Energy saving and network connectivity tradeoff in Opportunistic Mobile Networks

In Opportunistic Mobile Networks (OppNets), a large amount of energy is consumed by idle listening, instead of infrequent data exchanging. This makes energy saving become a serious problem in OppNets, as nodes are typically with limited energy supplies. Duty-cycle operation is a promising approach for energy saving in OppNets, however, it may cause the degradation of network connectivity. Therefore, there exists a tradeoff relationship between energy saving and network connectivity in duty-cycle OppNets. In this paper, we propose a model to quantify the contact probability (a metric of connectivity) in duty-cycle OppNets based on the realistic mobility trace. Then the tradeoff between energy saving and the contact probability under different situations is derived and analyzed. Our results show that the duty-cycled nodes can guarantee an energy saving of around 50% without impacting the contact probability if the period meets a certain condition, and higher energy saving can be achieved at the cost of reducing the contact probability. Finally, realistic trace-driven simulations are performed to validate the correctness of our results.