High-order modulation iteration frequency offset phase correction method and device

Abstract

The invention discloses a high-order modulation iteration frequency offset phase correction method and device, and the method comprises the steps: carrying out the initial estimation of frequency offset and phase offset at a known position based on the known sequence or pilot frequency information, calculating the initial estimation of signal frequency offset and phase offset at a high-order modulation symbol position, and carrying out the compensation of the frequency offset and phase offset; demodulating the signal after initial correction, and extracting constellation point estimation of the high-order modulation signal; calculating estimated update values of frequency offset and phase offset through the high-order modulation signal estimated value; and correcting the received signal by using the estimated phase offset and frequency offset, and carrying out loop iteration in sequence until the preset precision or iteration times is reached. According to the iterative joint correction method and device, the frequency offset and the phase error can be gradually reduced, and the demodulation accuracy of the high-order modulation signal is improved.

Description

Technical Field

[0001] The present invention relates to the field of millimeter wave communications, and in particular to a method and device for correcting high-order modulation iterative frequency deviation phase. Background Art

[0002] As people's demand for communication continues to increase, mobile communication technology has developed rapidly. People's mobile phones have evolved from the 1G era where only voice calls could be made to the current 5G era of the Internet of Everything with images, videos, and other multimedia services. As we all know, information can only be transmitted on a specific frequency band, but since our spectrum resources are limited, it is particularly important to expand the system capacity. High-order QAM modulation and demodulation technology not only has higher spectrum utilization and data transmission rate, but also can improve the transmission efficiency of the communication system and solve the problem of limited capacity. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to propose a method and device for iterative frequency offset and phase correction of high-order modulation, which inserts a leading sequence and extracts a QAM signal to perform iterative frequency offset and phase estimation, and performs frequency offset and phase correction, thereby reducing the influence of frequency offset and phase offset on the QAM signal.

[0004] In order to achieve the above object, the technical solution specifically adopted by the present invention is as follows:

[0005] A high-order modulation iterative frequency offset phase correction method, by inserting a preamble sequence and extracting a QAM signal, performs iterative frequency offset and phase estimation, and performs frequency offset phase correction; comprising the following steps:

[0006] S1. Initial estimation: Initial estimation of frequency deviation and phase deviation of QAM signal based on the pilot sequence, and frequency deviation and phase compensation;

[0007] S2, signal extraction: extract the QAM signal at the receiving end;

[0008] S3, using the QAM signals at both ends of the transmitter and receiver to estimate the frequency deviation and phase deviation;

[0009] S4, frequency offset and phase compensation are performed again, and then frequency offset and phase offset are iteratively estimated according to the QAM signal after RF demodulation and the QAM signal at the input end until convergence or a certain number of iterations is reached.

[0010] Furthermore, the step S1 comprises the following steps:

[0011] S11, the transmitting end inputs a bit sequence;

[0012] S12, performing channel coding on the input bit sequence;

[0013] S13, performing symbol mapping on the encoded sequence;

[0014] S14, concatenating the data sequence after symbol mapping with the known leading sequence into a composite sequence;

[0015] S15, performing pulse shaping filtering on the composite sequence;

[0016] S16, performing radio frequency modulation on the output data of the pulse shaping filter;

[0017] S17, adding frequency offset and phase offset to the composite sequence after RF modulation and passing through a Gaussian white noise channel;

[0018] S18. Perform an initial estimation of the frequency offset and phase offset of the QAM signal based on the preamble sequence, and perform frequency offset and phase offset compensation.

[0019] Furthermore, in step S2, the preamble sequence containing noise and the QAM signal are extracted from the composite sequence received at the receiving end.

[0020] Furthermore, step S3 includes the following steps:

[0021] S31, frequency deviation estimation: calculating an estimated value of the frequency deviation by estimating a phase change of the QAM signal;

[0022] S32, phase deviation estimation: Calculate the estimated value of the phase offset by estimating the phase of the QAM signal.

[0023] Furthermore, the step S4 comprises the following steps:

[0024] S41, performing frequency deviation and phase deviation compensation on the QAM signal;

[0025] S42, performing radio frequency demodulation on the compensated QAM signal;

[0026] S43, performing frequency deviation and phase deviation estimation based on the QAM signal after RF demodulation and the QAM signal at the input end;

[0027] S44, performing frequency deviation and phase deviation compensation on the QAM signal again;

[0028] S45, return to S43 to perform iterative estimation until the number of iterations reaches N;

[0029] S46, performing matched filtering on the QAM signal after the iteration is completed;

[0030] S47, performing symbol demapping on the output QAM signal of the matched filter;

[0031] S48, then perform channel decoding;

[0032] S49. The receiving end receives the bit sequence.

