CN114422008B - Multi-star cooperative ground communication system and communication method - Google Patents
Multi-star cooperative ground communication system and communication method Download PDFInfo
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Abstract
The invention discloses a multi-star cooperative earth communication system and a communication method. The system comprises: a plurality of in-orbit satellites and ground terminals. The on-orbit satellite comprises an inter-satellite interconnection unit, a low-speed receiving unit to the ground and a high-speed transmitting unit to the ground; the ground terminal comprises a navigation positioning unit, a satellite-to-satellite high-speed receiving unit and a satellite-to-satellite low-speed transmitting unit. The communication method comprises the following steps: the ground terminal sends data request information and state information to the satellite; establishing time synchronization among a plurality of satellites; establishing frequency synchronization among a plurality of satellites; establishing phase synchronization between a plurality of satellites and a ground terminal; the multiple satellites cooperatively transmit in-orbit data to ground. According to the method, the on-orbit data are transmitted to the ground terminal through cooperation of the satellites, so that the capacity and the transmission efficiency of the ground communication can be effectively improved.
Description
Technical Field
The invention belongs to the technical field of satellite communication and networks, and particularly relates to a multi-satellite cooperative earth communication system and a communication method.
Background
In recent years, in the aspect of commercial aerospace, a low-orbit constellation network business plan represented by 'one-net (OneWeb)', 'star link' (Starlink) ', ke Yiba (kupper)', and the like resonates with time concepts such as 5G, ioT and artificial intelligence at the same frequency, so that huge communication constellations with thousands of scales are pushed to gradually become reality from mania, and the role of satellite communication in human production and life is increasingly enlarged. Due to the vigorous construction of large-scale giant star constellation, a large number of communication satellites can be seen on any ground space of the world. Through cooperation among the satellites, a high-gain satellite-ground link can be constructed, and high-capacity information transmission is provided for ground application.
However, during satellite communications, the gain of a common antenna is low and the transmission capacity is weak because of the limitation of power volume of an in-orbit satellite. In addition to satellite-to-ground transmission links, thousands of kilometers are usually added, and even tens of thousands of kilometers can be achieved, so that signal attenuation is large. How to increase the transmission capacity of satellite-to-ground communication is a prominent problem in the widespread use of satellite communications.
In order to solve the above problems, the chinese patent application with patent application number 202110213278.7 proposes a multi-star multi-level cache allocation method for a star-earth cooperative communication system, which makes full use of a multi-star multi-level cache architecture in the star-earth cooperative communication system, and reduces content service delay in the star-earth cooperative communication system by cooperation between multi-level edge servers and cooperation between a plurality of satellite edge servers, so as to ensure transmission of delay sensitive services of users. However, the method does not improve the transmission capacity of satellite-to-ground communication, and does not solve or alleviate the problem of weak transmission capacity of the in-orbit satellite.
Disclosure of Invention
In order to solve the technical problems in the prior art, in one aspect of the present invention, a multi-satellite cooperative ground communication system is provided, which includes a plurality of in-orbit satellites and ground terminals. The on-orbit satellite further comprises an inter-satellite interconnection unit, a low-speed receiving unit to the ground and a high-speed transmitting unit to the ground; the ground terminal comprises a navigation positioning unit, a satellite-to-satellite high-speed receiving unit and a satellite-to-satellite low-speed transmitting unit. Wherein:
the inter-satellite interconnection unit is used for interconnection and intercommunication, time synchronization and frequency synchronization among a plurality of satellites;
the low-speed receiving unit is used for receiving the data request and the state information from the ground terminal by the satellite;
the high-speed transmission unit is used for transmitting high-speed data to the ground terminal by the satellite;
the navigation positioning unit is used for acquiring the position information of the ground terminal;
the satellite-to-satellite high-speed receiving unit is used for receiving high-speed data from satellites by the ground terminal;
the satellite low-speed transmitting unit is used for transmitting data requests and state information to satellites by the ground terminals.
Further, in the multi-satellite cooperative earth communication system, the plurality of in-orbit satellites are any of high, medium and low-orbit satellites.
