What are High Throughput Satellites?
High throughput satellites (HTS) are a class of communication satellites that provide significantly higher data transmission capacity compared to traditional satellites. They achieve this by utilizing advanced technologies and techniques such as frequency reuse, multiple spot beams, and higher frequency bands.
The primary objective of HTS is to deliver high-speed, reliable, and cost-effective communication services to a wide range of users. The satellites support a wide range of applications, including broadband internet services, cellular backhaul, data-intensive government and military communication, and in-flight connectivity for aircraft.
Thanks to their advanced technologies, HTS systems have a lower cost per transmitted bit compared to traditional satellites. This makes them more cost-effective for operators and users, allowing for more affordable broadband and communication services.
Key Features of HTS Satellites
Frequency Reuse
HTS satellites use advanced frequency reuse techniques, such as orthogonal frequency division multiplexing (OFDM), to maximize the available bandwidth and minimize interference between adjacent beams. This allows the satellite to transmit more data simultaneously.
Multiple Spot Beams
Traditional satellites typically use a single wide-beam to cover a large geographical area, which can lead to reduced capacity and signal quality. HTS satellites use multiple narrow spot beams, which allows them to focus their power and bandwidth on smaller, more targeted areas. This improves overall signal quality and capacity, especially in areas with high demand.
Higher Frequency Bands
HTS satellites often operate in higher frequency bands like Ka-band (26.5-40 GHz) and V-band (40-75 GHz), which have more available bandwidth compared to the widely-used Ku-band (12-18 GHz). These higher frequency bands enable faster data rates and higher capacity.
Advanced Modulation and Coding Schemes
HTS satellites employ advanced modulation and coding schemes to improve spectral efficiency, enabling them to transmit more data over the same amount of bandwidth. This results in higher overall data throughput.
Examples of Operational HTS Satellites
Several operational HTS provide services around the world. Here are some examples:
Launched in 2017 by Viasat, ViaSat-2 is an HTS that operates in the Ka-band. It provides broadband services across North and Central America, the Caribbean, and parts of South America, as well as air and maritime routes in the Atlantic Ocean. ViaSat-2 has a capacity of around 300 Gbps, making it one of the highest capacity satellites at the time of its launch.
HughesNet Jupiter-2 (EchoStar-19)
Launched in 2016 by Hughes Network Systems, the Jupiter-2 satellite provides broadband internet services in the Ka-band across the United States, including Alaska, as well as parts of Canada and Mexico. With a total capacity of around 220 Gbps, it was designed to support the growing demand for high-speed internet in North America.
Launched in 2018 by SES, the SES-12 HTS operates in both the Ku-band and Ka-band. It provides communications services for Asia-Pacific and the Middle East, including direct-to-home (DTH) broadcasting, very small aperture terminal (VSAT) networks, in-flight connectivity, and maritime communications.
Inmarsat Global Xpress (GX) Constellation
The Global Xpress constellation, operated by Inmarsat, consists of four Ka-band HTS satellites (Inmarsat-5 F1, F2, F3, and F4) that provide global broadband connectivity for a variety of applications, including government and military communications, maritime and aero connectivity, and land-based services. The first of these satellites, Inmarsat-5 F1, was launched in 2013, with the other three following in subsequent years.
Launched in 2020, Eutelsat Konnect is a Ka-band HTS operated by Eutelsat Communications. It has a capacity of around 75 Gbps and provides broadband services to unserved and underserved areas in Africa and Europe.
HTS Challenges
Gateways and Ground Infrastructure
HTS satellites typically require a network of ground stations or gateways to manage data traffic and provide connectivity to the end-users. These gateways are strategically located to ensure optimal communication with the satellite’s spot beams. This ground infrastructure is an important aspect of the overall HTS system and requires investment and maintenance.
Latency
Although HTS satellites offer higher throughput and capacity, they still suffer from latency issues, especially in geostationary orbits. The latency is caused by the long round-trip time it takes for signals to travel between the Earth and the satellite (approximately 36,000 km above the Earth). However, this latency is generally acceptable for many applications, such as streaming video or web browsing.
To address the latency issue, some companies are developing low Earth orbit (LEO) or medium Earth orbit (MEO) HTS constellations. Satellites in these orbits are closer to Earth, reducing the latency compared to geostationary satellites. Examples of such systems include SpaceX’s Starlink and OneWeb’s satellite constellation.
Interference Management
HTS satellites often require advanced interference management techniques to avoid or mitigate signal interference between adjacent spot beams or other satellites. Techniques like adaptive power control, advanced modulation schemes, and digital channelization help reduce interference.
Market Growth and Competition
The demand for HTS services has been growing rapidly, driven by the need for broadband connectivity worldwide, particularly in remote or underserved regions. This has led to increased competition among satellite operators, driving innovation and reducing prices for end-users.
Regulatory Challenges
HTS satellites operate in specific frequency bands that are regulated by national and international organizations, such as the International Telecommunication Union (ITU). Satellite operators need to obtain licenses and coordinate with other operators to avoid interference and ensure efficient use of the radio spectrum.