海面的散射特性导致VDES海上通信信道模型复杂多变,在VDE-SAT下行链路中,低仰角通信导致海浪反射带来的多径效应更加严重。针对此问题,提出一种基于球坐标系的VDE-SAT下行链路信道建模方法,根据不同海情级分析海浪反射对于信号接收特性的影响。首先,将海面散射特性的统计结果参数化,结合地球曲率的影响,建立基于球坐标系的星船通信几何模型,基于此,得到海面有效漫反射区。其次,建立星船通信链路的信号多径传播模型,基于G1139协议,根据各个路径的信道参数分析接收信号的功率分布,以及不同海情级下信号的接收特性。仿真结果表明：在海况较好时,该多径信道以镜面反射为主；海况较差时,以漫反射为主。相比于卷积码,Turbo码的抗多径性能更优。
The scattering characteristics of sea surface lead to the complex and changeable channel model of VDES maritime communication. In the VDE-SAT downlink, low elevation communication leads to more serious multipath effect caused by wave reflection. To solve this problem, a VDE-SAT downlink channel modeling method based on spherical coordinate system was proposed to analyze the influence of wave reflection on signal receiving characteristics according to different sea conditions. Firstly, the statistical results of sea surface scattering characteristics are parameterized and combined with the influence of earth curvature, a geometric model of satellite-ship communication based on spherical coordinate system is established. Based on this, the effective diffuse reflection area of sea surface is obtained. Secondly, the signal multipath propagation model of Satellite-Ship communication link is established. Based on G1139 protocol, the power distribution of received signals is analyzed according to the channel parameters of each path, as well as the receiving characteristics of signals at different sea levels. The simulation results show that the multipath channel is mainly specular reflection in good sea state and diffuse reflection in bad sea state. Compared with convolutional codes, Turbo codes have better anti-multipath performance.
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