Further, in the multi-satellite cooperative earth communication system, the ground terminal is a mobile terminal or a fixed terminal.
In order to solve the technical problems in the prior art, in another aspect of the present invention, a multi-star cooperative ground communication method implemented by using the multi-star cooperative ground communication system is provided, where the communication method includes:
step 1: the ground terminal sends data request information and state information to the satellite, wherein the ground terminal adopts a satellite low-speed sending unit to send the data request information and the state information to the satellite; the data request information comprises a ground terminal code identifier, a target satellite identifier and a data block identifier; the state information comprises time scale information, position information corresponding to a time scale and a channel intensity identifier of a satellite-to-satellite high-speed receiving unit, wherein the time scale information and the position information corresponding to the time scale are obtained by a navigation positioning unit, and the channel intensity identifier of the satellite-to-satellite high-speed receiving unit is obtained by calculation of the satellite-to-satellite high-speed receiving unit;
step 2: time synchronization is established among a plurality of satellites, and the method specifically comprises the following steps:
s21: the method comprises the steps that a plurality of in-orbit satellites adopt respective low-speed receiving units to ground to receive and analyze data request information and state information from a ground terminal;
s22: the satellite consistent with the target satellite identification of the ground terminal data request is set as a main satellite and is marked as S 0 The method comprises the steps of carrying out a first treatment on the surface of the Satellites inconsistent with the target satellite identification are all set as slave satellites and are marked as S 1 ，S 2 ，……，S n ；
S23: the main satellite S 0 The inter-satellite interconnection unit of (1) is set to be in a transmission mode; the slave satellite S 1 ，S 2 ，……，S n The inter-satellite interconnection unit of (1) is set to a receiving mode;
s24: main satellite S 0 Respectively and slave satellite S by adopting a double unidirectional measurement method 1 ，S 2 ，……，S n Establishing time synchronization; obtaining a main satellite S 0 And slave satellite S 1 ，S 2 ，……，S n Relative distance r between 01 ,r 02 ,r 03 ,…,r 0n And relative clock difference delta t 01 ,Δt 02 ,Δt 03 ,…,Δt 0n ；
Step 3: establishing frequency synchronization among a plurality of satellites specifically comprises:
s31: main satellite S 0 To slave satellite S 1 ，S 2 ，……，S n Broadcasting a frequency reference signal having a frequency f 0 ；
S32: from satellite S 1 ，S 2 ，……，S n Tracking a primary satellite S using a phase locked loop 0 A broadcast reference signal;
s33: from satellite S 1 ，S 2 ，……，S n Generating a downlink signal of the high-speed transmission unit to the ground through a frequency multiplier, wherein the working frequency of the downlink signal is f T The multiple of the frequency multiplier is set to f T /f 0 ；
Step 4: the method for establishing phase synchronization between the plurality of satellites and the ground terminal specifically comprises the following steps:
s41: the satellites establish phase coarse synchronization according to the ground terminal state information received by the ground low-speed receiving unit to obtain the value of the phase coarse synchronization
S42: the satellites transmit channel calibration signals to the ground terminal through the ground high-speed transmitting unit, and the working frequency of the channel calibration signals is f T Initial value of phaseIs thatThe transmitted channel calibration signal is marked as
in the formula ,representing the transmitted signal amplitude;
s43: the ground terminal receives the channel calibration signal by the star high-speed receiving unit and calculates the signal strength in real time, wherein
The received channel calibration signal is expressed as:
wherein ,to transmit attenuated signal amplitude, phi, via satellite-to-ground transmission link i The phase change caused by the signal delay after the satellite-ground transmission link transmission is adopted;
the received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 0 ；
S44: the satellites add random phase disturbance in the transmitted channel calibration signal, wherein the size of the random phase disturbance is delta i The channel calibration signal transmitted at this time becomes:
