A joint time domain equalization method under CPM modulation

Abstract

The application provides a joint time domain equalization method under CPM modulation, which comprises the following steps: receiving an initial signal, sampling, obtaining first data in local storage and processing, obtaining a first scattered pilot signal, respectively performing first processing and second processing on the first scattered pilot signal to obtain a first processed signal and a second processed signal, performing third processing on the first processed signal to obtain a third processed signal, performing fourth processing on the second processed signal to obtain a fourth processed signal, obtaining a channel estimation frequency response, performing signal-to-noise ratio estimation on the first processed signal to obtain a signal-to-noise ratio estimation value, obtaining a frequency domain equalization coefficient according to the channel estimation frequency response and the signal-to-noise ratio estimation value, obtaining second data and a tail scattered pilot, processing to obtain a fifth processed signal, and obtaining a time domain signal after single carrier equalization; by the method, the problem that a traditional frequency domain single carrier equalization method cannot correctly estimate channel parameters due to insufficient detection signal-to-noise ratio in a low signal-to-noise ratio condition can be solved.

Description

Technical Field

[0001] This application relates to the field of single-carrier equalization technology, specifically to a joint time-domain equalization method under CPM modulation. Background Technology

[0002] Single-carrier equalization is an effective method to combat frequency-selective fading. When a signal is transmitted from the transmitter to the receiver, under low signal-to-noise ratio conditions, especially when the signal is processed by CPM (Continuous Phase Modulation) modulation before transmission, noise in the transmission environment can cause interference during transmission, resulting in severe inter-symbol interference. This can prevent single-carrier equalization from working properly, causing the signal received by the receiver to be inconsistent with the signal transmitted by the transmitter. Summary of the Invention

[0003] The purpose of this application is to address the above problems by providing a joint time-domain equalization method under CPM modulation, including:

[0004] Receive an initial signal, which is obtained after CPM modulation processing. The initial signal includes bit synchronization information, which is used to characterize the start and end markers of data bits in the initial signal.

[0005] The initial signal is sampled according to the bit synchronization information at each first preset time interval;

[0006] According to the bit synchronization information, the first data stored locally is obtained. The first data includes an initial head dispersion pilot signal. The initial head dispersion pilot signal is subjected to the CPM modulation processing to obtain the first head dispersion pilot signal.

[0007] The first head dispersed pilot signal is processed to obtain a first processed signal, so as to realize the time-domain cross-correlation of the first head dispersed pilot signal;

[0008] The first-head dispersed pilot signal is subjected to a second processing to obtain a second processed signal, so as to realize the time-domain autocorrelation of the first-head dispersed pilot signal;

[0009] Perform a Fast Fourier Transform on the first processed signal to obtain the third processed signal, and perform a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal.

[0010] Using the third processed signal as the numerator and the fourth processed signal as the denominator, the channel estimated frequency response is calculated.

[0011] The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain an estimated SNR value.

[0012] The frequency domain equalization coefficients are calculated based on the estimated frequency response and signal-to-noise ratio values ​​of the channel.

[0013] The initial signal also includes second data and tail-dispersed pilot. A fast Fourier transform is performed on the second data and the tail-dispersed pilot to obtain the fifth processed signal.

[0014] Calculate the product of the fifth processed signal and the frequency domain equalization coefficients, and perform an inverse Fast Fourier Transform to obtain the sixth processed signal. Extract the first N segments of its corresponding sequence length. d N symbols are used to obtain the time-domain signal after single-carrier equalization, where N d This represents the total number of symbols in the second data.

[0015] According to the technical solution provided in the embodiments of this application, the method further includes:

[0016] Obtain the receiver filter coefficients;

[0017] The first processing of the first dispersed pilot signal to obtain the first processed signal includes:

[0018] The filter coefficients are convolved with the first head-dispersed pilot signal to obtain a first signal; the first signal is then subjected to a fast Fourier transform to obtain a second signal.

[0019] The initial signal also includes a head dispersion pilot signal, and the head dispersion pilot signal is obtained;

[0020] A third signal is obtained by performing a Fast Fourier Transform on the head-dispersed pilot signal;

[0021] The second signal and the third signal are multiplied by their conjugate to obtain the fourth signal;

[0022] The fourth signal is subjected to a fast Fourier inverse transform to obtain the first processed signal.

[0023] According to the technical solution provided in the embodiments of this application, the method further includes:

[0024] Obtain the second signal and the fourth signal;

[0025] The second processing of the first dispersed pilot signal to obtain a second processed signal includes:

[0026] The product of the second signal and the fourth signal is used to obtain the fifth signal;

[0027] The fifth signal is subjected to a fast Fourier transform to obtain the second processed signal.

