US-12627543-B2 - Adaptive equalization method and apparatus for probabilistic shaping system, and readable storage medium

Abstract

The present application discloses an adaptive equalization method and apparatus for a probabilistic shaping system, and a readable storage medium. The adaptive equalization method may include: determining a tap length of a filter, and setting an initial coefficient of an equalizer; performing butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; determining an error signal according to the two polarized output signals, wherein the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and adjusting the coefficient of the equalizer according to the error signal.

Inventors

• Liangjun ZHANG

Assignees

• ZTE CORPORATION

Dates

Publication Date

20260512

Application Date

20221009

Priority Date

20211013

Claims (20)

1. 1 . An adaptive equalization method for a probabilistic shaping system, comprising: determining a tap length of a filter, and setting an initial coefficient of an equalizer; performing butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; determining an error signal according to the two polarized output signals, wherein the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and adjusting the coefficient of the equalizer according to the error signal.
2. 2 . The adaptive equalization method of claim 1 , wherein the two polarized output signals are: x out = h x ⁢ x ⁢ x i ⁢ n + h x ⁢ y ⁢ y i ⁢ n y out = h y ⁢ x ⁢ x i ⁢ n + h y ⁢ y ⁢ y i ⁢ n wherein h xx , h xy , h yx , and h yy represent the coefficients of the equalizer, respectively; x in and y in represent the two polarized input signals, respectively; and x out and y out represent the two polarized output signals, respectively.
3. 3 . The adaptive equalization method of claim 2 , wherein the error signal is determined according to the following formula: ε x = min ⁡ ( R 1 - | x out | 2 , R 2 - | x out | 2 , … , R k - | x out | 2 ) + ( p - Σ | x out | 2 n ) ε y = min ⁡ ( R 1 - | y out | 2 , R 2 - | y out | 2 , … , R k - | y out | 2 ) + ( p - Σ | y out | 2 n ) wherein R 1 , R 2 , . . . , R k represent the target convergence radii, respectively, p represents the target average power, n represents a number of samples used, and min represents an operation of calculating a minimum value; and ε x and ε y are error signals of the two polarized output signals.
4. 4 . The adaptive equalization method of claim 3 , wherein the coefficient of the equalizer according to the error signal is adjusted according to the following formula: h x ⁢ x = h x ⁢ x + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h x ⁢ y = h x ⁢ y + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) h y ⁢ x = h y ⁢ x + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h y ⁢ y = h y ⁢ y + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) wherein μ represents a step size for adjusting the coefficient of the equalizer, and conj represents a conjugation operation.
5. 5 . The method of claim 1 , wherein a modulation format used by the probabilistic shaping system comprises a PS-16QAM format, a PS-64QAM format, or a PS-QAM format with an order higher than 64.
6. 6 . An adaptive equalization apparatus for a probabilistic shaping system, comprising: a processor; and a memory configured to store a computer program which, when executed by the processor, causes the processor to perform an adaptive equalization apparatus for a probabilistic shaping system method comprising: determining a tap length of a filter, and setting an initial coefficient of an equalizer; performing butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; determining an error signal according to the two polarized output signals, wherein the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and adjusting the coefficient of the equalizer according to the error signal.
7. 7 . The adaptive equalization apparatus of claim 6 , wherein the two polarized output signals are: x out = h x ⁢ x ⁢ x i ⁢ n + h x ⁢ y ⁢ y i ⁢ n y out = h y ⁢ x ⁢ x i ⁢ n + h y ⁢ y ⁢ y i ⁢ n wherein h xx , h xy , h yx , and h yy represent the coefficients of the equalizer, respectively; x in and y in represent the two polarized input signals, respectively; and x out and y out represent the two polarized output signals, respectively.
8. 8 . The adaptive equalization apparatus of claim 7 , wherein the error signal is determined according to the following formula: ε x = min ⁡ ( R 1 - | x out | 2 , R 2 - | x out | 2 , … , R k - | x out | 2 ) + ( p - Σ | x out | 2 n ) ε y = min ⁡ ( R 1 - | y out | 2 , R 2 - | y out | 2 , … , R k - | y out | 2 ) + ( p - Σ | y out | 2 n ) wherein R 1 , R 2 , . . . , R k represent the target convergence radii, respectively, p represents the target average power, n represents a number of samples used, and min represents an operation of calculating a minimum value; and ε x and ε y are error signals of the two polarized output signals.
