Satellite Constellations in Internet of Things

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2	references update and layout	Fanny Huang	Meta information modification	2069	2024-03-12 04:03:13	\|

This entry is adapted from the peer-reviewed paper 10.3390/electronics13030579

Artificial satellites serve various functions, such as communications, Earth observation, navigation, and global positioning. A satellite constellation is a group of satellites working together under centralized control to achieve a common objective. Positioned in complementary orbital planes and connected to global ground stations, these constellations aim to provide interconnected network capabilities for IoT communications. IoT communication satellites must effectively manage data frame repetitions, involving the capability to receive, process, and retransmit data from IoT devices operating in conditions of deficient coverage. IoT satellites prioritize compact form factors, simplicity, and scalability, aiming to support low-data-rate applications efficiently.

satellite IoT

1. Introduction

NewSpace represents a modern approach to space missions, characterized by three main elements: space privatization, satellite miniaturization, and the development of innovative services utilizing space data ^[1]. This concept diverges from traditional government-led space programs, emphasizing the role of private companies, like SpaceX and Rocket Lab, in satellite manufacturing and launching. The adaptation and screening of Commercial of The Shelf (COTS) components boosted the miniaturization of satellites, including cube, micro-, and nanosatellites, enabling deployment in a single launcher and facilitating more accessible access to low Earth orbits (LEOs) ^[2].

Satellites in LEOs, orbiting between 160 and 2000 km above Earth’s surface ^[1], offer various services. These include Earth observation, Internet connectivity, scientific research, satellite navigation, integration with 5G technology, and tracking for aeronautical and maritime purposes. These services result from the combined effects of space privatization and the trend toward smaller satellites ^[3].

NewSpace has catalyzed the emergence of the Satellite Internet of Things (IoT), enabling direct data collection from terrestrial sensors through compact, yet efficient, LEO satellites ^[4]. Previously, such data gathering would necessitate an extensive network of Earth stations. However, NewSpace advancements have facilitated cloud-based services that provide shared ground station networks and advanced computing capabilities for data processing. Furthermore, LEO constellations are transforming IoT connectivity, particularly in remote regions, with companies like FOSSA Systems, Sateliot, or Lacuna at the forefront of this development. The advent of satellite-based low-power wide area networks (LPWANs) marks a significant evolution in the IoT landscape, offering global connectivity to devices at costs competitive with terrestrial providers, thereby promising a substantial expansion of connected devices ^[5].

IoT is revolutionizing various industries by enabling connectivity across various devices, from sensors to autonomous vehicles, automating and enhancing operational processes. The advent of LEO satellite networks has broadened the connectivity possibilities for IoT devices in remote or isolated regions. It is a supplementary connectivity option in areas with terrestrial IoT networks. However, satellite IoT communications have challenges, including managing many devices, interference issues, and security concerns. Addressing these challenges is essential for the efficient and secure functioning of IoT satellite networks ^[6]^[7]^[8]^[9].

NewSpace’s emergence has notably transformed the space industry, increasing accessibility for various players ^[10]. The space economy is on a consistent growth trajectory, with forecasts suggesting a value ranging from several hundred billion to multiple trillion dollars by 2040 ^[11]. Concurrently, the IoT satellite market is anticipated to grow substantially, with expectations of its value escalating from USD 1.1 billion in 2022 to USD 2.9 billion by 2027 ^[12].

2. Satellite Constellations in IoT

Artificial satellites serve various functions, such as communications, Earth observation, navigation, and global positioning. However, a single satellite cannot provide global coverage simultaneously. To address this, satellite constellations, which consist of numerous satellites, have been developed to enhance coverage and ensure global reach ^[13].

A satellite constellation is a group of satellites working together under centralized control to achieve a common objective ^[14]. Positioned in complementary orbital planes and connected to global ground stations, these constellations aim to provide interconnected network capabilities for IoT communications. This design ensures that at least one satellite is visible in specific Earth regions, offering continuous coverage.

Each satellite has a specific role in an IoT communications constellation, collaborating to offer comprehensive global services. Utilizing advanced communication technologies, they connect with Earth-based users through various antennas, such as directional antennas, omnidirectional antennas, and satellite dishes, adapting to different used cases and environmental conditions. Advanced orbit control technology keeps satellites in the correct position in space. This involves the continuous monitoring of satellites from Earth and necessary adjustments to maintain their proper orbits ^[15].

