Contents I. Introduction
In an ad-hoc network, devices directly communicate with each other. They use the spontaneous establishment of connection because they often evade access point (like a router). Several ad-hoc networks are LAN networks where devices (computers, mobile phones) communicate directly without evading access point [1], [2] wired networks. When devices are connected wirelessly, they are termed wireless ad hoc networks, which is a dynamic and self-configuring network with freely moving nodes and is also known as a mobile ad-hoc network (MANET). It establishes infrastructure less network. Devices can join or leave the network whenever they want. When mobile devices are vehicles, that network is termed VANET [3]. So the VANET is a set of mobile (vehicles) and fixed (roadside units) entities working together to exchange critical information about road conditions and other vehicles [4]. Another kind of ad-hoc network is the Flying Ad-hoc Network (FANET). Table I compares these three types [5]. As can be seen, in VANET and FANET, the topology change is very frequent and fast. Also, the VANET node density is high comparing to MANET and FANET. Fig. 1 shows these types.
