# Research on Multi-Strategy Routing Protocol in Flying Ad Hoc Networks
## 5 Experimental Results and Discussion
However, after the node movement speed reached a certain level, the node movement speed was not the primary influence in ensuring the delivery rate. Due to faster path changes, routing holes became the main effect. At 150-300 m/s, as the movement speed became faster, path changes helped to break the routing hole. However, after more than 300 m/s, the node movement speed gradually increased in its impact on packet delivery because the  
Figure 16: The effect of velocity on routing overhead. Figure 15: The effect of velocity on average delay. location-aware efficiency of the routing protocols gradually decreased after the node speed increased to a certain level, which affected the accurate construction of paths. Figure 15 demonstrates that with an increase in the node movement speed, the average delay of AODV experienced a significant increase, mainly because the increase in the node movement speed would have led to more frequent changes in the network topology, and route interruptions would have been more likely to occur. Therefore, nodes would need to continuously send RREQs and RREPs to establish new transmission paths, which would cause a larger delay; at the same time, the delivery rate was the worst. GLFR and AntHocNet were not sensitive to topology changes, and the average delay increased more gently, while when the forwarding encountered a local minimum, the node could only passively wait for the recovery of the routing hole, so the average delay was higher than that of RGF. RGF was more stable than the other routing protocols because of the introduction of joint metric optimization in the process of reactive path building, allowing it to reduce the occurrence of route disruptions. Even if the reactive mechanism forwarding encountered route interruption, it could quickly switch to greedy forwarding, and when greedy forwarding encountered a local minimum, it could continue transmitting packets directly with projected face forwarding without additional waiting time, and the minimum local node would send RREQs at this time without causing packet waiting, so the average delay of RGF was lower than that of the other routing protocols. From Figure 15, we can see that the average delay was the highest when the node moved at 150-200 m/s. The reason is the same as the effect of node speed on the delivery rate, where location awareness was the main influence on packet delivery when the node speed was low or high, and the main impact on packet delivery at moderate speeds was jumping out of routing holes. As can be seen in Figure 16, the routing overhead of AODV, RGF, GLFR, and AntHocNet grew significantly as the node movement speed increased, while the routing overhead of greedy increased only slightly. The delivery rate of AODV decreased rapidly as the node movement speed increased, and because of the frequent route disruptions, a large number of control messages had to be generated to notify the source node as well as re-route discovery, resulting in an increase in the routing overhead, but since flooded HELLO messages were not required, the routing overhead was still the smallest among the five protocols. In greedy, the nodes required periodic network-wide flooding of HELLO messages and thus, it incurred the largest routing overhead, but since the number of flooded HELLO messages was only related to the number of nodes, and the delivery rate was relatively flat, the routing overhead hardly increased. In RGF, the nodes also needed to flood HELLO messages within a certain range, and because of the location-aware capability, they could detect topology changes earlier than AODV, so they also sent more other control packets; therefore, the routing overhead was still higher than that of AODV, despite the higher delivery rate than AODV. For the experimental results, with an increase in the node-mobility speed, the delivery rate of AODV, greedy, PSO-GLFR, and AntHocNet decreased significantly, while that of RGF was relatively stable.