received signal quality, reducing demodulation loss at the receiver, and achieving reliable and effective communication. Furthermore, this invention utilizes the residual signal error after carrier synchronization to characterize the degree of signal recovery, calculates the weights of constant-mode blind equalization error and decision-guided signal residual error in channel estimation, and dynamically changes the demodulation strategy based on the real-time demodulation status during demodulation, improving the robustness and accuracy of high-frequency signal demodulation recovery.

[0008] This invention discloses a signal recovery method combining weighted channel equalization and carrier synchronization, comprising the following steps:

[0009] Step 1: The receiving end performs channel equalization processing on the received signal to be recovered. Specifically, the sequence of symbols to be recovered received at the current time is shifted into the corresponding equalization tap and multiplied to calculate the equalizer output y(n). Based on the constant modulus blind equalization algorithm (CMA), the constant modulus equalization error e is calculated using the decision radius obtained from the equalizer output and the corresponding communication signal. CMA(n), utilizing the robustness provided by the constant modulus blind equalization algorithm CMA, reduces the interference of channel characteristics on carrier parameter estimation and compensation;

[0010] The receiving end performs channel equalization processing on the received signal to be recovered. The formula for calculating the equalizer output y(n) is shown in formula (1):

[0011] y(n)=w(n) T x(n) (1)

[0012] Where x(n) represents the symbol column vector of the signal to be recovered after sampling, affected by noise, inter-symbol interference (ISI), and carrier parameter offset; w(n) represents the equalization tap coefficient column vector; n represents the difference between the current time and the initial time; and y(n) represents the output of the equalizer at this n. The received signal sequence to be recovered is sequentially multiplied by the corresponding taps of the equalizer. Each time y(n) is calculated, the signal entering the tap is updated. The constant-mode blind equalization error is calculated synchronously to estimate channel characteristics and obtain ISI compensation information.

[0013] The constant-mode blind equalization error is calculated using the CMA constant-mode blind equalization algorithm, with the decision radius R obtained by comparing the equalizer output y(n) with the corresponding communication signal. CMA The calculation is complete; the constant-mode blind equalization error includes inter-symbol interference compensation information in the signal. The constant-mode blind equalization error e CMA The formula for calculating (n) is formula (2);

[0014] e CMA (n)=y(n)(|y(n| 2 -R CMA (2)

[0015] Where the decision radius R CMA =E(|s(n)|) 4 / E(|s(n)|) 2 s(n) is the set of symbols transmitted by the sending end;

[0016] Step 2: Calculate the channel equalization output y(n) and constant-mode blind equalization error e obtained in Step 1. CMA (n), entering the carrier synchronization stage, the carrier frequency and phase offset of the signal are estimated and compensated in a timely manner to obtain the carrier parameter compensated signal r(n), thereby improving signal quality. The carrier synchronization stage includes the following three sub-steps: frequency and phase discrimination sub-step, loop filtering sub-step, and NCO parameter update and carrier compensation sub-step;

[0017] The carrier synchronization phase specifically includes the following sub-steps;

[0018] Step 2.1, Frequency and Phase Discrimination: By adding a decision window to the diagonal region of the constellation points, the phase-locked loop (PLL) compensates for the frequency and phase offset of the received signal. Frequency and phase discrimination output results. Formula (3) is used.

[0019]

[0020] in, The output of the frequency and phase detector. q(n) is the output of the frequency and phase detector at the previous moment, and q(n) is the phase difference between y(n) and the corresponding standard symbol in the decision window;

[0021] Step 2.2, Loop Filtering: The output result of the frequency and phase detector calculated in Step 2.1. As the input to the loop filter, the loop filter determines... The sign of the sign is used to determine the recovery of carrier synchronization from carrier frequency offset and phase shift. The numerical adjustment loop filter output e LF (n), the output result of the second-order digital loop filter e LF (n) is from formula (4);

[0022]

[0023] Where C1 and C2 are loop parameters, e LF (n-1) represents the output of the loop filter at the previous time step.

[0024] Step 2.3, NCO parameter update and carrier compensation: The output of the loop filter is used as the input of the numerically controlled oscillator (NCO), and then the NCO outputs a phase adjustment value. The phase adjustment amount is as shown in equation (5). Compensation for carrier frequency offset and phase offset;

[0025]

[0026] The phase adjustment amount is a combination of the carrier frequency offset and phase offset that should be compensated to the corresponding signal y(n); the compensated phase adjustment amount θ output by the numerically controlled oscillator. NCO (n) is from formula (6):

[0027]

[0028] Where θ(n) is the phase of the input signal y(n) in the input carrier synchronization loop. The output θ of the numerically controlled oscillator... NCO (n) The equalizer output y(n) calculated in step 1 is compensated into the signal r(n) input to the decision maker for decision. The calculation of r(n) is given by formula (7).

