# VANET Clustering Based Routing Protocol Suitable for Deserts
## 6 Simulation and Results
### Results and Discussion  
During simulation, we realized that the main problem of the three protocols is that they have a limitation when used in desert environments to connect the source and destination located in different clusters, and there is no direct connection between them. As these protocols are originally designed for MANETs rather than VANETs, they have been utilized in VANETs in urban and highways scenarios. Moreover, deserts have no RSU to support intra-cluster communications. CBVRP bridges the gap, because it has been particularly designed for such environments. However, it would be also acceptable for any area to allow communication between randomly moving vehicles. Simulation results are shown in the following figures. The graphs show the election procedure result and comparison between the three mentioned protocols by using different parameter values as the basis of the above-mentioned metrics. Figure 11 shows all priority factors (\(P\), \(P_{e}\), \(P_{l}\) and \(P_{v}\)) with respect to the vehicle's IDs. According to the \(P\) value, vehicle ID Number 10 is elected as a CH. To elect the CH using only the velocity, as other routing protocols do, vehicle ID Number 1 will be elected, although it is equipped with VANET only and the location of it is quite worse. In addition, in the case of using the location, vehicle ID Number 7 has a high location priority, but its equipment and velocity are worse. The use of overall priority will solve the problem by using a weighting mechanism in order to achieve a better utilization of all vehicles and the optimum election. This problem has not been addressed by other existing protocols, which use location or velocity to elect the CH. Moreover, as can be seen from Figure 11, vehicles with ID Numbers 4 and 10 have the same overall priority factor. In this case, the vehicle with the best equipment will be elected as a CH, as specified in Equation (20). Figure 12 demonstrates the effect of CHE on the stability of the cluster structure when using different types of priority factors. The effect of \(P_{l}\) and \(P_{v}\) seems to be the same, because the location of vehicles is affected by the velocity. The variation in the velocity of the well-equipped vehicles may affect its overall priority. When \(P\) is used, the cluster structure is more stable, because the selection process considers all priority factors. Figure 11: VANET cluster head election (CHE) priority factors. Figure 13 shows that the cluster structure stability of CBRP and DSR is poor. This is because the CBRP algorithm uses only the ID of the vehicle as a basis for CHE. The smallest ID is elected as a CH. A cluster structure may change rapidly in the case of a vehicle moving with high velocity. In case of DSR, a separate periodic algorithm must be implemented to support and propagate the CH advertisements across the cluster. The response of the algorithm may affect the cluster structure. The CBVRP CHE process takes into consideration the movement of neighboring vehicles in addition to location and equipment, to reduce the probability of cluster change over time, to have a higher stability. Figure 14 shows comparison between CBVRP, AODV, CBRP and DSR protocols in terms of PDR. It is observed that PDR of CBVRP remains high while increasing the number of vehicles. The increase of the number of vehicles did not affect the PDR because of the high efficiency and cluster structure stability of the routing algorithm. The PDR of CBRP and DSR is less than that obtained by CBVRP and AODV, because the source node and the intermediate nodes store the next hop information corresponding to each flow for data packet transmission, but DSR and CBRP use source routing in  
Figure 12: Cluster reconstruction _versus_ time; here, the CH is elected according to different election priority factors. Figure 13: Cluster structure stability over time for cluster-based VANET routing protocol (CBVRP), CBRP and dedicated short-range (DSR) protocols. which a data packet carries the complete path to be traversed.