Stabilizing reconfiguration in wireless sensor networks

A commonly desired feature of large-scale, multi-hop, wireless sensor networks (WSNs) is the ability to reconfigure them after deployment. This reconfiguration could be as simple as changing a single parameter or as complex as replacing the entire application. Several protocols have been proposed to enable reconfiguration in WSNs, most of which use version numbers to distinguish new configurations from old ones. Due to constraints on memory and message sizes, version numbers are bounded and use wraparound arithmetic to handle rollover. While this simple scheme works well in the common case, we identify in this paper, a serious version management problem in existing protocols due to which a reconfiguration operation may never stabilize. We analyze potential causes of this problem and its effects on the quality and lifetime of the network. Through extensive simulations and experiments, we demonstrate the significant likelihood of this problem occurring in real deployments. Finally, we provide a solution to this problem using a novel approach which we call human-in-the-loop stabilization. Our stabilizing reconfiguration protocol uses local detectors and correctors that can detect version inconsistencies and prevent their propagation in a timely and efficient manner, while ultimately allowing the human operator to restore the network to the correct configuration. Our simulations and experiments also demonstrate the performance benefits of our solution over previous, non-stabilizing protocols