Ricerc@Sapienza

Acoustic communications in underwater environment are considerably influenced by the physical characteristics of the medium. This is even more true in the polar regions where the presence of icebergs and icy water layers represent an additional dependence to the signal propagation. Considering a MIMO scenario, we investigate how the channels spatial correlation is conditioned in the case of both frozen and fluid water surface. More, we evaluate the impact of the medium changes on the signal delay spread.

LTE-Advanced networks are spreading widely across the world and they are continuing to evolve as new device features such MIMO 4×4, Carrier Aggregation are being released to move towards the peak data rates introduced by 3GPP Release 12 and 13. Mobile network Operators are looking for technologies that guarantee higher spectral efficiency and wider spectrum usage but they have to deal with limitations due to commercial devices' RF components. This paper analyzes several scenarios, compares them and suggests deployment strategies.

Underwater acoustic communications performance are severely limited by the high number of reflections especially in shallow water environment so producing large delay spread on the signal during the propagation. Multiple-input-multiple-output (MIMO) solutions combined with spatial multiplexing (SM) techniques have been investigated in order to increase the communication rate despite the bandwidth-limited channel.

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.

In this paper, a non-line-of-sight multiple-input multiple-output space and time division multiple access optical camera communications system is proposed for an indoor environment. Mask matching and equal-gain combining (EGC) schemes as well as differential modulation and frame subtraction are used. We propose a unique packet structure to label the transmitters and a new detection method for data extraction from the captured video streams. We outline a comprehensive theoretical model and have developed an experimental testbed to evaluate the performance of the proposed system.