[0029]

[0030] Step 3: Decision output is performed on the carrier-compensated signal r(n) obtained in Step 2. Using the known amplitude and phase characteristics of the communication signal, the Euclidean distance between the received signal and the standard symbol in the complex plane coordinate system is compared. The standard symbol with the smallest Euclidean distance to the received signal is selected as the decision output for that received signal.

[0031] The aforementioned decision output: that is, using the standard symbol closest to the received signal under the corresponding rule to represent the recovered received signal, using... This indicates that the signal recovery for the current moment is complete. For the signal arriving at the next moment, the corresponding parameters need to be updated. The specific update steps are steps 4 to 6.

[0032] Step 4: Analyze the decision output signal obtained in Step 3. The residual signal error is extracted, and the residual signal error e' required in step 5 is obtained using a decision-guided algorithm and offset inverse compensation. DD (n);

[0033] The residual signal error is the difference between the received signal after compensation using the decision guidance algorithm (DD) and the corresponding standard symbol at the minimum Euclidean distance. The decision guidance algorithm uses the difference between the equalizer output value and the decision output value as the equalization error, which is then used to update the tap coefficients in the time-domain equalization algorithm. The decision guidance algorithm (DD) theoretically yields the smallest mean square error and has the best time-domain equalization performance, but it is greatly affected by carrier frequency offset, making it difficult to apply in high-frequency communication.

[0034] signal residual error e DD The calculation of (n) is given by formula (8);

[0035]

[0036] This refers to the standard symbol corresponding to the decision output; since carrier synchronization has already compensated for the frequency offset of the received signal, considering that the residual error required for updating the tap coefficients is the error before carrier parameter compensation, this is achieved by adjusting e... DD (n) Perform carrier parameter inverse compensation to eliminate channel estimation interference caused by repeated compensation. The residual signal error e' after inverse compensation DD (n) is from formula (9);

[0037]

[0038] The residual signal error is used in subsequent steps 5 and 6 to calculate the joint equalization error weight and update the equalization tap coefficients.

[0039] Step 5: Utilize the signal residual error e' from step 4 DD (n) Calculate the signal recovery degree weighting parameter k(n), and dynamically adjust the signal residual error e' through k(n). DD (n) and the constant-mode blind equalization error e in step 1 CMA (n) in the equilibrium joint estimation error e q The proportion of (n) in the calculation is increased by increasing e when the signal channel characteristics are difficult to estimate. CMA (n) The weights allow the Constant Mode Blind Equalization (CMA) algorithm to participate more in the joint error update. Leveraging the robustness of CMA, this ensures the continuous and stable operation of the communication system receiver. Once the receiver's channel equalization module stabilizes within the adjustable range of CMA, the weight values ​​k(n) are gradually adjusted to ensure the signal participates in the error e'. DD (n) The proportion of joint equalization error increases, and the accuracy of joint equalization error calculation is improved by utilizing the characteristics of the compensated residual channel features contained in the signal residual error.

[0040] Using the signal residual error e' from step 4 DD (n) Calculate the signal recovery degree weight parameter k(n), which is calculated by formula (10);

[0041]

[0042] Where R th λ is the distance threshold, defined as half the minimum distance between any two different standard symbols; λ∈[0,1) is the step value for weight updates, the magnitude of which relates to the speed of weight updates. - and k + Indicates the maximum cutoff range, and indicates the cutoff range to which [k] is defined. - ,k + The constraint is defined by k(n-1), which represents the weight value from the previous iteration. The residual error e' of the signal is dynamically adjusted using k(n). DD (n) and the constant-mode blind equalization error e in step 1 CMA (n) in the equilibrium joint estimation error e q The proportion of (n) in the calculation, the joint equilibrium error of the weight control equilibrium module refers to the constant mode blind equilibrium error e. CMA (n) Joint signal residual error e' DD (n). Joint equilibrium error e q The calculation of (n) is given by formula (11).

[0043] eq (n)=k(n)e CMA (n)+(1-k(n))e' DD (n) (11)

[0044] When the characteristics of the signal channel are difficult to estimate, e should be increased preferentially. CMA (n) Weights: Leveraging the robustness of the constant modulus blind equalization (CMA) algorithm, the receiver of the communication system operates continuously and stably. Once the system stabilizes within the adjustable range of the CMA algorithm, the weight values ​​k(n) are gradually adjusted to minimize signal interference error e'. DD (n) The proportion of joint equalization error increases, and the accuracy of joint equalization error calculation is improved by utilizing the characteristics of the compensated residual channel features contained in the signal residual error.

