CN-121984818-A - Coarse frequency offset estimation compensation method and device

CN121984818ACN 121984818 ACN121984818 ACN 121984818ACN-121984818-A

Abstract

The application discloses a coarse frequency offset estimation compensation method and a device, which relate to the technical field of communication, wherein the method comprises the steps of selecting a continuous section of sequence of one polarization from two polarizations in a clock period; the method comprises the steps of obtaining a sequence of the initial frequency offset estimation value in the positive and negative frequency offset compensation direction or the frequency offset estimation value transmitted in the previous clock cycle, carrying out frequency offset compensation on the sequence to obtain two output sequences in the positive and negative frequency offset compensation direction, determining two frequency point positions with the frequency point sequence numbers closest to each other and the largest amplitude difference, determining a first module value difference and a second module value difference of two frequency points in the positive and negative frequency offset compensation direction according to the two frequency point positions and the two output sequences, determining the direction and the size of the frequency offset compensation in the next clock cycle according to the first module value difference and the second module value difference, and repeatedly carrying out frequency offset compensation until the iteration condition is met, and outputting the frequency offset estimation value indicated by the first module value difference or the second module value difference of the corresponding clock cycle. The application can realize the coarse frequency offset estimation and compensation functions in the optical transmission channel and has low realization complexity.

Inventors

DONG XIAOBIN
CAO YUN
Chai jiao
ZHU QIXIONG
CHEN DENGCHAO

Assignees

烽火通信科技股份有限公司
武汉飞思灵微电子技术有限公司

Dates

Publication Date: 20260505
Application Date: 20260122

Claims (10)

