• OFDM
• Acoustic
• Covert
• Multi-Band
• Underwater

The goal of the project UCAC is to investigate digital communications in underwater acoustic channel, to develop and compare algorithms which meet requirements of covertness and efficiency and to demonstrate the feasibility of basic communication. The specific task is to develop an OFDM approach in this ostile communication scenario. Indeed, the underwater acoustic channel presents specific impairments that makes implementation of OFDM more challenging, with respect to the wireless communications. The present work relies on a transmitter architecture previously defined by TNO, that imposed fixed constraints on channel coding and interleaving, as well as data rate and transmitted streams. Thus, our goal was to concentrate on the transmitter and receiver implementation of the OFDM modulation and demodulation, respectively. Specifically, we considered a multi-band OFDM system, analyzing algorithms for equalization and channel estimation tested both by simulations and by real field data, obtained in the second sea trial of September 2007