Directional path loss characteristics of large indoor environments with 28 GHz measurements

For 5G communications, millimeter-wave frequency bands are considered strong candidates for new spectra. However, propagation studies in these bands are still in their initial stages. Using 28 GHz measurements collected in railway and airport passenger terminals, this paper investigates path loss characteristics of large indoor environments. In particular, we conducted measurement campaigns in passenger terminals at Seoul Railway Station and Incheon International Airport, which are representative of commercial areas with a dense population. By employing steerable directional antennas, we characterize path loss not only with respect to distance but also with respect to antenna orientation. Directional path loss exhibits near free space propagation characteristics for LOS conditions (path loss exponent is about 2.15-2.17) and a path loss exponent of about 2.68-3.03 for NLOS conditions. From the dependency on antenna orientation, we found the range of azimuthal orientations satisfying a certain power level from the peaks. Consequently, this information provides a tool for determination of the amount of power deviation due to beam mis-alignment.