Impact of Microscopic Vehicle Mobility on Cluster-Based Routing Overhead in VANETs

Node clustering is a potential solution to minimize the control signaling overhead of routing protocols in vehicular ad hoc networks (VANETs). High relative vehicle mobility and frequent network topology changes induce instability to node clusters. Node cluster instability inflicts new challenges on maintaining a long route between network nodes, thus increasing the routing overhead. As a result, cluster instability, foisted by vehicle mobility, is a crucial issue for cluster-based routing in VANETs. This paper presents a stochastic analysis of the cluster instability impact on generic routing overhead. A stochastic cluster instability model is adopted to capture the time variations of the cluster structure in terms of the cluster membership change rate and the cluster-overlap state change rate. Firstly, we derive the probability distribution of the intracluster routing overhead using the cluster membership change rate. Secondly, the intercluster routing overhead is modeled as a rooted tree with the tree-nodes representing the value of the overhead and the tree-edges weighted by probability of a cluster-overlap state change. Numerical results are presented to evaluate the proposed models, which demonstrate a close agreement between analytical and simulation results. Keywords—Vehicle mobility, cluster overlap, routing overhead, cluster instability.