RU2822689C1 - Method of selecting earth station by spacecraft for establishing high-speed communication on high-gain antenna systems in ranges whose radio transparency depends on state of atmosphere - Google Patents

Abstract

FIELD: communication equipment; cosmonautics.

SUBSTANCE: invention relates to communication in data exchange systems with spacecraft for various purposes, namely, to methods of establishing communication between spacecraft and earth stations. Technical result is achieved by the fact that the spacecraft for the purpose of selecting an earth station for establishing communication with it on high-gain antenna systems (HGA) receives beacon signals from different earth stations to a low-gain antenna system (LGA) in the radio range, which is strongly influenced by the state of the atmosphere, and determines the optimum earth station from the quality of these signals.

EFFECT: development of method for autonomous establishment of communication on HGA in high-speed communication lines in ranges above 10 GHz and in optical range without participation of technical personnel of the mission control centre (MCC), performing preliminary planning of communication and control sessions (CCS).

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Description

The invention relates to providing communication in information exchange systems (IIS) with spacecraft (SC) for various purposes, namely to methods for establishing communication between spacecraft and earth stations (ES) for the purpose of high-speed information transmission in radio bands above 10 GHz and in optical bands.

Modern communication systems, including satellite ones, are characterized by a significant increase in the volume of information and the speed of its delivery, which requires a wide frequency band and the use of highly directional antenna systems (HAS). Due to the existing high load on frequency bands, the most relevant now is the use of the Ka-band (20-30 GHz) and a transition to ranges above 30 GHz is planned, as well as the use of optical ranges characterized by high losses in the cloud layer of the atmosphere.

The process of automatically establishing communication in the optical range between the Earth and the spacecraft, where ONA is used, must be preceded by a procedure for the optimal automatic selection of an earth station by the spacecraft to establish communication with it, which must take into account the state of the atmosphere in the radio visibility zone (RZ) of the Earth. As noted above in the text, weather forecasting in the locations of the station does not have the necessary accuracy and therefore it is necessary to develop a method for assessing the current state of the optical permeability of the atmosphere in the radio visibility zone (RZ) of the station. Due to the high requirements for the state of the atmosphere, in order to ensure stable communication between the orbital constellation (OG) and the earth segment on the territory of Russia, the following conditions must be met:

1) dispersal of a large number of ES along the southern regions of Russia from Crimea to the Khabarovsk Territory in places with a high probability of favorable weather conditions, ensuring the presence of several ES in one air defense zone at elevation angles above the horizon of at least 10 degrees for Ka-band and at least 20 degrees for optical range;

2) connection of a spacecraft by inter-satellite communication lines into a network or the presence of relay satellites (CP) connected by inter-satellite communication lines into a network for the purpose of routing information flows to a spacecraft or CP located in the airspace of an earth station with favorable weather conditions and having established communication with it;

3) the use of technology for automatically establishing communication on BOTH in the VLAN between the station and the spacecraft, which includes the technology for the optimal automatic selection of an earth station by the spacecraft to establish communication with it, which should take into account the state of the atmosphere in the radio visibility zone of the station.

It is known from the state of the art that in domestic systems of information exchange with spacecraft, the principle of advance planning of communication and control sessions is currently applied, the application of which in modern multi-satellite constellations is a difficult task to implement, and to solve the problem of ensuring communication between a spacecraft and an earth station in the ranges , the radio transparency of which depends on the state of the atmosphere, especially in the optical range, it is not always advisable to use planning, since it is impossible to predict the state of the atmosphere with a high probability.

As an example of such an approach, the system and method of dynamic network planning can be chosen (see US 9119179 B1, published on August 25, 2015). The method may begin by determining network parameters for connecting nodes to the network and decision variables associated with radios and/or nodes in the network. Constraints can be set to narrow the possible values of network parameters and/or decision variables. The restrictions may be based on one or more of: values associated with connecting a radio to a node on the network, values associated with connecting two nodes on a network together over a communication link, whether a node can connect to a GIG node, and the flow balance at the GIG node. To find possible optimal communication channels, the method may minimize an equation based on network parameters, constraints, and decision variables to determine optimal communication channels between pairs of nodes in the network, pairs of nodes and radios, and/or pairs of radios.

This approach is too broad and its application to the objectives of this invention is impossible.

