# Data Naming Mechanism of LEO Satellite Mega-Constellations for the Internet of Things
## 2 LEO Mega Constellation for the IoT  
### IoT and LEO Mega Constellations  
The IoT connects people to things, and things to other things through machine-type communication (MTC) and man-machine communication (MMC). The IoT consists of a perception layer, a transmission layer, and an application layer, as shown in Figure 1. Generally, the perception layer uses radio frequency identification (RFID) [35], wireless sensor networks (WSN) [36], near field communication (NFC) [37], infrared and other technologies for object perception and data transmission using short-distance communication methods such as Bluetooth and ultra-wide band (UWB). The transmission layer uses the internet, public mobile communication technologies (4G, 5G [38]), mobile ad-hoc networks (MANETs) [39], satellite networks [40], vehicular ad-hoc network (VANET) [41], etc., to transmit collect data. At the application layer, data processing and analysis are completed by cloud computing [42], big data [43] and other means to provide services for end users. Figure 1: Components of the IoT. An important application in the 5G era is the interconnection of all things, while B5G or 6G requires seamless interconnection of all things under the condition of via space-air-ground-sea integration, and the transmission of IoT services requires low latency and high bandwidth. Generally, according to the orbital height, space-air-ground-sea integrated communication can be divided into three methods: high-orbit GEO, medium-orbit MEO, and low-orbit LEO. The networking features of these three methods are listed in Table 1.  
Table 1 shows that the three integrated communication methods have their own advantages and disadvantages. In recent years, small satellite technology, including Cubesat, has been developed rapidly, and LEO mega constellations for the IoT using intersatellite link networking technology have been highly valued globally, such as the SpaceX, Amazon, OneWeb, Hongyun and Hongyan systems in China, which primarily provide low-latency, high-bandwidth transmission services for IoT applications. A satellite constellation is a collection of multiple satellites with similar types and functions that are distributed on the same or complementary orbital planes and are coordinated to complete certain tasks under shared control. A constellation is typically a satellite network that is composed of multiple satellite rings that are configured in a specific way. This network can provide high performance, flexible wireless coverage and communication services to achieve global connectivity. The primary technical parameters and ground coverage of the primary constellations are shown in Table 2.  
The Iridium constellation is the pioneer of LEO mega networking and uses polar orbits and satellites to communicate with each other via intersatellite links (ISL). The satellite visualisation simulation software SaVi [44; 45] describes the structure and ground coverage of the Iridium constellation with six orbital planes, as shown in Figure 2.  
To achieve full coverage globally, the LEO mega constellation for the IoT is promising network architecture and a powerful complement to the ground-based IoT network. This constellation can provide the unique advantage of high flexibility for the global expansion of the networking market. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Constellation Category** & **Orbital Height (km)** & **Satellites for Full Coverage** & **Transmission Delay** \\ \hline GEO & 35,786 & Least & High \\ MEO & 2000–20,000 & Less & General \\ LEO & 500–2000 & Most & Low \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Constellation networking features.