RU2169433C1 - Multifunctional space telecommunication system - Google Patents

Abstract

FIELD: space communication technology. SUBSTANCE: system includes identical groups of coupled high-speed and low-speed communication satellites with aboard relaying complexes of regenerative type and group of monitoring satellites with equipment for remote sounding of the Earth placed in circular middle-altitude non-geostationary orbits, mobile and portable stationary subscriber's stations positioned at will, coordination stations of communication system which are integrated with ground relay stations executing communication between any pairs of communication satellites which are regional control stations and gateways to enter land communication systems and are located in precalculated points of ground surface. Satellite communicate without use of aboard relaying complexes. Data banks of all subscribers of system and devices for signal routing are located at coordination stations of high and low-speed communication located jointly. All stationary subscriber high- and low-speed communication stations are designed for group employment and serve as additional gateways to enter ground communication systems. EFFECT: decreased cost, universality, mutual supplement and unification of individual subsystems incorporated in proposed system.

Description

 The invention relates to the class of 3rd generation global mobile communication systems and meets all ITU requirements for these systems.

 The multifunctional space telecommunication system (MTCS) is built on the basis of satellite relay groups in non-geostationary orbits and is designed to provide stable continuous one- and two-way transmission of any kind of information in digital form with speeds from 1.2 kbit / s to 2048 kbit / s between stationary and mobile subscribers located anywhere in the world, as well as for global monitoring of the earth's surface.

 The system is integrated and includes a low- and high-speed communication subsystem and its associated monitoring subsystem.

 The closest analogue (prototype) of the proposed system is the global satellite-based mobile communication system "Iridium" [L-1], which provides telephone communications, data transfer, paging and other types of communications with speeds up to 9.6 kbit / s.

 The Iridium system consists of space and terrestrial segments.

 The space segment of the system includes 66 satellite repeaters in circular orbits with an altitude of 780 km.

 The earth segment includes regional and technological control stations (Home and Technology Gateway (GW)), which are also gateways for entry into terrestrial communication networks, and a fleet of subscriber stations of various modifications.

 The number of GWs in the world is planned at the first stage to be increased to 12, and subsequently to 22. In the Russian Federation and the CIS countries, only 2 GWs are planned - in the center and in the east of the country.

 System connectivity i.e. the ability to provide continuous communication between subscribers located anywhere in the world is carried out using inter-satellite communication lines (MLS), for which 4 repeaters are installed on each spacecraft - two for communication with the spacecraft in its orbit (front and rear) and two from the spacecraft to neighboring orbits.

 The airborne relay complex (DBK) of the spacecraft is a complex radio-technical device of a regenerative type.

 In addition to the aforementioned inter-satellite repeaters, it includes the following devices: a repeater of subscriber station signals with a multipath antenna: a repeater of GW signals, demodulators and decoders for all incoming signals: a RAM device for all subscribers of the system (and it is expected to have several millions) and their coordinates , as well as on free channels on all the spacecraft of the system (1400 channels on each spacecraft); routers that determine the signal transmission route at the request of subscribers: shapers of new signal flows for all 37 beams of a multipath antenna, etc.

Subscriber mobile stations (the simplest of them, such as a “tube”) must work at very small minimum elevation angles of 10 ^o , which creates difficulties when working on the ground due to shadowing of the signal from local objects (houses, structures, trees, folds, etc. .).

 Subscriber-to-subscriber communication through the Iridium system is carried out only if both subscribers have stations of this system. If the subscriber of the landline telephone, cellular or other communication networks wants to contact another stationary or mobile subscriber through the Iridium system, then to enter the Iridium system and exit from it, his signal will need to go another way along the land lines to the nearest GWs acting as gateways.