[0033] The present invention also provides a high-order modulation iterative frequency offset phase correction device, which adopts the above-mentioned high-order modulation iterative frequency offset phase correction method to realize high-order QAM modulation.

[0034] The present invention has the following characteristics and beneficial effects:

[0035] The present invention inserts a leading sequence and extracts a QAM signal, performs iterative frequency deviation and phase estimation, and performs frequency deviation and phase correction, thereby gradually reducing frequency deviation and phase errors and improving the demodulation accuracy of high-order modulation signals.

[0036] The present invention is applicable to various QAM modulation schemes and frequency deviation and phase estimation problems in communication systems, can be modulated and optimized according to system requirements, has strong robustness, and can effectively estimate frequency deviation and phase shift in a noisy environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0038] Figure 1 This is the constellation diagram of 1024QAM reception under the influence of frequency offset;

[0039] Figure 2 It is the 1024QAM receiving constellation diagram after the preamble sequence frequency offset estimation and compensation;

[0040] Figure 3 It is a frequency deviation estimation curve based on the preamble sequence 1024QAM;

[0041] Figure 4 This is the 1024QAM receiving constellation diagram under the influence of phase deviation;

[0042] Figure 5 It is the 1024QAM receiving constellation diagram after compensation based on the preamble sequence phase deviation estimation;

[0043] Figure 6 It is a curve diagram of the phase deviation estimation value based on the preamble sequence 1024QAM;

[0044] Figure 7 This is the 1024QAM receiving constellation diagram under the influence of frequency offset and phase offset;

[0045] Figure 8 It is the 1024QAM receiving constellation diagram after the preamble sequence frequency offset and phase offset estimation compensation;

[0046] Fig. 9It is the 1024QAM bit error rate curve diagram when the frequency deviation and phase deviation are superimposed;

[0047] Fig.10 It is a flow chart of iterative frequency offset and phase offset estimation algorithm;

[0048] Fig.11 It is the 1024QAM receiving constellation diagram after one iteration compensation;

[0049] Fig.12 This is the 1024QAM receiving constellation diagram after ten iterations of compensation;

[0050] Fig.13 The 1024QAM receiving constellation diagram after twenty iterations of compensation;

[0051] Fig.14 It is a 1024QAM bit error rate curve of iterative frequency offset and phase offset estimation. DETAILED DESCRIPTION

[0052] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0053] Figure 1 This is the 1024QAM receiving constellation diagram under the influence of frequency offset. The simulation parameters are set as follows: the symbol rate is 10000 (Baud), the number of samples per symbol is 10, the output signal-to-noise ratio range is 0-20 (dB), the data length is 10000, the preamble sequence length is 1000, the frequency offset is set to 8.3 (Hz), the modulation mode is 1024QAM, and there is no phase offset at this time. Figure 2 The 1024QAM receiving constellation diagram after the preamble frequency offset estimation compensation is obtained through MATLAB simulation calculation: EVM pct =3.3269%. It can be seen that compared with the signal before frequency offset estimation compensation, the signal quality after frequency offset estimation compensation is significantly improved.

[0054] Figure 4 This is the 1024QAM receiving constellation diagram under the influence of phase deviation. The simulation parameters are set as follows: the symbol rate is 10000 (Baud), the number of samples per symbol is 10, the output signal-to-noise ratio range is 0-20 (dB), the data length is 10000, the preamble sequence length is 1000, the set phase offset is 45°, the modulation mode is 1024QAM, and there is no frequency deviation at this time. Figure 5 The 1024QAM receiving constellation diagram after the preamble phase deviation estimation compensation is obtained through MATLAB simulation calculation: EVMpct =1.9901%. It can be seen that compared with the signal before phase offset estimation compensation, the signal quality after phase offset estimation compensation is significantly improved.

[0055] Figure 7 This is the 1024QAM receiving constellation diagram under the influence of frequency offset and phase offset. The simulation parameters are set as follows: the symbol rate is 10000 (Baud), the number of samples per symbol is 10, the output signal-to-noise ratio range is 0-8 (dB), the data length is 10000, the preamble sequence length is 1000, the set phase offset is 45°, the frequency offset is 8.3 (Hz), and the modulation mode is 1024QAM. Figure 8 The 1024QAM receiving constellation diagram after the preamble frequency offset and phase offset estimation compensation is obtained through MATLAB simulation calculation: EVM pct =2.3619%. It can be seen that compared with the signal before frequency offset and phase offset estimation compensation, the signal quality after frequency offset and phase offset estimation compensation is significantly improved.

