# Improved Road Segment-Based Geographical Routing Protocol for Vehicular Ad-hoc Networks
## 3 Improved Road Segment-Based Geographical Routing Protocol
### Routing Process, Flowchart and Algorithms
CBR: constant bit rate; SUMO-MOVE: simulation for urban mobility-mobility model generator for VANETs. the whole network. Figure 5 shows the PDR comparison in accordance with a different number of vehicle nodes in the network. It also shows the trend that ISR consistently increased data delivery due to the increasing connectivity probability with more vehicles in dense networks. The existing TASR had better results than the VBRP because of the applied cluster mechanism. The VBRP is based on a greedy forwarding mechanism that is not appropriate for VANETs. This was the main reason that VBRP was behind TASR and ISR. The results indicated better results of the proposed protocol can existing routing protocols. Furthermore, the proposed ISR protocol data delivery ratio increased more due to the increasing connectivity probability with higher traffic density in an urban environment. The next performance metric comparatively analyzed with simulation results was end-to-end delay, as shown in Figure 6. The delay of the all considered protocols consistently increased with larger network size due to the routing metric calculations from higher number of nodes in the neighborhood. However, the existing protocols TASR and VBRP had more delay than the proposed ISR protocol. This result also indicated that the clustering protocol TASR had a lower delay than the other protocol VBRP because more traffic had more beacon overhead and the next forwarder selection became difficult. The TASR protocol steeply increased the delay because this protocol initiated the decision based on distance, direction, and signal strength. Although more vehicle nodes centric congestion on road sometime leads to strong signal strength for vehicular communication. However, it results into longer delay due to the information processing at each node in the forwarding vehicles. The proposed ISR protocol addressed this issue by selecting the optimal traffic density road segments. Figure 5: Packet delivery ratio with increasing number of vehicular nodes in the network. Figure 6: Comparison of end-to-end delay with increasing number of vehicular nodes. Another performance metric that was analyzed was data throughput, as shown in Figure 7. The data throughput of all the considered protocols consistently decreased due to the routing metric calculation involving more nodes in the network. However, the existing protocols had less data throughput than the proposed protocol. This result also indicated that data throughput decreased when the network had a greater data load in the presence of a greater number of nodes. The TASR protocol steeply decreased throughput because this protocol initiated the decision based on distance, direction, and signal strength. Though the nodes in more congested road sometimes had strong signal strengths, they often had more delay and less throughput due to higher number of vehicle nodes. The proposed protocol addressed this issue by selecting the maximum traffic density road segments, and it thus had better data throughput results. Another analyzed performance metric was one hop link disconnection, as shown in Figure 8. It can be clearly observed that one hop link disconnection of ISR was nominal compared to other two existing protocols. It was also observed that with a greater number of nodes, the one hop disconnection increased. However, the one hop disconnection of the proposed ISR protocol consistently increased due to its routing metric calculations and greater amount of nodes in the network. However, the existing protocols had less one hop disconnection than other two existing protocols. This result also indicated that one hop disconnection increased when the network had a greater data load in the presence of a greater number of nodes. The TASR protocol steeply increased in one hop disconnection because this protocol initiated the decision based on distance, direction, and signal strength. although more vehicle nodes centric congestion on roads results into stronger signal strength for vehicular communication.