Enabling High-Speed Communication between Autonomous Underwater Vehicles

加拿大曾经有一个蓬勃发展的水下声学研究项目，用于敌舰的回声定位，由位于哈利法克斯的加拿大国防研究与发展部（DRDC）领导，但90年代初冷战结束后，这些项目的资金突然中断。**最近，人们对海底勘探的各种应用越来越感兴趣，例如海港监视，海洋行为分析和海上设备监测。例如，在海洋地区，在芬迪湾部署高效发电的涡轮机方面进行了大量投资。监测野生动物和海底设备对评估环境和经济影响至关重要。为了避免电缆的负担，提出了声通信。**在拟议的研究计划中，我们打算开发最先进的设备，用于在海底环境中进行声学通信。为了延长部署的水声设备的使用寿命，必须考虑低功率技术，但这将固有地限制传输范围。**为了帮助增加通信范围，我们建议使用自主水下航行器（auv）。然而，由于技术限制，这些设备的通信能力目前受到强烈限制。因此，一旦AUV发射，通常没有反馈机制，无法实时监测和控制AUV的任务。需要一个允许视频传输的可靠通信链路，并且需要100 kbps左右的高数据速率。**现有的水声调制解调器的吞吐量非常有限，大约为10 kbps，并且消耗大量功率，从而限制了auv电池的使用寿命。水下通信的技术挑战部分是由于用于水下传输的设备的低频操作，但主要是水下声音的不可预测传播。**与我们熟知的无线电-电传播信道相比，水声信道的损伤是相当严重的。可以想象，在海洋中，洋流和波浪创造了一个动态变化的环境，很难预测信号的失真。控制信号传播的物理现象的精确模型目前包括频率依赖的吸收、多径到达、由于迁移和小尺度波动引起的多普勒频移。**提出的工作旨在使用在定制处理器上实现的新算法将水下通信的吞吐量提高至少一个数量级。为了减轻失真，所提出的数字算法需要补偿水下传播的极端损伤。此外，发射器和接收器将配备多个换能器和水听器，以提高数据速率。**使用多个传感器将需要大量的内存和重要的计算资源。为了满足这些要求，信号处理将在定制的完全集成平台上进行编程。此外，为了允许模拟接口到处理器，从而最大限度地减少片外互连的数量，集成电路还将容纳高分辨率数据转换器。**该研究项目将为通信、信号处理和超大规模集成电路（VLSI）技术领域带来创新解决方案。加拿大被3个大水体包围，将从这个项目的研究中受益匪浅。这项研究将与哈利法克斯的当地工业合作进行，用于需要海底监测的商业和科学应用。

Canada once had a thriving research program in underwater acoustics for the echolocation of enemy vessels led by Defence Research & Development Canada (DRDC) in Halifax but the end of the Cold War in the early '90s brought a sudden interruption to the funding of these programs.**Recently there has been an increasing interest in subsea exploration for a variety of applications, such as seaport surveillance, oceanographic behaviour analysis and monitoring of offshore equipment. For example, in the Maritimes, there is significant investment in the deployment of turbines for efficient energy generation in the Bay of Fundy. Monitoring of the wildlife and subsea equipment is crucial to assess environmental and economic impacts. To avoid the burden of cables, acoustic communication is proposed.**In the proposed research program, we intend to develop state-of-the-art equipment to communicate acoustically in subsea environments. To extend the lifetime of deployed underwater acoustic equipment, low power techniques shall be considered, but will inherently limit transmission range.**To help increase the communication range, we propose to use autonomous underwater vehicles (AUVs). However, communication capabilities to these devices are currently strongly restricted, due to technology limitations. As a result, once an AUV is launched, there is typically no feedback mechanism and the AUVs' mission cannot be monitored and controlled in real-time. A reliable communication link that allows video transmission is needed and would require a high data rate on the order of 100 kbps.**Existing underwater acoustic modems have very limited throughput, on the order of 10 kbps and consume significant power, thus limiting the lifetime of the batteries in AUVs. The technical challenges for underwater communication are, in part, due to the low frequency of operation of the equipment used for underwater transmission, but primarily to the unpredictable propagation of sound underwater.**In comparison to the well-understood radio-electric propagation channel, the underwater acoustic channel impairments are quite severe. One can imagine that in the ocean where currents and waves create a dynamically varying environment, it is difficult to predict the distortion of the signal. An accurate model of the physical phenomena that govern the signal propagation currently includes frequency dependent absorption, multipath arrival, Doppler shift due to mobility and small-scale fluctuations.**The proposed work aims to improve the throughput of underwater communication by at least one order of magnitude using novel algorithms implemented on custom processors. In order to mitigate distortion, the proposed digital algorithms will need to compensate for the underwater propagation extreme impairments. Also, the transmitter and receiver will be equipped with multiple transducers and hydrophones to increase the data rate.**Using multiple transducers will require a significant amount of memory and important computation resources. To satisfy these requirements, the signal processing will be programmed on a custom fully integrated platform. Additionally, to allow an analog interface to the processor and consequently minimize the number of off-chip interconnections, the integrated circuit will also hold high-resolution data converters.**This research program shall lead to innovative solutions in the fields of communication, signal processing and very large scale integration (VLSI) technology. Canada being surrounded by 3 large bodies of water will benefit greatly from the research developed in this project. This research will be conducted in collaboration with local industry in Halifax for commercial and scientific applications that require sub sea monitoring.