Availability of Optical and mmWave Terrestrial Links at Low and Mid Latitudes

In the context of upcoming 6G networks, wireless links remain crucial for backhauling. Free-Space Optics (FSO) and mmWave technologies emerge as alternatives to traditional radio frequency (RF) links, meeting the high data rates required by 6G services. However, both mmWaves and optical waves are highly susceptible to adverse weather conditions, constraining their availability for a given path length or the maximum allowable path length for a target availability. For mmWave links, availability is prevalently influenced by local rainfall statistics, while fog significantly attenuates optical waves, especially in mid-latitude climates. In this study, we compare FSO and mmWave link availability at low and mid-latitudes, considering an FSO link at 1.55μm and a mmWave link at 73GHz. The Complementary Cumulative Distribution Function (CCDF) of total attenuation is derived, integrating results into link budget formulas. Results indicate that low-latitude FSO links can achieve up to 2.5km in range with 99.9% availability, while mid-latitude FSO links range from 300 to 500m to maintain the same availability. Considering the same design constraints on availability, the mmWave link range extends up to 900m at low latitudes and 1.1-1.9km at mid-latitudes with reduced heavy rainfall frequency.