1. The coarse frequency offset estimation compensation method is characterized by comprising the following steps of: In the clock period, selecting a continuous section of sequence of one polarization from two polarizations; According to the initial frequency offset estimation value in the positive and negative frequency offset compensation direction or the frequency offset estimation value transmitted in the previous clock period, performing frequency offset compensation on the sequence in the current clock period to obtain two output sequences in the positive and negative frequency offset compensation direction; Determining two frequency point positions with the nearest frequency point sequence numbers and the largest amplitude difference, and determining a first module value difference of two frequency points in a positive frequency offset compensation direction and a second module value difference of two frequency points in a negative frequency offset compensation direction according to the two frequency point positions and the two output sequences; And determining the direction and the magnitude of the frequency offset compensation of the next clock period according to the first module value difference and the second module value difference, repeating the frequency offset compensation until the iteration condition is met, and outputting the frequency offset estimation value indicated by the first module value difference or the second module value difference of the corresponding clock period as a final coarse frequency offset estimation value.
2. The method of coarse frequency offset estimation and compensation according to claim 1, wherein determining a first mode value difference between two frequency points in a positive frequency offset compensation direction and a second mode value difference between two frequency points in a negative frequency offset compensation direction according to the two frequency point positions and the two output sequences comprises: Invoking a dispersion compensation module to obtain fast Fourier transform FFT outputs of two output sequences; Selecting signals of two frequency points based on FFT output, and respectively calculating the modulus values of the two frequency points in the positive frequency offset compensation direction and the modulus values of the two frequency points in the negative frequency offset compensation direction; and calculating the first module value difference according to the module values of the two frequency points in the positive frequency offset compensation direction, and calculating the second module value difference according to the module values of the two frequency points in the negative frequency offset compensation direction.
3. The method of coarse frequency offset estimation and compensation according to claim 1, wherein determining a first mode value difference between two frequency points in a positive frequency offset compensation direction and a second mode value difference between two frequency points in a negative frequency offset compensation direction according to the two frequency point positions and the two output sequences comprises: respectively multiplying the two output sequences by butterfly conversion tables of two frequency points, taking the modulus value after summing to obtain the modulus value of the two frequency points in the positive frequency offset compensation direction and the modulus value of the two frequency points in the negative frequency offset compensation direction, Calculating the first module value difference according to the module values of the two frequency points in the positive frequency offset compensation direction, and calculating the second module value difference according to the module values of the two frequency points in the negative frequency offset compensation direction; The butterfly transformation table of the two frequency points is as follows: Wherein, the For the length of the selected polarized signal, Is the position of the 1-frequency point, Is the position of the 2 frequency points, Representing from 0 to 。
4. The coarse frequency offset estimation compensation method of claim 1, wherein: according to the formula: Determining two frequency point positions with the nearest frequency point sequence numbers and the largest amplitude difference value; Wherein, the For the roll-off coefficient of the pulse shaping filter, For the oversampling rate of the analog-to-digital converter ADC, For the length of the selected polarized signal.
5. The method of coarse frequency offset estimation and compensation according to claim 1, wherein determining the direction and the magnitude of the frequency offset compensation of the next clock cycle according to the first module value difference and the second module value difference, repeating the frequency offset compensation until the iteration condition is satisfied, outputting the frequency offset estimation value indicated by the first module value difference or the second module value difference of the corresponding clock cycle as the final coarse frequency offset estimation value, and includes: determining the maximum value of the first and second module value differences, if the maximum value is larger than a first threshold, setting the frequency offset compensation step length as a small step length, and if the maximum value is smaller than or equal to the first threshold, setting the frequency offset compensation step length as a large step length; determining the frequency offset value of the positive and negative frequency offset compensation directions estimated in the clock period according to the initial frequency offset estimation value or the frequency offset estimation value transmitted in the previous clock period and the determined frequency offset compensation step length; If the maximum value is greater than the second threshold, and the absolute value of the difference value between the first module value difference and the second module value difference is smaller than the third threshold, judging that the iteration condition is met, and taking the frequency offset estimation value indicated by the first module value difference or the second module value difference corresponding to the clock period as the final coarse frequency offset estimation value; If the maximum value is not satisfied and the absolute value of the difference value between the first and second module value differences is smaller than the third threshold, judging that the iteration condition is not satisfied, transmitting the frequency offset value in the positive and negative frequency offset compensation directions estimated in the clock period to the next clock period, and continuing the coarse frequency offset estimation compensation flow.
6. The coarse frequency offset estimation compensation method of claim 5, wherein: The small step size is 300MHz, and the large step size is 3GHz.
7. The method for coarse frequency offset estimation and compensation according to claim 1, further comprising, before determining the first modulus difference between the two frequency points in the positive frequency offset compensation direction and the second modulus difference between the two frequency points in the negative frequency offset compensation direction: filtering the module values of the two frequency points in the positive frequency offset compensation direction and the module values of the two frequency points in the negative frequency offset compensation direction: If the number of the filtering iterations is not reached, the frequency offset estimation value of the clock period is consistent with the frequency offset estimation value of the previous clock period; if the filter iteration times are reached, calculating a first module value difference of two frequency points in the positive frequency offset compensation direction and a second module value difference of two frequency points in the negative frequency offset compensation direction.
8. A coarse frequency offset estimation compensation device, characterized in that the coarse frequency offset estimation compensation device comprises: The frequency offset compensation module is used for selecting a continuous section of sequence of one polarization from the two polarizations, and carrying out frequency offset compensation on the sequence of the clock period according to an initial frequency offset estimation value in the positive and negative frequency offset compensation directions or a frequency offset estimation value transmitted in the previous clock period to obtain two output sequences in the positive and negative frequency offset compensation directions; The Fourier transform module is used for determining two frequency point positions with the frequency point serial numbers closest to each other and the largest amplitude difference value, and determining a first module value difference of the two frequency points in the positive frequency offset compensation direction and a second module value difference of the two frequency points in the negative frequency offset compensation direction according to the two frequency point positions and the two output sequences; and the frequency offset estimation module is used for determining the direction and the size of the frequency offset compensation of the next clock period according to the first module value difference and the second module value difference, repeatedly carrying out the frequency offset compensation until the iteration condition is met, and outputting the frequency offset estimation value indicated by the first module value difference or the second module value difference of the corresponding clock period as a final coarse frequency offset estimation value.
9. The coarse frequency offset estimation and compensation device of claim 8 wherein the fourier transform module determines a first modulus difference between two frequency points in a positive frequency offset compensation direction and a second modulus difference between two frequency points in a negative frequency offset compensation direction based on the two frequency point positions and the two output sequences, comprising: Invoking a dispersion compensation module to obtain fast Fourier transform FFT outputs of two output sequences; Selecting signals of two frequency points based on FFT output, and respectively calculating the modulus values of the two frequency points in the positive frequency offset compensation direction and the modulus values of the two frequency points in the negative frequency offset compensation direction; and calculating the first module value difference according to the module values of the two frequency points in the positive frequency offset compensation direction, and calculating the second module value difference according to the module values of the two frequency points in the negative frequency offset compensation direction.
10. The coarse frequency offset estimation and compensation device of claim 8 wherein the fourier transform module determines a first modulus difference between two frequency points in a positive frequency offset compensation direction and a second modulus difference between two frequency points in a negative frequency offset compensation direction based on the two frequency point positions and the two output sequences, comprising: respectively multiplying the two output sequences by butterfly conversion tables of two frequency points, taking the modulus value after summing to obtain the modulus value of the two frequency points in the positive frequency offset compensation direction and the modulus value of the two frequency points in the negative frequency offset compensation direction, Calculating the first module value difference according to the module values of the two frequency points in the positive frequency offset compensation direction, and calculating the second module value difference according to the module values of the two frequency points in the negative frequency offset compensation direction; The butterfly transformation table of the two frequency points is as follows: Wherein, the For the length of the selected polarized signal, Is the position of the 1-frequency point, Is the position of the 2 frequency points, Representing from 0 to 。

