Research On Code-aided Joint Receiving Technology In Dynamic Channel

With the rapid development of satellite industry in recent years,how to achieve synchronization at the receiver under high dynamic and low signal-to-noise ratio(SNR)has become a hot research topic.How to complete demodulation and decoding in low signal-to-noise ratio(SNR)is the key to successful communication.Although incoherent demodulation technology can complete demodulation without knowing the phase,it will cause 3dB performance loss.Coherent demodulation performs better than incoherent demodulation,but requires accurate carrier synchronization.The traditional carrier synchronization method uses non-linear operation,and its performance deteriorates significantly at low signal-to-noise ratio(SNR).In recent years,based on code-assisted iterative synchronization algorithm,soft information from decoding output such as Turbo code and LDPC code is used to feedback,and carrier synchronization demodulation and decoding are combined to achieve better demodulation and decoding under low signal-to-noise ratio.Aiming at the carrier recovery difficulty of communication receiver under high dynamic channel and low signal-to-noise ratio(SNR),a general low dynamic channel model and equivalent high dynamic channel model of LEO satellite are studied and established.The coding-assisted joint reception technology based on maximum likelihood estimation is studied.A code-assisted carrier synchronization method based on LDPC decoding soft information iteration is proposed.This method connects the decoder and demodulator through decoding soft information,ensures the reliability of the soft information used for synchronization by setting soft information threshold,and estimates the carrier phase difference through iteration between demodulation and decoding,and compensates the phase difference of each codeword separately.In addition,aiming at the channel tracking of high dynamic channel,this paper proposes a joint extended Kalman filter and code-assisted receiver technology,and gives the corresponding simulation evaluation combined with LEO satellite channel.The simulation results show that the proposed algorithm can achieve carrier synchronization and decoding well under the high dynamic channel model,and achieve near ideal synchronization reception performance.