Satellites in these constellations are strategically placed in different orbits, each optimized for specific tasks. The orbits, shown in Figure 1, include:

Figure 1. Types of orbits based on their orbital distances.

Low Earth Orbit (LEO): Satellites in LEOs are located at altitudes between 160 to 2000 km above the Earth’s surface. These satellites can provide constant global coverage due to their proximity and ability to orbit the Earth multiple times daily. They are primarily used for Earth observation, communication, and global positioning services.
Medium Earth Orbit (MEO): Satellites in MEOs are located between 2000 and 35,786 km above the Earth’s surface. They provide regional coverage and are typically used for satellite mobile telephone services, navigation, and global positioning.
Geosynchronous Equatorial Orbit (GEO): Satellites in GEOs are positioned at a constant altitude of around 35,786 km above the Earth’s surface and move at the same speed as the planet’s rotation. This allows them to stay in a fixed location relative to a specific point on Earth. Communication and meteorological observation services primarily use this region for uninterrupted coverage.

While advantageous for their reduced transmission power and ability to utilize smaller satellites, like CubeSats, LEO satellites face challenges. These include more satellites to cover larger areas and the Doppler effect impacting communications ^[16]. These challenges imply additional costs and complexities in designing and operating satellite communication systems.

Satellites are classified based on their application, orbit, and mass. The mass-based classification is the most common method (as shown in Table 1) due to its importance in determining the development and launch costs ^[17]. Large satellites have a useful lifespan of up to 10 years. They are designed for long-term operations, with redundant systems and electronic components resistant to space and cosmic radiation. They require more energy, which is generated by large photovoltaic solar panels. Due to their size, they are more complex to launch and require more powerful propulsion systems ^[17].

Table 1. Classification of satellites based on their mass.

Types of Satellites	Mass (kg)
Femtosatellites	<0.1
Picosatellites	0.1–1
Nanosatellites	01–10
Microsatellites	10–100
Minisatellites	100–500
Small Satellites	<500
Medium Satellites	500–1000
Large Satellites	>1000

The trend towards smaller, more affordable satellites is on the rise. Minisatellites weighing between 100 and 500 kg are becoming a popular alternative to large, expensive satellites. The miniaturized electronics in these satellites make them smaller and lighter, providing redundancy to ensure reliability. This miniaturization also reduces the launch costs, making it easier to launch them. Microsatellites weighing 10 and 100 kg are ideal for testing new technologies and capabilities before they are used for larger missions. They benefit scientific and exploration missions, where their small size and ability to be launched in groups provide flexibility and the capacity for simultaneous measurements at different points on Earth. The combined use of mini- and microsatellites is a growing trend in space exploration, providing a viable alternative to conventional large satellites.

Nanosatellites belong to the smallest satellite category, weighing between 1 and 10 kg. They are mainly used for technology demonstrations and educational missions due to their low cost, rapid development, and ease of deployment in small constellations. However, they are rapidly gaining popularity as an alternative to conventional satellites ^[18]. Among nanosatellites, CubeSats are the tiniest, measuring 10 cm × 10 cm × 11.35 cm and weighing less than 1.33 kg. Despite their small size, they include all the basic subsystems of larger satellites. Other satellite variants with even smaller sizes, such as PocketQubes, are also available ^[19].

Picosatellites weighing less than 1 kg are mainly used for technology demonstrations and educational missions. However, some satellite companies are presently using them to deploy low-cost constellations and offer commercial services. FOSSA Systems ^[20] is one such example. On the other hand, femtosatellites weigh less than 0.1 kg. They are primarily used for space fragmentation detection tests, the evaluation of tracking capabilities of various sensors used for space surveillance, and the detection of tiny objects ^[21].

The form factor, denoting a satellite’s size and shape, is another classification criterion. CubeSats are measured in units (U), with 1U equivalent to a cube with an edge of 10 cm. This measurement is essential for planning and designing small satellites ^[19]. CubeSats are available in different sizes, ranging from 1U to 6U. However, even larger sizes, such as 12U and 16U CubeSats, are expected to be developed. Conversely, pocket tubes have an even smaller form factor than CubeSats ^[19].

