Research On High Spectral-efficient Coded Modulation Technology Based On Probabilistic Shaping

With the rapid development of communication technology and the increasing demand of users,the sixth generation of mobile communications system puts forward higher requirements for high spectral-efficient transmission and high reliable transmission.High order quadrature amplitude modulation(QAM)constellations are usually used in most of the current communication systems for high spectral-efficient data transmission.When using the regular QAM constellations on additive white Gaussian noise(AWGN)channel,it will result in a loss of up to 1.53 dB toward the Shannon limit for high spectral-efficientcommunication.In order to obtain shaping gain,probabilistic shaping(PS)and geometric shaping(GS)can be used.Compared with GS,PS is easy for hardware implementation and flexible for rate adaptation,which has aroused wide attention.This thesis focuses on the research of high spectral-efficient coded modulation technology based on probabilistic shaping.By combining PS technology with faster-than-Nyquist(FTN)transmission and multiple-input multiple-output(MIMO)technologies,the reliable transmission performance can be improved in high spectral-efficient scenarios.The main research work and innovation of this thesis are described as follows.Firstly,the low-density parity-check(LDPC)code rate of the conventional PS coded modulation scheme on AWGN channel is not flexible.In this thesis,we propose a time sharing hybrid probabilistic shaping(HPS)scheme for nonbinary(NB)LDPC codes,where the NB LDPC information symbols use distribution matcher to generate QAM symbols with unequal probability distribution,and the NB LDPC parity symbols are utilized to yield QAM symbols with approximately uniform distribution.The LDPC code rate of the proposed scheme is not limited,and the rate matching is more flexible.The theoretical average mutual information(AMI)analysis and the simulated error performance verify the effectiveness of the proposed scheme.Compared with the NB LDPC-coded conventional PS scheme for non gray mapped 8QAM,32QAM and 128QAM constellations,the proposed NB LDPC-coded HPS scheme of this thesis can obtain better error performance.Secondly,the conventional FTN scheme adopts regular QAM constellation for high spectral-efficient transmission.In order to improve the reliability of the system,this thesis combines the PS technology with FTN transmission,and proposes a FTN PS scheme for 16QAM and 8QAM constellations,which can obtain the shaping gain.In order to further improve the reliability of the system,this thesis proposes a FTN precoding scheme based on PS.According to the AMI criterion,this thesis proposes a precoding optimization algorithm based on PS to optimize the precoding coefficients of FTN PS system.Compared with the non-precoded FTN PS scheme,the proposed FTN PS precoding scheme can obtain precoding gain.Thirdly,most of the current PS coded modulation schemes are assumed on AWGN channel.In wireless fading channel,the research on PS is less.In order to obtain diversity gain and shaping gain,two dimensional PS QAM constellations are considered on fading channel.In this thesis,the binary LDPC coded PS scheme is investigated in Rayleigh fading channel.In order to further improve the reliability of the system,this thesis proposes a NB LDPC-coded PS scheme for Rayleigh fading channel.At the same time,the optimal constellation rotation angle of the proposed binary and NB LDPC-coded PS modulation scheme is searched by traversal search based on AMI criterion to obtain diversity gain.Fourthly,the above three innovative works are all optimized in single antenna system.Considering the MIMO system,this thesis proposes a coded modulation scheme for MIMO system with modulation diversity based on PS in fading channel.The channel coding uses binary LDPC codes and NB LDPC codes.In the binary and NB LDPC-coded modulation scheme of MIMO system with modulation diversity based on PS,the optimal constellation rotation angle is searched by traversal search based on AMI criterion to obtain diversity gain.