s45: the ground terminal receives the channel calibration signal added with the random phase disturbance, calculates the signal intensity, and obtains a new channel calibration signal as follows:
the corresponding received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 1 ；
S46: comparing the signal intensity changes of the channel calibration, recording the channel intensity identification according to the comparison result, and feeding back the channel intensity identification to the satellite by the ground terminal through the satellite low-speed transmitting unit, wherein the method specifically comprises the following steps:
when A is 0 ≥A 1 When A is 0 The channel strength mark is marked as 0;
when A is 0 ＜A 1 When A is 0 ＝A 1 The channel strength flag is marked as 1;
s47: after receiving the channel intensity identification, the plurality of satellites adjust the sending phase through the low-speed receiving unit, and the method specifically comprises the following steps:
if the channel strength mark is 0, the value of the satellite coarse synchronization is not adjusted
If the channel strength mark is 1, the value of satellite coarse synchronization is adjustedThe adjusting method comprises the following steps: />
S48: selecting a phase synchronization coefficient lambda, and judging that a plurality of satellites and a ground terminal establish a phase synchronization state, wherein the method specifically comprises the following steps:
if it isThen the satellites and the ground terminal establish phase synchronization, and step 5 is entered, and the phase of the high-speed transmission unit of the satellites to the ground is recorded as +.>
If it isThe satellites do not establish phase synchronization with the ground terminal, and the steps S44 to S48 are repeated;
step 5: the method for transmitting the on-orbit data cooperatively and oppositely among the plurality of satellites specifically comprises the following steps:
multiple satellites according to phase valuesAnd sending a modulation signal, wherein a data block of the modulation signal is determined according to the data block identification in the data request information.
Further, in the above multi-star cooperative earth communication method, the step S24 includes:
s241: main satellite S 0 Through inter-satellite interconnection unit to slave satellite S 1 Transmitting ranging signals, primary satellite S 0 Recording the transmission time of the ranging signal as t 1 From satellite S 1 Recording the receiving time t of the ranging signal 2 ；
S242: from satellite S 1 After receiving the ranging signal, the ranging signal is transmitted to the main satellite S through the inter-satellite interconnection unit 0 Transmitting ranging signals from satellite S 1 Recording the transmitting time t of the ranging signal 3 Main satellite S 1 Recording the receiving time t of the ranging signal 4 ；
S243: according to the principle of double unidirectional ranging, calculating a primary satellite S 0 And slave satellite S 1 Relative distance r between 01 Sum clock difference delta t 01 The calculation method is that
Wherein c is the speed of light;
s244: according to the steps S241-S243, the main satellite S 0 Sequentially with the slave satellite S 2 ，……，S n Performing double unidirectional measurement to obtain relative distance r 02 ,r 03 ,…,r 0n Sum clock difference delta t 02 ,Δt 03 ,…,Δt 0n 。
Further, in the above-mentioned multi-star cooperative earth communication method, the step S41 includes:
s411: calculating signal transmission time delay between each satellite and ground terminal, and recording the signal transmission time delay between the ith satellite and ground terminal as ρ i I has the values of 0,1,2,3 …, n and ρ i The calculation method of (1) is as follows:
wherein ,representing the coordinates of satellite i, (x) g ，y g ，z g ) C represents the coordinate of the ground terminal, and is the speed of light;
s412: each slave satellite S 1 ，S 2 ，……，S n Calculation and Main satellite S 0 The difference in transmission delay between them is recorded as the ith slave satellite S i With main satellite S 0 The transmission delay difference between them is Deltaρ 0i The calculation method comprises the following steps:
Δρ 0i ＝ρ i -ρ 0
s413: clock difference correction is carried out on the transmission delay difference to obtain a corrected transmission delay differenceThe calculation method comprises the following steps:
s414: to correct the transmission delay differenceConversion to phase value>As a value for coarse phase synchronization
S415: calculating the sum of the clock difference and the signal transmission delay of each satellite, and recording the sum of the clock difference and the signal transmission delay of the ith satellite as eta i The calculation method comprises the following steps:
