Connecting the unconnected

Modern communication from space refers to the use of satellite-based communication systems to provide a wide range of services, including television broadcasting, internet connectivity, mobile telephony, and data communication. Communication satellites are used to transmit and receive signals to and from ground-based communication equipment, enabling fast and reliable communication over long distances. Today’s modern communication satellites are equipped with sophisticated communication equipment, such as high-powered transmitters, advanced software defined radio antennas, and digital signal processors that enable them to provide a wide range of services to users around the world.

One of the most significant advances in modern communication from space is the ability to provide broadband internet connectivity to remote and underserved areas. This approach is known as satellite broadband or satellite internet, and it has revolutionized the way people connect and communicate in remote and underserved areas.

BharatNet is one of the biggest rural telecom projects in the world, being implemented in a phased manner to all the Gram Panchayats (GPs) (~2.5 lakh) in the country for providing non-discriminatory access to broadband connectivity to all. The satellite component of the scheme is being implemented by BSNL and BBNL in 1408 GPs and 3753 GPs respectively.

Finally, modern communication from space also includes the use of satellite-based navigation systems, such as GPS (global positioning system), NavIC (navigation by Indian constellation), which enables users to determine their precise location and navigate to their desired destination. GPS is widely used in a range of applications, including aviation, maritime, land transportation, satellite-based television broadcasting services and military operations.

Motivation
One way to connect the unconnected using modern communication from space is through the use of satellite internet. Need for the country is to accelerate the penetration of accessible, available, and affordable broadband to digitally empower its citizens and act as a catalyst to transform their lives. (~50% presently). Then only we can achieve Digital India, smart cities, and 100-percent financial inclusion. The satcom penetration in India is very low when compared to US, EU etc., as shown in the table.

Overall, satellite internet is a powerful tool for connecting the unconnected, and it has the potential to bridge the digital divide by providing internet access to people in even the most remote corners of the world.

Communication from GEO and Indian national satellite system
Geostationary earth orbit (GEO). India has been operating communication satellites in the geostationary earth orbit (GEO) for several decades. These satellites have played a vital role in providing communication services to various sectors, including broadcasting, telecommunication and disaster management.

Indian national satellite (INSAT) system. India’s first communication satellite, Ariane Passenger Payload Experiment (APPLE) by Ariane-1, was launched on June 19, 1981 by the Soviet Union. However, it was not a GEO satellite but was placed in a low Earth orbit (LEO). India’s first GEO satellite, INSAT-1B, was launched in 1983 by the European Space Agency (ESA), using the Ariane launch vehicle. Since then, India has launched a series of communication satellites in the GEO to cater to the growing demand for communication, broadcasting, direct-to-home services, and broadband connectivity in the country.

Communication from low Earth orbit (LEO)
Low Earth orbit (LEO) satellites have revolutionized the way we communicate with each other, bringing a new era of connectivity and convenience to our daily lives. These satellites provide global coverage and enable a wide range of communication services, including voice, data, and multimedia services. They are used for both commercial and military applications, and their importance is only set to increase in the future.

Low Earth orbit (LEO). Low Earth orbit is a region of space that is roughly 160 to 2,000 km above the Earth’s surface. Satellites in LEO orbit the Earth at a high speed, typically at around 28,000 km per hour. These satellites are in constant motion, and are positioned in the Sun-synchronous orbit for optical imaging, or in inclined orbits for microwave imaging. LEO is an ideal location for communication satellites because they are close enough to the Earth’s surface to provide strong signals at faster rate (viz., 0.00167s), and they move fast enough to cover large areas quickly.

LEO communication satellites use a variety of technologies to transmit and receive signals, including radio frequency (RF), microwave, and optical systems. RF and microwave systems are used for most communication services, such as mobile phones, satellite TV, and broadband internet. These systems operate at frequencies ranging from a few hundred megahertz to several gigahertz and use directional antennas to communicate with ground stations and other satellites.

Optical systems, such as laser communication, are also used for LEO communication, particularly for high-speed data transfer between satellites or between satellites and ground stations. These systems use focused beams of light to transmit data, enabling much faster transfer rates than RF or microwave systems.

LEO communication systems also use advanced signal processing and encryption techniques to ensure reliable and secure communication. These techniques include error correction codes, spread spectrum, and frequency hopping, which help to reduce interference and improve signal quality. To use the service, customers will install an outdoor antenna – called as customer terminal – to communicate with satellites passing overhead. Traditionally, this equipment has been too large, too complex, and too expensive for many customers, making it difficult for LEO constellations to bridge the digital divide in a meaningful way. The present-day disruptive technology has made it possible to reduce the cost of small antennas to USD 500. These small antennas can provide high-speed internet speed up to 1 Gbps.

