Researchon Adaptive Communication Technology In VDE-TER Multilink Mode

The very high frequency data exchange system(VHF Data Exchange System,VDES)is a new type of maritime communication system,and it is also one of the basic communication methods of the e-navigation strategy led by the International Maritime Organization(IMO).In VDES communication,different data modulation and channel coding technologies are designed according to different wireless channel quality.How to efficiently and intelligently use different data modulation and channel coding strategies to improve the data throughput of VDES system is a high-performance VDES product to be solved.key technical issues.Therefore,this thesis studies the adaptive communication technology in the VDE-Terrestrial(VDE-TER)multi-link mode,focusing on the Turbo code coding and decoding technology and the adaptive modulation and coding technology,in order to achieve a variety of channel quality environments.The lower adaptive improves the data transmission efficiency of the system.This thesis firstly designs the VDE-TER channel configuration model according to the VDE-TER channel characteristics,and compares the bit error rate and throughput curves of π/4QPSK,8 PSK and 16 QAM modulation modes by simulation.And on this basis,the theoretical coding and decoding models of three channel coding techniques,Turbo code,LDPC code and Polar code,applied to VDE-TER channel are studied.The simulation analysis shows that the Max-Log-Map decoding algorithm of Turbo code is most suitable for VDE-TER system.Based on this,the throughput performance curves of 11-19 link IDs are simulated.The results show that the throughput curves of the 25 k Hz,50 k Hz and 100 k Hz channel bandwidths completely fit the throughput curves of the three modulation methods,and the overall performance is improved,which shows the effectiveness of the Turbo code technology in the VDE-TER system.Relying on the above model,this thesis studies the adaptive modulation and coding technology(Adaptive Modulation and Coding,AMC)in the VDE-TER system,and proposes an adaptive algorithm based on traditional fixed threshold and a Q-learning adaptive algorithm based on reinforcement learning.The VDE-TER adaptive selection modulation and coding strategy(Modulation and Coding Scheme,MCS)platform is built.Through simulation,the throughput performance of the two adaptive algorithms is simulated under two channel environments without SNR estimation error and with SNR estimation error.The simulation results show that the fixed threshold method performs well when there is no SNR estimation error,but cannot achieve normal functions when there is an SNR estimation error;while the Q-learning algorithm,regardless of whether there is an SNR estimation error,can achieve the correct signal-to-noise ratio threshold.It can switch the transmission link and has good robustness,which is more suitable for the adaptive modulation and coding algorithm of VDE-TER.This research can provide a theoretical basis for the subsequent revision of VDES technical characteristics,and is of great significance for improving VDES communication performance and its engineering implementation.