## 3 Results and Discussions
### Route Validity Time
The findings indicate a distinct preference for shorter route validity times in AODV, while GPSR benefits from longer validity durations. This contrast highlights the differing operational dynamics and requirements of  
Figure 9: Throughput comparison between VANET scenarios and route validity time. these two routing protocols under varying mobility conditions. In the case of AODV, the observed delay variations are minimal, less than 0.007 s, regardless of the route validity time employed. This stability suggests that AODV is effective in maintaining low delay even when the route validity time is adjusted. AODV's reactive routing mechanism, which involves establishing routes on-demand, means that shorter validity times facilitate frequent updates. Although this might seem counterintuitive, in scenarios where network topology changes are less frequent--such as in a city--AODV can quickly adapt to any changes without incurring significant delays. Therefore, the preference for shorter route validity times in AODV enhances its efficiency by reducing the likelihood of routing failures, ensuring timely packet delivery with minimal delay. Conversely, GPSR exhibits a pronounced response to route validity time, particularly in urban environments where the delay improves significantly with longer validity periods. The observed variation in delay for GPSR exceeds 0.05 s in the city and is below 0.01 s on highways. In city conditions characterized by lower mobility and relatively stable topologies, longer route validity times reduce the frequency of route discovery processes. When route validity times are extended, the protocol can maintain existing routes longer, thus minimizing unnecessary overhead associated with frequent updates. This decrease in protocol overhead directly correlates with improved network performance, as less routing traffic leads to reduced congestion and lower overall delay. In essence, GPSR's reliance on longer route validity times allows it to capitalize on the stable node density characteristic of city environments, leading to enhanced efficiency in data transmission. The differences in delay response between AODV and GPSR can also be attributed to their underlying routing mechanisms. AODV's design favors adaptability through shorter route validity periods, which allows it to respond quickly to changes in the network topology, albeit with a trade-off in slightly increased delay. Conversely, GPSR's performance benefits from maintaining routes for extended durations, reducing the need for constant route discovery and thus mitigating delays. The ability of GPSR to harness higher node densities and stable connectivity in urban settings allows it to thrive under conditions that would impose greater delay on AODV. In summary, the delay observations in Figure 10 highlight the contrasting routing strategies of AODV and GPSR in relation to route validity time. While AODV achieves low delay with shorter validity periods by fostering rapid route adjustments, GPSR capitalizes on the stability afforded by longer validity times to enhance performance in urban settings. These findings underscore the necessity of tailoring routing protocols to the specific characteristics of their operating environments to optimize delay and overall network performance. Understanding these dynamics is crucial for the development of efficient routing strategies in both high-mobility and stable network scenarios. Figure 10: Delay comparison between VANET scenarios and route validity time. Figure 11 illustrates the Packet Delivery Ratio (PDR) of AODV and GPSR under varying route validity times in both urban and highway environments. The results indicate that AODV's PDR demonstrates a relatively limited response, with fluctuations of only 1.5% across different route validity times in both scenarios. In contrast, GPSR exhibits a clear upward trend in PDR with increasing route validity times, suggesting that longer durations are more favorable for enhancing packet delivery efficiency.