η i ＝ρ i +Δt 0i
wherein the main satellite S 0 Is the sum eta of the clock differences and the signal transmission delays 0 Is eta 0 ＝ρ 0 。
Further, in the above multi-star cooperative earth communication method, the random phase disturbance δ i Obeys uniform distribution delta i ～uniform(-π/3,π/3)。
The multi-star cooperative earth communication system and the communication method have the following advantages and beneficial effects: the method can relieve the problems of low gain and weak transmission capacity of a common antenna due to the limitation of the power volume of the in-orbit satellite, fully utilizes the transmission resources of a plurality of in-orbit satellites, and jointly transmits in-orbit data to the ground terminal through multi-satellite cooperation, improves the transmission gain of a satellite-ground link, and is beneficial to providing high-capacity information transmission for the ground.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will briefly introduce the drawings that are required to be used in the embodiments or the prior art descriptions, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. In the drawings:
FIG. 1 is a block diagram of a multi-star collaborative to ground communication system in accordance with an embodiment of the present invention;
fig. 2 is a flowchart of a multi-star collaborative ground communication method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, the multi-satellite cooperative earth communication system provided by an embodiment of the present invention includes a plurality of in-orbit satellites and a ground terminal, where the in-orbit satellites further include an inter-satellite interconnection unit, an earth low-speed receiving unit, and an earth high-speed transmitting unit; the ground terminal comprises a navigation positioning unit, a satellite-to-satellite high-speed receiving unit and a satellite-to-satellite low-speed transmitting unit, wherein: the inter-satellite interconnection unit is used for interconnection and intercommunication, time synchronization and frequency synchronization among a plurality of in-orbit satellites; the low-speed receiving unit is used for receiving the data request and the state information from the ground terminal by the satellite; the ground high-speed transmitting unit is used for transmitting high-speed data to the ground terminal by the satellite; the navigation positioning unit is used for acquiring the position information of the ground terminal; the satellite high-speed receiving unit is used for receiving high-speed data from satellites by the ground terminal; the satellite low-speed transmitting unit is used for transmitting data requests and state information to satellites by the ground terminal.
Specifically, in the embodiment of the present invention, the inter-satellite interconnection unit may use a 26Ghz operating band.
Specifically, in the embodiment of the invention, the navigation positioning unit can adopt a GPS/BD multimode positioning module, and can specifically adopt a UM220-IV NL module of Xingxintong company to support multimode positioning of GPS and Beidou (BD).
Specifically, in the embodiment of the present invention, the multiple in-orbit satellites may be any of high, medium, and low orbit satellites. Preferably, the plurality of in-orbit satellites may employ low-orbit communication satellites and the satellite orbit may employ 500 km orbit.
Specifically, in the embodiment of the present invention, the ground terminal may be a mobile terminal or a fixed terminal. Preferably, the ground terminals are fixed terminals.
In addition, an embodiment of the present invention further provides a multi-star cooperative earth communication method implemented by using the multi-star cooperative earth communication system, where the communication method includes the following contents:
step 1: the ground terminal transmits data request information and status information to the satellite.
The ground terminal adopts a satellite low-speed transmitting unit to transmit data request information and state information to satellites.
The data request information comprises a ground terminal code identifier, a target satellite identifier and a data block identifier.
The state information comprises time mark information, position information corresponding to the time mark and the channel intensity identification of the satellite pair high-speed receiving unit. The time mark information and the position information corresponding to the time mark are obtained by the navigation positioning unit, and the channel intensity identification of the satellite-to-satellite high-speed receiving unit is calculated by the satellite-to-satellite high-speed receiving unit.
