Characterization of the underwater medium as an acoustical horizontal transmission channel

From many results obtained in the laboratory, the authors try to characterize the underwater medium as a horizontal acoustic communication channel. They distinguish two fields. The first one deals with short or middle range transmission (between 1 and 15 km) in which many parameters have an influence: those connected to the physics of the medium (sound velocity graph, influence of the current, the sea state, etc.) and to the transmission conditions (emission depth, directivity of the array, etc.). The second one deals with long range communication (exceeding 15 km) which primarily depends on the ray refraction phenomenon. Therefore, short range transmissions are more critical, essentially due to interference. The worst case is in shallow water. The undersea channel, within the communication frequencies range (less than 10 kHz), does not behave like a Rayleigh channel. As the propagation distance increases, the deterministic part of the channel response increases.<>