VANET as a subclass of MANET is composed of a set of vehicles equipped with wireless transceivers, to build dynamic networks without the need of any pre-existing infrastructure. Over the last few decades, the area of routing protocols in VANETs has been extensively studied. Nevertheless, this area remains even more challenging due to some features of VANETs, such as the high speed of vehicles, the often-disconnected links and the particular mobility pattern. Routing protocols in VANETs could be splitted into four categories: topology, position, multicast and broadcast-based routing protocols. In this paper, we provide a novel detailed taxonomy of routing protocols in VANETs then we present the advantages and drawbacks of each category. Moreover, we clear up the techniques adopted by each of the most popular routing protocols based on the vehicles' position and the topology of the networks. To explore the strengths and weaknesses of each routing protocols, basing on their suitability for VANET, we implemented them by using SUMO and NS3 as simulation tools applied on a real street map of Oujda city. We have extracted the used map from Open Street Map (OSM). Finally, we present our future works used for optimizing the greedy forwarding technique that is adopted by some position-based routing protocols in VANETs. Our suggested technique is based on the angle direction and three other important parameters of the relaying node.
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