[0045] Step 6: Utilize the joint error e obtained in Step 5 q (n) Calculate the tap coefficient update value w(n+1), and feed the calculation result back to the equalization output calculation module in step 1. This will update the tap coefficients in a direction that more accurately estimates the channel characteristics and compensates for inter-symbol interference, thereby improving the accuracy of the recovery of the new symbol arriving at the next moment, improving the quality of the received signal, solving the problem of the decline in decision-guided equalization performance caused by carrier parameter offset, reducing the demodulation loss at the receiver of the communication system, improving the performance of the equalizer, and realizing the recovery of high-frequency communication signals.

[0046] The tap coefficient update value w(n+1) is calculated using formula (12);

[0047] w(n+1)=w(n)-μe q (n)x * (n) (12)

[0048] Where μ is the equalizer step value, the symbol * denotes complex conjugate, and w(n+1) represents the tap coefficient value at the next time step after w(n). By updating the tap coefficients, the equalizer can better estimate and compensate for inter-symbol interference, thereby improving signal quality, reducing demodulation loss at the receiver of the communication system, and enhancing the robustness and accuracy of high-frequency signal demodulation recovery.

[0049] Beneficial effects:

[0050] 1. The present invention discloses a signal recovery method combining weighted channel equalization and carrier synchronization. By feeding back the signal recovery error after carrier synchronization to the equalization module, the inter-symbol interference and carrier parameter offset of the received signal are compensated in a timely manner. Compared with the traditional module cascade demodulation method, the present invention enhances the anti-mixed interference capability of the receiving end of the communication system.

[0051] 2. The present invention discloses a signal recovery method combining weighted channel equalization and carrier synchronization. By calculating the signal recovery degree parameter as the weight of constant mode blind equalization error and signal residual error, the method can dynamically adjust the proportion of constant mode blind equalization error and signal residual error in the equalizer tap coefficients according to the current signal recovery degree. Through the calculation and compensation of the updated tap coefficient values, the accuracy of recovery for new symbols arriving at the next time moment is improved, thereby improving the quality of received signals, solving the problem of performance degradation of decision-guided equalization caused by carrier parameter offset, reducing demodulation loss at the receiver of the communication system, improving equalizer performance, and achieving effective recovery of high-frequency communication signals.

[0052] 3. The present invention discloses a signal recovery method combining weighted channel equalization and carrier synchronization. It uses the signal residual error obtained by the decision-guided algorithm to calculate the weight of the equalization error of different equalization algorithms in the joint error, dynamically adjusts the joint error, and uses the robustness of constant modulus equalization to keep the receiver stable when the channel characteristics of the terahertz high-frequency band are difficult to estimate. It gradually increases the weight of the signal residual error to complete the accurate estimation of complex channel environment. Attached Figure Description

[0053] Figure 1 This is a diagram of the combined architecture of a signal recovery method that combines weighted channel equalization and carrier synchronization.

[0054] Figure 2 This is a constellation diagram of a 16QAM modulated signal that is affected by inter-symbol interference and carrier offset before processing, which is a signal recovery method combining weighted channel equalization and carrier synchronization.

[0055] Figure 3 This is a schematic diagram of the carrier synchronization module frequency and phase detector for a signal recovery method combining weighted channel equalization and carrier synchronization on a 16QAM modulated signal.

[0056] Figure 4 This is a carrier synchronization module loop filter structure for a signal recovery method that combines weighted channel equalization and carrier synchronization.

[0057] Figure 5 The output diagram of the loop filter of the carrier synchronization module is shown in the figure, which is a signal recovery method combining weighted channel equalization and carrier synchronization, to recover the signal when there is a carrier offset signal.

[0058] Figure 6 The constellation diagram, tap coefficient output, and loop filter output are processed by the traditional CMA equalized cascaded carrier synchronization signal recovery method.

[0059] Figure 7 This is a constellation diagram of a 16QAM modulated signal after processing by a signal recovery method combining weighted channel equalization and carrier synchronization.

[0060] Figure 8 This diagram illustrates the error weight transformation when estimating terahertz channel characteristics using a signal recovery method that combines weighted channel equalization and carrier synchronization.

[0061] Figure 9 The figure shows the magnitude of the joint equalization error when estimating the characteristics of a terahertz channel using a signal recovery method that combines weighted channel equalization and carrier synchronization.

[0062] Figure 10 This is an iterative update diagram of the center tap coefficients when estimating terahertz channel characteristics using a signal recovery method that combines weighted channel equalization and carrier synchronization.

[0063] Figure 11 This is a comparison of the bit error rate (BER) curves of a signal recovery method combining weighted channel equalization and carrier synchronization with the traditional constant modulus equalization cascaded carrier synchronization method after recovering a 16QAM signal, and the BER curves of the theoretical BER curves.

