Measured channel impulse responses for a mobile source in the northeastern sea off Taiwan

While our understanding of underwater acoustic communications has improved, communications involving mobile assets (e.g., gliders and AUVs) remains quite challenging. In September 2011, the MArine Cable Hosted Observatory (MACHO) was launched in the northeastern sea off Taiwan for surveillance of submarine earthquakes, tsunami, and the ocean environment. The MACHO system, administrated by the Central Weather Bureau, is the first submarine observatory for various science research projects in Taiwan and was used to study underwater acoustic channel in 2012. This paper presents preliminary results of measured underwater acoustic channel impulse response for mid-frequency band of 4-6kHz in the northeastern sea off Taiwan by using a mobile source with MACHO system. The data transmitted by the source moving along a track across canyon, listened by a fixed bottom mounted hydrophone in the system of marine hosted cable, is analyzed and compared to a more typical channel: the flat-bottom channel. The results shows that the across-canyon track presents low SNR at certain locations as the mobile source was moving across the canyon, which will break the communication between mobile sources and receiving stations. However, communication performance can be improved by spatial diversity, obtained from a virtual horizontal array generated by the moving transmitter and the fixed receiver, referred to as a synthetic aperture communication.