Rural macrocell path loss models for millimeter wave wireless communications

Little is known about millimeter wave (mmWave) path loss in rural areas with tall base station antennas; yet, as shown here, surprisingly long distances (greater than 10 km) can be achieved in clear weather with less than 1 W of power. This paper studies past rural macrocell (RMa) propagation models and the current third generation partnership project (3GPP) RMa path loss models for frequencies from 0.5 to 30 GHz adopted from the International Telecommunications Union-Radiocommunication Sector (ITU-R). We show that 3GPP and ITU-R RMa path loss models were derived for frequencies below 6 GHz, yet are being asserted for use up to 30 GHz. Until this paper, there has not been published data to support mmWave RMa path loss models. In this paper, 73-GHz measurements in rural Virginia are used to develop a new RMa path loss model that is more accurate and easier to apply for varying transmitter antenna heights than the existing 3GPP/ITU-R RMa path loss models, and may be used for frequencies from 0.5 to 100 GHz. The measurement system used here has a measurement range comparable to a wideband (800-MHz radio frequency bandwidth) channel sounder with 21.7-dBW effective isotropic radiated power. Measured data verify a new path loss model that uses a close-in free space reference distance with a novel height-dependent path loss exponent (CIH model). This work shows that the CIH model is accurate and stable, and is frequency-independent beyond the first meter of propagation, and effectively models the path loss dependence on base station height in rural channels.