State-of-the-Art Underwater Acoustic Communication Modems: Classifications, Analyses and Design Challenges.

Acoustic modem is one of the key elements of an underwater wireless sensor network (UWSN). Compared to a terrestrial wireless sensor network (WSN), designing a UWSN is more time consuming and expensive due to harsh conditions of the aquatic environment. Commercial modems provide better characteristics, but they consume more energy and are more expensive, while research modems have exploited diverse alternatives with varying success. The main contribution of the article is a comparative analyses of commercial and research modems based on their characteristics and design constraints, in order to describe the current trends and more promising techniques. This paper is focused on the state-of-the-art underwater acoustic modems designed, developed and implemented in the last few years. Various parameters of the modems are considered and analyzed: operating range, data-rate, modulation schemes, center frequency, bandwidth, power consumption, bit error rates, etc. Finally, design challenges, which need to be addressed, are identified. This study is useful for the engineering community to comprehend the characteristics, trends and design challenges of state-of-the-art underwater acoustic communication modems. [ABSTRACT FROM AUTHOR]