# Intersection-Based Routing with Fuzzy Multi-Factor Decision for VANETs
## 5 Discussion  
As shown in Figure 5, with the same number of vehicles, it is clear that the IRFMF has more hop counts than the GSR and the GPCR. That is because to ensure that the link has a longer lifetime, in Scheme IRFMF, the vehicle sacrifices the distance and chooses the neighbor vehicle with a longer contact time. The longer the contact time, the closer the current vehicle is to the neighbor vehicle. In the extreme case where the path is the same (the same road segments), the number of vehicles on the path is the same, and the path is crowded (that is, all vehicles are traveling at almost zero speed), the hops in IRFMF are twice as many as in other routing protocols. The lower number of hops of the GSR leads to the lower delivery ratios, while the higher delivery ratios of the IRFMF and the GPCR come at the cost of many hops. In order to deal with the local optimal solution problem, the GPCR has more hops. The IRFMF also pays a higher price for more robust and stable links than the GSR and the GPCR.  
As the density of vehicles increases, so does the delivery ratio as present in Figure 6. That is because as the vehicle density increases, the links become more robust and less likely to break. This provides more opportunities for data to be transmitted to its destination. The IRFMF shows a better performance on delivery ratio than other protocols. First, because of the introduction of multiple factors, the decision on the selection of the next road segment becomes more sensible, and second, the speed-based limited greedy forwarding makes the link more robust and the link lifetime longer. Moreover, the link paths have been established when the packet arrives at the intersection; thus, before the data is forwarded at the intersection, it is known whether the link is connected and whether a lifetime can ensure that the packet can reach the next intersection, to ensure that the data can reach the next intersection smoothly. Therefore, the data delivery rate is significantly improved. Although the GSR considers the characters of the VANETs and the topology of streets when it selects the next hop for forwarding, it does not guarantee that the link between two intersections is connected. The delivery ratio of the GSR is low due to the incomplete links. Compared with the GSR, the GPCR has a higher delivery ratio because the intersections are introduced and specially designed for forwarding.  
On the end-to-end delivery, as shown in Figure 7, it is clear that the IRFMF and the GPCR almost perform similarly, but there is a boundary value. When the number of vehicles exceeds this boundary value, the number of hops in the link increases and so does the delay, and the IRMF would have a higher delay than the GPCR. This is determined by characteristics of speed-based limited greedy forwarding of the IMFMF. Unsurprisingly, the lifetime of the link also becomes longer until the density of vehicles reaches the point where vehicles cannot move. The GSR has the highest delay because when the GSR calculates the Dijkstra shortest path without considering the connectivity between the junctions, this makes it possible for the packet to be carried for a long time, which increases the delay.  
In order to improve the data delivery ratio and reduce delivery delay, but also to extend the lifetime and improve the stability of the links, we sacrifice the number of hops in the link. In the future, we will pay attention to improving the speed-based limited greedy forwarding. Our goal is to minimize the number of hop counts in the link while the link lifetime is maintained long enough.