## 3 Results and Discussions
### Beacon/Hello Interval  
Figure 6 shows the throughput behavior of AODV and GPSR in city and highway environments for various Hello/Beacon Intervals. AODV's throughput in city environments shows an increasing trend with longer Hello intervals, whereas in highway scenarios, throughput decreases as the Hello interval increases. For GPSR, throughput declines consistently with increasing Beacon intervals in both city and highway environments. AODV relies on Hello packets to update its routing table, which is broadcasted at intervals defined by the HELLO_INTERVAL parameter. Increasing the frequency of Hello packets ensures that routing information remains fresh and up-to-date, which is especially important in high-mobility environments like highways, where frequent topological changes occur. On highways, vehicles are moving at higher speeds, causing network topology to change rapidly. Therefore, a shorter Hello interval ensures faster updates to the routing table, allowing AODV to adapt quickly to the changing routes, reducing packet loss and maintaining higher throughput. However, as the Hello interval increases in highway environments, the delay in updating the routing table leads to stale route information, increasing packet drops and resulting in reduced throughput. In contrast, city environments are characterized by lower mobility, with vehicles moving at slower speeds and experiencing fewer topological changes. In this setting, sending Hello packets too frequently may introduce unnecessary protocol overhead. Each Hello packet consumes bandwidth and processing resources, contributing to network congestion without significantly benefiting route freshness since the topology does not change as rapidly. This overhead reduces the available bandwidth for actual data transmission, explaining the increase in AODV's throughput with longer Hello intervals in cities, where fewer Hello packets translate into reduced overhead and more bandwidth for data packets. The behavior of GPSR differs from AODV in that GPSR's throughput decreases with longer Beacon intervals in both city and highway environments. GPSR uses Beacon packets to maintain information about neighboring nodes, and the protocol operates in a stateless manner. In city environments, where node density is higher, the greedy mode in GPSR can more easily find intermediate nodes between the source and destination. As a result, when Beacon intervals are short, GPSR can quickly and effectively discover neighboring nodes, leading to efficient routing and higher throughput. However, as the Beacon interval increases, the availability of up-to-date neighbor information diminishes, causing GPSR to rely more on recovery modes, which are less efficient. This results in lower throughput as the Beacon interval increases in both city and highway scenarios. For GPSR in highway environments, longer Beacon intervals further exacerbate the reduction in throughput, as node mobility is high, and routes can break frequently. A shorter Beacon interval is critical in maintaining up-to-date neighbor information, allowing GPSR to respond quickly to changes in the topology. When the Beacon interval increases, the protocol's ability to maintain valid routes diminishes, leading to higher packet loss and reduced throughput. In summary, the trends observed in Figure 6 highlight the critical role that Hello/Beacon intervals play in routing protocol performance across different environments. AODV benefits from shorter Hello intervals in highway scenarios due to the high mobility of nodes, while in city environments, longer Hello intervals reduce overhead and improve throughput. For GPSR, shorter Beacon intervals are essential in both city and highway environments to maintain efficient route discovery and neighbor information, as longer intervals degrade performance. These observations underline the importance of optimizing protocol parameters based on network conditions to achieve maximum throughput.