What are Mobile Satellite Services?

The biggest feature of mobile communication satellites is that they can provide communication services for mobile users, such as vehicle, aircraft, ship, and even personal communications, and have the advantages of a wider coverage area, unconstrained by geographical barriers, and user movement restrictions. Communication is beyond reach, so it is increasingly valued and welcomed. ^[1]

With the continuous development of international communications satellites, especially since 1982,

One is geostationary orbit like ordinary communication satellites. Its typical representative is the International Mobile Satellite No. 3, which was used for communications during flood control in China in 1998. However, due to the long communication distance, weak signals, and large ground equipment, it can only be used for communications of large mobile users such as ships, airplanes, and vehicles. Even advanced portable ground terminals, before calling, they must first find the international mobile satellite, and they cannot move during the call. However, a geostationary orbit mobile communication satellite capable of serving personal mobile phones has been developed, and the Asian Cellular System lifted off in 2000 (

Satellite communications are radio communications between earth stations or between spacecraft and earth stations using satellite transponders. They mainly include four major fields: fixed satellite communications, satellite mobile communications, direct satellite broadcasting and satellite relay communications. The first three are performed using satellite transponders between earth stations, and the latter are used between spacecraft and earth stations

Among the most well-known medium-orbit satellite mobile systems are the Odyssey system and the ICO system. In addition, ESA has also designed a MAGSS -14 system. However, due to some commercial reasons, they have been cancelled or have not yet run successfully. The new O3b mid-orbit satellite communication system attempts to provide voice communication services based on satellite broadband access.

Odyssey (Odyssey) system is a medium orbit satellite mobile communication system introduced by TRW [10]. The Odyssey system can be used as a supplement and extension to existing terrestrial cellular mobile communication systems, supporting dynamic, reliable, automatic, user-transparent services. The main user terminal of the system is the handset. The system can provide a variety of services, including voice, fax, data, paging, messages, positioning, and so on. The data rate of the handset can reach 2.4 kbit / s, and it can also provide data rates of 4.8 to 19.2 kbit / s. For commercial reasons with the ICO system, the Odyssey system was cancelled in December 1997, and TRW became a major shareholder of the ICO.

ICO (Intermediate Circular Orbit) Global Satellite Communication System is operated by ICO Global Communications Co., Ltd. The ICO system consists of a space segment and a ground segment group. The space segment is 12 stars located in a circular orbit, and the ground segment is called ICONET. The ICO system is connected with the existing ground fixed and mobile communication networks, and forms a complete world-to-world system, enabling multi-mode mobile phones or other terminals to communicate anytime and anywhere. The space segment of the ICO system consists of 12 satellites at a medium orbit altitude (MEO), of which 10 are main satellites and the other 2 are in-orbit backup satellites. The system uses inclined circular orbits with an orbital height of 10 390 km and an orbital inclination angle of 45 °. All satellites are distributed on two mutually orthogonal orbital planes, each of which has a backup satellite. The launch weight of the ICO satellite is 2 600 kg, and the design life is about 12 years. The satellite uses gallium arsenide solar cells, which can provide more than 8700 W of power at the end of the life of the satellite. Each satellite can provide 4,500 channels. ICO satellites use independent user link transceiver antennas. The two antennas are installed on the ICO satellite, the diameter of which is more than 2 m, and digital beamforming technology is used. Each user link antenna consists of 127 radiating elements, which are used to generate 163 transmitting or transmitting spot beams. Each ICO spot beam will provide a user link with a minimum 8 dB link margin in excess of 10 dB on average.

MAGSS-14 (Medium Altitude Global Satellite System) is a medium orbit satellite mobile communication system designed to support voice communications between handsets and mobile terminals, developed by ESA. The space segment of the MAGSS -14 system includes a constellation of 14 medium-orbit satellites. This design is very conducive to the system's step-up upgrade and can achieve global coverage. The system can communicate with user terminals on the L-band. The system has not yet been successfully deployed.