[0028] According to the technical solution provided in the embodiments of this application, the method further includes:

[0029] Obtain the second sequence length of the first processed signal;

[0030] The process of performing a Fast Fourier Transform on the first processed signal to obtain the third processed signal includes:

[0031] When it is determined that the length of the second sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the first processed signal to obtain the third processed signal;

[0032] If the length of the second sequence does not meet the Fast Fourier Transform rule, the length of the second sequence is padded and a Fast Fourier Transform is performed to obtain the third processed signal.

[0033] According to the technical solution provided in the embodiments of this application, the method further includes:

[0034] Obtain the third sequence length of the second processed signal;

[0035] The process of performing a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal includes:

[0036] When it is determined that the length of the third sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the second processed signal to obtain the fourth processed signal;

[0037] If the length of the third sequence does not meet the Fast Fourier Transform rule, the length of the third sequence is padded and a Fast Fourier Transform is performed to obtain the fourth processed signal.

[0038] According to the technical solution provided in the embodiments of this application, the method further includes:

[0039] The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain the SNR curve.

[0040] The step of estimating the signal-to-noise ratio (SNR) of the first processed signal to obtain an estimated SNR value includes:

[0041] Obtain the peak value of the signal-to-noise ratio curve;

[0042] Calculate the data variance of the data other than the peak value in the signal-to-noise ratio curve;

[0043] The square of the peak value is calculated, and the signal-to-noise ratio estimate is obtained by using the square of the peak value as the numerator and the data variance as the denominator.

[0044] According to the technical solution provided in the embodiments of this application, the method further includes:

[0045] The step of calculating the frequency domain equalization coefficients based on the channel estimated frequency response and signal-to-noise ratio estimated values ​​specifically includes:

[0046] The first value is obtained by performing a conjugate multiplication on the estimated channel frequency response.

[0047] The second value is obtained by multiplying the first value by the estimated channel frequency response.

[0048] The third value is obtained by summing the second value with the estimated signal-to-noise ratio value.

[0049] The frequency domain equalization coefficient is obtained by multiplying the first value as the numerator and the third value as the denominator.

[0050] According to the technical solution provided in the embodiments of this application, the fourth sequence length of the second data is obtained, and the fifth sequence length of the tail-dispersed pilot is obtained;

[0051] The length of the sixth sequence is obtained by summing the lengths of the fourth and fifth sequences.

[0052] The step of performing a Fast Fourier Transform on the second data and the tail-dispersed pilot to obtain the fifth processed signal includes:

[0053] When it is determined that the length of the sixth sequence satisfies the Fast Fourier Transform rule, Fast Fourier Transform is performed on the second data and the tail dispersion simultaneously to obtain the fifth processed signal;

[0054] If the length of the sixth sequence does not meet the Fast Fourier Transform rule, the length of the sixth sequence is padded and a Fast Fourier Transform is performed to obtain the fifth processed signal.

[0055] According to the technical solution provided in the embodiments of this application, the method further includes:

[0056] Obtain the first sequence length of the first signal;

[0057] The step of performing a Fast Fourier Transform on the first signal to obtain the second signal includes:

[0058] When the length of the first sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the first signal to obtain the second signal;

[0059] If the length of the first sequence does not meet the Fast Fourier Transform rule, the length of the first sequence is padded and a Fast Fourier Transform is performed to obtain the second signal.

[0060] According to the technical solution provided in the embodiments of this application, the sequence length corresponding to the head-dispersive pilot is obtained;

[0061] The step of performing a Fast Fourier Transform on the head-dispersed pilot signal to obtain a third signal includes:

[0062] When it is determined that the sequence length of the head-dispersed pilot signal satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the head-dispersed pilot signal to obtain the third signal;

[0063] If the sequence length of the head-dispersed pilot signal does not meet the Fast Fourier Transform rule, the sequence length of the head-dispersed pilot signal is padded and a Fast Fourier Transform is performed to obtain the third signal.

[0064] Compared with the prior art, the beneficial effects of this application are as follows:

[0065] This application receives and samples the initial signal after CPM modulation processing, performs CPM modulation processing on the initial head-dispersed pilot signal in the locally stored first data to obtain a first head-dispersed pilot signal, performs a first processing on the first head-dispersed pilot signal to achieve time-domain cross-correlation, performs a second processing on the first head-dispersed pilot signal to achieve time-domain autocorrelation, performs a fast Fourier transform on the first processed signal to obtain a third processed signal, performs a fast Fourier transform on the second processed signal to obtain a fourth processed signal, calculates the channel estimated frequency response using the third processed signal as the numerator and the fourth processed signal as the denominator, performs signal-to-noise ratio estimation on the first processed signal to obtain a signal-to-noise ratio estimate, obtains a frequency domain equalization coefficient based on the channel estimated frequency response and the signal-to-noise ratio estimate, performs a fast Fourier transform on the second data in the initial signal and the tail-dispersed pilot to obtain a fifth processed signal, and finally obtains the time-domain signal after single-carrier equalization based on the fifth processed signal and the frequency domain equalization coefficient.

