In this letter, we investigate rural large-scale path loss models based on the measurements in a central area of South Korea (rural area) in spring. In particular, we develop new close-in (CI) path loss models incorporating a diffraction component. The transmitter used in the measurement system is located on a hill and utilizes omnidirectional antennas operating at 1400 and 2250 MHz frequencies. The receiver is also equipped with omnidirectional antennas and measures at positions totaling 3,858 (1,262 positions for LOS and 2,596 positions for NLOS) and 4,957 (1,427 positions for LOS and 3,530 positions for NLOS) for 1400 and 2250 MHz, respectively. This research demonstrates that the newly developed CI path loss models incorporating a diffraction component significantly reduce standard deviations (STD) and are independent of frequency, especially for LOS beyond the first meter of propagation, making them suitable for use with frequencies up to a millimeter-wave.

翻译：本文基于春季在韩国中部地区（乡村区域）的测量数据，研究了乡村大尺度路径损耗模型。特别地，我们开发了融入衍射分量的新型近距离（CI）路径损耗模型。测量系统中发射机架设于山丘上，采用工作在1400 MHz和2250 MHz频率的全向天线。接收机同样配备全向天线，在1400 MHz和2250 MHz频段分别测量了3858个位置（其中视距路径1262个，非视距路径2596个）和4957个位置（其中视距路径1427个，非视距路径3530个）。研究表明，新开发的含衍射分量的CI路径损耗模型显著降低了标准差（STD），且具有频率无关性（尤其在首个传播米之外的视距路径中），使其适用于高达毫米波频段。