So, for example, to pass a signal from one stationary subscriber with a home telephone A ₁ to another with a cell phone A ₂ you need to go through the chain: telephone A ₁ - landline - GW ₁ - KA ₁ - MLS ₁ -...- MLS _n - KA _n - GW _n - landline - cellular telephone A ₂ . If one subscriber is located in the region of Kazakhstan, and the second in Kamchatka, then the signal of the first subscriber must travel hundreds of kilometers via subscribed land lines to the Moscow region where one of the GWs is located, enter the Iridium system, go through the spacecraft chain, and then in the Khabarovsk region, where another GW is installed, exit the system and again, via extended land lines, reach the second subscriber in Kamchatka.

The main disadvantages of the Iridium system are:
1) Low data transfer rates, which does not meet the ITU requirements for 3rd generation mobile systems.

 2) The large length of land lines that need to be subscribed so that the fixed subscriber of the local telephone, cellular and other communication networks available in this region can enter or leave the Iridium system through the nearest GW. And this is the most special case when one of the subscribers, or even both subscribers, is either at the home or office phone, or in motion with a cell phone.

 3) Ensuring the connectivity of the system through inter-satellite communication lines, which greatly complicates the onboard relay complex of the spacecraft, since it requires the installation of 4 inter-satellite relays, each of which must maintain continuous communication with a narrow beam with all neighboring spacecraft, which is especially difficult with spacecraft on neighboring orbits that constantly make evolution relative to a given spacecraft in angle and distance.

 4) The complexity of the DBK also increases due to the fact that it must store and process a huge amount of information about millions of system subscribers and their coordinates, as well as about free channels on all SCs, and all these data must be continuously updated, which significantly increases the workload channels.

 5) The low altitude of the spacecraft constellation (780 km) requires a large number of spacecraft (66) even for very low minimum elevation angles of subscriber stations for the global coverage of the Earth's surface with radio visibility zones (66). In addition, at low altitudes, the dynamics of communication conditions is high when the spacecraft moves in orbits, which leads to frequent changes in the spacecraft during communication and an increase in the number of relayings on the route from one subscriber to another.

6) Low minimum elevation angles of subscriber stations (10 ^o ), which sharply worsens the communication conditions due to various shading on the signal path from the subscriber station to the spacecraft and in the opposite direction.

 As noted earlier, the proposed multifunctional space telecommunication system includes a communication subsystem and a monitoring subsystem based on it.

 Communication subsystems are built on the basis of medium-orbit satellite transponders and provide high-quality telephone communications, video conferencing, image transmission, inter-machine communication, Internet access and other multimedia services on a global scale with speeds from 1.2 kbps to 2948 kbps.

 In contrast to the prototype, they are connected using ground-based relays included in control stations (coordinating stations) and located at calculated points on the earth's surface at the intersection of radio visibility zones of neighboring spacecraft.

 The system consists of space and terrestrial segments.

 The space segment includes 3 groups of spacecraft (SC) - for the subsystem of high and low speed communications and monitoring. The first two groups include 24 spacecraft in orbits with an altitude of 10,360 km, and the monitoring group includes 8-12 spacecraft at an altitude of 600 km.

 The earth segment consists of 12-14 coordinating stations combined with control stations of the monitoring subsystem and playing the role of regional control stations and ground repeaters, as well as a fleet of mobile and stationary subscriber stations for low and high-speed communications, including personal wearable stations; stations located on mobile vehicles and portable stationary stations. The latter are used as group stations or are located at local telephone exchanges that integrate the telephone network, or at relay stations of a cellular network to which subscribers with cellular phones access. The coordinating stations are connected to an interconnected communications network (BCC) of the country, which also includes Internet providers. Connection to BCC and the Internet is also carried out through stationary subscriber stations.

 System throughput: 9800 channels with a speed of 2.4 kbit / s for low-speed communication and 3.9 Gbit / s for high-speed communication. Mobile subscriber stations operate in the 2.2 / 2.6 GHz band for low-speed communications and 20/30 GHz for high-speed communications. Feeder lines communicating with coordinating stations and fixed subscriber stations operate in the 10/12 GHz band.

