Satellite Internet mainly refers to the broadband Internet service model that uses satellite as the access medium, which belongs to the information infrastructure in the new infrastructure." Xiang Kaiheng, chief designer of the "Hongyun Project" of China Aerospace Science and Industry Corporation, said that at present, satellite Internet mainly refers to the low-orbit broadband Internet satellite Internet realized by using low-orbit satellites. Compared with high-orbit satellites, it has the characteristics of low latency and easy global coverage.
The terrestrial network relies on communication with base stations, and the satellite Internet relies on satellite communication technology to access the Internet, which is like moving the terrestrial base station into space, and each satellite is a mobile base station.
According to the different orbits of communication satellites, satellite Internet can be divided into high-orbit and low-orbit.
The orbit of high-orbit satellites is about 36,000 kilometers from the ground, also known as geostationary orbit. Although they all move at high speed, the orbital period of the satellites in this orbit is strictly consistent with the period of rotation of the Earth, and they remain "stationary" relative to the ground. The area they cover is also fixed, so it is relatively easy to establish communication services. Taking advantage of this feature, broadband communication can be achieved through high-orbit satellites, and the number of satellites required does not need to be very large. However, there are physical limitations to high-orbit satellite Internet. The radius of the Earth is only 6,378 kilometers.
The use of high-orbit satellites to achieve communication services is equivalent to sending signals from the Earth's surface to a distance of 36,000 kilometers. The round trip, as well as signal processing and other processes, lead to a large delay. It is acceptable for general calls or website visits, but cannot meet the needs of applications with high real-time requirements, such as online games and drone remote control. In addition, the ground terminal receiving high-orbit satellite signals must be relatively large to receive such long-distance signals well.
Therefore, people have turned their attention to low Earth orbit, within the range of 500-2,000 kilometers. In this orbit, the communication transmission delay between the ground and the satellite is milliseconds, which is enough to meet the needs of vehicle networking, automatic driving, etc. The receiving terminal can be made portable and accessible via smartphone.
The rise of satellite Internet is driven by both demand and technological capabilities." Huang Hua said that the integration of satellite Internet into the new infrastructure reflects the demand brought about by digitalization and informatization. With the advancement of aerospace and communications technology, it has become possible to provide such services.
Experts believe that from the perspective of development trends, digitalization and informatization have fundamentally changed people's lives, and mobile phone users hope to be able to connect to the Internet anytime and anywhere. Although the terrestrial network is well developed, the cost of relying on terrestrial network coverage in many specific scenarios is too high to recover the cost. Relevant data also shows that there are still 3.5 billion people in the world who do not have access to the Internet and 700 million people who do not have communication services. Therefore, the deployment of "base stations" in near-Earth space has become an option. In addition, unlike the narrow-band and low-speed satellite Internet such as Iridium in the 1990s, the new satellite Internet aims to achieve broadband network services similar to those on the ground, that is, low-orbit broadband satellite Internet.
How to achieve low-orbit broadband satellite Internet? Taking the 1,000-kilometer low-Earth orbit as an example, a satellite orbits the Earth for more than 100 minutes, and hundreds of thousands of satellites form a constellation at this orbital height to achieve seamless coverage of the world. For users, although the satellites are constantly moving, there are satellites flying overhead at any moment, and the network signals always maintain stable coverage.
In China, on December 22, 2018, the first satellite of the "Hongyun Project", the technical verification satellite, was sent into orbit, marking a significant step in the construction of my country's low-orbit broadband satellite communication system. "Hongyun Project" is a global low-orbit broadband satellite communication system led by China Aerospace Science and Industry Corporation. By building an Internet satellite system consisting of 156 small satellites, it achieves free access to broadband Internet without dead ends around the world. Almost simultaneously, on December 29, 2018, the first satellite of the "Hongyan" constellation was successfully launched and entered the predetermined orbit. The "Hongyan" constellation is a low-orbit satellite communication system independently developed by China Aerospace Science and Technology Corporation. It aims to build a well-connected information channel in space that covers the world. It plans to use 60 core satellites and hundreds of broadband communication satellites to form a system to achieve Internet access anywhere in the world.