[0056] Based on the above conclusions, the present invention provides an iterative frequency deviation and phase correction method for high-order modulation. First, an initial estimation of the frequency deviation and phase deviation at a known position is performed based on a known sequence or pilot information, and then an initial estimation of the signal frequency deviation and phase deviation at the high-order modulation symbol position is calculated to compensate for the frequency deviation and phase deviation; then the signal after initial correction is demodulated to extract the constellation point estimation of the high-order modulation signal; the estimated update value of the frequency deviation and phase deviation is calculated based on the estimated value of the high-order modulation signal; finally, the estimated phase deviation and frequency deviation are used to correct the received signal, and the iteration is repeated in sequence until a predetermined accuracy or number of iterations is reached.

[0057] like Fig.10 As shown, a high-order modulation iterative frequency deviation and phase correction method of the present invention comprises the following steps:

[0058] Assuming that the received signal is r(t), the received signal with frequency deviation and phase deviation added can be expressed as:

[0059]

[0060] Where s(t) is the transmitted QAM signal, f d is the frequency deviation, is the phase shift.

[0061] S1. Initial estimation: Perform initial estimation of the frequency offset and phase offset of the QAM signal based on the preamble sequence, and perform frequency offset and phase offset compensation.

[0062] S11, frequency offset estimation: In order to estimate the frequency offset f d, the autocorrelation function or cross-correlation function of the signal can be used. A common method is to use a preset sequence (preamble) to estimate the frequency offset. Assuming the preamble sequence is p(t) and its length is N, the convolution of the received signal r(t) and the preamble sequence p(t) can be used to estimate the frequency offset. The frequency offset formula can be expressed as:

[0063]

[0064] Where R(n) is the nth sampling point of the received signal r(t) in the time domain, P * (n) is the conjugate of the nth sampling point of the leading sequence p(t) in the time domain, and arg(.) represents the amplitude angle.

[0065] S12, phase deviation estimation: Based on the phase deviation estimation of the preamble sequence, the phase deviation can also be estimated by using the autocorrelation function or cross-correlation function of the signal. Assuming that the known preamble sequence is p(t), the phase offset can be estimated by calculating the cross-correlation function of the received signal r(t) and the preamble sequence p(t). The specific formula is as follows:

[0066]

[0067] in, is the estimated phase offset, p * (t) represents the complex conjugate of the leading sequence, T s represents the symbol time interval, and τ represents the time delay caused by the phase.

[0068] S2. Signal extraction: Use a known QAM reference signal and correlate the received signal with it to extract the QAM signal.

[0069] S21. An M-order QAM signal can be expressed as:

[0070]

[0071] Among them, a k are the amplitude and phase of the symbol, p(t) is the pulse shaping function, T is the symbol duration, and K is the total number of symbols transmitted.

[0072] Correlate the received signal with the known QAM signal:

[0073]

[0074] By maximizing the correlation value, the received symbol can be estimated:

[0075]

[0076] Finally, the received symbols are judged and the closest QAM symbol is selected as the demodulation result.

[0077] S3, using the QAM signals at both ends of the transmitter and receiver to estimate the frequency deviation and phase deviation;

[0078] S31, frequency deviation estimation: Calculate the estimated value of frequency deviation by estimating the phase change of the QAM signal. This can be achieved using a differential phase detector, whose output can be expressed as:

[0079]

[0080] Where T is the sampling time and n is the sampling index. The frequency offset is then estimated by integrating the phase change:

[0081]

[0082] Where K f is a proportional gain.

[0083] S32, phase deviation estimation: Calculate the estimated value of the phase offset by estimating the phase of the QAM signal. This can be achieved using a phase-locked loop (PLL) or similar technology, and its output can be expressed as:

[0084]

[0085] S4, iterative estimation: Use the estimated frequency offset and phase offset to correct the received signal, and then iteratively estimate the frequency offset and phase offset based on the QAM signal after RF demodulation and the QAM signal at the input end until convergence or a certain number of iterations is reached. Specifically:

[0086] In order to iteratively estimate the frequency offset and phase offset, the mean square error (MSE) can be used as the optimization target. Assume that the QAM signal at the input end is s(t) and the demodulated signal at the receiving end is The error is defined as:

[0087]

[0088] Then, the iterative correction of frequency offset and phase shift can be achieved by minimizing the mean square value of the error. The specific iterative formula can be expressed as:

[0089]

[0090] Where E is the energy of the error, and α and β are step size parameters that control the speed of the update.