[0064] Figure 12 This is a flowchart of a signal recovery method that combines weighted channel equalization and carrier synchronization. Detailed Implementation

[0065] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0066] Example 1:

[0067] like Figure 1 As shown in the figure, the signal recovery method combining weighted channel equalization and carrier synchronization disclosed in this embodiment has the following specific implementation steps:

[0068] Step 1, as follows Figure 2 As shown, the signal x(n) received by the receiver is a 16QAM signal to be recovered, affected by non-ideal channel characteristics and carrier offset. Specific parameters are: modulation scheme is 16QAM, symbol rate is 2.5 Gsps, channel parameters are C = [-0.005 -0.004j 0.009 +0.03j -0.024 -0.104j 0.854 +0.52j -0.218 +0.273j 0.049 -0.074j -0.016 +0.02j], carrier frequency offset is 5 MHz, phase offset is 0.2π, and the number of symbols is 1.2 × 10⁻⁶. 6 The signal-to-noise power ratio E bN0 = 50dB. The receiver channel equalization tap coefficient w(n) is initialized with the center tap set to 1 and the remaining taps set to 0. The receiver performs channel equalization on the received signal to be recovered. Specifically, the received sequence of symbols to be recovered at the current time is shifted into the corresponding equalization tap w(n) and multiplied to calculate the equalizer output y(n). Based on the constant mode blind equalization algorithm CMA, the constant mode equalization error e is calculated using the equalizer output and the decision radius obtained from the 16QAM standard constellation points. CMA (n), utilizing the robustness provided by the constant modulus blind equalization algorithm CMA, reduces the interference of channel characteristics on carrier parameter estimation and compensation;

[0069] The receiving end performs channel equalization processing on the received signal to be recovered. The formula for calculating the equalizer output y(n) is shown in formula (1):

[0070] y(n)=w(n) T x(n) (1)

[0071] Where x(n) represents the symbol column vector of the signal to be recovered after sampling, affected by noise, inter-symbol interference (ISI), and carrier parameter offset; w(n) represents the equalization tap coefficient column vector; n represents the difference between the current time and the initial time; and y(n) represents the output of the equalizer at this n. The received signal sequence to be recovered is sequentially multiplied by the corresponding taps of the equalizer. Each time y(n) is calculated, the signal entering the tap is updated. The constant-mode blind equalization error is calculated synchronously to estimate channel characteristics and obtain ISI compensation information.

[0072] The constant-mode blind equalization error is calculated using the CMA constant-mode blind equalization algorithm, with the decision radius R obtained by comparing the equalizer output y(n) with the corresponding communication signal. CMA The calculation is complete; the constant-mode blind equalization error includes inter-symbol interference compensation information in the signal. The constant-mode blind equalization error e CMA The formula for calculating (n) is formula (2);

[0073] e CMA (n)=y(n)(|y(n| 2 -R CMA (2)

[0074] Where the decision radius R CMA =E(|s(n)|) 4 / E(|s(n)|) 2 s(n) is the set of symbols transmitted at the 16QAM signal transmitter.

[0075] Step 2: Calculate the channel equalization output y(n) and constant-mode blind equalization error e obtained in Step 1. CMA(n) Entering the carrier synchronization stage, the carrier frequency and phase offset of the signal are estimated and compensated in a timely manner to obtain a carrier parameter compensated signal, thereby improving signal quality. The carrier synchronization stage includes the following three sub-steps: frequency and phase discrimination sub-step, loop filtering sub-step, and NCO parameter update and carrier compensation sub-step;

[0076] The carrier synchronization phase specifically includes the following sub-steps;

[0077] Step 2.1, Frequency and Phase Discrimination: By adding a decision window in the diagonal region of the constellation points, the phase-locked loop (PLL) compensates for the frequency and phase offset of the received signal. For example... Figure 3 As shown, the inner four points and outer four points of the 16QAM signal participate in the decision-making process, with normalized decision amplitudes of 6 and 14 respectively, where r is the symbol amplitude before carrier recovery. Frequency and phase discrimination output results. Formula (3) is used.

[0078]

[0079] in, The output of the frequency and phase detector. q(n) is the output of the frequency and phase detector at the previous moment, and q(n) is the phase difference between y(n) and the corresponding standard symbol in the decision window;

[0080] Step 2.2, Loop Filtering: The structure of the loop filter is as follows... Figure 4 As shown, the parameter is set to C1 = 2 -8 C2 = 2 -17 The output result of the frequency and phase detector obtained through step 2.1 As the input to the loop filter, the loop filter determines... The sign of the sign is used to determine the recovery of carrier synchronization from carrier frequency offset and phase shift. The numerical adjustment output amount is used to restore the loop filter output e during the recovery process in Example 1. LF (n) such as Figure 5 As shown. Output result e of the second-order digital loop filter. LF (n) is from formula (4);

[0081]

[0082] Where C1 and C2 are loop parameters, e LF (n-1) represents the output of the loop filter at the previous time step. According to... Figure 5 It can be seen that after the initial loop carrier parameter acquisition, the loop filter can achieve stable tracking of the carrier parameters. Figure 6Compared with the traditional CMA equalization cascaded frequency and phase discrimination carrier synchronization signal recovery method under the same parameters, it is clear that although the carrier synchronization loop filter used in the present invention is slower in acquisition speed, the output amplitude oscillates less and the output is more stable.

