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ate companies, 90 GHz band propagation experiments in various railway environments including a viaduct and tunnel.e experiment on propagation measurement in the viaduct environment was conducted using a maglev test line in Miyazaki, Japan. In millimeter wave based train-trackside radiocommunication, it is generally assumed to implement a set of communication areas along the train line. In this experiment, directional antennas were installed and they are directed to the train line (see Fig.1). Figure 2 shows the schematic diagram of the propagation measure-ment system used in the experiment, and Figure 3 shows the results of propagation loss measurement (path loss vs. transmission distance) and estimated regression curves. In this experiment, transmitter (Tx) and receiver (Rx) anten-nas were installed at the same height (1 m or 2 m), and the transmitter signal was vertically-polarized. For refer-ence, a theoretical free space loss (path loss coecient n = 2) by calculating equations (1) and (2) is also plotted in the gure.dB][log100100ddnLPL(1)dB][8log20100fL(2)where, the reference distance d0 is 10 m, and the fre-quency f is in MHz.Path loss coecients of regression lines were calculated from the propagation loss data using the least squares method assuming the reference distance d0 = 10 m. e estimated coecients are: n = 1.52 (for antenna height 2 m) and n = 1.13 (for antenna height 1 m). ese results clearly indicate that the pass loss coecient becomes smaller as the antenna height becomes lower.e experiment also included path loss measurements using dierently polarized signal and power delay prole measurements using modulated waves. By analyzing these results, the authors proposed propagation models and delay spread models to ITU-R SG3 Working Party 3K (WP3K).2.2Millimeter waves propagation characteristics for mobile communication use in urban environment[3]Frequency identication in the millimeter wave band (24.25–86 GHz) to be added to the IMT band is scheduled to be discussed as AI 1.13 in WRC-19. A new specication of suitable frequencies involves frequency sharing analysis, requiring the development of a propagation model. e authors conducted experiments using each of the candidate millimeter band frequencies to characterize their propaga-tion properties in an urban environment. is section outlines the results from these experiments.Measurement items of the experiment include: ① Propagation loss measurement — development of a path loss model to be used in link budget design and interfer-ence evaluation, ② power delay prole measurement — to be used for the development of a channel model (impulse response model) that helps in the evaluation of the physi-FiF2　Propagation measurement system in 90 GHz band(Copyright(C)2017 IEICE, [2] Fig. 4)AWGSGUP-conv.LOOscilloscopePCDown-conv.LO～500mANTANTTX side (MS)RX side (BS)FiF3Path loss characteristics in 90 GHz band (Measured with vertical polarized signal)(Copyright(C)2017 IEICE, [2] Fig. 5)105010050090100110120130Distance (m)Path loss (dB) Free space Antenna height 2m Antenna height 1mFiF1　Propagation measurement in viaduct environment(Copyright(C)2017 IEICE, [2] Fig. 4)TX AntennaRX AntennaTX sideRX side2 Terrestrial Communication Technology Research and Development20　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)