An asynchronous architecture, consisting of asynchronous sampling strategies and an active MAC protocol, is proposed to achieve a better tradeoff between energy efficiency and application's performance in wireless sensor networks (WSNs). Motivated by the data correlation in dense WSNs, asynchronous sampling strategies assign time shifts to nodes' sampling moments to obtain asynchronous sensory data, which is proved to contain more information than the synchronous sensory data at the same sampling rate. Regarding event report scenario, the proposed active MAC protocol adopts the optimal random slot selection probability not only for the medium access control but also for the sampling moments of nodes. By forming an asynchronous architecture of WSNs, the approach is able to achieve energy efficiency for data gathering applications and event detection applications, respectively.
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