Efficient Location Training Protocols for Heterogeneous Sensor and Actor Networks

Sensor networks are expected to evolve into longlived, autonomous networked systems whose main mission is to provide in-situ users – called actors – with real-time information for specific goals supportive of their mission. The network is populated with a heterogeneous set of tiny sensors. The free sensors alternate between sleep and awake periods, under program control in response to computational and communication needs. The periodic sensors alternate between sleep periods and awake periods of predefined lengths, established at the fabrication time. The architectural model of an actor-centric network used in this work comprises in addition to the tiny sensors a set of mobile actors that organize and manage the sensors in their vicinity. We take the view that the sensors deployed are anonymous and unaware of their geographic location. Importantly, the sensors are not, a priori, organized into a network. It is, indeed, the interaction between the actors and the sensor population that organizes the sensors in a disk around each actor into a shortlived, mission-specific, network that exists for the purpose of serving the actor and that will be disbanded when the interaction terminates. The task of setting up this form of actor-centric network involves a training stage where the sensors acquire dynamic coordinates relative to the actor in their vicinity. The main contribution of this work is to propose an energyefficient training protocol for actor-centric heterogeneous sensor networks. Our protocol outperforms all known training protocols in the number of sleep/awake transitions per sensor needed by the training task. Specifically, in the presence of k coronas, no sensor will experience more than 1+⌈log k⌉ sleep/awake transitions and awake periods.