  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.
