Riding Stress Wave: Underwater Communications Through Pipeline Networks

The majority of research works on underwater communications have been struggling against the water medium for a long time. Either acoustic, electromagnetic, or optical waves suffer from specific propagation defects in the water. Briefly, acoustic waves suffer from long propagation delay and frequency-selective fading. Electromagnetic waves are susceptible to the significant attenuation in the conductive seawater. Strong absorption and severe Rayleigh scattering make wireless optical communication vulnerable. Therefore, a reliable, long-range (up to kilometer), and high data-rate (up to megabits per second) wireless communication is still unavailable in the underwater environments so far. Fortunately, in the past few decades, massive offshore pipeline networks have been deployed for oil and gas transportation. These pipelines provide a new medium for realizing underwater communications, in which the acoustic wave propagates in the pipe wall (also known as stress wave). This stress wave assisted communication scheme overcomes some drawbacks within the aforementioned modalities. So, in this article, we propose a brand new underwater communication paradigm, namely underwater stress wave communications, which utilizes stress wave and offshore pipeline networks for underwater data transmission. Fundamentally different from the conventional underwater communication schemes, stress wave signals propagate through the solid pipe instead of water. Therefore, underwater stress wave communications exhibit several unique and promising features, including 1) lower latency and higher bandwidth compared with acoustic communications; 2) longer communication range than electromagnetic and optical communications; and 3) nearly deterministic and constant channel conditions. To fully utilize these promising features to establish reliable, secure, and high-data-rate communication links along offshore pipelines, this article investigates the stress wave channel characteristics including path loss, available bandwidth, and channel response. Furthermore, we demonstrated a stress wave communication along a steel pipe both in the air and water, and experiment results indicated the feasibility of stress-wave-based communications.