Path loss measurements and models at 28 GHz for 90% indoor coverage

Achieving adequate coverage with high gain antennas is key to realizing the full promise of the wide bandwidth available at mm/cm bands. We report an extensive indoor measurement campaign at 28 GHz, with over 500 links with and without Line-of-Sight (LOS) measured in 2 office buildings using a specialized narrowband channel sounder. We use a 10 ^° (24 dBi) receiving horn antenna spun at speeds up to 300 rpm to capture azimuthal angular power and a 50 ^° (10 dBi) transmit antenna. Measured path gain-distance dependence in both LOS and NLOS is well represented by power-law models, with log-normal deviation of 3.1 dB in NLOS and are within 3.5 dB RMS error of the mode-diffusion model. Mean excess loss at 28 GHz suffered penetrating into a room was found to be 32 dB, in contrast to 20 dB excess loss into a room found previously at 2 GHz.