Also known from the prior art are more targeted ways to overcome the problems associated with the problem of signal transmission in bands whose radio transparency depends on the state of the atmosphere, especially in the optical range.

For example, a system and method for mitigating the effects of atmospheric conditions such as rain, fog, clouds in a broadband access system using drones/UAVs (see US 9479964 B2, published 10/25/2016). In one embodiment, the terminal and drone radio subsystems and transmission media comprise multiple transmission media. In one embodiment, in response to changes in atmospheric conditions, the drone's radio communications subsystem switches the transmission medium to reduce the influence of atmospheric conditions. In another embodiment, the radio subsystems of the terminal and the drone equalize data rates between the terminals in response to changes in atmospheric conditions observed by the different terminals. In another embodiment, the drone's radio subsystem adjusts downlink transmit power to different terminals according to fading due to atmospheric conditions on each link.

The method indicated as an analogue is not reliable, since for the uninterrupted operation of the system it is necessary that all the UAVs included in it be active, which is difficult, since the UAV must be refueled periodically.

The closest analogue of the claimed invention is a method for reducing interference for use in a wireless communication system (see US 8140018 B2, March 20, 2012), formed by a plurality of radio access networks, each radio access network having a network manager configured to communicate with a plurality of associated nodes with a network by an administrator, and each radio access network has a frequency spectrum divided into a plurality of subchannels used for wireless communication by the nodes, the frequency spectrum at least partially overlapping with the frequency spectrum of one or more other radio access networks; a method comprising the steps of: a network administrator of each radio access network performing a spectrum allocation process to allocate subchannels to its nodes; nodes of each radio access network performing wireless communications using subchannels allocated to them; the network manager of one radio access network receives from its associated nodes data indicating the actual level of interference experienced by the nodes, the interference originating either within the radio access network or externally from other radio access networks; The network manager of one radio access network compares the actual level of interference with the estimated level of interference originating within the radio access network to determine whether or not there is a need to coordinate with another network manager to reduce interference originating from outside the radio access network. - the network manager of one radio access network notifies the network manager of at least one of the other radio access networks about this need; and the network manager of the other radio access network again performs the process of allocating spectrum to its associated nodes to reduce the level of interference experienced by the nodes of the same radio access network.

In this method, preferably the comparison step includes determining whether the actual interference level exceeds the estimated level by at least a threshold amount.

Preferably also, if the network manager of one radio access network determines that there is no need to coordinate with another radio access network to reduce interference, the network manager again performs the process of allocating spectrum to its associated nodes in an attempt to reduce interference occurring within the radio access network.

If the system nodes are transceivers, the receive step is preferably initiated by the network administrator receiving the estimated interference level, detecting that the estimated level is greater than a specified level, and requesting the nodes to send data indicating the actual interference level.

The choice of the preferred radio access network is carried out by the network manager based on the principle of least interference.

The method of reducing interference indicated as the closest analogue for use in a wireless communication system is close to solving the problem solved by the claimed method, but does not solve the problem in the most effective way.

The use of highly directional antenna systems in high-speed air-to-ground communication lines in the ranges above 10 GHz is effective in the absence of rain, and in the optical range communication is possible only with line of sight, i.e. in the absence of clouds, fog, etc., and in addition requires high accuracy of ONA guidance. Weather forecasting in places of station deployment is not an effective solution to the problem of planning communication sessions in air-to-ground communication lines, because lacks accuracy.

This invention is aimed at solving a technical problem associated with the optimal selection of an earth station by a spacecraft for autonomously establishing high-speed communications to the OHA without prior planning.

The novelty of the proposed invention lies in the fact that the objects of the information exchange system (i.e., spacecraft and satellites), before establishing communication, assess the state of the atmosphere by changing its transparency in the radio range, which is highly influenced by the state of the atmosphere (for example, in K, Ka or Q -ranges).

The technical result of the invention is the creation of a method for autonomously establishing communication on ONA in high-speed communication lines KA-ZS and KA-SR-ZS in the ranges above 10 GHz and in the optical range without the participation of technical personnel of the flight control center (MCC), carrying out preliminary planning of communication sessions and management (SSU).

The technical result is achieved due to the fact that the spacecraft, in order to select an earth station to establish communication with it on the ONA, receives beacon signals from different earth stations to a low-directional antenna system (MNA) in the radio range, which is highly influenced by the state of the atmosphere, and determines by the quality of these signals optimal earth station.

