基于双簇模型的无人机对车辆信道多普勒特性研究

Doppler Characteristics of UAV-to-Vehicle Channel Based on Twin-Cluster Model

  • 摘要: 凭借低成本、易操作和高机动的优势,无人机已成为空地通信系统的重要组成部分。基于实际传播场景中无人机对车辆通信的多输入多输出信道,本文提出了一种考虑无人机机身散射效应和三维旋转的无人机对车辆信道双簇模型。该模型中,信道由视距路径、一次反射路径和随机散射路径组成。在散射路径中同时考虑了地面散射体以及无人机自身带来的散射效应,从而将随机散射路径分解为发射天线到机身散射体、机身散射体到地面散射体以及地面散射体到接收天线三个部分。本文研究了无人机的六维运动,包括三维平移和三维旋转,以及地面车辆以任意速度和任意方向移动的场景,通过引入时变姿态矩阵,实时更新机身散射体和发射天线的位置矢量。此外,还分析了各种路径时的多普勒频移和信道统计特性,包括时间自相关函数和多普勒功率谱密度。研究结果表明,无人机机身散射和六维运动对传输信号的多普勒效应和对系统性能的平稳性都有明显影响。无人机的三维平移和三维旋转分别导致了传输信号的宏多普勒频移和微多普勒频移,其中宏多普勒频移占主导。三维平移速度越大,传输信号时间自相关函数衰减越快,信道平稳性也相应越差;三维旋转引入的微多普勒频移会导致多普勒功率谱密度周期性波动。为确保动态运行条件下的可靠通信,将无人机六维运动模型集成到无人机对车辆信道框架中是必要的。

     

    Abstract: With the advantages of low cost, ease of operation, and high mobility, Unmanned Aerial Vehicles (UAVs) have become a crucial component of air-to-ground communication systems. For the multiple-input multiple-output channel derived from real-world propagation scenarios in the context of UAV-to-Vehicle (U2V) communication link, this study proposed a twin-cluster U2V channel model incorporating UAV fuselage scattering effects and three-dimensional (3D) rotation. In this model, the channel consisted of a line-of-sight path, a single-bounce reflection path, and some randomly scattered paths. In the scattering path, the scattering effects introduced by both the ground scatterers and UAV itself were simultaneously taken into account. Consequently, the propagation process of the signal along the random scattering path was decomposed into three segments: from the transmitting antenna to the fuselage scatterer, from the fuselage scatterer to the ground scatterer, and from the ground scatterer to the receiving antenna. We investigated the six-dimensional (6D) motion of UAVs, including 3D translation and rotation, as well as scenarios where ground vehicles moved at arbitrary speeds and in arbitrary directions. We introduced a time-varying attitude matrix to update the position vectors of fuselage scatterers and antennas in real time. Additionally, we analyzed the Doppler shifts and channel statistical characteristics of various paths, including the Time Autocorrelation Function (TCF) and Doppler Power Spectral Density (DPSD). The study findings indicated that fuselage scattering and 6D motion significantly affected the Doppler effect on the transmitted signal and stationarity of system performance. The UAV’s 3D translation and rotation led to macro- and micro-Doppler shifts in the transmitted signal, respectively, with macro-Doppler shifts being dominant. The greater the 3D translation velocity, the faster the decay of the transmission signal TCF, and accordingly, the poorer the signal stability. The micro-Doppler frequency shift introduced by the 3D rotation caused periodic fluctuations in the DPSD. Thus, to ensure reliable communication under dynamic operating conditions, integrating the UAV’s 6D motion model into the U2V channel framework is essential.

     

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