Characterization of high-frequency underwater acoustic channel around 100 kHz in a shallow water

In order to attain high data rate in underwater acoustic communication the use of a high carrier frequency is inevitable due to the limited ratio between the bandwidth and the center frequency. Recently studies on communication systems using carrier frequencies of a few hundred kHz have been done for this purpose. Currently Korea Research Institute of Ships and Ocean Engineering (KIRSO) is also developing a high-frequency communication system and is considering the use of a carrier frequency of 100 kHz. For channel characterization and the design of an acoustic modem an experiment of channel measurement was performed in April 2016. Various channel parameters, such as probability density functions and K-factors, are estimated using narrow-band signals. Channel impulse responses including Doppler spread and RMS delay spread are also analyzed for multi-path time-varying channel characterization. The results show that two or three paths are observed for short range communication. We also found that coherence time lies around a few hundred ms and coherence bandwidth is around a few hundred Hz.