The claimed invention is illustrated by the following drawings:

Fig. 1 - diagram of the organization of communication between spacecraft and station;

Fig. 2 - algorithm for selecting an earth station by a spacecraft to establish communication in the optical range;

Fig. 3 - algorithm for the subprocess of calculating the state of the atmosphere in the Earth's air defense system

The positions in the figures indicate the following:

1 - spacecraft (SV);

2 - earth station (ES);

3 - low-directional antenna system (MNA) of the on-board equipment (BA) of the low-speed radio communication link (LSL) of the spacecraft;

4 - onboard equipment of the low-speed radio communication link of the spacecraft;

5 - on-board operation control complex (OCU) of the on-board relay complex (BRTC) of the spacecraft;

6 - antenna guidance system (ANS) of the highly directional antenna system (HAS) of the spacecraft;

7 - onboard equipment of a high-speed communication line (VLS) of the spacecraft;

8 - highly directional antenna system of a high-speed communication line of a spacecraft;

9 - receiver of navigation signals (NS) of the spacecraft;

10 - on-board navigation system (ONS);

11 - database (DB) of the on-board navigation system;

12 - low-directional antenna system of the earth station;

13 - low-speed radio communication equipment of the earth station;

14 - computer for controlling the operation (CU) of the earth station antenna guidance system;

15 - guidance system of a highly directional antenna system of a high-speed communication line of an earth station.

16 - high-speed communication line equipment of the earth station;

17 - highly directional antenna system of a high-speed communication line of an earth station;

18 - database of parameters of orbital motion of spacecraft;

19, 20, 21, 22 - GLONASS spacecraft.

The declared system for autonomous calculation of the parameters of the orbital motion of a satellite communication system works as follows. When the spacecraft 1 is in orbital flight, the coordinates of the spacecraft 1 are constantly calculated on the basis of received signals from the GLONASS navigation satellites (SNS) 19, 20, 21 and 22, on the basis of which the on-board navigation system 10 of the spacecraft 1 calculates the orbital forecast parameters movements. The parameters of the orbital motion are recorded in the database 11 of the on-board navigation system 10 of the spacecraft 1. The parameters of the orbital motion are recorded in the form of discrete reports of the coordinates of the spacecraft and the current time corresponding to them.

The sampling rate of these reports depends on the required ONA pointing accuracy. The required accuracy of SHE guidance is determined by the values of: the speed of circular rotation of the spacecraft, maintaining the orientation of the spacecraft platform, and also the width of the SHE directional pattern.

The period for which the orbital motion parameters are calculated depends on the required accuracy of these parameters and can range from 1 orbit to one day.

The composition of the devices of the spacecraft 1 involved in the process of establishing communication with the station 2 (see figure 1):

- on-board radio technical complex (BRTC), consisting of: on-board equipment of a low-speed radio communication line 4 with a low-directional antenna system 3, on-board equipment of a high-speed communication line 7 with a highly directional antenna system 8 and an antenna guidance system 6, on-board control complex BRTK 5;

- on-board navigation system 10, consisting of: a navigation signal receiver 9, equipped with an omnidirectional antenna system and a database 11.

The composition of the devices of earth station 2 involved in the process of establishing communication with spacecraft 1 (see figure 1):

- a radio technical complex (RTC), consisting of: equipment for a low-speed radio communication line 13 with a low-directional antenna system 12, equipment for a high-speed communication line 16 with a highly directional antenna system 17 and an antenna guidance system 17, a computer for controlling the operation of 14 APs and an orbital motion database 18.

In KA-ZS communication lines, high-speed communication is carried out in the VLAN on the ONA, and low-speed communication is carried out in the NLS on the MNA. When establishing communication between a spacecraft and an earth station, pilot signals are first received in the NLS and the state of the atmosphere is assessed based on the accepted value of the signal-to-noise ratio (SNR), and the earth station is selected based on this criterion to establish communication, sending a request to establish communication and forecast the orbital motion of a selected earth station in a low-speed radio communication link that performs the functions of a service communication channel.

The algorithm for establishing communication between spacecraft 1 and earth station 2 in the VLS using ONA is shown in Figure 2 and is as follows.

