Long-distance propagation measurements of mobile radio channel over sea at 2 GHz

A long-distance channel measurement campaign with a maximum distance of 45 km was performed in Trondheimsfjorden, Norway. In this paper, we give a detailed description of the channel measurements including route, RX and TX antenna sites and other channel parameters. The results of received signal level (RSL) obtained by using two different signal processing methods are demonstrated, and it is found that the influence of unwanted interference and noise becomes more than 2 dB at distances beyond 20 km, which proves the necessity of employing an interference-reduction method. The inbound trip RSL is found to be larger (similar to 6 dB) than for the outbound trip, which is assumed to be due to the "inbound" TX antenna resting on the furthermost edge of a large horizontal metal plane, which might act as a mirror to create its image. The path loss has been compared with the free-space model, 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. However, some important deep fadings visible in our measurements are not seen in these models. Finally, the channel spatial correlation coefficient between the two RX-antennas is found to be less than 0.7 beyond a distance of 3 km. The ship turning and shadowing effect caused by other ships might, however, reduce the spatial correlation between the two RX channels.