Toward a Practical Energy Conservation Mechanism With Assistance of Resourceful Mules

As wireless sensor networks (WSNs) gradually move from specialized fields such as military and industry toward domains with general purposes, more and more sensors locate around our living areas. The reality that various wireless devices coexist in new circumstances encourages us to come up with new ideas to solve the extremely energy-constrained problem in WSNs. In this paper, we propose energy conservation with assistance of resourceful mules (ECARM), a mechanism that opportunistically utilizes resourceful mules (RMs) such as specifically designed powerful sensors or ubiquitously used laptops, tablet PCs, and smart phones to act as assistants and save energy for WSNs. We verify ECARM through extensive simulations written on the OMNET$boldsymbol{++}$ platform. Single RM simulation shows that 43% sensors in an RM´s communication range enjoy power reduction by decreasing their wake-up time to 16% at most. Multiple RM simulations illustrate that 86% sensors in the simulated network benefit from 14 RMs, and wake-up time of 56% sensors decrease to 50% below. We emphasize that ECARM can also be applied in duty-cycled WSNs that adopt schemes such as ContikiMAC and X-MAC. Simulation results demonstrate that the duty-cycling ratio of ContikiMAC is further decreased by at least 20.9% after the ECARM application.