## 3 Results and Discussions
### Route Validity Time  
Route validity time is a critical parameter in routing protocols, as it defines the duration a route remains in the routing table before being invalidated. In AODV, this is determined by the ACTIVE_ROUTE_TIME_OUT, while in GPSR, it is governed by the NEIGHBOR_VALIDITY_TIME. Figure 9 illustrates the throughput performance of both AODV and GPSR across different city and highway environments, highlighting the relationship between throughput and route validity time. The throughput observations indicate that AODV experiences a minimal response to route validity time in both scenarios, with a general declining trend as this time period increases. Conversely, GPSR exhibits a more complex interaction with route validity time, demonstrating a proportional relationship in urban settings and an inverse correlation on highways. The throughput response of AODV suggests a need for balance in route validity time. As this time increases, the potential for stale route information grows, which can lead to increased packet loss or delays in data transmission. This is particularly important in dynamic environments, such as highways,  
Figure 8: PDR comparison between VANET scenarios and Beacon/Hello Interval. where node mobility is high. Shorter route validity times enhance the frequency of routing table updates, ensuring that the protocol has access to current information about available routes. However, excessive updates can also contribute to increased routing overhead, which may detrimentally impact throughput. The observed decrease in AODV throughput with longer validity times reflects this balance; longer durations may improve stability but can also lead to outdated routing decisions, resulting in reduced performance. In the case of GPSR, the varying trends in city and highway environments underscore the impact of mobility patterns on throughput. In urban scenarios, where vehicles move at slower speeds and within confined paths, increasing route validity time correlates with enhanced throughput. This behavior can be attributed to the higher density of nodes in urban areas, which allows for more consistent neighbor connectivity. Thus, maintaining a valid route for a longer duration reduces the need for frequent updates, lowering the overall protocol overhead. In contrast, on highways, where vehicles experience rapid movement and dynamic routing conditions, a shorter route validity time is preferable. This ensures that GPSR maintains accurate routing information, facilitating efficient data transmission and minimizing the chances of packet loss due to outdated neighbor data. The differences in the throughput responses of AODV and GPSR to route validity time highlight the unique operational mechanisms of each protocol. AODV's reliance on reactive routing leads to stable throughput performance across varying conditions, while GPSR's performance is significantly influenced by the density of nodes and the predictability of vehicle movements. In scenarios where node density is high, such as city environments, GPSR benefits from longer route validity times that support data flow without frequent updates. In contrast, highway scenarios necessitate more dynamic routing adjustments, and as such, GPSR throughput is enhanced by shorter validity periods that facilitate timely updates. In summary, the observations in Figure 9 emphasize the importance of route validity time in optimizing throughput for routing protocols like AODV and GPSR. While AODV displays a relatively stable performance with a slight decrease in throughput as validity time increases, GPSR benefits from tailored validity periods that correspond to the specific mobility patterns of the environment. Understanding these dynamics is essential for the effective deployment of routing protocols in diverse scenarios, ensuring that they can adapt to the varying needs of network conditions to maintain optimal performance. Figure 10 presents the delay performance of AODV and GPSR across various route validity times in both city and highway environments.