# VANET Clustering Based Routing Protocol Suitable for Deserts
## 4 Clustering and Cluster Management  
In this paper, a cluster is the basis of the designed model. After considering the direction of the vehicles, this paper classified vehicles into four categories depending on the communication equipment. These categories are the main factor in clustering classification and play an important role in cluster composition and CHE. The four categories include the vehicles equipped with VANET communication only, vehicles equipped with mobile communication, vehicles equipped with satellite communication and vehicles equipped with both mobile and satellite communication. We used the notation \(V\), \(V_{m}\), \(V_{s}\) and \(V_{ms}\) to represent the aforementioned four categories, respectively. The movement of the vehicles dynamically yields different types of clusters. However, this paper only considers the four main clusters shown in Figure 3. The first cluster type consists of \(V\) only, as in Figure 3a; the second type contains both \(V\) and \(V_{m}\), as in Figure 3b; the third type consists of both \(V\) and \(V_{s}\), as shown in Figure 3c; and the fourth type is a combination of \(V\) and \(V_{ms}\), as shown in the Figure 3d. All of them are able to communicate with the outside network, except the first type. Figure 3: The main four clusters’ structures. (**a**) Cluster type \((V)\); (**b**) Cluster type \((V,V_{m})\); (**c**) Cluster type \((V,V_{s})\) and (**d**) Cluster type \((V,V_{ms})\). Figure 2: Logical structure model. Figure 4 shows a sample of possible other types of clusters, which can be formed according to the vehicle's categories. However, the main four types in Figure 3 can represent all. A CH should be elected for each type of cluster. For the first type, the CH should be elected according to the location, and velocity. Other types will follow the election procedure described in Section 4.2. According to the logical structure, the CH and the neighboring CH can communicate directly; however, in the actual situations, the CH and the neighboring CHs are not necessarily located within the same VANET communication range. For that reason, the CH may select one of the boundary cluster members to act as a gateway for forwarding traffic information (both control and data messages) between the neighboring CHs. After the completion of the CHE process, each CH collects and stores the location, direction, velocity and equipment information of its cluster members; later, it uses this information to calculate the routes. When a cluster member requests a communication, it will send a request message to its CH. The CH checks whether the destination is within its cluster members or not. If the destination is one of its cluster members, it will directly forward the requested route information to the source member. In case the destination vehicle is located in another cluster, the CH, directly or using adjacent cluster members as a gateway, forwards the route information to the destination CH. The destination CH returns the requested route information to the source CH. Finally, the source CH sends the route information to its intended cluster member. Therefore, the clustering process is not only the election of the, CH but also includes the operation of determining boundary vehicles used to communicate between the adjacent clusters. In Figure 5, we assume three clusters \(C_{1}\), \(C_{2}\) and \(C_{3}\) with their clusters heads \(CH_{1}\), \(CH_{2}\) and \(CH_{3}\), respectively. As the distance between \(CH_{1}\) and \(CH_{2}\) is beyond the coverage of the VANET, the CHs can use the adjacent cluster members \(V_{3}\) and \(V_{4}\) to communicate with each other, because these two vehicles are within the same VANET coverage; however, they belong to different clusters. The communication between \(CH_{1}\) and \(CH_{3}\) will be through a mobile or satellite solution, because not only the distance between them is out of the coverage area, but also the distance between the adjacent neighbors is out of the VANET communication coverage.