[0066] During use, the initial signal after CPM modulation is first received. At first preset time intervals, the initial signal is sampled based on the synchronization information in the initial signal to obtain locally stored first data. The initial head-dispersed pilot signal in the first data is then subjected to the same CPM modulation process to obtain the first head-dispersed pilot signal. A first processing step is then performed to obtain a first processed signal, which enables time-domain cross-correlation of the first head-dispersed pilot signal. A second processing step is then performed on the first head-dispersed pilot signal to obtain a second processed signal, which enables time-domain autocorrelation of the first head-dispersed pilot signal. The first processing step... The first processed signal is subjected to a Fast Fourier Transform (FFT) to obtain a third processed signal. The second processed signal is subjected to a FFT to obtain a fourth processed signal. Based on the fourth and third processed signals, the channel estimated frequency response is obtained. The first processed signal is then subjected to a signal-to-noise ratio (SNR) estimate to obtain an SNR estimate. Based on the SNR estimate and the channel estimated frequency response, the frequency domain equalization coefficients are obtained. The second data and the tail-dispersion pilot in the initial signal are subjected to a FFT. Based on the obtained fifth processed signal and the frequency domain equalization coefficients, the time domain signal after single-carrier equalization is obtained. The obtained signal is consistent with the signal transmitted by the transmitting end.

[0067] The method described in this application solves the problem that traditional frequency-domain single-carrier equalization methods cannot accurately estimate channel parameters due to insufficient detection signal-to-noise ratio (SNR) under low SNR conditions. This application improves the detection SNR effectively through correlation gain by performing time-domain correlation on the received signal, including time-domain positive correlation and time-domain autocorrelation, thus ensuring the accuracy of frequency-domain single-carrier equalization under low SNR conditions. It also solves the problem that the channel parameter estimation effect deteriorates in multipath environments due to inter-symbol interference inherent in CPM modulation, thus ensuring the accuracy of CPM modulation frequency-domain single-carrier equalization in multipath environments. Attached Figure Description

[0068] Figure 1 A flowchart of a joint time-domain equalization method under CPM modulation provided in an embodiment of this application;

[0069] Figure 2 This is a signal structure diagram provided for an embodiment of this application;

[0070] Figure 3 The constellation diagram before equalization in a multipath channel during GMSK modulation using the method described in this application is provided in the embodiments of this application.

[0071] Figure 4 The constellation diagram after equalization in a multipath channel during GMSK modulation using the method described in this application is provided in the embodiments of this application.

[0072] Figure 5The simulation comparison results of bit error rate before and after equalization in multipath channel during GMSK modulation provided in the embodiments of this application are as follows. Detailed Implementation

[0073] To enable those skilled in the art to better understand the technical solution of this application, the application will be described in detail below with reference to the accompanying drawings. The description in this section is only exemplary and explanatory, and should not be used to limit the scope of protection of this application.

[0074] CPM, or Continuous Phase Modulation, is a phase modulation technique characterized by continuous phase and excellent spectral characteristics. Compared to PSK modulation (a digital modulation technique that uses carrier phase to represent the input signal), it has higher bandwidth utilization.

[0075] Single-carrier equalization is an effective method to combat frequency-selective fading. When a signal is transmitted from the transmitter to the receiver, under low signal-to-noise ratio conditions, especially when the signal is processed by CPM (Continuous Phase Modulation) modulation before transmission, noise in the transmission environment can cause interference during transmission, resulting in severe inter-symbol interference. This can prevent single-carrier equalization from working properly, causing the signal received by the receiver to be inconsistent with the signal transmitted by the transmitter.

[0076] This application addresses the above problems by providing a joint time-domain equalization method under CPM modulation. The channel estimation is performed in both the time and frequency domains, thereby ensuring that the final single-carrier equalized time-domain signal is consistent with the signal transmitted from the transmitter.

[0077] The joint time-domain equalization method under CPM modulation provided in this application is as follows: Figure 1 As shown, it includes:

[0078] S1. Receive an initial signal, which is obtained after CPM modulation processing. The initial signal includes bit synchronization information, which is used to characterize the start and end markers of data bits in the initial signal.

[0079] S2. The initial signal is sampled according to the bit synchronization information at each first preset time interval;

[0080] S3. Based on the bit synchronization information, obtain the first data stored locally, the first data including the initial head dispersion pilot signal, and perform the CPM modulation processing on the initial head dispersion pilot signal to obtain the first head dispersion pilot signal;

[0081] S4. Perform a first processing on the first head dispersed pilot signal to obtain a first processed signal, so as to realize the time-domain cross-correlation of the first head dispersed pilot signal;

[0082] S5. Perform a second processing on the first head dispersed pilot signal to obtain a second processed signal, so as to realize the time-domain autocorrelation of the first head dispersed pilot signal;

[0083] S6. Perform a Fast Fourier Transform on the first processed signal to obtain the third processed signal, and perform a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal.

