Many Wireless Sensor Network (WSN)systems are deployed in unattended areas using nonrechargeable batteries.To enable sustainable operations,most WSN systems employ duty-cycling mechanisms,such as Low Power Listening (LPL)For reliable delivery of each packet with LPL,the sender has to transmit a preamble that is long enough to span over a complete sleep interval of the receiver.In this way,the sensor nodes avoid idle listening,however,at the cost of remarkably increased end-to-end delay of multi-hop packet transmissions.To address this issue,in this paper we propose a new duty-cycling mechanism called DCGear.DC-Gear exploits a “ sleep less but save more” phenomenon,which means increasing the duty cycle in a timely and appropriate manner while minimizing the overall energy cost and satisfying the end-to-end delay constraint We have implemented DC-Gear with TelosB motes and demonstrated its performance advantages through extensive experiments.