Ricerc@Sapienza

The achievement of an optimal trade-off between reliability and rate has always been one of the most challenging issues in underwater acoustic links. In this context, the implementation of suitable transmission techniques on Multiple-Input Multiple-Output (MIMO) architectures results to be an efficient solution to improve the communication performance. Following this direction, we investigate a space-time block coding scheme for MIMO-PPM (Pulse Position Modulation) systems that is able to provide a satisfactory compromise between rate and reliability.

A new blind estimator of the sampling phase is proposed to support fractionally spaced equalization in underwater digital links employing pulse position modulation. Stemming from the relationship between the “spikiness” of the channel impulse response and the deviation from Gaussianity of the received signal, the sampling phase is estimated by exploiting non-Gaussianity measures offered by nonlinear statistics. In particular, the fourth order (kurtosis) and the first order nonlinear sample moments are considered and the resulting receiver performance is analyzed.

Underwater acoustic digital communications suffer from inter-symbol interference deriving from signal distortions caused by the channel propagation. Facing such kind of impairment becomes particularly challenging when dealing with shallow water scenarios characterized by short channel coherence time and large delay spread caused by time-varying multipath effects. Channel equalization operated on the received signal represents a crucial issue in order to mitigate the effect of inter-symbol interference and improve the link reliability.

Visible Light Communication (VLC) is based on the dual use of the illumination infrastructure for wireless data communication. The major interest on this communication technology lies on its specific features to be a secure, cost-effective wireless technology. Recently, this technology has gained an important role as potential candidate for complementing traditional RF communication systems. Anyway a major issue for the VLC development is a deep comprehension of the noise and its impact on the received signal at the receiver.