[0084] S7. Using the third processed signal as the numerator and the fourth processed signal as the denominator, calculate the channel estimated frequency response;

[0085] S8. Perform signal-to-noise ratio estimation on the first processed signal to obtain a signal-to-noise ratio estimate;

[0086] S9. Calculate the frequency domain equalization coefficient based on the estimated channel frequency response and signal-to-noise ratio.

[0087] S10. The initial signal also includes second data and tail-dispersed pilot. A fast Fourier transform is performed on the second data and the tail-dispersed pilot to obtain the fifth processed signal.

[0088] S11. Calculate the product of the fifth processed signal and the frequency domain equalization coefficients, and perform inverse Fast Fourier Transform to obtain the sixth processed signal. Extract the first N segments of its corresponding sequence length. d N symbols are used to obtain the time-domain signal after single-carrier equalization, where N d This represents the total number of symbols in the second data.

[0089] Specifically, in this embodiment, an initial signal is first received from the transmitter. This initial signal is obtained after CPM modulation processing. The initial signal includes bit synchronization information, which is used to characterize the start and end of data bits in the initial signal. The initial signal also includes a head scatter pilot, a second data scatter pilot, and a tail scatter pilot. Every first preset time interval, the second data and the tail scatter pilot in the initial signal are sampled according to the bit synchronization information. The expression of the sampled signal is as follows:

[0090] r(n) = [C(n)] c1 t s -τ0) D(n d t s C(n) c2 t s -τ0)],n=0,1,...,N-1

[0091] In the formula: r(n) represents the sampled signal;

[0092] C(n c1 t s ) represents n c1 t s Head-dispersion pilot at sampling time, n c1 =0,1,......,N c -1, N c Represents the length of the tail-dispersion pilot;

[0093] t s The time-domain sampling interval is defined as the duration of a symbol, i.e., the first preset duration.

[0094] τ0 represents the initial phase of the head-spread pilot;

[0095] D(n d t s ) represents n d t s The third data at the sampling time, which is the data other than the head scatter pilot and the tail scatter pilot, i.e., the useful data, n d =N c N c +1,...,N c +N d -1, N d Represents the length of the third data;

[0096] n represents the sampling point;

[0097] C(n c2 t s ) represents n c2 t s Tail-dispersed pilot at sampling time, n c2 =Nc+Nd,Nc+Nd-1,....,N-1.

[0098] According to the bit synchronization information, the first data stored locally is obtained. The first data also stores bit synchronization information. According to the bit synchronization information in the initial signal, the bit synchronization information in the first data is obtained so that the sampled signal is consistent with the locally stored signal. The first data includes an initial head dispersion pilot signal. The initial head dispersion pilot signal is subjected to the same CPM modulation processing as the initial signal to obtain the first head dispersion pilot signal.

[0099] The expression for the first head-dispersed pilot signal is:

[0100]

[0101]

[0102] In the formula: s mod This represents the first dispersed pilot signal;

[0103] exp(·) represents the exponentiation operation;

[0104] E represents the energy of each symbol in the first-head dispersed pilot signal;

[0105] This is the initial phase;

[0106] t s The time-domain sampling interval is defined as the duration of a symbol, i.e., the first preset duration.

[0107] a i This represents the transmitted symbol sequence in base M, with values ​​ranging from {±1,±3,...,±M-1}.

[0108] h is the modulation index;

[0109] j represents a complex number;

[0110] Indicates the phase of the modulated signal;

[0111] i represents the phase accumulation sampling point of the modulated signal;

[0112] t represents time, for example, t is 0~1s, ts is 1ms;

[0113] n represents the sampling point;

[0114] q(t) is the integral of the Gaussian minimum phase shift keying pulse g(t), that is:

[0115]

[0116] g(t) = Q[2πB(tt)] s / 2) / (ln2) 0.5 ]-Q[2πB(t+t s / 2) / (ln2) 0.5 ]

[0117]

[0118] Where B represents the channel bandwidth.

[0119] Furthermore, the method also includes:

[0120] Obtain the receiver filter coefficients;

[0121] The first processing of the first dispersed pilot signal to obtain the first processed signal includes:

[0122] The filter coefficients are convolved with the first head-dispersed pilot signal to obtain a first signal. The first signal is then subjected to a fast Fourier transform to obtain a second signal.