 Information transmission methods: on the uplink — multiple access with code compression at a number of frequencies (CDMA / FDM), on the downlink — with time division multiplexing (TDMA).

 The type of modulation is frequency shift with small shift (MMS), coding is cascade (convolutional plus the Reed-Solomon code).

 The airborne relay complex is a regenerative type relay, i.e. with signal processing (demodulation and decoding) and their switching. Service signals (call, request, answer, etc.) are transmitted through the nearest spacecraft via feeder lines directly to the coordinating station, which, having information about all subscribers of the system and their coordinates, as well as data on free channels on all spacecraft, makes itinerary routes signals from one subscriber to another and gives a command about their switching to the spacecraft. If the called subscriber is in the radio visibility zone of another spacecraft, then the coordinating station performs the functions of a ground repeater and transmits a signal in accordance with the developed route to a neighboring spacecraft, etc., until the signal reaches the spacecraft in the zone of which the called subscriber.

 In order to exclude costly land lines from fixed subscribers to the nearest CS (large gateway), the subsystem of low-speed communication provides a fleet of portable stationary subscriber stations (CAC) of the VSAT type, which act as mini-gateways and are installed at local telephone exchanges, cellular network repeaters and etc., which allows subscribers who have any means of communication — a home or office phone, a cell phone of any standard, an Internet terminal, etc. to enter the Rostelestat satellite communication system and zatsya with any other party in any part of the world, that is, the system "Rostelesat" provides global roaming any local communication systems.

In the subsystem of high-speed communication of small gateways, all stationary stations also perform. The signal flow from one stationary subscriber A ₁ with any communication terminal through the proposed global system to another subscriber A _{2 is} as follows:
A ₁ -CAC ₁ -CA ₁ -CS ₁ -CA ₂ -...- KA _n -CFC _n -A ₂ .

 If one or both subscribers have Rostelest stations, then the signal from them is sent directly to the spacecraft or from the spacecraft to the subscriber.

 The organization of communication in the system is as follows: a call from a mobile or stationary subscriber of the system to any type of communication is sent through the service channel to the spacecraft and then sent via the feeder line to the coordinating station, which, having addresses (coordinates) of all subscribers, spacecraft ephemeris and data about free channels, determines the signal path and sends a call to the called subscriber (if the latter is in the zone of another spacecraft, then through the appropriate coordinating station).

 If the called subscriber agrees to the communication, the coordinating station assigns a channel (or channels for duplex communication) to both subscribers and commutes, and after the end of the session, fixes the type and duration for subsequent payment and disconnects the channels. Communication between subscribers in the area of one spacecraft after switching channels is carried out directly, the coordinating station performs only control functions.

 Signals in the system, as a rule, will be carried out in batch mode using ATM protocols, except for duplex telephone communication, which will be carried out through a permanent subscriber-to-subscriber connection, which is switched for the duration of the session.

 Given the uneven distribution of system subscribers on the ground, the bandwidth of the cells of the multi-beam DBK antennas within certain limits is controlled by the switching of frequency bands from neighboring beams.

Thus, the main advantages of the proposed system compared to the Iridium system, which, according to the authors, have the distinguishing features of the invention are the following:
1) The ability to transmit not only low-speed, but also high-speed multimedia information with speeds up to 2948 kbit / s.

 2) A new way to ensure the connectivity of the system is through terrestrial repeaters instead of inter-satellite communication lines.

 3) Transfer from the onboard relay complex of the spacecraft to the coordinating stations of all major devices, including inter-satellite relays and devices that provide communication functions in the system, which greatly simplifies it.

 4) The inclusion in the communication system, along with personal wearables and other mobile stations, of a fleet of low- and high-speed stationary subscriber stations used as mini-gateways for subscribers of terrestrial communication networks to enter the satellite system and eliminating the need to subscribe to landlines from a fixed subscriber before entering the system through coordinating stations (large gateways).

