Mobility Reduces Uncertainty in MANETs

Evaluating and quantifying trust stimulates collaboration in mobile ad hoc networks (MANETs). Many existing reputation systems sharply divide the trust value into right or wrong, thus ignoring another core dimension of trust: uncertainty. As uncertainty deeply impacts a node´s anticipation of others´ behavior and decisions during interaction, we include uncertainty in the reputation system. Specifically, we use an uncertainty metric to directly reflect a node´s confidence in the sufficiency of its past experience, and study how the collection of trust information may affect uncertainty in nodes´ opinions. Higher uncertainty leads to higher transaction cost and reduced acceptance of communication and cooperation. After defining a way to reveal and compute the uncertainty in trust opinions, we exploit mobility, one of the important characteristics of MANETs, to efficiently reduce uncertainty and to speed up trust convergence. A two-level mobility assisted uncertainty reduction scheme (MAURS) that offers controllable trade-off between time and cost to achieve a convergence objective of trust is also provided. Extensive analytical and simulation results are presented to support our proposal.