Research And Impletation Of Frame Synchronization System Based On VDES

Automatic Identification System(AIS)is a ship tracking system operating in the maritime VHF band.It is an important marine communication tool used to avoid ship collision.However,with the increasing number of ships using AIS systems,the AIS system has exposed data network congestion due to the narrow VHF band and small communication capacity.In order to achieve higher and faster data exchange capabilities,VHF Data Exchange System(VDES)is proposed.Because VDES system has a wide coverage,many links and large differences between links,there exists synchronization problems and signal collision problems in VDES.This article mainly studies t(?)synchronization problem and the synchronization problem under signal conflict conditions.First of all,this paper introduces the research background,research status of VDES system and frame synchronization technology,as well as the significance of VDES frame synchronization system.Afterwards,this article has thoroughly investigated the related technologies of VDES,including the physical layer frame structure and the principle of slot collision generation.This article also researches and simulates the signal characteristics of VDES system.It also introduces the frame synchronization algorithm and serial interference cancellation technology.Secondly,based on the related technology and channel characteristics of VDES system,this paper proposes and implements an improved time-frequency joint frame synchronization algorithm,and proposes a single-channel multi-user frame synchronization algorithm by introducing a serial interference cancellation algorithm to solve the synchronization parameter estimation problem under signal conflict conditions.Finally,based on the research of channel characteristics,frame synchronization algorithm and serial interference cancellation algorithm,this paper designs a frame synchronization system based on VDES.Based on MATLAB,the system-level simulation of the frame synchronization system is performed.The accuracy of the system under different SNRs,delays and frequency offsets is calculated and the feasibility and correctness of the algorithm are verified.After that,the effect of the frame synchronization system on the error frame rate of the ASM link under different frequency offset conditions is simulated,and the performance optimization of the frame synchronization system is designed.The simulation result shows that the frame synchronization performance is very good for collision-free signals.For the conflict signals,the frame synchronization performance is related to the power difference between signals,and the greater the power difference,the better the synchronization performance.