O3b is a new medium-orbit satellite communication system that provides broadband network access through satellites and can provide voice communication and data transmission services. It was developed by O3b Networks. O3b Networks is an Internet access service company formed in 2007 by organizations such as Internet giant Google, media giant John Malone's overseas cable TV operator Liberty Global, and HSBC. O3b provides satellite communications services in more than 150 countries in Asia, Africa, Latin America, and the Middle East, and provides a fiber-optic satellite backbone network for telecommunications operators and ISPs. O3b will be the world's first satellite network using MEO satellites with ultra-low latency, Ka-band, and fiber-optic rates. The O3b satellite repeater has 3 to 4 times the capacity of the GEO satellite system, which allows users to enjoy network bandwidth similar to fiber access. Due to the use of MEO satellites, the round-trip delay of the network is only about 100 ms. The O3b satellite constellation is planned to be deployed in 2012. It will first launch 8 satellites to form the first phase of the constellation, and it will be expanded to 16 satellites in the future. ^[4]

Since the 1990s, low-orbit satellite mobile communication systems have received wide attention. Countries around the world have developed multiple low-orbit satellite mobile communication systems. The bankruptcy of the Iridium system in 2000 caused this boom to cool rapidly. Several typical LEO satellite mobile communication systems include Iridium, Globalstar, Orbcomm, Teledesic, etc. At present, only three systems, Iridium, Globalstar, Orbcomm, have been successfully operated.

The Iridium system is a global mobile communication system for low-orbit satellites composed of 66 low-orbit satellites. Commercial operations began in November 1998, went bankrupt in March 2000, and a new Iridium satellite company was established in 2001, and communication services were re-established. The global coverage of the system includes bipolar regions. The on-board transponder uses advanced processing and switching technologies, multi-point beam antennas, and interstellar links. It is the most advanced low-orbit satellite communication system. Its interstellar and feeder links are Ka band, the user link is the L band, which provides services such as telephone, fax, data, and paging. User terminals include single-mode, dual-mode, and tri-mode mobile phones, vehicle-mounted units, and fixed terminals. After the establishment of the new Iridium company, thanks to government support and large orders from the US military, it is now operating well. Iridium Satellite is currently actively developing its new "NEXT" satellite constellation program. NEXT is a bold idea for the second-generation satellite constellation. NEXT follows the existing Iridium constellation structure and completes 100% coverage of the entire planet. Designed 81 satellites (66 instead of existing constellations, 6 on-orbit backups, 9 ground backups). NEXT will greatly enhance existing Iridium mobile communication services (higher data rates, stronger services and equipment, which can take advantage of IP technology and be backward compatible with existing equipment). NEXT can also provide businesses, governments, scientific research institutions and other services to place sensor loads on satellites, which can achieve 7 × 24 hours on the earth's surface and the atmosphere.

The size and transmit power of the transmitting and receiving antennas of mobile communication satellites are generally high, and L-band transmission signals are used to reduce rain-induced attenuation and signal transmission loss. The purpose is to reduce the size of ground user terminals, facilitate portability and ensure communication quality.

Mobile communication satellites can not only provide communication services for large mobile users, such as ships, airplanes, and vehicles, but also enable individual mobile phones to directly perform satellite communications. The launched "Yixing" and "Global Star" are typical. In specific cases, they embody other

So, can users directly watch or listen to the programs retransmitted by satellite? Mobile communication satellites can directly provide voice communication services for users, but cannot forward TV programs. Forwarding TV shows is done by live TV satellites. Users can directly watch or listen to programs transmitted by satellites, but generally can only watch and listen to programs in fixed locations. Live TV satellites have become a hot spot in contemporary development. The characteristics of this satellite are roughly similar to mobile communication satellites, that is, high-power transmission of downlink signals, a large area solar cell array (guaranteed to provide power above kW level), high-precision orbit control, and antenna pointing. These are to reduce the burden on ground users and make their receiving terminals small. In other words, it is left to the satellites and the convenience to the users.

Contemporary TV live satellites use digital video compression technology, which greatly saves the bandwidth and increases the rate of transmitting video data. This type of satellite using digital video compression technology can provide hundreds of TV programs. A family only needs to install an antenna with a diameter of 0.45 meters and a receiving decoder to watch high-quality satellite TV programs directly on the TV.