Channel characterization including path loss and Doppler effects with sea reflections for mobile radio propagation over sea at 2 GHz

Maritime communication plays an important role in marine activities, but insufficient knowledge of radio channel characteristics over sea limits the development of wideband wireless communication systems for maritime applications. Therefore a land-to-ship (L2S) radio channel measurement assignment has been performed in Trondheim, Norway. In this paper we have focused open sea propagation environments, and results of the channel characterization from measurements are presented, such as path-loss, channel correlation and Doppler effects due to sea reflections, along with the reflection coefficient of the sea surface. The received signal level (RSL) has been compared to the Okumura-Hata model, the COST 231-Hata model and the ITU-R P.1546-2 model, and it has been found that the ITU-R model for open cold sea corresponding to field-strength value exceeded at 50% of the locations fits the measurement results best. By using two receiver antennas with 1.865 m spacing, partly channel correlation has been revealed when the distance between the transmitter (TX) and receiver (RX) is within 2 km, while the two channels are found to be highly correlated when the boat is further away from the shore. When the distance between the TX and RX is within the range 3 km to 12 km, a fading beat frequency is found to be 0.16 Hz, i.e. about 0.16 Hz Doppler shift caused by the sea movement. Finally, the reflection coefficient of the sea surface turns out to be about 0.11 in the same range, which does not comply with the Kirchhoff theory for effective reflection coefficient.