Acoustic underwater channels are very challenging, because of limited bandwidth, long propagation delays, extended multipath, severe attenuation, rapid time variation and large Doppler shifts. A plethora communication techniques have been developed for dealing with such a complexity, mostly tailoring specific applications scenarios which can not be considered as one-size-fits-all solutions. Ind...

In this paper we address the cooperative navigation of Autonomous Underwater Vehicles (AUVs), where navigation data is exchanged by the vehicles with acoustic modems, with the goal of improving their individual position estimates. The following key points are considered: (i) the fact that the system is continuous but the communications are discrete, and (ii) and the problem of deciding when sho...

Underwater acoustic signal processing aims to reconstruct the shallow water acoustic channel from both direct arrival and delayed multipath reflections. This enables accurate acoustic communications in shallow water, such as between underwater autonomous vehicles (UAVs), which are essential for coastal surveillance and other applications. In this work, we take a previously implemented algorithm...

This proposal concerns component development for a novel hybrid lidar-radar system for underwater surveillance. Computer simulations and laboratory measurements of pulsed lidar revealed a 17 dB suppression of the water backscatter signal (clutter) and corresponding target contrast enhancement. Preliminary ocean experiments have confirmed the potential of pulsed lidar to be a superior detection ...

This poster reports the theory and current implementation of a decentralized navigation system that enables simultaneous single-beacon navigation of multiple underwater vehicles.We summarize the architecture and design of the acoustic communications (Acomms) system consisting of an underwater acoustic modem, synchronous clock, and the software necessary to run them; the salient results from the...

The interest in deployment of multiple autonomous underwater vehicles (AUVs), such as AUV swarms, has been increasing. AUV swarms can reduce mission completion times and increase the system reliability. One of the basic constraints of these multiple vehicle systems is the limited communication between AUVs through the very challenging underwater acoustic channel. Even though reliable point-to-p...

The long-term objective is to develop knowledge of factors controlling the mean and the variability of acoustic fields in the shallow ocean environment, in the frequency band 50 Hz to 3000 Hz. Propagation variability is an inescapable complicating factor for both active and passive sonar systems, and for underwater acoustic communications. Reliable predictions of temporal and spatial variabilit...

Broadband underwater acoustic communication signals undergo either a compression or dilation in the presence of relative motion between a source and a receiver. Consequently, underwater acoustic communications with a mobile source/receiver require Doppler compensation through resampling. However, resampling may not be necessary when a channel-estimate-based time reversal approach is applied wit...