Step 2: time synchronization is established between a plurality of satellites. The method specifically comprises the following steps:
s21: each in-orbit satellite adopts a respective low-speed receiving unit to receive and analyze the data request information and the state information from the ground terminal;
s22: the satellite consistent with the target satellite identification of the ground terminal data request is set as a main satellite and is marked as S 0 The method comprises the steps of carrying out a first treatment on the surface of the Satellite inconsistent with target satellite identificationAre all set as slave satellites, denoted as S 1 ，S 2 ，……，S n ；
S23: the main satellite S 0 The inter-satellite interconnection unit of (1) is set to be in a transmission mode; the slave satellite S 1 ，S 2 ，……，S n The inter-satellite interconnection unit of (1) is set to a receiving mode;
s24: main satellite S 0 Respectively and slave satellite S by adopting a double unidirectional measurement method 1 ，S 2 ，……，S n Establishing time synchronization; obtaining a main satellite S 0 And slave satellite S 1 ，S 2 ，……，S n Relative distance r between 01 ,r 02 ,r 03 ,…,r 0n And relative clock difference delta t 01 ,Δt 02 ,Δt 03 ,…,Δt 0n 。
Step 3: frequency synchronization is established between a plurality of satellites. The method specifically comprises the following steps:
s31: main satellite S 0 To slave satellite S 1 ，S 2 ，……，S n Broadcasting a frequency reference signal having a frequency f 0 ；
S32: from satellite S 1 ，S 2 ，……，S n Tracking a primary satellite S using a phase locked loop 0 A broadcast reference signal;
s33: from satellite S 1 ，S 2 ，……，S n Generating a downlink signal of the high-speed transmission unit to the ground through a frequency multiplier, wherein the working frequency of the downlink signal is f T The multiple of the frequency multiplier is set to f T /f 0 。
Step 4: the plurality of satellites establish phase synchronization with the ground terminal. The method specifically comprises the following steps:
s41: the satellites establish phase coarse synchronization according to the ground terminal state information received by the ground low-speed receiving unit to obtain the value of the phase coarse synchronizationWhere i=0, 1,2, … …, n;
s42: multiple satellites pass through the ground at high speedThe transmitting unit transmits a channel calibration signal to the ground terminal, wherein the working frequency of the channel calibration signal is f T The initial value of the phase isThe channel calibration signal is marked as
in the formula ,representing the signal amplitude;
s43: the ground terminal receives the channel calibration signal through the star high-speed receiving unit and calculates the signal strength in real time, wherein
The received channel calibration signal may be expressed as:
wherein ,to transmit attenuated signal amplitude, phi, via satellite-to-ground transmission link i The phase change caused by the signal delay after the satellite-ground transmission link transmission is adopted;
the received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 0 ；
S44: the satellites add random phase disturbance in the transmitted channel calibration signal, wherein the size of the random phase disturbance is delta i The channel calibration signal transmitted at this time becomes:
s45: the ground terminal receives the channel calibration signal added with the random phase disturbance, calculates the signal intensity, and obtains a new channel calibration signal as follows:
the corresponding received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 1 ；
S46: and comparing the signal intensity changes of the channel calibration, recording the channel intensity identification according to the comparison result, and feeding back the channel intensity identification to the satellite by the ground terminal through the satellite low-speed transmitting unit. Specifically comprises
When A is 0 ≥A 1 When A is 0 The channel strength mark is marked as 0;
when A is 0 ＜A 1 When A is 0 ＝A 1 The channel strength flag is marked as 1;
s47: and after the plurality of satellites receive the channel intensity identifiers through the low-speed receiving unit, the transmitting phase is adjusted. The method specifically comprises the following steps:
if the channel strength mark is 0, the value of the satellite coarse synchronization is not adjusted
If the channel strength mark is 1, the value of satellite coarse synchronization is adjustedThe adjusting method comprises the following steps: />
S48: and selecting a phase synchronization coefficient lambda, and judging that a plurality of satellites and a ground terminal establish a phase synchronization state.
If it isThe satellites and the ground terminal establish phase synchronization, and enter step 5, wherein the phases of the high-speed transmission units to the ground of the satellites are recorded as +.>
If it isThe satellites do not establish phase synchronization with the ground terminal and the steps S44 to S48 are repeated.
Step 5: the multiple satellites cooperatively transmit in-orbit data to ground.
Multiple satellites according to phase valuesAnd sending a modulation signal, wherein a data block of the modulation signal is determined according to the data block identification in the data request information.
