Active Wireless Sensing: Space-Time Information Retrieval from Sensor Ensembles

Existing approaches for information extraction in wireless sensor networks are heavily geared towards in-network processing, which generally incurs excess delay and energy consumption due to the attendant tasks of information routing and coordination between nodes. In this paper, we introduce an alternative concept of active wireless sensing in which a wireless information retriever (WIR) interrogates a select ensemble of nodes for rapid and energy-efficient retrieval of desired information. Active wireless sensing has two primary attributes: i) the sensor nodes are "dumb" in that they have limited computational ability, and ii) the WIR is computationally powerful, is equipped with an antenna array, and directly interrogates the sensor ensemble with wideband space-time waveforms. Our approach is based on an intimate connection between active wireless sensing and wideband multi-antenna wireless channels in multipath propagation environments: the sensor nodes play the role of active scatterers and generate a multipath response to WIR\´s interrogation signals. We illustrate the basic communication architecture in active wireless sensing and the corresponding signal processing at the WIR. Preliminary simulation results are presented to illustrate a fundamental rate versus reliability tradeoff in active wireless sensing