# A Semi-Random Elliptical Movement Model for Relay Nodes in Flying Ad Hoc Networks
## 5 Performance Evaluation  
### Simulation Setup  
To evaluate the performance of the proposed SREM model, simulations were conducted using the NS-3 network simulator. The simulation environment was configured as a two-dimensional plane of size \(1000\times 1000\,\mathrm{m}^{2}\), in which a total of 50 UAV nodes were deployed to fly at a fixed altitude. Each UAV was equipped with a communication range of 100 m and assigned a movement speed within the range of 20 to 40 m/s. The total simulation duration was 100 s, and to assess variability in mobility behavior, each scenario was executed 10 times. The three mobility models compared were RWP, SRCM, and the proposed SREM. In the simulation setup, the source node was fixed at coordinate \((0,500)\), located on the left edge of the area, and the destination node was fixed at \((1000,500)\), on the right edge. Since the distance between the two nodes exceeded the communication range, multi-hop relay paths through intermediate UAV nodes were required. The objective of this experiment was to compare the effectiveness of each mobility model in forming relay paths and delivering packets in such a scenario. The key simulation parameters used in this study are summarized in Table 3.  
All UAV nodes utilized the Ad hoc On-Demand Distance Vector (AODV) routing protocol, dynamically establishing routes through route discovery messages. Packets were discarded if no route could be established, and key performance metrics--including packet delivery ratio, end-to-end delay, and average hop count--were measured accordingly. Traffic was generated using a Constant Bit Rate (CBR) model, in which the source node transmitted 100 packets of 64 bytes each at a rate of 1 Mbps. The MAC layer was based on the IEEE 802.11a standard, and all UAVs were equipped with omnidirectional antennas. HELLO messages were broadcast every 100 ms. The traffic type was configured as TCP. In the SREM model, the straight line connecting the source and destination nodes was designated as the major axis of the ellipse, with the center of the ellipse positioned at the \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Simulation tool & NS-3 \\ Environment size & \(1000\times 1000\,\mathrm{m}^{2}\) \\ Number of UAVs & 50 \\ Mobility model & SREM, SRCM, RWP \\ SREM ellipse (a, b) & \(a=500\,\mathrm{m}\), \(b=250\,\mathrm{m}\) \\ SRCM maximum radius & 500 m \\ RWP pause time & 1 s \\ RWP speed & 40 m/s \\ Source node location & (0, 500) \\ Destination node location & (1000, 500) \\ Routing protocol & AODV \\ Traffic model & Constant Bit Rate (CBR) \\ Traffic type & TCP \\ Packet size & 64 bytes \\ CBR rate & 1 Mbps \\ HELLO interval & 100 ms \\ MAC protocol & IEEE 802.11a \\ Antenna type & Omni-directional \\ UAV velocity & 20\(\sim\)40 m/s \\ Simulation runtime & 100 s \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters. center of the simulation area, \((500,500)\). The semi-major and semi-minor axes were set to \(a=500\,\mathrm{m}\) and \(b=250\,\mathrm{m}\), respectively. Each UAV selected two random points on the elliptical boundary and traveled in a straight line between them. In the RWP model, each UAV randomly selected a destination within the simulation space and moved toward it in a straight line. Upon reaching the target, the UAV paused for one second before immediately selecting a new destination and repeating the process. Initial positions were randomly assigned without synchronization among nodes. In the SRCM model, UAVs selected random start and end points along the boundary of a circle with a maximum radius of \(500\,\mathrm{m}\) and moved along the corresponding circular arc. To comprehensively evaluate communication stability and efficiency in a FANET environment, the simulation performance assessment was conducted using the following five key metrics:  
* Packet Delivery Ratio (PDR): The ratio of packets successfully delivered to the destination. * Throughput: The total amount of valid data received per unit time.