Further, in the above-mentioned multi-star cooperative earth communication method, the specific implementation manner of step S24 is as follows:
s241: main satellite S 0 Through inter-satellite interconnection unit to slave satellite S 1 Transmitting ranging signals, primary satellite S 0 Recording the transmission time of the ranging signal as t 1 From satellite S 1 Recording the receiving time t of the ranging signal 2 ；
S242: from satellite S 1 After receiving the ranging signal, the ranging signal is transmitted to the main satellite S through the inter-satellite interconnection unit 0 Transmitting ranging signals from satellite S 1 Recording the transmitting time t of the ranging signal 3 Main satellite S 0 Recording the receiving time t of the ranging signal 4 ；
S243: according toDouble unidirectional ranging principle, calculating main satellite S 0 And slave satellite S 1 Distance r between 01 Sum clock difference delta t 01 The calculation method is that
Wherein c is the speed of light;
s244: according to the steps S241-S243, the main satellite S 0 Sequentially with the slave satellite S 2 ，……，S n Performing double unidirectional measurement to obtain relative distance r 02 ,r 03 ,…,r 0n Sum clock difference delta t 02 ,Δt 03 ,…,Δt 0n 。
Further, in the above-mentioned multi-star cooperative earth communication method, the specific embodiment of step S41 is as follows:
s411: calculating signal transmission time delay between each satellite and ground terminal, and recording the signal transmission time delay between the ith satellite and ground terminal as ρ i I has the values of 0,1,2,3 …, n and ρ i The calculation method of (1) is as follows:
wherein ,representing the coordinates of satellite i, (x) g ，y g ，z g ) The coordinates of the ground terminal are indicated, and c is the speed of light.
S412: each slave satellite S 1 ，S 2 ，……，S n Calculation and Main satellite S 0 And a transmission delay difference between them. Record the ith slave satellite S i With main satellite S 0 The transmission delay difference between them is Deltaρ 0i The calculation method comprises the following steps:
Δρ 0i ＝ρ i -ρ 0
s413: clock difference correction is carried out on the transmission delay difference to obtain a corrected transmission delay differenceThe calculation method comprises the following steps:
s414: to correct the transmission delay differenceConversion to phase value>As a value of the phase coarse synchronization;
s415: each satellite calculates the sum of its own clock difference and signal transmission delay. The sum of clock difference and signal transmission delay of the ith satellite is recorded as eta i Then eta i The calculation formula of (2) is
η i ＝ρ i +Δt 0i
Wherein the main satellite S 0 Is the sum eta of the clock differences and the signal transmission delays 0 The method comprises the following steps:
η 0 ＝ρ 0
further, in the above-mentioned multi-star cooperative earth communication method, the random phase disturbance δ in step 44 i Obeys uniform distribution delta i ～uniform(-π/3,π/3)。
Specifically, in the embodiment of the present invention, the phase synchronization coefficient λ is selected to be 0.9.
Specifically, in the embodiment of the invention, the signal amplitude of all satellites after attenuation is transmitted through the satellite-to-ground transmission linkEqual, all are set as a 0 After multi-satellite cooperation, the signal intensity can be increased by 0.9 (n+1) times compared with that of single satellite ground transmission.
Therefore, the multi-satellite cooperative earth communication system and the communication method can relieve the problems that the in-orbit satellite is low in common antenna gain and weak in transmission capacity due to the limitation of the power volume, fully utilize the transmission resources of a plurality of in-orbit satellites, transmit in-orbit data to the ground terminal through multi-satellite cooperative cooperation, improve the transmission gain of a satellite-earth link, and are beneficial to providing high-capacity information transmission for the ground.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. In this context, "front", "rear", "left", "right", "upper" and "lower" are referred to with respect to the placement state shown in the drawings.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting thereof; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. A multi-star cooperative ground communication method implemented by a multi-star cooperative ground communication system comprises a plurality of in-orbit satellites and ground terminals; the plurality of in-orbit satellites are any of high, medium and low orbit satellites, and comprise an inter-satellite interconnection unit, a low-speed receiving unit to the ground and a high-speed transmitting unit to the ground; the ground terminal is a mobile terminal or a fixed terminal and comprises a navigation positioning unit, a satellite-to-satellite high-speed receiving unit and a satellite-to-satellite low-speed transmitting unit, wherein: