On the Research Paradigm of Underwater Networks: Issues and Solutions

• Speaker: Won-Yong Shin
• Abstract: Compared with our human being’s familiarity with land, there are still many un-explored areas with underwater research. Along with a variety of studies in terrestrial radio networks, the interest in study of underwater networks has been growing with recent advances in acoustic communication technology. Note that the research of underwater networks is attracting for military and commercial purposes. In this talk, we first introduce the concept of underwater networks, and then review some recent developments with their broad applications. We also address a main feature that distinguishes underwater systems from wireless radio links. We now would like to inquire what are the fundamental capabilities of future underwater networks in supporting a multiplicity of autonomous nodes that wish to communicate with each other over an acoustic channel. To answer this question, asymptotic capacity scaling laws are analyzed as the number of nodes tends to infinity. More specifically, we characterize an attenuation parameter that depends on the transmission distance and also on the carrier frequency, and then identify fundamental path-loss attenuation regimes according to the parameter. Provided that the frequency scales relative to the number of nodes, information-theoretic upper bounds and achievable throughputs are obtained as functions of the attenuation parameter in a variety of underwater network scenarios. As a result, vital information for fundamental limits of multi-user underwater networks is provided.

Introduction

Introduction to Underwater Networks

• Today: point-to-point acoustic links
• Future: autonomous networks for ocean observation
• Examples of future networks
  • AUV
    • Ocean Monitoring: recording data, taking photos, or collecting water samples

Main Applications

• Application scenarios
  • Environmental monitoring: climate recording, prediction of natural disasters
  • Undersea exploration
  • etc.
• Gulf Oil Spill Recovery
  • Siphon tube with stopper
    • plug the inside of the riser w/ the stopper
• Underwater Hotel
  • Poseidon undersea resort
    • World's 1st underwater hotel
    • Set up on Fiji mystery island

System Modeling

• Choose Acoustics (not RF or Optical)

Network Architecture

• 2D underwater sensor network
  • Ocean bottom monitoring
  • Constituted by sensors that are anchored to the bottom of the ocean
  • Connected to uw-sinks via direct links or multi-hop (MH) paths
• 3D Underwater sensor network
  • Ocean column monitoring
    • Monitoring of ocean pheonomena: bio-geo-chemical processes, water streams, polution, etc
• 3D underwater sensor network with AUVs
  • Fixed portions composed of anchored sensors
  • Mobile portions constitued by AUVs

Research Methodology

• Information-theoretic capacity
  • Upper bound
    • Shows a fundamental limit of a given system
  • Lower bound
    • Can be characterized by designing an explicit protocol
• Why Scaling Laws?
  • Recent challenge in network inf.theory
    • Multiple-access channel (MAC), broadcast channel, relay channel, and interference channel
  • In (many-to-many) ad hoc networks

Our System model

• Simplified channel model
• Network configuration
  • Network size: extended/dense networks
  • Node distribution: regular network
  • Dimension: planar (2D) network
• Basic Assumptions
  • Randomly pick a matching of S-D pairs

Future Work

• Further studies on the network capacity
  • Modeling of node mobility
  • Capacity scaling with mobil networks
    • Hybrid network with mobile AUVs
  • Consideration of feasible channel environments
• Transceiver design of underwater systems
  • Sparse channel estimation
  • Initial synchronization issues
  • Training design