Robust mobility adaptive clustering scheme with support for geographic routing for vehicular ad hoc networks

There are a number of critical problems related to road safety in intelligent transportation systems (ITS) caused by increased vehicle usage, urbanisation, population growth and density, and faster rates of movements of goods and people. It is envisaged that vehicular ad hoc networks (VANETs) will bring about a substantial change to the way our road transport operates to improving road safety and traffic congestion. A major challenge in VANETs is to provide real-time transfer of information between vehicles within a highly mobile environment. The authors propose a new clustering scheme named robust mobility adaptive clustering (RMAC) to strategically enable and manage highly dynamic VANETs for future ITS. It employs a novel node precedence algorithm to adaptively identify the nearby 1-hop neighbours and select optimal clusterheads based on relative node mobility metrics of speed, locations and direction of travel. Furthermore, the zone of interest concept is introduced for optimised approach to the network structure such that each vehicular node maintains a neighbour table of nodes, beyond its communications range, that reflects the frequent changes on the network and provides prior knowledge of neighbours as they travel into new neighbourhoods. RMAC predominantly employs more reliable unicast control packets and supports geographic routing by providing accurate neighbour information crucial when making routing decisions in multi-hop geographic routing. It is shown by simulations that RMAC on IEEE802.11 ad hoc WLAN protocol is very effective in a highly dynamic VANETs environment, being robust on link failures, and having very high cluster residence times compared to the well known distributed mobility clustering scheme.