Estimation and reduction of effects of sea surface reflection on underwater vertical channel

Sea surface wave presents significant challenges for underwater acoustic communication system. Surface waves can cause (1) substantial fluctuations in the delay of the surface scattered signals and (2) obvious wave front focusing, implying doppler spread effect, intersymbol interference, and signal estimation residual error for communication signals. This paper presents the effect of doppler spread and of strong reflected wave caused by sea surface waves, which can be potentially eliminated by passive phase conjugation for a single channel. Results of theoretical analysis and vertical channel impulse response measurement conducted by Taiwan Ocean Research Vessels 3 in Kauping canyon/Zichi-Bay reveal that both effects can be efficiently reduced. This work provides prediction of channel impulse response induced by surface wave and a potential and efficient way to reduce surface wave effects on vertical channel communications or underwater sensor network implemented by surface buoys in deep sea region. This work is supported by National Science Council of Taiwan.