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.

声学调制解调器是水下无线传感器网络（UWSN）的关键要素之一。与陆地无线传感器网络（WSN）相比，由于水生环境的恶劣条件，设计UWSN既耗时又昂贵。商用调制解调器具有更好的特性，但是它们消耗更多的能量并且更昂贵，而研究型调制解调器已经开发了多种替代方案，并取得了不同的成功。本文的主要贡献是根据商业和研究调制解调器的特性和设计约束条件对它们进行比较分析，以描述当前的趋势和更有希望的技术。本文重点介绍了最近几年设计，开发和实施的最新的水下声学调制解调器。考虑并分析了调制解调器的各种参数：工作范围，数据速率，调制方案，中心频率，带宽，功耗，误码率等。最后，确定了需要解决的设计难题。这项研究对工程界来说，有助于了解最新的水下声通信调制解调器的特性，趋势和设计挑战。