9. 9 . The adaptive equalization apparatus of claim 8 , wherein the coefficient of the equalizer according to the error signal is adjusted according to the following formula: h x ⁢ x = h x ⁢ x + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h x ⁢ y = h x ⁢ y + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) h y ⁢ x = h y ⁢ x + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h y ⁢ y = h y ⁢ y + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) wherein μ represents a step size for adjusting the coefficient of the equalizer, and conj represents a conjugation operation.
10. 10 . The adaptive equalization apparatus of claim 6 , wherein a modulation format used by the probabilistic shaping system comprises a PS-16QAM format, a PS-64QAM format, or a PS-QAM format with an order higher than 64.
11. 11 . A Data Signal Processing (DSP) chip, comprising the adaptive equalization apparatus of claim 6 .
12. 12 . The chip of claim 11 , wherein the two polarized output signals are: x out = h x ⁢ x ⁢ x i ⁢ n + h x ⁢ y ⁢ y i ⁢ n y out = h y ⁢ x ⁢ x i ⁢ n + h y ⁢ y ⁢ y i ⁢ n wherein h xx , h xy , h yx , and h yy represent the coefficients of the equalizer, respectively; x in and y in represent the two polarized input signals, respectively; and x out and y out represent the two polarized output signals, respectively.
13. 13 . The chip of claim 12 , wherein the error signal is determined according to the following formula: ε x = min ⁡ ( R 1 - | x out | 2 , R 2 - | x out | 2 , … , R k - | x out | 2 ) + ( p - Σ | x out | 2 n ) ε y = min ⁡ ( R 1 - | y out | 2 , R 2 - | y out | 2 , … , R k - | y out | 2 ) + ( p - Σ | y out | 2 n ) wherein R 1 , R 2 , . . . , R k represent the target convergence radii, respectively, p represents the target average power, n represents a number of samples used, and min represents an operation of calculating a minimum value; and ε x and ε y are error signals of the two polarized output signals.
14. 14 . The chip of claim 13 , wherein the coefficient of the equalizer according to the error signal is adjusted according to the following formula: h x ⁢ x = h x ⁢ x + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h x ⁢ y = h x ⁢ y + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) h y ⁢ x = h y ⁢ x + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h y ⁢ y = h y ⁢ y + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) wherein μ represents a step size for adjusting the coefficient of the equalizer, and conj represents a conjugation operation.
15. 15 . The chip of claim 11 , wherein a modulation format used by the probabilistic shaping system comprises a PS-16QAM format, a PS-64QAM format, or a PS-QAM format with an order higher than 64.
16. 16 . A non-transitory computer-readable storage medium, storing a computer-executable instruction which, when executed by a computer, causes the computer to perform an adaptive equalization method comprising: determining a tap length of a filter, and setting an initial coefficient of an equalizer; performing butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; determining an error signal according to the two polarized output signals, wherein the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and adjusting the coefficient of the equalizer according to the error signal.
17. 17 . The non-transitory computer-readable storage medium of claim 16 , wherein the two polarized output signals are: x out = h x ⁢ x ⁢ x i ⁢ n + h x ⁢ y ⁢ y i ⁢ n y out = h y ⁢ x ⁢ x i ⁢ n + h y ⁢ y ⁢ y i ⁢ n wherein h xx , h xy , h yx , and h yy represent the coefficients of the equalizer, respectively; x in and y in represent the two polarized input signals, respectively; and x out and y out represent the two polarized output signals, respectively.
18. 18 . The non-transitory computer-readable storage medium of claim 17 , wherein the error signal is determined according to the following formula: ε x = min ⁡ ( R 1 - | x out | 2 , R 2 - | x out | 2 , … , R k - | x out | 2 ) + ( p - Σ | x out | 2 n ) ε y = min ⁡ ( R 1 - | y out | 2 , R 2 - | y out | 2 , … , R k - | y out | 2 ) + ( p - Σ | y out | 2 n ) wherein R 1 , R 2 , . . . , R k represent the target convergence radii, respectively, p represents the target average power, n represents a number of samples used, and min represents an operation of calculating a minimum value; and ε x and ε y are error signals of the two polarized output signals.
19. 19 . The non-transitory computer-readable storage medium of claim 18 , wherein the coefficient of the equalizer according to the error signal is adjusted according to the following formula: h x ⁢ x = h x ⁢ x + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h x ⁢ y = h x ⁢ y + μ * ε x * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) h y ⁢ x = h y ⁢ x + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( x i ⁢ n ) h y ⁢ y = h y ⁢ y + μ * ε y * c ⁢ o ⁢ n ⁢ j ⁡ ( y i ⁢ n ) wherein μ represents a step size for adjusting the coefficient of the equalizer, and conj represents a conjugation operation.