[0123] The initial signal also includes a head-dispersive pilot signal. The head-dispersive pilot signal is acquired, and a fast Fourier transform is performed on the head-dispersive pilot signal to obtain a third signal.

[0124] The second signal and the third signal are multiplied by their conjugate to obtain the fourth signal;

[0125] The fourth signal is subjected to a fast Fourier inverse transform to obtain the first processed signal.

[0126] Specifically, in this embodiment, the coefficients of the filter in the receiving end are obtained, and the coefficients of the filter are convolved with the first head-dispersed pilot signal to obtain the first signal. For the first signal To obtain the second signal, a Fast Fourier Transform (FFT) is performed on the first signal. When performing the FFT on the first signal, the length of the first sequence corresponding to the first signal needs to be obtained. If the length of the first sequence satisfies the FFT rules, the first signal is subjected to the FFT to obtain the second signal. If the length of the first sequence does not satisfy the FFT rules, the length of the first sequence is padded, and the padded first signal is subjected to the FFT to obtain the second signal. Then, a Fast Fourier Transform (FFT) is performed on the head-scattered pilot in the initial signal to obtain the third signal. When performing the FFT on the head-scattered pilot, the length of the sequence corresponding to the head-scattered pilot needs to be obtained. If the length of the sequence corresponding to the head-scattered pilot satisfies the FFT rules, the head-scattered pilot is subjected to the FFT to obtain the third signal. If the length of the sequence corresponding to the head-scattered pilot does not satisfy the FFT rules, the length of the sequence corresponding to the head-scattered pilot is padded, and the padded head-scattered pilot is subjected to the FFT to obtain the third signal.

[0127] The second signal and the third signal are multiplied by their conjugates to obtain a fourth signal. Then, the fourth signal is processed by an inverse Fast Fourier Transform (IFFT) to obtain a first processed signal. This process achieves time-domain cross-correlation of the first head-dispersed pilot signal, thereby improving the signal-to-weight ratio of the first head-dispersed pilot. The specific expression for the above processing is as follows:

[0128]

[0129] In the formula: FFT(·) represents performing FFT processing on the time-domain signal. The length of the FFT processing is an integer power of 2 greater than Nc (for example, if the length of the first signal is 10, then the processing length of the FFT is 2). 4 (i.e., 16);

[0130] IFFT(·) represents performing IFFT processing on a frequency domain signal;

[0131] (·)* indicates that the signal is conjugate;

[0132] Indicates the first signal;

[0133] C(n c1 t s ) represents n c1 t s Head-dispersion pilot at sampling time, n c1 =0,1,......,N c -1, N c Represents the length of the tail-dispersion pilot;

[0134] r sx This represents the time-domain cross-correlation result between the signal and the dispersed pilot of the received signal;

[0135] Furthermore, the method also includes:

[0136] Obtain the second signal and the fourth signal;

[0137] The second processing of the first dispersed pilot signal to obtain a second processed signal includes:

[0138] The product of the second signal and the fourth signal is used to obtain the fifth signal;

[0139] The fifth signal is subjected to a fast Fourier transform to obtain the second processed signal.

[0140] Specifically, in this embodiment, the second signal and the fourth signal are obtained, the second signal and the fourth signal are multiplied to obtain the fifth signal, and the fifth signal is then processed by inverse fast Fourier transform (IFFT) to obtain the second processed signal, thereby realizing the time-domain autocorrelation of the first head dispersed pilot signal;

[0141] The specific expression for the above processing is:

[0142]

[0143] r xx This indicates the autocorrelation result.

[0144] Furthermore, the method also includes:

[0145] Obtain the second sequence length of the first processed signal;

[0146] The process of performing a Fast Fourier Transform on the first processed signal to obtain the third processed signal includes:

[0147] When it is determined that the length of the second sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the first processed signal to obtain the third processed signal;

[0148] If the length of the second sequence does not meet the Fast Fourier Transform rule, the length of the second sequence is padded and a Fast Fourier Transform is performed to obtain the third processed signal.

[0149] Specifically, in this embodiment, the second sequence length of the first processed signal is obtained, and when it is determined that the second sequence length satisfies the Fast Fourier Transform rule, the first processed signal is directly subjected to Fast Fourier Transform to obtain the third processed signal;

[0150] The system determines whether the length of the second sequence satisfies the Fast Fourier Transform (FFT) rule, which is an integer power of 2 greater than the length of the second sequence. If it does not satisfy the rule, the length of the second sequence in the first processed signal needs to be padded. For example, if the length of the second column is 10, then the processing length of the FFT is 2. 4 That is, 16, which need to be padded with 6 zeros on the basis of the second sequence length to meet the FFT processing rules. After padding, the first processed signal after padding is subjected to fast Fourier transform to obtain the third processed signal.

