# 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
This often leads to longer delay and more one-hop disconnection due to the greater number of vehicle nodes and different vehicle speeds. The proposed protocol addressed this issue by selecting the maximum traffic density road segments, and it had a better percentage of one hop disconnection. Figure 7: Comparison of data throughput with increasing number of vehicular nodes. #### 4.1.2 Speed of Vehicle Analysis

This section shows the analysis of results based on increasing vehicle node speed in terms of the packet delivery ratio and the average delay in the network. Figure 9 shows a comparison of the data delivery ratio of the ISR, TASR and VBRP routing protocols. It can be seen that the increasing vehicle speed resulted into lower PDR in the network for all protocols. However, the proposed ISR had better results due to the removal of beacon messages in the whole network. This mechanism also helped to reduce the consumption of bandwidth and memory to store the neighbor node information. Additionally, the multi-metric protocol supported the protocol to select the appropriate next forwarder node for data delivery towards the destination. On the other hand, the TASR protocol had one mechanism where this protocol determined the distance, direction, and vehicle density metric to select the next forwarder. Additionally, the VBRP used beacon messages in the whole network, which increased the network overhead and led to a packet dropping issue. The high speed also caused the staleness of neighbor node information. The results showed that the proposed protocol had an even better packet delivery ratio when the vehicle node speeds were set to 35 and 40 km/h. The PDR's decreasing trend indicated that vehicle speed was the cause of low data delivery in the network, but ISR still had better results due to the removal of beacon messages in the whole network for next forwarder node selection. This strategy supported the consumption of less bandwidth than the position-based routing protocols. The TASR protocol also had fewer packet drops than the VBRP due to its multi-metric and clustering strategy. In addition, the high speed caused staleness. The result showed that ISR had better results when the vehicle node speed was set between 50 and 60 km/h in the network, and it gradually decreased when speed reached 100 km/h. Figure 10 shows the comparison of the average delay results with vehicle speed analysis. The results indicated that the proposed ISR protocol had a lower delay than the TASR and VBRP. Whenever the vehicle speed reached 35 and 40 km/h, the delay was greater due to the high velocity of nodes where the information became outdated and frequent next forwarder selection was needed. Compared to the VBRP, the TASR and ISR had lesser delays. The higher velocity led to more chances for packet dropping. On the other hand, the TASR protocol steeply increased the delay because it initiated the decision based on distance, direction, and vehicle density. although more vehicle nodes centric congestion on road results in better signal strength for vehicular communication. However, it might lead to longer delay in communication due to the higher speed of vehicles and local information processing during forwarding at each node. The proposed protocol addressed this issue by selecting the maximum traffic density segment. Figure 8: Comparison of one-hop link disconnection with increasing number of nodes. The proposed ISR routing protocol had better results in terms of delay compared to the TASR and VBRP even though the vehicle speed was set at 40-60 km/h. The proposed protocol is the best option for urban areas where vehicle speed lies at a similar normal level. On the contrary, the existing protocols suffered a higher delay when the vehicle speed increased in the network. The TASR clustering protocol had lesser delays than the VBRP because the higher speed of vehicle nodes led to packet dropping and the protocol again checked the neighbor node information to initiate the routing decision.