20. 20 . The non-transitory computer-readable storage medium of claim 16 , wherein a modulation format used by the probabilistic shaping system comprises a PS-16QAM format, a PS-64QAM format, or a PS-QAM format with an order higher than 64.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a national stage filing under 35 U.S.C. § 371 of international application number PCT/CN2022/124163, filed Oct. 9, 2022, which claims priority to Chinese patent application No. 202111191070.6 filed Oct. 13, 2021. The entire contents of these applications are incorporated herein by reference in their entirety. TECHNICAL FIELD The present disclosure relates to the field of communication technologies, and in particular, to an adaptive equalization method and apparatus for a probabilistic shaping system, and a readable storage medium. BACKGROUND With the development of big data, 4K video, virtual reality and the increasingly urgent demand of 5G bearer, optical transmission systems need to provide a higher transmission capacity. As early as 1948, Shannon, the founder of information theory, proved in his paper “A Mathematical Theory of Communication” that when the source distribution accords with the channel distribution, the channel has the maximum transmission capacity. Probability Shaping (PS) optical communication systems have been studied in recent years, which improve the transmission performance of the system by changing the probability distribution of the source to make it close to a Gaussian distribution. Digital Signal Processing (DSP) technologies are usually used to compensate for the loss of devices and channels in optical communication systems, including dispersion compensation, adaptive equalization compensation, clock recovery, carrier phase recovery, etc. The introduction of probabilistic shaping leads to the failure of some conventional DSP algorithms. For example, in the case of a high degree of probabilistic shaping, the conventional Constant Module Algorithm (CMA) fails and cannot correctly compensate for the polarization crosstalk and polarization mode dispersion in the channels. As a result, the system cannot operate. SUMMARY The present disclosure provides an adaptive equalization method and apparatus for a probabilistic shaping system, and a readable storage medium. In accordance with a first aspect of the present disclosure, an embodiment provides an adaptive equalization method for a probabilistic shaping system, which may include: determining a tap length of a filter and setting an initial coefficient of an equalizer; performing butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; determining an error signal according to the two polarized output signals, where the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and adjusting the coefficient of the equalizer according to the error signal. In accordance with a second aspect of the present disclosure, an embodiment provides an adaptive equalization apparatus for a probabilistic shaping system, which may include: a setting module, configured to determine a tap length of a filter and set an initial coefficient of an equalizer; a filtering module, configured to perform butterfly filtering on two polarized input signals according to the coefficient of the equalizer to obtain two polarized output signals; an error calculation module, configured to determine an error signal according to the two polarized output signals, where the error signal is a sum of a first error which is a minimum value of differences between a target convergence radius and squares of modulus of the output signals, and a second error which is a difference between an average value of squares of modulus of a plurality of output signals and a target average power; and an adjustment module, configured to adjust the coefficient of the equalizer according to the error signal. In accordance with a third aspect of the present disclosure, an embodiment provides a DSP chip, which may include the adaptive equalization apparatus in the embodiment of the second aspect of the present disclosure. In accordance with a fourth aspect of the present disclosure, an embodiment provides a computer-readable storage medium, storing a computer-executable instruction which, when executed by a computer, causes the computer to implement the adaptive equalization method in the embodiment of the first aspect of the present disclosure. Additional features and advantages of the present disclosure will be set forth in the subsequent description, and it will in part be obvious from the description, or may be learned by the practice of the present disclosure. The objects and other advantages of the present disclosure can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS The drawings are provided for a further understandin