State-of-the-art approach to clustering protocols in VANET: a survey

Vehicular ad hoc network (VANET) assists in improving road safety, traveller comfort, and intelligent transportation systems to a great extent. Dedicated short-range communications technology is specially designed for VANET to form communication among vehicles and vehicles to infrastructure. The lack of router devices in the flat vehicle-to-vehicle network structure of VANET may raise complicated issues like scalability, resource scarcity, reliability, and hidden terminal problem inside the network. The concept of vehicle clustering is introduced in VANET to improve network performance by handling all such issues. This paper provides an in-depth classification of clustering protocols in VANET based on their design objectives. Two broad categories, generalized and application dependent, are considered to review on clustering protocols in VANET. In generalized clustering protocol, cluster design aims to achieve their primary objective, i.e., the formation of a robust cluster having a long sustainable life, While in application dependent clustering protocols, cluster design aims to improve the performance of specific applications (i.e., target tracking, traffic estimation, misbehaviour detection, privacy preservation, certificate revocation, etc.) on various performance metrics. After this, the paper explores essential research contributions of each category comprehensively. Detailed analysis of existing research contributions is also provided after comparing them on many important metrics. Finally, the merits and demerits of existing protocols are also listed. Our attempt to encourage researchers of the concerned field by providing an extensive analysis of clustering in VANET.