The sound of communication in underwater acoustic sensor networks: (Position paper)

Underwater environments have never been much of a constraint to the rich animal life they support at all depths of our seas and oceans. Indeed, nature has taken advantage of this environment to develop a rich variety of efficient communication strategies through evolutionary change and adaptation. The wealth of knowledge to be discovered will continue to dazzle and fascinate the world. For underwater sensor network communication, acoustic signalling is the preferred choice for designers because sound propagation is the most efficient when compared to other forms, like thermal, light, and electromagnetic. It is within this acoustic environment that researchers have to innovate and develop new ideas and methodologies so as to advance the state-of-the-art. In this paper, several fundamental issues and connections are discussed that arise in the study of underwater wireless sensor networks. A variety of ideas and solutions for further research is proposed and fundamental issues in topology control, directional underwater transducers, and monitoring and surveillance are disc

Strong connectivity of sensor networks with double antennae

Inspired by the well-known Dipole and Yagi antennae we introduce and study a new theoretical model of directional antennae that we call double antennae. Given a set P of n sensors in the plane equipped with double antennae (with either dipole-like or Yagi-like propagation patterns) of angle ϕ, we study the connectivity and stretch factor problems, namely finding the minimum range such that there exists an orientation of the double antennae of that range that guarantees strong connectivity or stretch factor of the resulting network. We introduce the new concepts of (2, ϕ)-connectivity and ϕ-angular range and use them to characterize the optimality of our algorithms. We prove that the ϕ-angular range is a lower bound on the range required for strong connectivity and show how to compute it in time polynomial in n. We give an algorithm for orienting the antennae so as to attain strong connectivity using optimal range when ϕ ≥ 3π/4 and an algorithm that approximates the range to 3 times the optimal range for ϕ ≥ π/2. For ϕ < π/3, we show that the problem is NP-complete to approximate within a factor √3. For ϕ ≥ π/2, we give an algorithm to orient the antennae so that the resulting connectivity network has a stretch factor of at most 4 compared to the underlying unit disk graph

Strong connectivity of sensor networks with double antennae

Inspired by the well-known Dipole and Yagi antennae we introduce and study a new theoretical model of directional antennae that we call double antennae. Given a set P of n sensors in the plane equipped with double antennae of angle φ and with dipole-like and Yagi-like antenna propagation patterns, we study the connectivity and stretch factor problems, namely finding the minimum range such that double antennae of that range can be oriented so as to guarantee strong connectivity or stretch factor of the resulting network. We introduce the new concepts of (2,φ)-connectivity and φ-angular range r φ (P) and use it to characterize the optimality of our algorithms. We prove that r φ (P) is a lower bound on the range required for strong connectivity and show how to compute r φ (P) in time polynomial in n. We give algorithms for orienting the antennae so as to attain stro