Diversity Based Coverage Improvement for Air-to-Ground Wireless Channels

Air-to-Ground (A2G) wireless communications using Unmanned Aerial Vehicles (UAVs) as Low Altitude Platforms (LAPs) have become a hot topic in recent decades. Among all the A2G channel models that can be used for A2G channel characterization, the two-ray ground reflection path loss model can be used for environments with fewer scatterers such as over water, suburban and mountainous. In such environments, signal down-fades appear due to the destructive combination of the direct component and the ground reflected component. This paper presents a frequency diversity approach to improve the coverage in such an environment. Our results show that frequency diversity can improve coverage at least by 17% when two frequencies are used assuming the threshold to be -80 dBm. Moreover, this work analyses the coverage improvement that can be obtained through polarization diversity. Our results show that having both horizontal and vertical polarizations can improve the coverage by 10%-95%, assuming the transmission frequency to be 700MHz and UAV altitude is between 100 m-300 m.