# A Semi-Random Elliptical Movement Model for Relay Nodes in Flying Ad Hoc Networks
## 5 Performance Evaluation
### Simulation Results
The SRCM model exhibited a slightly higher average EED of around 0.09 s, though it remained generally stable. This is likely due to the model's circular trajectory, which ensures a baseline level of coverage and route availability but lacks alignment with the communication axis. This misalignment occasionally leads to suboptimal relay paths, as reflected in its average hop count of 14.5. In contrast, the RWP model showed the highest EED, averaging approximately 0.18 s, with the greatest variation among trials. The random and non-deterministic nature of RWP often results in frequent link breaks and repeated route discoveries, degrading the overall consistency of relay network. Its average hop count was 21.7--the highest among the three models. Connection time, defined as the average duration for which a link between UAVs remains valid, is a key metric for evaluating communication stability in FANETs. The simulation results demonstrate that the differences in mobility structures and alignment strategies across the models lead to substantial variations in average connection time. The SREM model, which guides UAVs along elliptical trajectories aligned with the communication axis, inherently induces orbital overlap among nodes and results in prolonged periods of contact within communicable ranges. Simulation results demonstrate that SREM achieved the highest average connection time of approximately 23.8 s, indicating its superior capability in maintaining persistent links in FANET environments. In contrast, the SRCM model, though based on structured circular motion, lacks explicit alignment with the communication axis. While it facilitates occasional node encounters due to its repeated orbital nature, its average connection time was measured at around 18.1 s--lower than SREM--highlighting the limitations of its trajectory structure in sustaining long-term links. The RWP model exhibited the shortest average connection time, approximately 10.4 s. Due to its random, memoryless movement characteristics, frequent link disruptions and re-establishments were observed. This volatility in node positions and density over time makes it difficult to maintain stable communication paths, leading to reduced link persistence and increased transmission uncertainty. These findings underscore the importance of structurally aligned mobility models for achieving stable communication in FANET scenarios. Unlike models that merely ensure coverage or path diversity, SREM's design prioritizes relay-oriented alignment, resulting in higher packet delivery rates, shorter paths, and more persistent connections. Collectively, the results validate SREM as an effective mobility model optimized for relay-based UAV communication networks. Although this study provides a quantitative evaluation of the SREM model's communication performance using the NS-3 simulator, numerical results may differ when implemented in other simulation platforms such as PX4 or ArduPilot. These discrepancies can arise from variations in physical-layer modeling, control architectures, and system-level constraints. Factors such as actuator delays, sensor noise, and hardware limitations can influence observed outcomes. Nonetheless, the theoretical analysis of node distribution and the structured properties of the elliptical trajectory presented in this paper offer strong support that SREM is inherently well-suited for relay-centric FANET communications, independent of the simulation environment.