[0083] Step 2.3, NCO parameter update and carrier compensation: The output of the loop filter is used as the input of the numerically controlled oscillator (NCO), and then the NCO outputs a phase adjustment value. The phase adjustment amount is as shown in equation (5). Compensation for carrier frequency offset and phase offset;

[0084]

[0085] The phase adjustment amount is a combination of the carrier frequency offset and phase offset that should be compensated to the corresponding signal y(n); the compensated phase adjustment amount θ output by the numerically controlled oscillator. NCO (n) is from formula (6):

[0086]

[0087] Where θ(n) is the phase of the input signal y(n) in the input carrier synchronization loop. The output θ of the numerically controlled oscillator... NCO (n) The equalizer output y(n) calculated in step 1 is compensated into the signal r(n) input to the decision maker for decision. The calculation of r(n) is given by formula (7).

[0088]

[0089] The signal recovered by the method used in this invention is as follows: Figure 7 As shown, in E b When N0 = 50dB, the constellation points of the signal are clearly visible, compared to... Figure 6 The signal obtained by traditional methods is recovered by the present invention with more clustered signal constellation points, resulting in better signal recovery.

[0090] Step 3: Decision output is performed on the carrier-compensated signal r(n) obtained in Step 2. Utilizing the amplitude and phase characteristics of the 16QAM signal, the Euclidean distance between the received signal and the standard symbol in the complex plane coordinate system is compared. The standard symbol with the smallest Euclidean distance to the received signal is selected as the decision output for that received signal. Signals were recovered using different methods under varying noise conditions. The bit error rate (BER) was obtained by comparing the transmitted data with the recovered data. Figure 11 As shown, the bit error rate curve obtained by the present invention is superior to the traditional recovery method in the recovery effect of 16QAM signals in the terahertz band.

[0091] The aforementioned decision output: that is, using the standard symbol closest to the received signal under the corresponding rule to represent the recovered received signal, using... This indicates that the signal recovery for the current moment is complete. For the signal arriving at the next moment, the corresponding parameters need to be updated. The specific update steps are steps 4 to 6.

[0092] Step 4: Analyze the decision output signal obtained in Step 3. The residual signal error is extracted, and the residual signal error e' required in step 5 is obtained using a decision-guided algorithm and offset inverse compensation. DD (n);

[0093] The residual signal error is the difference between the received signal after compensation using the decision guidance algorithm (DD) and the corresponding standard symbol at the minimum Euclidean distance. The decision guidance algorithm uses the difference between the equalizer output value and the decision output value as the equalization error, which is then used to update the tap coefficients in the time-domain equalization algorithm. The decision guidance algorithm (DD) theoretically yields the smallest mean square error and has the best time-domain equalization performance, but it is greatly affected by carrier frequency offset, making it difficult to apply in high-frequency communication.

[0094] signal residual error e DD The calculation of (n) is given by formula (8);

[0095]

[0096] This refers to the standard symbol corresponding to the decision output; since carrier synchronization has already compensated for the frequency offset of the received signal, considering that the residual error required for updating the tap coefficients is the error before carrier parameter compensation, this is achieved by adjusting e... DD (n) Perform carrier parameter inverse compensation to eliminate channel estimation interference caused by repeated compensation. The residual signal error e' after inverse compensation DD (n) is from formula (9);

[0097]

[0098] The residual signal error is used in subsequent steps 5 and 6 to calculate the joint equalization error weight and update the equalization tap coefficients.

[0099] Step 5: Utilize the signal residual error e' from step 4 DD (n) Calculate the signal recovery degree weighting parameter k(n), and dynamically adjust the signal residual error e' through k(n). DD (n) and the constant-mode blind equalization error e in step 1 CMA (n) in the equilibrium joint estimation error e q The proportion of (n) in the calculation is increased by increasing e when the signal channel characteristics are difficult to estimate.CMA (n) The weights allow the Constant Mode Blind Equalization (CMA) algorithm to participate more in the joint error update. Leveraging the robustness of CMA, this ensures the continuous and stable operation of the communication system receiver. Once the receiver's channel equalization module stabilizes within the adjustable range of CMA, the weight values ​​k(n) are gradually adjusted to ensure the signal participates in the error e'. DD (n) The proportion of joint equalization error increases, and the accuracy of joint equalization error calculation is improved by utilizing the characteristics of the compensated residual channel features contained in the signal residual error.