the inter-satellite interconnection unit is used for interconnection and intercommunication, time synchronization and frequency synchronization among a plurality of satellites; the low-speed receiving unit is used for receiving the data request and the state information from the ground terminal by the satellite; the high-speed transmission unit is used for transmitting high-speed data to the ground terminal by the satellite; the navigation positioning unit is used for acquiring the position information of the ground terminal; the satellite-to-satellite high-speed receiving unit is used for receiving high-speed data from satellites by the ground terminal; the satellite-to-satellite low-speed transmitting unit is used for transmitting a data request and state information to a satellite by a ground terminal; the multi-star cooperative earth communication method is characterized by comprising the following steps of:
step 1: the ground terminal sends data request information and state information to the satellite, wherein the ground terminal adopts a satellite low-speed sending unit to send the data request information and the state information to the satellite; the data request information comprises a ground terminal code identifier, a target satellite identifier and a data block identifier; the state information comprises time scale information, position information corresponding to a time scale and a channel intensity identifier of a satellite-to-satellite high-speed receiving unit, wherein the time scale information and the position information corresponding to the time scale are obtained by a navigation positioning unit, and the channel intensity identifier of the satellite-to-satellite high-speed receiving unit is obtained by calculation of the satellite-to-satellite high-speed receiving unit;
step 2: time synchronization is established among a plurality of satellites, and the method specifically comprises the following steps:
s21: the method comprises the steps that a plurality of in-orbit satellites adopt respective low-speed receiving units to ground to receive and analyze data request information and state information from a ground terminal;
s22: a satellite consistent with the target satellite identification of the ground terminal data request is set asMain satellite, denoted S 0 The method comprises the steps of carrying out a first treatment on the surface of the Satellites inconsistent with the target satellite identification are all set as slave satellites and are marked as S 1 ，S 2 ，……，S n ；
S23: the main satellite S 0 The inter-satellite interconnection unit of (1) is set to be in a transmission mode; the slave satellite S 1 ，S 2 ，……，S n The inter-satellite interconnection unit of (1) is set to a receiving mode;
s24: main satellite S 0 Respectively and slave satellite S by adopting a double unidirectional measurement method 1 ，S 2 ，……，S n Establishing time synchronization; obtaining a main satellite S 0 And slave satellite S 1 ，S 2 ，……，S n Relative distance r between 01 ,r 02 ,r 03 ,…,r 0n And relative clock difference delta t 01 ,Δt 02 ,Δt 03 ,…,Δt 0n ；
Step 3: establishing frequency synchronization among a plurality of satellites specifically comprises:
s31: main satellite S 0 To slave satellite S 1 ，S 2 ，……，S n Broadcasting a frequency reference signal having a frequency f 0 ；
S32: from satellite S 1 ，S 2 ，……，S n Tracking a primary satellite S using a phase locked loop 0 A broadcast reference signal;
s33: from satellite S 1 ，S 2 ，……，S n Generating a downlink signal of the high-speed transmission unit to the ground through a frequency multiplier, wherein the working frequency of the downlink signal is f T The multiple of the frequency multiplier is set to f T /f 0 ；
Step 4: the method for establishing phase synchronization between the plurality of satellites and the ground terminal specifically comprises the following steps:
s41: the satellites establish phase coarse synchronization according to the ground terminal state information received by the ground low-speed receiving unit to obtain the value of the phase coarse synchronization
S42: multiple satellites transmit at high speed through earthThe transmitting unit transmits a channel calibration signal to the ground terminal, wherein the working frequency of the channel calibration signal is f T The initial value of the phase isThe transmitted channel calibration signal is marked as
in the formula ,representing the transmitted signal amplitude;
s43: the ground terminal receives the channel calibration signal by the star high-speed receiving unit and calculates the signal strength in real time, wherein
The received channel calibration signal is expressed as:
wherein ,to transmit attenuated signal amplitude, phi, via satellite-to-ground transmission link i The phase change caused by the signal delay after the satellite-ground transmission link transmission is adopted;
the received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 0 ；
