Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

中文翻译：

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高速列车环境的经验毫米波宽带传播特性

由于与进行毫米波 (mmWave) 现场测量相关的困难，尤其是在高速列车 (HST) 环境中，大多数毫米波 HST 传播通道已使用基于模拟而非测量的方法进行研究。在本研究中，考虑到沿铁路安装基站的线性小区布局，在两种流行的 HST 场景中以 28 GHz 的速度以高达 170 公里/小时的速度进行了测量：高架桥和隧道场景。通过观察信道脉冲响应，我们可以识别由铁路静态结构（如架空线路设备）引起的单次和双次反弹多径分量 (MPC)。这些 MPC 会显着影响延迟扩展和多普勒特性。此外，我们观察到两种情况下不同的路径损耗行为，尽管两者都被视为视线 (LoS) 场景。在隧道场景中，由于波导效应，路径损耗指数 (PLE) 为 1.3，这表明路径损耗相对于距离几乎是恒定的。但是，高架桥场景中的 LoS PLE 为 2.46，略高于自由空间损耗。