[0100] Using the signal residual error e' from step 4 DD (n) Calculate the signal recovery degree weight parameter k(n), which is calculated by formula (10);

[0101]

[0102] Where R th It is a distance threshold, defined as half the minimum distance between any two different standard symbols. In this embodiment, R th =1; λ∈[0,1), is the step value for weight updates, and its magnitude is related to the speed of weight updates. In this embodiment, λ=0.99. - and k + Indicates the maximum cutoff range, and indicates the cutoff range to which [k] is defined. - ,k + Due to limitations, k in this embodiment... - =0,k + =1. k(n-1) is the weight value of the previous iteration. The iteration curve of the weight value k(n) is as follows: Figure 8 As shown, in the initial stage of equalizer startup, the weight values ​​oscillate up and down because the carrier synchronization has not yet converged, and the residual signal error e' DD The value of (n) fluctuates, causing frequent oscillating updates to the weight values. In this case, the CMA equalization error dominates the update of the tap coefficients. After carrier synchronization gradually converges, e' DD As k(n) gradually decreases until it approaches 0, the weight values ​​gradually stabilize, eventually oscillating with very low amplitude near a minimum value. The residual signal error then dominates the equalization channel estimation. The residual signal error e' is dynamically adjusted by k(n). DD (n) and the constant-mode blind equalization error e in step 1 CMA (n) in the equilibrium joint estimation error e q The proportion of (n) in the calculation, the joint equilibrium error of the weight control equilibrium module refers to the constant mode blind equilibrium error e. CMA (n) Joint signal residual error e' DD(n). Joint equilibrium error e q The calculation of (n) is given by formula (11).

[0103] e q (n)=k(n)e CMA (n)+(1-k(n))e' DD (n) (11)

[0104] Joint equilibrium error e q (n) Update curve as shown Figure 9 As shown, when the signal channel characteristics are difficult to estimate, e should be increased preferentially. CMA (n) Weights: Utilizing the robustness of the constant-mode blind equalization algorithm (CMA), the receiver of the communication system is ensured to operate continuously and stably. At this point, the joint equalization error exhibits severe oscillations. Once the system stabilizes within the adjustable range of the CMA algorithm, the weight values ​​k(n) are gradually adjusted to ensure the signal participates in the error e'. DD (n) The proportion of n in the joint equalization error increases. By utilizing the characteristic of adjusting information based on the compensated residual channel features contained in the signal residual error, the accuracy of the joint equalization error calculation can be improved, such as... Figure 9 After approximately 9000 symbol iterations, the joint equalization error stabilizes to near 0 because the weight values ​​are completely biased towards the signal participation error, indicating that the signal residual error is almost zero, and the estimation and compensation of channel characteristics and carrier parameters have been completed.

[0105] Step 6: Utilize the joint error e obtained in Step 5 q (n) Calculate the updated value of the tap coefficient w(n+1), and the update curve of the real part of the center tap coefficient is as follows. Figure 10 As shown, the initial value of the center tap is 1, and it eventually stabilizes at around 0.55. This is achieved by... Figure 6 A comparison with traditional signal recovery methods shows that the method used in this invention exhibits smoother tap updates and a more stable coefficient update curve. The taps updated using the joint error are updated along with the equalization joint error, and the calculation results are fed back to the equalization output calculation module in step 1. This allows the tap coefficients to be updated in a direction that more accurately estimates channel characteristics and compensates for inter-symbol interference, thereby improving the accuracy of recovery for new symbols arriving at the next time step, enhancing the quality of the received signal, solving the problem of decreased performance in decision-guided equalization caused by carrier parameter offset, reducing demodulation loss at the communication system receiver, improving equalizer performance, and achieving effective recovery of high-frequency communication signals.

[0106] The tap coefficient update value w(n+1) is calculated using formula (12);

[0107] w(n+1)=w(n)-μe q (n)x * (n) (12)

[0108] Where μ is the equalizer step value, the symbol * denotes complex conjugate, and w(n+1) represents the tap coefficient value at the next time step after w(n). By updating the tap coefficients, the equalizer can better estimate and compensate for inter-symbol interference, thereby improving signal quality, reducing demodulation loss at the receiver of the communication system, and achieving reliable and effective communication.

