Energy Efficiency and Contact Opportunities Tradeoff in Opportunistic Mobile Networks

To discover neighbor nodes, nodes in opportunistic mobile networks (OppNets) have to probe their environment continuously. This can be an extremely energy-consuming process. If nodes probe very frequently, a lot of energy will be consumed in the contact probing process and might be inefficient. On the other hand, infrequent contact probing might cause nodes to miss many of their contacts. Therefore, there exists a tradeoff between energy efficiency and contact opportunities in OppNets. To investigate this tradeoff, we first propose a model to investigate the contact probing process based on the random-waypoint model and obtain the expressions of the single detecting probability and the double detecting probability. Moreover, we also demonstrate that among all contact probing strategies with the same average probing interval, which do not have preknowledge of the contact process, the strategy that probes at a constant interval performs better than any arbitrary probing strategy in expectation in the single contact probing process. Then, extensive simulations are conducted to validate the correctness of our proposed model. Finally, based on the proposed model, we analyze the tradeoff between energy efficiency and the total number of effective contacts in the single and double contact probing processes. Our results show that the total number of effective contacts in the single and double contact probing processes has a lower bound and an upper bound, and the good tradeoff points are obviously different when the speed of nodes is different.