节点文献
星载VDES接收系统关键技术研究
【作者】 黄敏；
【作者基本信息】 南京理工大学 ， 通信与信息系统， 2021， 硕士
【摘要】 为了缓解船舶自动识别系统(Automatic Identification System,AIS)的负载压力,国际海事组织提出了甚高频(Very High Frequency,VHF)数据交换系统(VHF Data Exchange System,VDES)的概念。星载VDES在星载AIS的基础上增加了特殊应用报文(Application Specific Message,ASM)和甚高频数据交换(VHF Data Exchange,VDE)两大模块,具备更佳的数据传输性能。本文重点对三个子系统信号的解调技术、单通道和多通道星载接收碰撞信号分离算法进行研究,主要工作如下:(1)在分析AIS、ASM、VDE子系统物理层技术标准的基础上,采用维特比差分解调、基带和中频差分解调以及提出的一种改进的基于幅度值星座点解映射方法分别对AIS信号、ASM信号和VDE信号进行解调。MATLAB仿真验证了所提出的解调方式均具有良好的误码率性能。(2)提出一种基于随机近端梯度张量分解的多通道碰撞信号分离算法。在经典张量分解的基础上提出采用塔克(Tucker)分解对张量进行压缩得到核张量,简化计算复杂度;同时提出引入随机近端梯度算法优化求解核张量的过程,加快分解速度。仿真结果显示在适定和欠定情况下源信号与分离信号相关系数均达到90%以上,表明该算法对两种情况下多通道碰撞信号的分离能取得不错的效果。(3)提出一种基于灰狼优化变分模态分解的单通道碰撞信号分离算法。针对经典变分模态分解(Variational Mode Decomposition,VMD)在分离单通道碰撞信号时由于人为选择参数而出现的过度分解或分解不足的情况,利用灰狼优化算法对VMD初始信号个数和惩罚因子两个参数进行自适应选择,算法拥有全局最优搜索能力和较快收敛速度。仿真证明该算法对单通道碰撞信号具有较好的分离性能。(4)给出星载VDES系统接收机的总体设计方案和数字信号处理模块的具体流程设计,完成数字信号处理板硬件实现,并对接收机的多普勒频偏适应范围和碰撞信号分离性能进行测试,验证了设计的正确性。
【Abstract】 In order to alleviate the load pressure of the Automatic Identification System(AIS),the International Maritime Organization proposed the concept of Very High Frequency(VHF)Data Exchange System(VDES).In VDES,Application Specific Message(ASM)and VHF Data Exchange(VDE)are added based on the Automatic Identification System(AIS),which can improve the performance of data transmission.This paper focuses on the demodulation technology of three subsystems and the collided signals separation algorithms with singlechannel and multi-channel satellite receiver.The main work of this paper is shown as follows:(1)Based on the analysis of technical standards on AIS,ASM and VDE subsystems,Viterbi differential demodulation method,baseband and intermediate frequency differential demodulation method and a demodulation method based on amplitude of constellation point are proposed to demodulate the AIS,ASM and VDE signals separately.Simulation results verify that the proposed methods have a good performance on bit error rate.(2)A multi-channel collided signals separation algorithm based on tensor decomposition is proposed,which is improved by stochastic proximal gradient algorithm.Tucker decomposition is utilized to compress the tensor and obtain kernel tensor,which can simplify the computational complexity.At the same time,the stochastic proximal gradient algorithm is introduced to speed up decomposition.Simulation results show that under well-posed and underdetermined conditions,the correlation coefficient between the source signals and the separated signals is greater than 90%,which indicates the proposed algorithm can achieve good separation performance for multi-channel collided signals.(3)Gray wolf optimized variational mode decomposition algorithm is proposed for singlechannel collided signals separation.The over-decomposition or under-decomposition may occurs when the classical variational mode decomposition(VMD)is used to separate the singlechannel collided signals because of the uncertainty of parameters.To solve this problem,the gray wolf optimization algorithm is utilized to determine the number of VMD initial signals and the penalty factor,which has better global search efficiency and faster convergence speed.Simulation proves that the algorithm has good separation performance for single-channel collision signals.(4)The overall design of the VDES satellite receiver is proposed.Detailed design process of the digital signal processing module is given and hardware implementation of the digital signal processing board is completed.The adaptability of Doppler shift of the receiver and the separation performance of collided signals are tested to verify the feasibility of the design.