Traditional Satellite vs. IoT Satellite

The satellite design for IoT communications has been comprehensively investigated in the scientific literature, providing invaluable insights into the efficiency and cost optimization. Ref. ^[19] focuses on adapting satellites for IoT applications, characterized by low data rates, within a bandwidth of approximately one hundred kilohertz. These satellites, characterized by their compact dimensions and straightforward hardware-like half-wave dipole antennas, need advanced functionalities, such as beamforming or inter-satellite links. Furthermore, they operate in lower frequency bands, like very-high frequency (VHF) and ultra-high frequency (UHF), aspects influenced by the prevailing scientific literature on communication hardware design.

In ^[22], scientific consideration is given to the efficiency and cost-effectiveness of small or nanosatellites. The proposal involves adopting 12U CubeSats arranged in a 2 × 2 × 3 configuration, orbiting at 500 km altitude. This scientific configuration is presented as a balanced solution, aligning with the findings from the scientific literature, meeting both cost and service requirements, and allowing the periodic access of IoT terminals to the satellites.

Furthermore, ref. ^[23] outlines the hardware design considerations for IoT communication satellites. These considerations include the necessity for signal transmission and reception capabilities within suitable IoT application frequency bands, such as the L and S bands. Additionally, the requirement for antennas and signal processing systems enabling communication with IoT devices on the Earth’s surface is emphasized. Given the substantial transmission distance in satellite communication, adequate power and signal amplification systems are essential to overcome increased path loss compared to typical terrestrial scenarios.

Moreover, IoT communication satellites must effectively manage data frame repetitions, involving the capability to receive, process, and retransmit data from IoT devices operating in conditions of deficient coverage. Consequently, satellites should be equipped with data storage and processing systems to handle frame repetitions efficiently, enhancing the probability of successful data transmissions from IoT devices ^[24].

Additionally, the critical differences with traditional communication satellites lie in the emphasis on miniaturization, commercial technology utilization, and cost-effective design philosophies. Unlike their traditional counterparts, IoT satellites prioritize compact form factors, simplicity, and scalability, aiming to support low-data-rate applications efficiently. Table 2 compares the main features of the two satellite communication solutions.

Table 2. Comparison between IoT satellite and traditional satellite communications.

Aspect	Satellite IoT Communications	Traditional Satellite Communications
Main objective	Facilitate connectivity among IoT devices and gather small volumes of data (e.g., sensors) to provide specialized services.	Provide global telecommunications services, such as television, telephony, and high-speed data transmission, to large audiences.
Type of transmitted data	Small data and control messages from IoT devices, such as sensors and meters.	Larger volumes of data, such as video, voice transmissions, and high-speed data.
Bandwidth	Lower bandwidth is required for transmitting low-speed and low-volume IoT data.	Higher bandwidth is required to handle high-speed transmissions and large data volumes.
Latency	Tolerant to higher latencies, as IoT data are often less time-sensitive.	Requires lower latency to ensure high quality of real-time transmissions, such as video conferencing and television broadcasts.
Network design	Oriented towards wide-area networks (WANs) to cover extensive geographical areas and connect distributed devices.	Designed for wide-area networks (WANs) or local area networks (LANs) to transmit data globally or regionally.
Power requirements	Focus on energy efficiency to meet the limitations of battery-powered and processing-constrained IoT devices.	Higher power supply capacity for traditional satellites and ground terminals with higher power requirements.
Number of connected devices	Scalability to support a large number of IoT devices scattered in different locations.	Less concern about the number of devices, with a focus on the quality and quantity of data transmitted per user.
Flexibility and configurability	Greater flexibility to adapt to different protocols and specific requirements of IoT devices.	More robust and specialized configuration to manage different types of telecommunications services.
Cost	Emphasis on cost-effective solutions to enable widespread adoption of IoT devices.	Higher budgets, as traditional satellite communication services, require a more complex infrastructure and powerful equipment.
Orbit type	Generally, LEO facilitates direct communication with IoT devices and reduces latency.	GEO or MEO to provide constant coverage over specific areas or regions of the planet.
Hardware components	Specialized transceivers and antennas for efficient communication with IoT devices.	More powerful communication equipment, including transponders, power amplifiers, and high-gain antennas, for long-distance signal transmission and reception.

References

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1. Introduction

2. Satellite Constellations in IoT

Traditional Satellite vs. IoT Satellite

References