Underwater Backscatter Networking for Subsea IoT: A Link-Budget Analysis in Practical Ocean Channels

Underwater backscatter is an emerging technology for ultra-low-power communication and networking. Unlike traditional underwater acoustical modems, which communicate by generating their own acoustical signals, underwater backscatter nodes communicate by reflecting external acoustical signals, enabling them to operate at 5–6 orders of magnitude less power than existing low-power modems. Yet, before the practical adoption of this technology, it remains necessary to understand its link budget in practical ocean channels. In this article, we perform a comprehensive investigation of the underwater backscatter link budget in practical channels considering various sources of signal and noise that are unique to backscatter communication systems. We develop a closed-form end-to-end link-budget model of underwater backscatter and perform experimental validations in real-world environments. For the first time, we experimentally verify the end-to-end analytical model of the signal-to-noise ratio (SNR) as a function of distance and source level. Not only does this model enable us to predict the expected SNR within a median of 0.75 dB of the experimentally measured one, but also to identify new methods that improve the performance of underwater backscatter and extend its range over state-of-the-art past work. We then use this validated model to simulate backscatter performance under practical ocean channels and understand the impact of system and environmental parameters on the end-to-end performance. By developing and validating the link budget model, this article paves the way for the practical adoption of underwater backscatter in applications of ocean climate change monitoring, scientific studies, and coastal resilience.