Impulse response analysis of an ultrasonic human body channel Abstract   Ultrasounds have been successfully and safely employed in underwater communications and for health diagnosis in the last 60 years because of their good performance in environments with high water concentration. Recently it has been proposed also to employ them for supporting intrabody communications; however exploitation of ultrasounds inside the body calls for a deep understanding of their features and a full characterization of the impulse response inside these challenging channels. In this paper we provide a complete experimental characterization of the impulse response inside a human body communication channel, composed for more than 6570% of water. To this purpose we developed a testbed which employs a human phantom of ballistic gel to emulate the human body propagation features and performed a set of measurements to fully discuss the channel behavior as a function of different parameters such as the employed frequency, the channel composition and the distance. Our results show that, it is possible to clearly identify the three main components generated by multipath propagation inside the human phantom, i.e. the direct, lateral and reflected waves. Also, it is possible to observe that the excess delay which measures the time elapsed between the first and the last arriving waves, increases approximately as 10 xcexbcs per cm. Our analysis provides interesting has strong implications on the design of communication protocols for intrabody scenarios.

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.