[0091] Fig.11 This is the 1024QAM receiving constellation diagram after one iteration compensation. After Matlab simulation calculation, we get: EVM pct=1.5131%. Fig.12 This is the 1024QAM receiving constellation diagram after ten iterations of compensation. After MATLAB simulation calculation, we get: EVM pct =0.9168%. Fig.13 This is the 1024QAM receiving constellation diagram after twenty iterations of compensation. After MATLAB simulation calculation, we get: EVM pct =0.1818%. It can be seen that as the number of iterations increases, the received signal will become closer and closer to the original signal.

[0092] Fig.14 This is the 1024QAM bit error rate curve of iterative frequency offset and phase offset estimation. Comparing the last two curves, when SNR = 7 (dB), the bit error rate BER1 of the curve after 20 iterations of compensation is 2.59x10 -5 , the bit error rate of the curve after 10 iterations of compensation is BER = 5.0x10 -6 ; When the bit error rate BER=1x10 -5 When , the output signal-to-noise ratio SNR1 of the curve after 20 iterations of compensation is 6.7, and the output signal-to-noise ratio SNR2 of the curve after 10 iterations of compensation is 7.5. It can be seen that the greater the number of iterations, the smaller the bit error rate of the signal, and the smaller the required output signal-to-noise ratio.

[0093] The iterative QAM frequency offset and phase offset estimation algorithm of the present invention has the following main advantages: first, the iterative algorithm is applicable to frequency offset and phase estimation problems in various QAM modulation schemes and communication systems; second, the iterative algorithm can be modulated and optimized according to system requirements, such as adjusting the iteration step size, selecting a suitable initial estimation value, etc.; third, the iterative algorithm is usually highly robust and can effectively estimate the frequency offset and phase offset in a noisy environment; fourth, some iterative algorithms can be implemented by simple hardware, have low computational complexity, and are suitable for real-time processing.

[0094] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-order modulation iterative frequency offset phase correction method, characterized in that: By inserting the preamble sequence and extracting the QAM signal, iterative frequency offset and phase estimation is performed, and frequency offset and phase correction is performed.

2. A high-order modulation iterative frequency offset phase correction method as claimed in claim 1, characterized in that: The steps include: S1. Initial estimation: Initial estimation of frequency deviation and phase deviation of QAM signal based on the pilot sequence, and frequency deviation and phase compensation; S2, signal extraction: extract the QAM signal at the receiving end; S3, using the QAM signals at both ends of the transmitter and receiver to estimate the frequency deviation and phase deviation; S4, frequency offset and phase compensation are performed again, and then frequency offset and phase offset are iteratively estimated according to the QAM signal after RF demodulation and the QAM signal at the input end until convergence or a certain number of iterations is reached.

3. A high-order modulation iterative frequency offset phase correction method as claimed in claim 2, characterized in that: The step S1 comprises the following steps: S11, the transmitting end inputs a bit sequence; S12, performing channel coding on the input bit sequence; S13, performing symbol mapping on the encoded sequence; S14, concatenating the data sequence after symbol mapping with the known leading sequence into a composite sequence; S15, performing pulse shaping filtering on the composite sequence; S16, performing radio frequency modulation on the output data of the pulse shaping filter; S17, adding frequency offset and phase offset to the composite sequence after RF modulation and passing through a Gaussian white noise channel; S18. Perform an initial estimation of the frequency offset and phase offset of the QAM signal based on the preamble sequence, and perform frequency offset and phase offset compensation.

4. A high-order modulation iterative frequency offset phase correction method as claimed in claim 2, characterized in that: In step S2, a preamble sequence containing noise and a QAM signal are extracted from the composite sequence received at the receiving end.

5. A high-order modulation iterative frequency offset phase correction method as claimed in claim 2, characterized in that: The step S3 comprises the following steps: S31, frequency deviation estimation: calculating an estimated value of the frequency deviation by estimating a phase change of the QAM signal; S32, phase deviation estimation: Calculate the estimated value of the phase offset by estimating the phase of the QAM signal.

6. A high-order modulation iterative frequency offset phase correction method as claimed in claim 2, characterized in that: The step S4 comprises the following steps: S41, performing frequency deviation and phase deviation compensation on the QAM signal; S42, performing radio frequency demodulation on the compensated QAM signal; S43, estimating frequency deviation and phase deviation according to the QAM signal after RF demodulation and the QAM signal at the input end; S44, performing frequency deviation and phase deviation compensation on the QAM signal again; S45, return to S43 to perform iterative estimation until the number of iterations reaches N; S46, performing matched filtering on the QAM signal after the iteration is completed; S47, performing symbol demapping on the output QAM signal of the matched filter; S48, then perform channel decoding; S49. The receiving end receives the bit sequence.

7. A high-order modulation iterative frequency offset phase correction device, characterized in that: It adopts the high-order modulation iterative frequency offset phase correction method as described in any one of claims 1-6 to realize high-order QAM modulation.

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