Vertical handover techniques in VANETs

VANET refers to an ad-hoc network made up of different nodes where a node can be a vehicle or a roadside unit. Two types of communication mainly occur in VANET, i.e., V2V or V2I. Since vehicles are mobile devices that are always in transit, there is a need to switch from one network to another network. This process of switching from one network to another network is known as handover and has become a very interesting topic of research for VANET research community. In this paper, we have started with the basics of handover techniques then moved specifically to the vertical handover technique in detail. The different phases of the handover process are explained along with the literature survey in each of them during the last decade (2008-2018). This study thus contributes to the understanding of the available options and gaps for further studies and standardisation activities in this area of research. Statistical information along with number of tables is also given in this paper which provides comparison and information about various parameters of VANET algorithms. In the end, several open research issues in this field are also listed along with the conclusion of the paper.