Towards mobility-rich analysis in ad hoc networks: using contraction, expansion and hybrid models

A wireless ad hoc network is an infrastructureless network where nodes are mobile. The evaluation of ad hoc networking protocols is very sensitive to mobility. As a result, exploring a set of rich mobility models in ad hoc networks is essential. The purpose of this paper is to introduce a classification of various mobility models, in addition to proposing the contraction, expansion, and hybrid mobility models. These proposed models cover scenarios in which nodes merge, scatter, or switch to different movement patterns over time. We also investigate a set of mobility metrics to capture characteristics of mobility. We implement our mobility models in the IMPORTANT framework in NS-2. We use our framework to evaluate the performance of ad hoc routing protocols. Our study shows that no one metric is sufficient to capture mobility, but average node degree and link duration are very useful in capturing mobility dynamics. We note a wide spectrum of performance outcomes with mobility. Also, we observe that in some scenarios (involving contraction) performance improves with added velocity.