5) Transfer of spacecraft from low to medium orbits, which reduces the number of spacecraft in the group and control stations needed for global customer service, and improves communication quality by reducing the dynamics of changes in communication conditions when the spacecraft moves in orbits and the number of relayings, as well as by increasing the minimum elevation angles of subscriber stations to 40 ^o .

 Since this application proposes only a way to integrate the monitoring subsystem with the communication subsystems, and not itself, it is not necessary to describe its analogues.

 The space monitoring constellation is divided into spacecraft for optical and radar surveillance.

 The equipment for optical monitoring spacecraft is built on a modular basis. Each module is an independent optoelectronic device with its own information output. Pairing modules and linking them into a single system is achieved by appropriate re-targeting of their optical axes.

 As the modules, large-format photosensitive CCDs of line-frame type operating in progressive mode, or wide-format photosensitive CCDs are used.

 The main informational characteristics of the modules (linear resolution on the ground and the capture band) are selected based on the requirements of the consumer market for monitoring services. Modules are capable of functioning both in panchromatic and in spectrozonal shooting modes. Each spacecraft accommodates 2-4 modules.

 A radar surveillance satellite uses a side-scan radar developed by NPO Vega as a module.

 In order to accelerate the receipt and delivery of the required monitoring information to users, applications for monitoring a particular object or territory are transmitted via communication channels immediately to that control station (coordinating station) in the area of which the required satellite is located, and after receiving information on it, it is reset to after processing, the nearest control station is again transmitted via low- or high-speed communication channels (depending on its type) in real time to users anywhere in the world surface.

The proposed system, along with the functional elements of the prototype system, also contains a number of elements of other systems presented in the published projects: Globalstar, ICO, Teledesic, Skybridge, Spot, Landsat, etc. However, Globalstar and ICO are low-speed satellite communications systems and are not global; they are focused on a minimum angle of work of subscriber stations of 10 ^o (which extremely limits the choice of place for reliable communication to subscribers), require the use of subscribed external communication channels to enter the satellite system of subscribers of terrestrial networks (telephone, cellular, etc.). Teledesic and Skybridge systems are high-speed satellite communications systems that perform only part of the functions of the proposed system. The same limitation is inherent in the Spot and Landsat monitoring systems.

 The only proposed Rostelestat system is universal, combining the functions of all these systems, and it is based not on duplication of the individual subsystems, elements and devices included in it, but on their mutual complement or unification. Therefore, the cost of developing the proposed system is relatively low, and the estimated tariffs are minimal, which allows us to consider it highly profitable and competitive. These advantages of the proposed system are the technical result of the invention.

Claims (1)

 A multifunctional space telecommunication system designed to transmit digital information from mobile and stationary subscribers of the system, as well as information from monitoring satellites of the Earth and their switching, including a group of connected satellites placed in circular orbits, a group of monitoring satellites with remote sensing equipment of the Earth, arbitrarily located connected mobile and stationary subscriber stations located at the settlement points of the Earth, coordinating communication stations, connecting terrestrial repeaters, characterized in that the group of monitoring satellites is located in low-altitude circular orbits, and the groups of connected satellites are located in medium-high circular orbits, use one group of connected satellites for high-speed communication, and the other for low-speed communication, each of which provides a global overview of the earth’s surface by the radio-visibility zones of their satellites at minimum elevation angles of subscriber station antennas of 40 °, and the connected satellites of both groups are made in the form of a unification Of these modules, ground repeaters are configured to communicate between any pair of connected satellites and are regional control stations, as well as gateways for entering terrestrial communication networks, coordinating communication stations are combined for high-speed and low-speed communications and contain signal routing devices and data banks on all subscribers of the system and means for communication with monitoring satellites and for transmitting user applications for monitoring and user transfer services lam monitoring results through the subscriber stations.