A Multicarrier Underwater Acoustic Modem with Precise-Ranging Capability

智能优点：该项目研究了水声通信从单载波传输到正交频分多路复用(Ofdm)形式的多载波调制的范式转变。在处理长色散信道上的高速率传输方面，ofdm具有独特的优势，并已在最近的宽带无线无线电应用中占据主导地位。然而，由于水声信道具有较大的带宽载频比、较大的传播时延、较大的多径扩展和较快的信道变化，使得水声信道比无线电信道更具挑战性。结合水声信道的独特特点，我们的首要任务是使ofdm能够在具有快速移动平台的水下环境中工作。初步的实验结果表明，即使在发射机和接收机之间的相对速度高达10节的情况下，我们提出的方法也是有效的，这是目前的技术状态。在我们的第二项任务中，我们为多载波调制解调器配备了精确测距能力。关键是开发精确的同步算法，能够在密集的多径条件下定位“第一到达”，并且能够在快速变化的水下信道中很好地工作。在我们的第三项任务中，我们开发了一个基于数字信号处理器的独立调制解调器原型，该原型集成了本项目中开发的收发算法。广泛影响：提供具有测距功能的多载波水声调制解调器，该项目有可能直接受益于各种应用的水下无线传感器网络的发展。由于水声信道具有较大的带宽载频比，所提出的方法和算法也可能对宽带和超宽带无线电应用产生影响。该项目将研究和教育相结合，以增强本科生和研究生课程的内容，特别是提供创新的高级设计项目。

Intellectual Merit: This project investigates a paradigm shift in acoustic underwater communication from single-carrier transmission to multi-carrier modulation in the form of orthogonal frequency division multiplexing (OFDM). OFDM has its unique strength in handling high-rate transmissions over long dispersive channels and has prevailed in recent broadband wireless radio applications. However, underwater acoustic channels are far more challenging than their radio counterparts due to their large bandwidth-to-carrier-frequency ratio, large propagation delay, large multipath spread, and fast channel variations. Incorporating the unique characteristics of underwater acoustic channels, our first task is to make OFDM work in underwater environments with fast-moving platforms. Preliminary experimental results have demonstrated the effectiveness of our proposed approach even when the relative speed between the transmitter and the receiver is up to 10 knots, which is the current state of the art. In our second task, we equip the multi-carrier modem with precise-ranging capability. The key is to develop precise synchronization algorithms that can locate the "first arrival" in the presence of dense multi-path conditions and that can work well in fast-varying underwater channels. In our third task, we develop a standalone modem prototype based on a digital signal processor that integrates the transceiver algorithms developed in this project.Broader Impact: Providing a multi-carrier acoustic modem with ranging capability, this project has the potential to directly benefit the development of underwater wireless sensor networks for a variety of applications. Due to the large bandwidth-to-carrier-frequency ratio of underwater acoustic channels, the proposed methodology and algorithms may, also, have an impact on wideband and ultra-wideband radio applications. This project integrates research and education to enhance the content of undergraduate and graduate classes and, in particular, provides innovative senior design projects.