Reduction of the Multipath Propagation Effect in a Hydroacoustic Channel Using Filtration in Cepstrum During data transmission in a hydroacoustic channel, one of the problems is the multipath propagation effect, which leads to a decrease in the transmission parameters and sometimes completely prevents it. Therefore, we have attempted to develop a method, which is based on a recorded hydroacoustic signal, that allows us to recreate the original (generated) signal by eliminating the multipath effect. In our method, we use cepstral analysis to eliminate replicas of the generated signal. The method has been tested in simulation and during measurements in a real environment. Additionally, the influence of the method on data transmission in the hydroacoustic channel was tested. The obtained results confirmed the usefulness of the application of the developed method and improved the quality of data transmission by reducing the multipath propagation effect.

Single Carrier Block Transmission Schemes for Acoustic Communications and Their Field Evaluation Results This paper proposes transmission technologies for acoustic communications in order to mitigate doublyselective environments. The single carrier block (SCB) transmission schemes using frequency domain equalization (FDE) are effective for frequency selectivity, but it suffers from performance degradation due to time selectivity. This paper proposes SCB transmission schemes for acoustic communications which introduce a frame format suitable for channel interpolation (CI), and employs cyclic delay diversity (CDD) in order to extend communication distance. In particular, the proposed schemes can mitigate tracking error caused by timevarying channels, owing to CI based on multiple estimated channel impulse responses (CIRs). Finally, it is confirmed that the proposed schemes of 8kbps have excellent performance in a delay spread of up to 10msec and a Doppler frequency of around 1Hz, on the basis of field evaluation results in terrestrial and shallow underwater environments.