Standby mode of operation of the spacecraft.

Action 1. Spacecraft 1 is in a state of receiving GLONASS SNS navigation satellites and pilot signals from the station.

Step 1. The spacecraft 1 constantly calculates, based on the received signals from the navigation satellites SNS GLONASS 19, 20, 21 and 22, its coordinates x _a , y _a , z _a in the rectangular geocentric Greenwich coordinate system, based on which the on-board navigation system 10 of the spacecraft 1 and periodically calculates the parameters of the orbital motion forecast, which are recorded in the database 11 of the on-board navigation system 10 of the spacecraft 1.

Step 2. SC 1 constantly receives pilot signals in the NLS on MNA 3, carrying information about the AP number.

If it is necessary to initialize the establishment of communication, SC 1 switches to the initialization mode of establishing communication at the stage of calculation and selection of the AP.

Action 2. Let's consider determining the state of the atmosphere above the earth stations from which pilot signals are received using the example of one of the earth stations.

Step 1. On-board navigation system 10 of spacecraft 1 based on the coordinate values of earth stations 2 ϕ _g , y _g , z _g in the rectangular geocentric Greenwich coordinate system from which the raft signals were received, and the current coordinates of spacecraft 1 x _a , y _a , z _a in the rectangular geocentric Greenwich coordinate system recorded in the database 11 of the on-board navigation system 10 of the spacecraft 1, determines the current values of the distance d to the GS 2 according to the formula:

Note: The value of the coordinates of stationary earth stations 2 ϕ _g , y _g , z _g in the rectangular geocentric Greenwich coordinate system and the coordinates of earth stations 2 ϕ _g , λ _g , r _g (latitude, longitude, radius vector) in the spherical geocentric Greenwich coordinate system is recorded in the database 11 of the onboard navigation system 10 of each spacecraft, and the value of similar coordinates of mobile earth stations in the rectangular geocentric Greenwich coordinate system and in the spherical geocentric Greenwich coordinate system are transmitted to the spacecraft from the station in the pilot signal.

Step 2. Onboard navigation system 10 of spacecraft 1 based on the coordinate values of earth stations 2 ϕ _g , λ _g , r _g (latitude, longitude, radius vector) in the spherical geocentric Greenwich coordinate system based on the current coordinates of spacecraft 1 x _g , y _g , z _g in rectangular geocentric Greenwich coordinates 1, recorded in the database 11 BNS 10 of spacecraft 1, calculates the current values of the coordinates of spacecraft 1 x' _g , y' _g , z' _g in the rectangular topocentric coordinate system 1 and determines the current values angle of the radio horizon of the NLS with ES 2 according to the formula:

k _сЗ coefficient of compression of the globe.

Step 3. The on-board control complex BRTK 5 of spacecraft 1 calculates the signal attenuation at a distance from ES 2 to SC 1 using the formula:

d - distance from ES 2 to KA 1 (m);

λ - NLS wavelength (m).

Step 4. The on-board control complex BRTK 5 of spacecraft 1 calculates the permissible signal attenuation in a dry atmosphere A _o from ES 2 to SC 1, taking into account the radio horizon angle a using the formula:

h _o - height of the dry layer of the atmosphere (m);

γ _o - linear attenuation in a dry atmosphere (dB/km);

α is the angle of the radio horizon of the NLS from ES 2 to KA 1 (rad).

Note: the values of the height of the dry layer of the atmosphere h _o and the linear attenuation in the dry atmosphere γ _o are calculated experimentally for each range, for each region and for each season.

Step 5. The on-board control complex BRTK 5 of spacecraft 1 calculates the permissible signal attenuation in a humid atmosphere A _w from ES 2 to SC 1, taking into account the angle of the radio horizon a using the formula:

h _w - height of the humid layer of the atmosphere (m);

γ _w - linear attenuation in a humid atmosphere (dB/km);

α is the angle of the radio horizon of the NLS from ES 2 to KA 1 (rad).

Note: the values of the permissible height of the humid layer of the atmosphere h _w and the permissible linear attenuation in the humid atmosphere γ _w are calculated experimentally for each range, for each region and for each season.

