# Towards Strengthening the Resilience of IoV Networks--A Trust Management Perspective
## 2 From Vehicular Ad Hoc Networks to Internet of Vehicles  
### Vehicle Ad Hoc Networks (VANETs)  
The MANET is one of the important components of the Wireless Ad Hoc Network (WANET). From the perspective of computer technology, MANET is defined as the working group of mobile ad hoc networks. There are two types of ad hoc network: fixed nodes and mobile nodes. MANET refers to an ad hoc network with mobile nodes, and it comprises:  
* _Vehicle Ad Hoc Networks (VANETs)_--VANETs realize the coordination of vehicles, people, and roads through V2X, which is an artificial intelligence technology that can help vehicles take actions in an intelligent way when they encounter danger. Its appearance has greatly improved traffic safety and traffic efficiency;
* _Smart Phone Ad Hoc Networks (SPANs)_--SPANs create peer-to-peer networks using existing hardware devices, independent of cellular operator networks, wireless access points or traditional network infrastructure;
* _Internet-based Mobile Ad Hoc Networks (IMANETs)_--IMANETs support internet protocols such as TCP/UDP and IP;
* _Hub-Spoke MANET_--A plurality of sub-mobile ad hoc networks can be connected to the traditional central radiating VPN to create geographically distributed mobile ad hoc networks;
* _Military or Tactical Wireless Ad Hoc (MWANET)_--MWANET is a special self-organizing network for military departments, with special emphasis on data security, real-time requirements, data rate, radio range and integration, and fast routes in terms of mobility requirements;
* _Flying Ad Hoc Networks (FANETs)_--FANETs consist of drones, which can achieve great mobility and provide connectivity with remote areas. VANET is a special commercial application of the traditional mobile ad hoc network. The evolutionary history of VANET is shown in Figure 3. VANET may be deployed by communication operators, content service providers, and government agencies, or jointly deployed by them, representing what is essentially a heterogeneous wireless network. C2 CCC, the European vehicle-mounted communication alliance, provides a guiding architecture consisting of three domains, as shown in Table 1.  
VANET has some advantages because its network nodes are all vehicles and roadside devices:  
* The vehicle can achieve sufficient energy support, and the carrying space of the vehicle can also ensure the good performance of its wireless communication equipment. At the same time, its storage and computing capabilities are also very powerful. In the same way, the traffic facilities on both sides of the road also have sufficient energy supply, and the computing storage capacity and wireless communication capacity are guaranteed;
* The popularity of GPS and GIS (Geographic Information System) makes VANET rich in external auxiliary information, including not only its own location information but also the geographical information of its area, such as road direction, traffic light distribution, etc. ; \begin{table}
\begin{tabular}{p{28.5 pt} p{28.5 pt}} \hline \hline
**Domain** & **Function** \\ \hline In-Vehicle Domain & Communication between the OBU and application units (AUs) within the vehicle. AU can be a specific device, such as a mobile phone, or a virtual module integrated into an OBU. The connection can be wired or wireless, such as WiFi or Bluetooth. \\ \hline Ad Hoc Domain & The wireless communication between OBUs and RSUs can be single-hop or multi-hop, namely V2V and V2R. \\ \hline Infrastructure Domain & OBU and RSU communicate with infrastructure components, such as satellite, hot spot, and 5G, to access the Internet. For RSUs, the connection can be wired. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Three domains of VANET. Figure 3: Evolution history of the VANET. * As compared with other MANETs, the nodes of VANET move more regularly. The network topology is relatively stable when vehicles travel in the same direction, but when vehicles run in the opposite direction, the network topology will change very quickly, and the life of the whole link will be shortened.