Traffic aware routing in vehicular ad hoc networks: characteristics and challenges

Vehicular ad hoc networks (VANETs) are gaining tremendous interest among researchers and industries. Although the main reason for developing VANETs is traffic safety, many applications such as traffic status monitoring, road traffic management, routing and distribution of data, have emerged. VANETs exploit multi-hop communications among vehicles to deliver data packets. However, with fast mobility and intermittent link connectivity between vehicles, efficient and reliable routing in VANETs is becoming a challenging task. In order to make routing protocols robust to frequent communication disruptions and aware of unstable traffic and network conditions, several new routing metrics have been integrated with routing protocols. Such protocols are called traffic aware routing (TAR) protocols as their routing decisions are influenced by traffic and network status. The goal of this paper is to review the most recent traffic aware routing protocols while emphasising on traffic and network conditions awareness issues. In addition, this review investigated TAR protocols capabilities and limitations in terms of routing process, routing metrics measurement, forwarding mechanisms and recovery techniques. Moreover, challenges, critical issues and open research problems were discussed in the “Challenges and issues to consider” sections.