Description

Coarse frequency offset estimation compensation method and device Technical Field The application relates to the technical field of communication, in particular to a coarse frequency offset estimation compensation method and device. Background In the technical field of optical fiber communication, when a coherent optical communication system is used, the same frequency of a receiving end laser and a transmitting end laser is required, however, the center frequency cannot be completely the same due to the limitation of the manufacturing process of the lasers, namely, certain frequency deviation exists. The frequency offset generated by the low-cost transceiver laser may be larger, and the frequency offset of the system may exceed the compensation capability of the conventional quadric algorithm at present, if the frequency offset is not pre-estimated and compensated, the modules such as self-adaptive equalization and the like may not work normally, so that the equalization capability of the receiver is adversely affected. The coherent optical communication system mainly adopts a phase increment algorithm and a frequency offset estimation algorithm based on spectrum power to carry out frequency offset estimation. The phase increment algorithm removes the modulated data phase by a fourth power operation, and calculates the frequency offset according to the average value of the phase increment of adjacent symbols. However, the frequency offset estimation range of the algorithm is only + -Rs/8 (Rs is the baud rate), and the estimation range is smaller. The frequency offset estimation algorithm based on the frequency spectrum power utilizes FFT (Fast Fourier Transform ) to transform the data after the oversampling of the receiving end to the frequency domain, and the power of the symmetrical frequency spectrum is obtained through filtering, so that the frequency offset is estimated. However, the algorithm has high implementation complexity, and the balance between the complexity and the system performance is difficult to achieve. Disclosure of Invention The application provides a coarse frequency offset estimation compensation method and a coarse frequency offset estimation compensation device, which can realize coarse frequency offset estimation and compensation functions in an optical transmission channel and have low realization complexity. In a first aspect, an embodiment of the present application provides a coarse frequency offset estimation compensation method, where the coarse frequency offset estimation compensation method includes the following steps: In the clock period, selecting a continuous section of sequence of one polarization from two polarizations; According to the initial frequency offset estimation value in the positive and negative frequency offset compensation direction or the frequency offset estimation value transmitted in the previous clock period, performing frequency offset compensation on the sequence in the current clock period to obtain two output sequences in the positive and negative frequency offset compensation direction; Determining two frequency point positions with the nearest frequency point sequence numbers and the largest amplitude difference, and determining a first module value difference of two frequency points in a positive frequency offset compensation direction and a second module value difference of two frequency points in a negative frequency offset compensation direction according to the two frequency point positions and the two output sequences; And determining the direction and the magnitude of the frequency offset compensation of the next clock period according to the first module value difference and the second module value difference, repeating the frequency offset compensation until the iteration condition is met, and outputting the frequency offset estimation value indicated by the first module value difference or the second module value difference of the corresponding clock period as a final coarse frequency offset estimation value. With reference to the first aspect, in an implementation manner, the determining, according to the two frequency point positions and the two output sequences, a first mode value difference between two frequency points in the positive frequency offset compensation direction and a second mode value difference between two frequency points in the negative frequency offset compensation direction includes: Invoking a dispersion compensation module to obtain fast Fourier transform FFT outputs of two output sequences; Selecting signals of two frequency points based on FFT output, and respectively calculating the modulus values of the two frequency points in the positive frequency offset compensation direction and the modulus values of the two frequency points in the negative frequency offset compensation direction; and calculating the first module value difference according to the module values of the two frequency points in the positi