Applications of communication from LEO
Mobile communication. Mobile communication is one of the most important applications of LEO satellites. Satellites in LEO can be used to provide mobile phone coverage to remote and underdeveloped areas, where traditional infrastructure is unavailable.

Navigation. LEO satellites can be used for navigation services, such as GPS, which is essential for transportation, logistics, and emergency services. This technology is used in everyday life, from finding directions on a map to tracking shipments across the globe.

There are more than a dozen proposed/operational constellations that aim to provide internet services from the LEO. Some of the most notable ones include: SpaceX Starlink, OneWeb, Kuiper Systems (Amazon and Facebook), Telesat Lightspeed, Lynk Global, AST Space Mobile, Kepler Communications, Swarm Technologies, LeoSat, Globalstar, Iridium, Orbcomm, Teledesic, and Viasat, Inc.

GEO versus LEO for communication
Communication satellites orbiting the Earth can be classified into two categories, based on their altitude: geostationary Earth orbit (GEO) and low Earth orbit (LEO). While both types of satellites are used for communication purposes, they differ in several key ways. In this essay, we will compare communication from GEO and LEO and discuss their advantages and disadvantages.

Advantages and disadvantages of communication from GEO
Continuous coverage. GEO satellites provide continuous coverage of a specific area on the Earth’s surface. This makes them ideal for applications, such as television broadcasting, where a large number of viewers need to be reached simultaneously.

Stable signals. Since GEO satellites remain stationary, relative to a fixed point on the Earth’s surface, they provide stable signals that are not affected by the movement of the satellite.

High altitude: The high altitude of GEO satellites means that they require large, powerful antennas on the ground to receive their signals.

Delayed signals. The large distance between GEO satellites and the Earth’s surface means that signals transmitted from the Earth can take a significant amount of time to reach the satellite and be relayed back to the ground. The typical signal travel time from GEO to the ground station is ~0.1194 sec.

Advantages and disadvantages of communication from LEO
Real-time communication. LEO satellites provide real-time communication, which is essential for applications, such as mobile communication and emergency services.

Low latency. The close proximity of LEO satellites to the Earth’s surface means that signals are transmitted with low latency, resulting in fast and responsive communication. The typical signal travel time from LEO at 500 km to ground station is ~0.0016678 sec. This is around 71 times faster than the signal from GEO.

Limited coverage. Since LEO satellites move quickly, relative to the Earth’s surface, they provide limited coverage of any given area. This means that multiple satellites are needed to provide continuous coverage of a large area.

Short lifespan. LEO satellites have a shorter lifespan than GEO satellites due to the harsh environment of space and the constant exposure to radiation and debris.

Communication from space in 5G band
The fifth generation (5G) of mobile networks promises to revolutionize the way we communicate and connect with one another. One of the significant advantages of 5G is its ability to provide high-speed and reliable connectivity, which can be further enhanced by the use of satellite communication in the 5G band.

5G band is the range of frequencies allocated for 5G communication, and millimeter wave bands (26, 28, 38, and 60 GHz) are 5G, and offer performance as high as 20 gigabits per second. For India, the 5G radio frequency spectrum as defined by the Third-Generation Partnership Project is 24.5 to 29.5 GHz. The high-frequency range of the 5G band is known as millimeter-wave (mmWave), which offers high-speed connectivity but has limited range and is susceptible to interference from obstacles.

Satellite communication in the 5G band can overcome the limitations of terrestrial communication by providing high-speed connectivity over a large area. Communication satellites in the 5G band can operate in two ways, either as a part of the terrestrial 5G network or as a standalone satellite network. The satellite spectrum is allotted by International Telecommunication Union.

In the first approach, communication satellites can be used as a part of the terrestrial 5G network to provide coverage in remote areas, where terrestrial infrastructure is not available. This approach is known as satellite backhaul, where the satellite is used to provide connectivity to remote cell sites. Satellite backhaul can also be used to enhance the capacity of the terrestrial 5G network by providing additional bandwidth. In the second approach, communication satellites can operate as a standalone satellite network to provide connectivity to areas that are not covered by terrestrial infrastructure. This approach is known as satellite-to-user communication, where the satellite communicates directly with the user’s device. This approach can provide high-speed connectivity to remote areas, such as rural and maritime areas.

One of the significant advantages of using satellite communication in the 5G band is its ability to provide high-speed connectivity to moving objects, such as airplanes and ships. This approach is known as the satellite-to-air or satellite-to-ship communication and can provide a reliable and high-speed connection to these objects.

India has also been working on developing space-based communication systems to enhance its communication infrastructure. The Indian Space Research Organization (ISRO) has launched several communication satellites in the past, such as the GSAT-11/19/29 and provides high-speed connectivity to remote areas.