[0109] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for joint signal recovery of weighted channel equalization and carrier synchronization, characterized in that: Comprising the following steps, Step 1, the receiving end carries out channel equalization processing to the received signal to be recovered, specifically, the receiving end moves the received symbol sequence at the current time into the corresponding equalization tap to multiply, and calculates the equalizer output y(n); according to the constant modulus blind equalization algorithm CMA, the constant modulus equalization error e(n) is calculated by using the decision radius obtained from the equalizer output result and the corresponding signal of communication; and the robustness provided by the constant modulus blind equalization algorithm CMA is used to weaken the interference of channel characteristics on carrier parameter estimation and compensation. CMA (n), using the robustness provided by the constant modulus blind equalization algorithm CMA, the interference of channel characteristics on carrier parameter estimation and compensation is weakened. The received signal to be recovered is processed by the receiving end for channel equalization, and the equalizer output y(n) is calculated according to formula (1): y(n) = w(n) T x(n) (1) Wherein, x(n) represents the symbol column vector of the signal to be recovered after sampling, affected by noise, intersymbol interference and carrier parameter offset, w(n) represents the equalization tap coefficient column vector, n represents the difference value of the current time relative to the initial time, y(n) represents the output of the equalizer at this n; the received signal sequence to be recovered is multiplied with the corresponding tap entering the equalizer in sequence, and the signal entering the tap is updated once for each calculation of y(n); the constant modulus blind equalization error is calculated synchronously to estimate the channel characteristics and obtain the intersymbol interference compensation information; Step 2, the channel equalization output y(n) and the constant modulus blind equalization error calculation result e obtained according to step 1 CMA (n), into the carrier synchronization stage, the carrier frequency and phase offset of the signal are estimated and compensated in time, and the signal r(n) after carrier parameter compensation is obtained, and the signal quality is improved; the carrier synchronization stage includes the following three sub-steps: frequency and phase detection sub-step, loop filtering sub-step, NCO parameter updating and carrier compensation sub-step; Step 3, the carrier-compensated signal r(n) obtained in Step 2 is outputted, and the Euclidean distance of the received signal and the standard symbol in the complex plane coordinate system is compared according to the amplitude and phase characteristics of the known communication signal, and the standard symbol with the minimum Euclidean distance of the received signal is taken as the output of the received signal The decision output is represented by the standard symbol closest to the received signal under the corresponding rule, i.e. the recovered received signal is represented by . Step 4, signal output from step 3 is subjected to decision Step 5, signal residual error e' is obtained by using decision directed algorithm and offset decompensation DD (n); The signal residual error is the difference between the received signal compensated by the decision-directed algorithm DD and the corresponding standard symbol at the minimum Euclidean distance; the decision-directed algorithm directly subtracts the equalizer output value from the decision output value as the equalization error, and returns to update the tap coefficient value in the time domain equalization algorithm; Step 5, signal residual error e' is calculated by using the signal of step 4 DD (n) Calculate signal recovery degree weight parameter k(n), dynamically adjust signal residual error e' by k(n) DD (n) and constant modulus blind equalization error e in step 1 CMA (n) The proportion of e in the calculation of joint equalization error e q (n) When the signal channel characteristics are difficult to estimate, increase the weight of e CMA (n) to let the constant modulus blind equalization algorithm CMA participate more in the joint error update, use the constant modulus blind equalization algorithm CMA to ensure the continuous and stable work of the receiving end of the communication system, and gradually adjust the weight value k(n) after the receiving end channel equalization module is stable to the range that can be adjusted by the constant modulus blind equalization algorithm CMA, so that the signal participation error e DD (n) The proportion in the joint equalization error is increased, and the characteristics of the compensation residual channel characteristics adjustment information contained in the signal residual error are used to improve the accuracy of the joint equalization error calculation; The step 5 is implemented by the method of, Step 4 signal residual error amount e DD (n) Calculate signal recovery degree weight parameter k(n), the calculation of signal recovery degree weight parameter k(n) is formula (10); wherein R th is a distance threshold defined as half of the minimum distance between any two different standard symbols; λ ∈ [0, 1) is a step value for weight updating, which size is related to the speed of weight updating; k - and k + represent the maximum truncation range, indicating the limitation of truncation to the range [k - , k + ]; k(n-1) is the weight value of the last time; the dynamic adjustment of k(n) controls the proportion of the signal residual error e' DD (n) and the constant modulus blind equalization error e CMA (n) in step 1 in the calculation of the equalization joint estimation error e q (n), and the joint equalization error of the weight control equalization module refers to the constant modulus blind equalization error e CMA (n) and the signal residual error e' DD (n); the calculation of the joint equalization error e q (n) is formula (11) e q (n) = k(n)e CMA (n) + (1 - k(n))e' DD (n) (11) Prioritize increasing e when signal channel characteristics are difficult to estimate CMA (n) The weight ensures the continuous and stable work of the receiving end of the communication system by using the robustness of the constant modulus blind equalization algorithm CMA. After the system is stable within the range that can be adjusted by the constant modulus blind equalization algorithm CMA, the weight value k(n) is gradually adjusted to make the signal participate in the error e DD (n) The proportion in the joint equalization error is increased, and the accuracy of the joint equalization error calculation is improved by using the characteristics of the compensation residual channel characteristics adjustment information contained in the signal residual error. Step 6, using the joint error e obtained in step 5 q (n) calculating the tap coefficient update value w(n+1), and feeding back the calculation result to the equalization output calculation module in step 1, so that the tap coefficient is updated in the direction of more accurately estimating the channel characteristics and compensating the intersymbol interference, so as to enhance the accuracy of the recovery of the new symbol coming at the next moment, and improve the robustness and accuracy of the demodulation and recovery of the high-frequency signal.

