Collision-Free Routing in Sink-Centric Sensor Networks with Coarse-Grain Coordinates

Abstract

We propose novel localization and routing protocols in an actor-centric wireless sensor network consisting of an actor node and a large number of energy-constrained sensors operating under L different periodic sleepawake schedules. Specifically, we propose a semidistributed localization algorithm in which a small subset of sensors extracts their positions in polar coordinates based on the messages received from the actor, and subsequently localizes (also in polar coordinates) the remaining sensors. By modeling the deployed sensors as a two-dimensional Poisson point process and applying well-known results from the coupon collector's problem and Chernoff bounds, we analytically derive and also validate, by simulation, the sensor density required to localize all sensors in the network with high probability. The actor-centric network can be modeled by a cluster adjacency graph G with the help of the already localized polar coordinates that logically partition the network into concentric coronas (around the actor), each subdivided in a varying number of clusters (of almost the same area). To avoid intercluster collisions in G, sensors in different clusters transmit on different channels. A lower bound on the number of channels required to schedule the transmissions without collisions is obtained by solving a distance-2 vertex coloring problem on G. Optimal and quasioptimal fully distributed algorithms are provided to determine the channel assigned to each cluster in constant time. Finally, we apply these results to develop a geographic routing protocol: the messages generated from the sensors in a given cluster are routed toward the actor through the unique shortest path of G that starts from the node associated with the cluster and goes up to the corona where the actor resides. In each cluster, to avoid redundant retransmissions toward the actor, we select L leaders, one for each periodic sleepawake schedule.Keywords: wireless sensor and actor networks; sleep-awake schedules; localization protocols; distributed protocols; stochastic analysis; optimal node coloring usually deployed by an unmanned vehicle and remain unattended in a vast, possibly hostile, geographical area for long periods of time. The sensors are periodically awake to sense the area to be monitored. According to a predefined monitoring schedule, actors can roam the environment to collect data, because effective data communications over the entire network are difficult to achieve due to the large number of communication hops [1,23]. Abstracting from this real world application, we envision a DC-WSAN as shown in Figure 2, where each actor is mobile ,and upon reaching a specific location, stations there to organize an actor-centric network (gray disks in Fig. 2) for collecting sensed data.This article deals with three fundamental problems arising in the context of DC-WSAN: (i) localization, (ii) routing, and (iii) collision avoidance. Our solution methodology relies on network modeling at different levels of abstraction. In particular, for the localizati...

VIBE: An energy efficient routing protocol for dense and mobile sensor networks

“…Still the VIBE protocol can be applied as its behavior is independent of the sink location. However, having coordinates too far from the actual ones could considerably degrade the performances (see [22] for an idea of routing on sink-centric WSNs with coarse-grain coordinates).…”