Research On Coded Modulation Technology Based On Probabilistic Shaping

In the case of limited spectrum resources,high-order modulation is widely used to improve spectrum efficiency.However,in the bandwidth limited additive white Gaussian noise(AWGN)channel,higher-order modulation will bring some shaping loss when the input is evenly distributed.Probability shaping is considered to be a promising technology in the future optical fiber communication system to meet the business requirements of high data rate applications.In order to obtain shaping gain and improve spectrum efficiency,this paper studies the coding and modulation technology based on probability shaping by processing the input signal with approximate Gaussian distribution.Firstly,aiming at the shaping loss caused by uniform quadrature amplitude modulation(QAM),the shaping gains of probability shaping high-order modulation systems based on long code(low-density parity check block code with code length of 12000)and short code(polarization code with code length of 256)are studied and compared.The simulation results show that the Eb/NO shaping gain of 0.5?0.7 dB and 0.8?0.95 dB can be obtained when the BER is 1E-5 under 16QAM and 64QAM,respectively.Secondly,aiming at the characteristics of faster-than-Nyquist(FTN)transmission which can improve the spectrum efficiency,the performance of probability shaping in FTN system is studied,and it is combined with a new spatial coupled LDPC code.Specifically,the FTN transmission signal is output after distribution matching at the transmitter,and serial iterative equalization is adopted at the receiver for the stream decoding characteristics of spatially coupled LDPC.Finally,the simulation results show that the FTN gain of 0.66?0.83 dB and the PS gain of 0.48?0.53 dB are obtained when the BER is 1E-5.Thirdly,aiming at the high complexity signal detection problem caused by inter symbol interference introduced by FTN signal,the transceiver of low complexity system based on probability shaping is designed.By introducing pre equalization into FTN system,it is combined with probability shaping.Finally,the simulation results show that the proposed method can greatly reduce the complexity of the system without degradation of system performance,thus greatly simplifying the signal processing process of the receiver and transmitter.