# Data Naming Mechanism of LEO Satellite Mega-Constellations for the Internet of Things
## 4 Simulation Settings  
### Design of LEO Mega Constellation Simulation Platform  
The NS-3 simulator is a discrete event-driven network simulator that consists of interdependent modules, such as the core module, network module, application module, internet module, point-to-point module and ndnSIM module, and provides different functions for network simulation. The ndnSIM module is the latest NDN simulation module based on NS-3, which implements the basic components of NDN modularly. The current NS-3 does not provide an LEO satellite network simulation module [11], nor does it have high-speed LEO mobile and dedicated protocol stacks for satellite-to-ground communications, such as DVB-RCS2. ndnSIM can only provide the lower layer support of the NDN protocol stack, such as content storage CS, pending interest table PIT, forwarding interest database FIB, forwarding strategy and cache replacement strategy [32]. Therefore, this article expands the NS-3 structure by adding LEO satellite modules and develops a hierarchical LEO mega constellation simulation platform, as shown in Figure 12. From top to bottom, the simulation platform consists of four layers, infrastructure, network model, network configuration and control, and supports three-dimensional position and movement characteristics analysis. The infrastructure layer primarily includes the LEO mega constellation and the ground station used to communicate with the satellite constellation. The network model layer considers the number of orbital planes in the network, the number of satellites in each orbital plane, the orbital height of the satellite constellation, and ISLs to construct an LEO satellite constellation mobile model. For each orbital plane, the  
Figure 12: Architecture of the LEO mega constellation simulation platform. satellite closest to the equator is selected as the \"reference satellite\", referring to the satellite geometry analysis in Section 2.2. The displacement between the reference satellite and the nearest satellite on the adjacent orbital plane is used as an increment to automatically determine the closest satellite to every other satellite in the orbital plane. The initial position of the satellite is set according to the orbital coordinates of each constellation. As time passes, the satellite orbits the Earth, and the distance between the satellites at a specific time point is calculated according to the ISL distance formula in Section 2.2. The network model layer also incorporates modules such as flow-monitoring and point-to-point in NS-3. The point-to-point module creates an in-plane link between the two satellite nodes that remains unchanged throughout the simulation period. The carrier sense multiple access (CSMA) module establishes a dynamic interplane satellite link and a link between the ground station and the satellite. CSMA also allows dynamic linking through connection and separation functions; the flow-monitor module allows traffic monitoring to be enabled on all nodes in the satellite-to-earth network. The data collected using traffic monitoring include data packet transmission delay and throughput. The delay of the communication of the LEO mega constellation in the NS-3 code is calculated using the speed of light and the distance between the satellite and ground nodes [54]. The network configuration layer configures the broadcast channel for the LEO mega constellation, configures the requester and content provider for the ground station model, and installs the corresponding NDN protocol or IP protocol for different network environments. The control layer first applies the relevant mobile model to network the satellite constellation network nodes in the orbital planes and ground stations. The communication between the ground station and the satellite is dynamic. Because the ground station remains stationary, the ground station must switch when updating the connection to the satellite to ensure that it is still connected to the nearest satellite.