Enabling fast and reliable network-wide event-triggered wakeup in WSNs

Event-triggered wake-up, in which sensor nodes wake up to work in the presence of some predefined events, has been widely used in wireless sensor networks (WSNs) to save energy while still fulfilling the tasks required. However, existing mechanisms for event-triggered wake-up, such as using auxiliary low-power sensors or via wireless radio communication, cannot be applied to some domain-specific applications such as structural health monitoring (SHM) and volcano monitoring(VM). These applications have different requirements about the wake-up from 'conventional' WSN applications. Firstly, the wake-up should be network-wide and nodes to be woken up are not limited to those close to event location. In addition, the wake-up should be reliable to avoid unnecessary false wake-ups. Finally, the wake-up should be fast to capture the short events in these applications. How to realize network-wide, reliable and fast wake-up in a WSN is a challenging task that has not been addressed in literature. In this paper, based on the developed two types of wake-up units, we designed a novel chain-reaction wake-up mechanism to fulfill the task. As the key in this mechanism, we identify the sentry ode placement problem in which some nodes used to initialize the wake-up process are carefully selected such that the wake-up delay is minimized under the false alarm constraint. We propose two greedy algorithms and a randomized one which leverages the solution to the classic Knapsack problem. The performance of the proposed wake-up mechanism is demonstrated through both simulation and experiments.