Step 6. The on-board control complex BRTK 5 of spacecraft 1 calculates the permissible signal attenuation for propagation, taking into account the radio horizon angle a using the formula:

Step 7. Onboard control complex BRTK 5 of spacecraft 1 calculates SNR in the form of the ratio of bit energy to the spectral noise density at the input of the receiving device E _b /N _o (dB) according to the formula:

P _T is the radiation power of the transmitting device ES 2 (dB) - the BRTK of the spacecraft 1 is known in advance;

G _T - coefficient of the transmitting antenna ES 2 (dB) - constant;

G _R - coefficient of the receiving antenna of spacecraft 1 (dB) - a constant value;

с'=- 10lgc (dBbit/s) - information transmission rate in logarithmic form in the pilot signal, where: с - information transmission rate (bit/s) - a constant value and should not exceed 2.4 kbit/s;

L _Σ - calculated permissible propagation signal attenuation taking into account the radio horizon angle a (dB);

L _o - other types of attenuation (dB) (attenuation in the receiving path of spacecraft 1 and attenuation due to the ellipticity of the circular polarization of the received signal) - are determined experimentally and are known in advance by the BRTK of spacecraft 1;

Z is the permissible energy reserve of the radio link BRTK of spacecraft 1 - is determined experimentally and is known in advance by the BRTK of spacecraft 1 and, as a rule, does not exceed 3 dB;

N _o - spectral density and noise (dB) at the input of the receiving device - is determined experimentally and is known in advance by the BRTK of spacecraft 1.

Step 8. The on-board control complex BRTK 5 of spacecraft 1 calculates the attenuation value in the humid atmosphere A _{w of} the real received signal from ES 2, taking into account the angle of the radio horizon a using the formula:

E _b /N _o - actual accepted value;

A _o - calculated value;

pre-known constant parameters.

Step 9. The on-board control complex BRTK 5 of spacecraft 1 compares the calculated value of attenuation in a humid atmosphere A _w with the real value in the received pilot signals, and if the real value of attenuation in a humid atmosphere A _w exceeds the calculated value, then this characterizes the unfavorable state of the atmosphere above this earth station.

Note: the action of determining the state is repeated a certain number of times, the duration of which is determined experimentally and should not exceed 1 minute.

Initialization mode for establishing a connection with the station.

Action 3. Selecting the most suitable station for establishing communication in the VLAN.

Step 1. Comparison of the values of SNR and attenuation in a humid atmosphere A _w in the received pilot signals from different ES and selection of the most suitable one for establishing communication in the VLAN.

Step 2. If several earth stations meet the specified requirements, then the station with the maximum duration of the communication session is selected from among them. The maximum duration of a communication session from an earth station is selected based on the Doppler frequency shift value of the pilot signal. The maximum duration of a communication session corresponds to the maximum value of the Doppler frequency shift of the pilot signal.

Steps 4. Send a connection request.

Step 1. BRTK 7 of spacecraft 1 generates a request signal to establish communication from the selected earth station, which, in addition, contains information about the forecast of the orbital movement of spacecraft 1 (for example, for one orbit), and sends it to the NLS with MNA 3 on-board equipment NLS 4.

Step 2. Earth station 2 receives a request signal from spacecraft 1 to the low-directional antenna 12 of the NLS equipment and the earth station operation control computer 14 assesses whether earth station 2 can communicate with the calling spacecraft 2. As a result of the assessment, the load of station 2 is analyzed and calling spacecraft priority 1.

Step 3. The computer for controlling the operation 14 of the earth station 2 generates a response to the request signal and sends it from the low-directional antenna system 12 of the satellite navigation system 13 to the spacecraft 1.

Actions 5. Receiving a response from the AP to the connection request.

Step 1. MNA 3 of the on-board equipment NLS 4 receives the response signal and transmits it to the BRTK 5 KA 1 BCU, which analyzes it and, if the response signal is positive, the procedure for mutual guidance of highly directional optical antenna systems is started.

Step 2. If the response signal is negative, SC 1 continues the procedures for analyzing the input pilot signals and selecting a suitable earth station 2.

The algorithm for establishing communication between earth station 2 and spacecraft 1 in the VLAN using OHA (that is, when the initiator of establishing communication is the earth station) is as follows:

Action 1. Calling a spacecraft.

Step 1. The computer for controlling the operation 14 of the earth station 1, based on the information on orbital motion available in the databases 11, determines that the called spacecraft 2 is in its radio visibility zone (RV).