2. The signal recovery method combining weighted channel equalization and carrier synchronization as described in claim 1, characterized in that: The step 1 is implemented by the method of, The constant modulus blind equalization error: using CMA constant modulus blind equalization algorithm, using the equalizer output result y(n) and the decision radius R derived from the communication corresponding signal CMA After the calculation, the constant modulus blind equalization error contains the intersymbol interference compensation information in the signal; the constant modulus blind equalization error e CMA The calculation formula of the constant modulus blind equalization error e(n) is formula (2). e CMA (n) = y(n) (|y(n)| 2 -R CMA ) (2) where the decision radius R CMA = E(|s(n) |) 4 = E(|s(n) |) 2 , s(n) is the set of transmitted symbols.

3. The method of claim 2, wherein the step of performing the weighted channel equalization and carrier synchronization jointly comprises the steps of: The step 2 comprises the following sub-steps, ​ Step 2.1, frequency and phase discrimination: through adding a decision window in the diagonal area of the constellation point, the phase-locked loop realizes the compensation of the frequency deviation and phase deviation of the received signal; frequency and phase discrimination output result is formula (3); wherein is the output of the frequency and phase discriminator, is the output of the frequency and phase discriminator at the previous time instant, q(n) is the phase difference between y(n) and the corresponding standard symbol within the decision window; Step 2.2, Loop Filtering: The output result of the frequency and phase detector calculated in Step 2.

1. As the input to the loop filter, the loop filter determines... The sign of the sign is used to determine the recovery of carrier synchronization from carrier frequency offset and phase shift. Numerical adjustment of output quantity e LF (n), the output result of the second-order digital loop filter e LF (n) is from formula (4); wherein C1, C2 are loop parameters, e LF (n-1) is the output of the loop filter at the previous time instant; Step 2.3, NCO parameter update and carrier compensation: the output quantity of the loop filter is taken as the input of the numerically controlled oscillator NCO, and then the numerically controlled oscillator NCO outputs a phase adjustment quantity The phase adjustment quantity is shown as formula (5) The carrier frequency offset and the phase offset are compensated. The phase adjustment amount is a combination of a carrier frequency offset amount and a phase offset amount that should be compensated to the corresponding signal y(n); the numerically controlled oscillator outputs a compensated phase adjustment amount θ NCO (n) is formula (6): where θ(n) is the phase of the input carrier synchronization loop input signal y(n); θ NCO (n) compensates the equalizer output y(n) calculated in step 1 to the signal r(n) for the input decision device to make a decision, and the calculation of r(n) is formula (7); 。 4. The method of claim 3, wherein the step of performing the weighted channel equalization and carrier synchronization jointly comprises the steps of: The step 4 is implemented by the method of, ​ Signal residual error e DD The calculation of (n) is formula (8); Since the carrier synchronization has compensated the frequency offset of the received signal, the residual error amount required for updating the tap coefficient is the error before the compensation of the carrier parameter. The residual error e DD (n) is compensated by the carrier parameter, and the channel estimation interference caused by the repeated compensation is eliminated. The residual error e DD (n) of the formula (9) is compensated. The signal residual error is used for the joint equalization error weight calculation and equalization tap coefficient update in the subsequent steps 5 and 6.

5. The signal recovery method combining weighted channel equalization and carrier synchronization as described in claim 4, characterized in that: The step 6 is implemented by the method of, The calculation of the updated tap coefficient value w(n+1) is formula (12); w(n + 1) = w(n) - μe q (n)x * (n) (12) Wherein, μ is the equalizer step value, the symbol * represents the complex conjugate, and w(n+1) represents the tap coefficient value at the next time after w(n); through the update of the tap coefficient, the equalizer can better estimate and compensate the intersymbol interference, so as to improve the signal quality, reduce the demodulation loss of the receiving end of the communication system, and improve the robustness and accuracy of the demodulation and recovery of the high frequency signal.

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