Pathloss and Fading Characterization for E-Band Long-Range Propagation Over Sea

Millimeter-wave (mm-wave) communication using the E-band, i.e., the 71-76 and 81-86 GHz spectrum, can offer high capacity in the order of Gigabits per second (Gbps), thus becomes a candidate technology for wireless backhaul over sea. Compared to submarine fiber-optic cables, E -band backhaul systems are much more flexible to deploy and easier to maintain. Before designing such systems, we need to characterize E-band long-range propagation in over-sea environments. In the paper, based on channel measurements at 74 GHz conducted on a 12-km link across the sea near Sanya Bay, China, we study pathloss and fading properties which are crucial for wireless connectivity. Meteorological data were also recorded during the measurements, allowing us to analyze over-sea propagation in different weather conditions. Our experimental results show an average of 0.2-0.7 dB/km attenuation additional to free-space propagation loss. The additional attenuation can be largely affected by meteorological conditions above the sea surface, especially the amount of water vapour in the atmosphere. We also find that vertically-polarized waves have significantly lower propagation loss than horizontally-polarized. The pathloss model suggested by the International Telecommunication Union (ITU) Radio-communication Sector, known as the ITU-R model, well predicts the horizontally-polarized wave propagation loss but overestimates the vertical. On the 12-km across-sea link, severe fading was observed, although the transmitter and receiver were both firmly fixed. The variation of propagation attenuation can reach 15 dB in a very short time. The overall results may contribute to E-band channel modeling and future system design for wireless backhaul in oversea environments.