Step 2. The computer for controlling the operation 14 of the earth station 1 generates a call signal to the spacecraft 2 and sends it from the low-directional antenna system 12 of the equipment of the satellite 13 to the satellite to the spacecraft 1.

Step 3. Spacecraft 1 receives a call signal in the NLS to the low-directional antenna system 3 of the on-board equipment of the NLS 4.

Then, the onboard control complex BRTK 5 of the spacecraft starts the procedure for selecting the optimal earth station 2 for establishing communication, which were described in detail in the previous algorithm for establishing communication between the spacecraft and the earth station, and actions 1-5 described in the previous algorithm are carried out.

Note: if communication with the earth station is lost and if it is necessary to make a relay transition to another earth station, actions 1-5 described in the previous algorithm for establishing communication between the spacecraft and the earth station are carried out.

Claims (4)

1. A method for selecting an earth station by a spacecraft to establish high-speed communication on highly directional antenna systems in bands, the radio transparency of which depends on the state of the atmosphere, including establishing communication between the spacecraft and the earth station in a high-speed communication line using highly directional antennas, in which it is constantly calculated based on received signals from GLONASS navigation satellites, the coordinates of the spacecraft, on the basis of which the onboard navigation system of the spacecraft periodically calculates orbital motion forecast parameters, which are recorded in the database of the onboard navigation system of the spacecraft, constantly receives pilot signals in a low-speed communication line to a low-directional antenna , carrying information about the number of the earth station, characterized in that they determine the state of the atmosphere above the earth stations as follows - the onboard navigation system of the spacecraft, based on the values of the coordinates of the earth stations recorded in the database of the onboard navigation system of the spacecraft, determines the current values of the distance to the earth station , from which it receives the pilot signal, calculates the current coordinates of the spacecraft, calculates the signal attenuation at a distance from the earth station to the spacecraft and calculates the permissible signal attenuation in a dry and humid atmosphere, calculates the permissible signal attenuation for propagation taking into account the angle of the radio horizon, calculation signal-to-noise ratio in the form of the ratio of bit energy to the spectral density of noise at the input of the receiving device, calculates the attenuation value in a humid atmosphere of the actual received signal from an earth station, taking into account the angle of the radio horizon, compares the calculated attenuation value in a humid atmosphere with the real value in the received pilot signals and if the actual value of attenuation in a humid atmosphere exceeds the calculated value, then this characterizes the unfavorable state of the atmosphere above a given earth station, while selecting the most suitable earth station for establishing communication in a high-speed communication link by comparing the values of the signal-to-noise ratio and attenuation in a humid atmosphere in the received pilot signals from different earth stations and selecting the most suitable one for establishing communication in a high-speed communication line, the stage of sending a request to establish communication is carried out, in which the on-board relay complex of the spacecraft generates a request signal to establish communication with the selected earth station, in which, in addition In addition, it contains information about the forecast of the orbital motion of the spacecraft, and sends it over a low-speed communication line from the low-directional antenna of the on-board equipment, the earth station receives a request signal from the spacecraft to the low-directional antenna of the low-speed communication line equipment, and the earth station operation control computer evaluates whether the earth station enters into communication with the calling spacecraft, generates a response to the request signal and sends it from the low-directional antenna system of the low-speed communication line equipment to the spacecraft, the low-directional antenna of the on-board equipment receives the response signal and transmits it to the on-board control complex of the on-board relay complex, which analyzes and, if the response signal is positive, the procedure for mutual guidance of highly directional optical antenna systems is started; if the response signal is negative, the spacecraft continues the procedures for analyzing the input pilot signals and selecting a suitable earth station. 2. The method for selecting an earth station by a spacecraft for establishing high-speed communication according to claim 1, characterized in that if several earth stations meet the specified requirements, then the station with the maximum duration of the communication session is selected from among them. 3. The method for selecting an earth station by a spacecraft to establish high-speed communication according to claim 2, characterized in that the maximum duration of a communication session with the earth station is selected based on the value of the Doppler frequency shift of the pilot signal. 4. The method for selecting an earth station by a spacecraft to establish high-speed communication according to claim 3, characterized in that the maximum duration of the communication session corresponds to the maximum value of the Doppler frequency shift of the pilot signal.