[0151] Specifically, it can be represented as follows:

[0152] R sx =FFT([r sx z i1 ])

[0153] In the formula, z i1 Indicates r sx The zero-padding sequence is the number of zeros padded to the length of the second sequence.

[0154] Furthermore, the method also includes:

[0155] Obtain the third sequence length of the second processed signal;

[0156] The process of performing a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal includes:

[0157] When it is determined that the length of the third sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the second processed signal to obtain the fourth processed signal;

[0158] If the length of the third sequence does not meet the Fast Fourier Transform rule, the length of the third sequence is padded and a Fast Fourier Transform is performed to obtain the fourth processed signal.

[0159] The length of the third sequence of the second processed signal is obtained, and it is determined whether the length of the third sequence satisfies the Fast Fourier Transform rule. The Fast Fourier Transform rule is an integer power of 2 greater than the length of the third sequence. If the length of the third sequence satisfies the Fast Fourier Transform rule, the second processed signal is directly subjected to Fast Fourier Transform to obtain the fourth processed signal.

[0160] If the conditions are not met, the length of the third sequence of the second processed signal needs to be padded. For example, if the length of the third sequence is 10, then the processing length of the FFT is 2. 4 That is, 16, which need to be padded with 6 zeros on the basis of the length of the third sequence to meet the FFT processing rules. After padding, the second processed signal after padding is subjected to fast Fourier transform to obtain the fourth processed signal.

[0161] Specifically, it can be represented as follows:

[0162] R xx =FFT([r xx z i2 ])

[0163] In the formula, z i2 Indicates r xx The zero-padding sequence is the number of zeros padded to the length of the third sequence.

[0164] Furthermore, the method also includes:

[0165] The specific steps for obtaining the channel estimated frequency response based on the third processed signal and the fourth processed signal include:

[0166] The estimated channel frequency response is obtained by multiplying the third processed signal as the numerator and the fourth processed signal as the denominator.

[0167] Specifically, in this embodiment, the channel estimated frequency response Λ is obtained by multiplying the third processed signal as the numerator and the fourth processed signal as the denominator, as shown in the following formula:

[0168] Λ=R sx / R xx .

[0169] The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain an estimated SNR value.

[0170] Furthermore, the method also includes:

[0171] The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain the SNR curve.

[0172] The step of estimating the signal-to-noise ratio (SNR) of the first processed signal to obtain an estimated SNR value includes:

[0173] Obtain the peak value of the signal-to-noise ratio curve;

[0174] Calculate the data variance of the data other than the peak value in the signal-to-noise ratio curve;

[0175] The square of the peak value is calculated, and the signal-to-noise ratio estimate is obtained by using the square of the peak value as the numerator and the data variance as the denominator.

[0176] Specifically, in this embodiment, the signal-to-noise ratio (SNR) is estimated on the first processed signal to obtain an SNR curve. The peak value of the SNR curve is then obtained and recorded as A. sx At the same time, it is also necessary to calculate the signal-to-noise ratio curve, except for the peak value A. sx The variance of all other data except for σ is recorded as σ. sx The square of the peak value is calculated, and the signal-to-noise ratio (SNR) estimate is obtained by using the square of the peak value as the numerator and the data variance as the denominator. The expression for the SNR estimate is as follows:

[0177]

[0178] Furthermore, the step of calculating the frequency domain equalization coefficients based on the channel estimated frequency response and signal-to-noise ratio estimated values ​​specifically includes:

[0179] The first value is obtained by performing a conjugate multiplication on the estimated channel frequency response.

[0180] The second value is obtained by multiplying the first value by the estimated channel frequency response.

[0181] The third value is obtained by summing the second value with the estimated signal-to-noise ratio value.

[0182] The frequency domain equalization coefficient is obtained by multiplying the first value as the numerator and the third value as the denominator.

[0183] Specifically, in this embodiment, the channel estimated frequency response is first subjected to conjugate multiplication to obtain a first value. The product of the first value and the channel estimated frequency response is calculated to obtain a second value. The sum of the second value and the signal-to-noise ratio estimate is calculated to obtain a third value. The frequency domain equalization coefficient H is obtained by dividing the first value as the numerator and the third value as the denominator.

[0184] Based on the estimated channel response Λ and the estimated signal-to-noise ratio SNR, the specific expression for calculating the frequency domain equalization coefficient H is as follows:

[0185]

[0186] Λ * This represents the conjugate multiplication of the channel estimated frequency response Λ.

[0187] Furthermore, the method also includes:

[0188] Obtain the fourth sequence length of the second data, and obtain the fifth sequence length of the tail-dispersed pilot;

[0189] The length of the sixth sequence is obtained by summing the lengths of the fourth and fifth sequences.

