## 5 Simulation Results and Discussions
### Impact of CBR Connections  
In this subsection, we investigate the impact of different CBR traffic intensities on network performance. By varying the number of CBR connections, we analyze the differences between Traj-Q-GPSR and traditional GPSR in the four key performance metrics mentioned above. This evaluation provides a direct insight into each protocol's network carrying capacity and congestion resilience, assessing their adaptability and robustness under varying traffic loads. The simulation scenario in this section involves 70 UAV nodes with node mobility ranging from 15 m/s to 25 m/s. Each simulation setting was run 30 times, and the results are reported with a 95% confidence interval. As shown in Figure 5(a), as the number of CBR connections increases from 10 to 50, the network load intensifies, resulting in more frequent link contention and collisions, which collectively lead to a general rise in packet loss rate. Under such conditions, the traditional GPSR protocol sees its loss rate increase from approximately 33.4% to 39.3%, highlighting the limitations of its single-hop greedy forwarding strategy. This approach often leads to routing voids and excessive retransmissions under high load. In contrast, Traj-Q-GPSR achieves a packet loss rate of 28.5% even at 10 CBR connections, which rises to 33.3% at 20 connections due to increasing contention. However, aided by two-hop neighbor information, trajectory prediction, and queue-aware optimization, the loss rate decreases to 29.8% and 30.3% at 30 and 50 pairs, respectively--consistently maintained around 30%. Notably, under the heavy-load condition of 50 CBR pairs, Traj-Q-GPSR achieves a 30.3% loss rate, which represents a reduction of approximately 23% compared to GPSR. This result  
Figure 5: Impact of node velocity on network performance: (a) Impact of node velocity on packet loss rate. (b) Impact of node velocity on average end-to-end delay. (c) Impact of node velocity on routing efficiency. (d) Impact of node velocity on throughput. clearly demonstrates Traj-Q-GPSR's superiority in mitigating congestion and avoiding routing voids recovery failures under high-traffic conditions. As illustrated in Figure 6b, end-to-end delay increases significantly with the growth of CBR traffic intensity. This is primarily due to aggravated link contention, increased MAC-layer retransmissions, and the accumulation of queueing delays. In the traditional GPSR protocol, the delay surges from approximately 305.9 ms to 3209.5 ms, indicating the considerable overhead caused by frequent route recoveries and retransmissions triggered by its single-hop greedy forwarding under high traffic loads. In contrast, the delay in Traj-Q-GPSR only rises from 82.2 ms to 859.0 ms, consistently staying below one second. This trend is also consistent with the packet loss patterns observed in Figure 4a. As corroborated by earlier experimental results, Traj-Q-GPSR demonstrates substantial improvement in end-to-end latency, further validating its capability to maintain low delay in high-load communication scenarios. As shown in Figure 6c, the routing efficiency of GPSR declines significantly with the increase in the number of CBR pairs. When the CBR count reaches 50, its routing efficiency drops by 40.4% compared to the case with only 10 CBR pairs. Moreover, during moderate traffic conditions, GPSR exhibits marked fluctuations, reflecting its unstable forwarding performance due to frequent routing voids and retransmissions under heavy loads. In contrast, Traj-Q-GPSR maintains a consistently high level of routing efficiency, with variations contained within 5% across all tested loads. Under the maximum traffic load of 50 pairs, Traj-Q-GPSR improves routing efficiency by 77.8% compared to GPSR, demonstrating a significantly enhanced data delivery success rate per unit of forwarding cost. Figure 6: Impact of CBR connections on network performance: (**a**) Impact of CBR connections on packet loss rate. (**b**) Impact of CBR connections on average end-to-end delay.