Frequency offset estimation method and system for 32-system quadrature amplitude modulation signal

Abstract

The invention discloses a frequency offset estimation method and system for a 32-system quadrature amplitude modulation signal. According to the method and system, the method comprises the steps: rotating a class II signal sequence and a class IV signal sequence in a received 32-system quadrature amplitude modulation signal sequence in the same direction to form a rotation modulation signal sequence, and then using each amplification coefficient with the maximum peak-to-average power ratio for amplifying the rotation modulation signal sequence to obtain an amplified modulation signal sequence;performing the fast Fourier transform of the fourth power of the amplified modulation signal sequence based on the above, thereby obtaining the frequency corresponding to the peak of the spectrum amplitude; finally determining the frequency offset estimation value of the 32-system quadrature amplitude modulated signal sequence according to the frequency corresponding to the peak value of the spectrum amplitude. The method and system provided by the invention have high frequency offset estimation precision, good signal to noise ratio threshold performance, strong practicability and good application prospect.

Description

technical field [0001] The invention relates to the field of coherent optical communication systems, in particular to a frequency offset estimation method and system for 32-ary quadrature amplitude modulation signals. Background technique [0002] The 32-ary quadrature amplitude modulation (32-QAM) coherent optical communication system is very likely to become the next generation optical communication system with a data rate as high as 400Gb / s to 1Tb / s. This is mainly because the system has higher spectral efficiency and channel capacity than previous transmission systems under the quadrature phase shift keying (QuadraturePhase Shift Keying, QPSK) and 16-QAM modulation formats. In a digital coherent receiver, frequency offset (FO) estimation method needs to be used to estimate and compensate the frequency offset between the transmitting laser and the local oscillator laser before carrier phase recovery. [0003] Due to the particularity of the constellation diagram of the 3...

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Problems solved by technology

[0003] Due to the particularity of the constellation diagram of the 32-QAM system, there are very few high-performance frequency offset estimation methods

The traditional fast Fourier transform (FFT)-based frequency offset estimation method (FFT-FOE) cannot be successfully used for frequency offset estimation in 32-QAM systems with small data lengths (such as hundreds)

The reason is that the constellation diagram of 32-QAM is different from that of 16-QAM and 64-QAM, and it is not strictly rectangular distribution, resulting in the severe weakening of the spectrum peak in the low signal-to-noise ratio area.

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