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

Abstract

The invention discloses a frequency offset estimation method and system for 32-ary quadrature amplitude modulation signals. In the frequency offset estimation method and system provided by the present invention, first, the type II signal sequence and the type IV signal sequence in the received 32-ary quadrature amplitude modulation signal sequence are rotated in the same direction to form a rotation modulation signal sequence, and then the rotation modulation signal sequence is formed by using Each amplification factor with the largest peak-to-average power ratio amplifies the rotation modulation signal sequence to obtain the amplified modulation signal sequence; on this basis, fast Fourier transform is performed on the fourth power of the amplified modulation signal sequence, so that the spectrum amplitude can be obtained The frequency corresponding to the peak value; finally, the estimated value of the frequency offset of the 32-ary quadrature amplitude modulation signal sequence is determined according to the frequency corresponding to the peak value of the spectrum amplitude. The frequency offset estimation method and system provided by the invention have high frequency offset estimation accuracy, good signal-to-noise ratio threshold performance, strong practicability, and good application prospects.

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...

AI Technical Summary

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.

Images