[0190] The step of performing a Fast Fourier Transform on the second data and the tail-dispersed pilot to obtain the fifth processed signal includes:

[0191] When it is determined that the length of the sixth sequence satisfies the Fast Fourier Transform rule, Fast Fourier Transform is performed on the second data and the tail dispersion simultaneously to obtain the fifth processed signal;

[0192] If the length of the sixth sequence does not meet the Fast Fourier Transform rule, the length of the sixth sequence is padded and a Fast Fourier Transform is performed to obtain the fifth processed signal.

[0193] Specifically, in this embodiment, the fourth sequence length of the second data is obtained, the fifth sequence length of the tail-dispersed pilot is obtained, the fourth sequence length and the fifth sequence length are summed to obtain the sixth sequence length, and if the sixth sequence length satisfies the Fourier transform rule, then the second data after being combined and the tail-dispersed pilot are subjected to a fast Fourier transform to obtain the fifth processed signal;

[0194] If the length of the sixth sequence does not satisfy the Fast Fourier Transform (FFT) rule, the length of the sixth sequence is padded to satisfy the FFT rule, and a FFT is performed on the padded second data and the tail-dispersed pilot to obtain the fifth processed signal; the specific formula is as follows:

[0195] R = FFT([rz) k ])

[0196] In the formula: r represents the combined second data and the tail-dispersion pilot in the sampled signal r(n);

[0197] z k This represents the number of zeros used to fill the length of the sixth sequence.

[0198] Furthermore, the step of obtaining the time-domain signal after single-carrier equalization based on the fifth processed signal and the frequency domain equalization coefficient specifically includes:

[0199] The product of the fifth processed signal and the frequency domain equalization coefficient is calculated, and then a fast Fourier transform is performed to obtain the sixth processed signal.

[0200] Obtain the length of the sixth sequence of the sixth processed signal, and truncate the first N. d N symbols are used to obtain the time-domain signal after single-carrier equalization, where N d This represents the total number of symbols in the second data.

[0201] The fifth processed signal is multiplied by the frequency domain equalization coefficient, and then subjected to an inverse Fast Fourier Transform to obtain the sixth processed signal. The length of the sixth sequence in the sixth processed signal is obtained, and the first N bits are truncated. d The symbols are used to obtain the time-domain signal after single-carrier equalization.

[0202] The specific expression is as follows:

[0203] r h =IFFT(R×H)

[0204]

[0205] In the formula: r h The result is obtained by performing an inverse Fast Fourier transform on the product of the fifth processed signal and the frequency domain equalization coefficients.

[0206] n h This represents the number of bits in the symbol in the second data.

[0207] like Figure 3 and Figure 4 As shown: Figure 3 This shows the constellation diagram before equalization in a multipath channel during GMSK modulation, as described in this application.

[0208] Figure 4 The constellation diagram after equalization in a multipath channel under the method described in this application is shown by comparison. It can be seen that the constellation diagram before equalization is scattered, while the constellation diagram after equalization is corrected to the correct position.

[0209] Figure 5 The simulation results show the bit error rate before and after equalization in a multipath channel when the method described in this application is used for GMSK modulation. The comparison shows that the bit error rate is extremely high before equalization, and the bit error rate is significantly reduced after equalization. The demodulation threshold is reduced by about 10dB compared with the theoretical bit error rate.

[0210] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A joint time-domain equalization method under CPM modulation, characterized in that, include: Receive an initial signal, which is obtained after CPM modulation processing. The initial signal includes bit synchronization information, which is used to characterize the start and end markers of data bits in the initial signal. The initial signal is sampled according to the bit synchronization information at each first preset time interval; According to the bit synchronization information, the first data stored locally is obtained. The first data includes an initial head dispersion pilot signal. The initial head dispersion pilot signal is subjected to the CPM modulation processing to obtain the first head dispersion pilot signal. The first dispersed pilot signal is processed to obtain a first processed signal, so as to realize the time-domain cross-correlation of the first dispersed pilot signal; The first-head dispersed pilot signal is subjected to a second processing to obtain a second processed signal, so as to realize the time-domain autocorrelation of the first-head dispersed pilot signal; Perform a Fast Fourier Transform on the first processed signal to obtain the third processed signal, and perform a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal. Using the third processed signal as the numerator and the fourth processed signal as the denominator, the channel estimated frequency response is calculated. The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain an estimated SNR value. The frequency domain equalization coefficients are calculated based on the estimated frequency response and signal-to-noise ratio values ​​of the channel. The initial signal also includes second data and tail-dispersed pilot. A fast Fourier transform is performed on the second data and the tail-dispersed pilot to obtain the fifth processed signal. Calculate the product of the fifth processed signal and the frequency domain equalization coefficients, and perform an inverse Fast Fourier Transform to obtain the sixth processed signal. Extract the first N segments of its corresponding sequence length. d N symbols are used to obtain the time-domain signal after single-carrier equalization, where N d This represents the total number of symbols in the second data.

2. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The method further includes: Obtain the receiver filter coefficients; The first processing of the first dispersed pilot signal to obtain the first processed signal includes: The filter coefficients are convolved with the first head-dispersed pilot signal to obtain a first signal; the first signal is then subjected to a fast Fourier transform to obtain a second signal. The initial signal also includes a head dispersion pilot signal, and the head dispersion pilot signal is obtained; A third signal is obtained by performing a Fast Fourier Transform on the head-dispersed pilot signal; The second signal and the third signal are multiplied by their conjugate to obtain the fourth signal; The fourth signal is subjected to a fast Fourier inverse transform to obtain the first processed signal.

3. The joint time-domain equalization method under CPM modulation according to claim 2, characterized in that, The method further includes: Obtain the second signal and the fourth signal; The second processing of the first dispersed pilot signal to obtain a second processed signal includes: The product of the second signal and the fourth signal is used to obtain the fifth signal; The fifth signal is subjected to a fast Fourier transform to obtain the second processed signal.

4. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The method further includes: Obtain the second sequence length of the first processed signal; The process of performing a Fast Fourier Transform on the first processed signal to obtain the third processed signal includes: When it is determined that the length of the second sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the first processed signal to obtain the third processed signal; If the length of the second sequence does not meet the Fast Fourier Transform rule, the length of the second sequence is padded and a Fast Fourier Transform is performed to obtain the third processed signal.

5. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The method further includes: Obtain the third sequence length of the second processed signal; The process of performing a Fast Fourier Transform on the second processed signal to obtain the fourth processed signal includes: When it is determined that the length of the third sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the second processed signal to obtain the fourth processed signal; If the length of the third sequence does not meet the Fast Fourier Transform rule, the length of the third sequence is padded and a Fast Fourier Transform is performed to obtain the fourth processed signal.

6. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The method further includes: The signal-to-noise ratio (SNR) of the first processed signal is estimated to obtain the SNR curve. The step of estimating the signal-to-noise ratio (SNR) of the first processed signal to obtain an estimated SNR value includes: Obtain the peak value of the signal-to-noise ratio curve; Calculate the data variance of the data other than the peak value in the signal-to-noise ratio curve; The square of the peak value is calculated, and the signal-to-noise ratio estimate is obtained by using the square of the peak value as the numerator and the data variance as the denominator.

7. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The step of calculating the frequency domain equalization coefficients based on the channel estimated frequency response and signal-to-noise ratio estimated values ​​specifically includes: The first value is obtained by performing a conjugate multiplication on the estimated channel frequency response. The second value is obtained by multiplying the first value by the estimated channel frequency response. The third value is obtained by summing the second value with the estimated signal-to-noise ratio value. The frequency domain equalization coefficient is obtained by multiplying the first value as the numerator and the third value as the denominator.

8. The joint time-domain equalization method under CPM modulation according to claim 1, characterized in that, The method further includes: Obtain the fourth sequence length of the second data, and obtain the fifth sequence length of the tail-dispersed pilot; The length of the sixth sequence is obtained by summing the lengths of the fourth and fifth sequences. The step of performing a Fast Fourier Transform on the second data and the tail-dispersed pilot to obtain the fifth processed signal includes: When it is determined that the length of the sixth sequence satisfies the Fast Fourier Transform rule, Fast Fourier Transform is performed on the second data and the tail dispersion simultaneously to obtain the fifth processed signal; If the length of the sixth sequence does not meet the Fast Fourier Transform rule, the length of the sixth sequence is padded and a Fast Fourier Transform is performed to obtain the fifth processed signal.

9. The joint time-domain equalization method under CPM modulation according to claim 2, characterized in that, The method further includes: Obtain the first sequence length of the first signal; The step of performing a Fast Fourier Transform on the first signal to obtain the second signal includes: When the length of the first sequence satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the first signal to obtain the second signal; If the length of the first sequence does not meet the Fast Fourier Transform rule, the length of the first sequence is padded and a Fast Fourier Transform is performed to obtain the second signal.

10. The joint time-domain equalization method under CPM modulation according to claim 2, characterized in that, The method further includes: Obtain the sequence length corresponding to the head-dispersed pilot; The step of performing a Fast Fourier Transform on the head-dispersed pilot signal to obtain a third signal includes: When it is determined that the sequence length of the head-dispersed pilot signal satisfies the Fast Fourier Transform rule, a Fast Fourier Transform is performed on the head-dispersed pilot signal to obtain the third signal; If the sequence length of the head-dispersed pilot signal does not meet the Fast Fourier Transform rule, the sequence length of the head-dispersed pilot signal is padded and a Fast Fourier Transform is performed to obtain the third signal.

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