# Research on Communication Stability of Inter-Cannonball Network Based on OPNET
## 4 Modelling Scene Setup
### OPNET Scene Modeling Configuration  
This paper focuses on inter-cannonball network communication, with emphasis on the changes in network characteristics when nodes move over the air and when failures occur. First, we build a simple fixed node ad hoc network as shown in Figure 8. All nodes use AODV routing protocol to construct a data transmission connection between _node_0_ and _node_35_, and then setup _node_7_ to be damaged after 500 s in order to monitor the change in communication link after node damage. As shown in Figure 8, dark blue and light blue represent the paths before and after the node damage, respectively. The AODV protocol selects the routing table _node_0_-> _node_7_-> _node_14_-> _node_21_-> _node_28_-> _node_35_ with a routing hop count of 5 once the simulation begins. After 500 s, _node_7_ is damaged and the original communication route is compromised, thus _node_0_ will retry the route discovery and send RREQ packets to the nodes in communication range in order to circumvent the injured node. When _node_14_ receives the RREQ packet, it returns the RREP packet since it has a routing table to _node_35_, and a new routing table is successfully constructed between _node_0_ and _node_35_. The routing table changes to _node_0_-> _node_6_-> _node_13_-> _node_14_-> _node_21_-> _node_28_-> _node_35_, and the route hop count rises to 6. The inter-cannonball self-organizing network is similarly based on this paradigm, but it is not a fixed data connection and needs routing modifications for network topology changes. We set the scenario as an ideal environment, where all nodes are at the same level when moving in the air, with a total of 36 cannonball nodes and one FTP service node at the beginning. The minimum spacing between cannonball nodes is 10 km, and the communication frequency is 2401 MHz. To ensure that the nodes can communicate with  
Figure 8: Changes in routing after _node_7_ is damaged. each other, the ideal environment is assumed, and the reception sensitivity is \(-95\) dB. In this environment, according to Equation (1), \(Loss(\text{dB})=120\) dB, then the minimum transmit power should be set to 25 dBm, corresponding to 0.316 W. Considering the retention margin, the node's transmit power is set to 0.4 W.  
In order to compare the effects of node mobility and survival rate on the communication network, we build two networks as shown in Figure 9, where all fixed nodes are used on the left side, and all mobile nodes are used on the right side with white arrows showing node movement trajectories, and the rest of the simulation settings are the same. We set all communication nodes to use the AODV protocol, used the FTP data service, set the data transfer file size to 2 Mbit, and performed concurrent data transfer every 5-10 s [38]. The backend traffic start time was 60 s, and the simulation time was 30 min. To speed up the simulation, the Rx Group Config node was utilized to set the maximum communication distance between communication nodes to 15,000 m. The simulation parameters are presented centrally in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Model Parameters** & **Parameter Description** & **Parameter Setting** \\ \hline Simulation scene size & The size of the range in which the node can be moved during simulation & 100 km \(\times\) 100 km \\ \hline Number of nodes & Number of nodes present in the simulation scenario & 36 \\ \hline Maximum communication range & Maximum communication distance between two nodes & 15 km \\ \hline Routing protocol & Routing protocols used by communication nodes & AODV \\ \hline Transmission power & Transmitting power when the node transmits information & 0.4 w \\ \hline Data size & Size of transmitted packets & 2 Mbit \\ \hline Backend traffic start time & Delay in the start time of background traffic as specified in the traffic browser & 60 s \\ \hline Total simulation time & The total simulation time set & 30 min \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameter table.