After the launch of the "Hongyun Project" technology verification satellite, all functions and performance tests under various working conditions, such as different weather conditions and different business scenarios, were completed in 2019. The testers accessed the Internet through satellite user terminals and successfully implemented standard Internet services such as web browsing, WeChat sending, e-commerce shopping, video calling, and high-definition video on demand. Short video applications can also be used normally. All functions and indicators of the satellite's in-orbit measurement meet or even exceed expectations. The user experience rate of this test satellite exceeds 10 megabits.
After the system is built, whether we are in the desert, the ocean, or on the plane, we can enjoy the same Internet speed and service experience as at home." Xiang Kaiheng said that satellite Internet can achieve Internet access anytime and anywhere, especially in remote places where traditional mobile communications cannot reach, such as high mountains, deserts, deep seas, and oceans, which is more advantageous.
Although the maximum speed of satellite Internet is not as fast as that of terrestrial fiber optics, the actual user experience will not be much different. Satellite Internet and terrestrial networks, such as 5G networks, will be complementary. In areas with developed terrestrial communications, such as large cities, people give priority to using terrestrial networks. In areas where terrestrial networks cannot reach, including scientific missions in Antarctica and the Arctic, outdoor adventures and other scenarios, satellite Internet is more suitable. Satellite Internet can meet the needs of areas with poor information infrastructure, fill the information gap, and make network connection possible and convenient.
The services provided by satellite Internet are not limited to broadband connection, but also include navigation enhancement functions that can improve positioning and timing accuracy, and the Internet of Things that can monitor aviation, navigation and ocean cargo. For example, the "Hongyun Project" is an integrated communication, navigation and remote sensing system that can meet the needs of applications with high real-time requirements, such as emergency communications, sensor data collection, industrial Internet of Things, and remote control of unmanned equipment. The "Hongyan" constellation is a system combining broadband and narrowband access. Users can use portable terminals to make calls, surf the Internet, and use navigation enhancement functions.
Through the close integration with 5G, industrial Internet, Internet of Things, big data, etc., the application scenarios of satellite Internet in the future will be very rich. Satellite Internet is more like a platform in space. With 5G payload, it can meet broadband communication. with a camera, it can achieve remote sensing. with navigation enhancement, it can support autonomous driving.
The basic technologies s must be addressed, and industrial development must achieve a virtuous circle. At present, commercial aerospace is developing rapidly. As a product of the combination of satellite communication and the Internet, satellite Internet, especially low-orbit satellite Internet, has outlined a business plan that people long for. However, it is not easy to actually build a system and put it into practical application, especially to give users a good experience.
Although we have a certain understanding of satellite and communication technology, the construction of satellite Internet is not easy. It cannot be achieved overnight and requires further innovation,/p>
Compared to high-orbit satellites that are relatively stable and easy to “catch”, low-orbit satellites orbit the Earth at a speed of more than 7 kilometers per hour. second. The frequency changes and dynamic switching of satellite signals caused by this rapid movement are not much different from terrestrial networks. In order to avoid network outages and provide users with a good experience, many key technologies must be addressed. In addition, in order to reduce the cost of ground maintenance, it is necessary for thousands of satellites in orbit to achieve autonomous operation in orbit through information, which must also be achieved through technological innovation.
In addition to solving technical problems, experts believe that the key to the real use of satellite Internet lies in its acceptance by the general public and its ease of use and affordability. This requires satellite networking to achieve low cost and ground terminals to achieve low cost and miniaturization. "For example, through mass production, satellite Internet satellites will be cheaper. Through technical research, chips will become smaller and smaller, and antennas will be transformed from "bricks" to "tiles."
Complex systems such as satellite Internet have very high requirements for system design, technology path selection, and industrial supporting facilities. It is necessary to consider comprehensive factors such as cost, industry maturity, ground conditions, and actual application needs at the beginning of the design. "The inclusion of satellite Internet in the new infrastructure has added confidence and vitality to the rapid development of the industry, and has promoted the industry chain to provide more cost-effective satellites, payloads, and ground terminal products, allowing the entire industry chain to reduce costs." Xiang Kaiheng said that on the one hand, as the application of low-orbit satellite Internet continues to expand, the communication capacity will continue to expand. As the scale becomes larger and larger, the cost will continue to decrease. on the other hand, through government-level guidance and market-level practice, resources will be integrated, and through industrialization and commercialization, cost reduction and efficiency improvement will be achieved, forming a virtuous circle of industrial development. Experts predict that it may take several years for ordinary users to use satellite Internet as they do on a telephone call.