S44: the satellites add random phase disturbance in the transmitted channel calibration signal, wherein the size of the random phase disturbance is delta i The channel calibration signal transmitted at this time becomes:
s45: the ground terminal receives the channel calibration signal added with the random phase disturbance, calculates the signal intensity, and obtains a new channel calibration signal as follows:
the corresponding received channel calibration signal strength is:
the signal intensity of the channel calibration at this time is marked as A 1 ；
S46: comparing the signal intensity changes of the channel calibration, recording the channel intensity identification according to the comparison result, and feeding back the channel intensity identification to the satellite by the ground terminal through the satellite low-speed transmitting unit, wherein the method specifically comprises the following steps:
when A is 0 ≥A 1 When A is 0 The channel strength mark is marked as 0;
when A is 0 ＜A 1 When A is 0 ＝A 1 The channel strength flag is marked as 1;
s47: after receiving the channel intensity identification, the plurality of satellites adjust the sending phase through the low-speed receiving unit, and the method specifically comprises the following steps:
if the channel strength mark is 0, the value of the satellite coarse synchronization is not adjusted
If the channel strength mark is 1, the value of satellite coarse synchronization is adjustedThe adjusting method comprises the following steps: />
S48: selecting a phase synchronization coefficient lambda, and judging that a plurality of satellites and a ground terminal establish a phase synchronization state, wherein the method specifically comprises the following steps:
if it isThen the satellites and the ground terminal establish phase synchronization, and step 5 is entered, and the phase of the high-speed transmission unit of the satellites to the ground is recorded as +.>
If it isThe satellites do not establish phase synchronization with the ground terminal, and the steps S44 to S48 are repeated;
step 5: the method for transmitting the on-orbit data cooperatively and oppositely among the plurality of satellites specifically comprises the following steps:
multiple satellites according to phase valuesAnd sending a modulation signal, wherein a data block of the modulation signal is determined according to the data block identification in the data request information.
2. The multi-star collaborative ground communication method according to claim 1, wherein step S24 comprises:
s241: main satellite S 0 Through inter-satellite interconnection unit to slave satellite S 1 Transmitting ranging signals, primary satellite S 0 Recording the transmission time of the ranging signal as t 1 From satellite S 1 Recording the receiving time t of the ranging signal 2 ；
S242: from satellite S 1 After receiving the ranging signal, the ranging signal is transmitted to the main satellite S through the inter-satellite interconnection unit 0 Transmitting ranging signals from satellite S 1 Recording the transmitting time t of the ranging signal 3 Main satellite S 1 Recording the receiving time t of the ranging signal 4 ；
S243: according to the principle of double unidirectional ranging, calculating a primary satellite S 0 And slave satellite S 1 Relative distance r between 01 Sum clock difference delta t 01 The calculation method is that
Wherein c is the speed of light;
s244: according to the steps S241-S243, the main satellite S 0 Sequentially with the slave satellite S 2 ，……，S n Performing double unidirectional measurement to obtain relative distance r 02 ,r 03 ,…,r 0n Sum clock difference delta t 02 ,Δt 03 ,…,Δt 0n 。
3. The multi-star collaborative ground communication method according to claim 1, wherein step S41 comprises:
s411: calculating signal transmission time delay between each satellite and ground terminal, and recording the signal transmission time delay between the ith satellite and ground terminal as ρ i I has the values of 0,1,2,3 …, n and ρ i The calculation method of (1) is as follows:
wherein ,representing the coordinates of satellite i, (x) g ，y g ，z g ) C represents the coordinate of the ground terminal, and is the speed of light;
s412: each slave satellite S 1 ，S 2 ，……，S n Calculation and Main satellite S 0 The difference in transmission delay between them is recorded as the ith slave satellite S i With main satellite S 0 The transmission delay difference between them is Deltaρ 0i The calculation method comprises the following steps:
Δρ 0i ＝ρ i -ρ 0
s413: clock difference correction is carried out on the transmission delay difference to obtain a corrected transmission delay differenceThe calculation method comprises the following steps:
s414: to correct the transmission delay differenceConversion to phase value>Value ∈phase coarse synchronization>
S415: calculating the sum of the clock difference and the signal transmission delay of each satellite, and recording the sum of the clock difference and the signal transmission delay of the ith satellite as eta i The calculation method comprises the following steps:
η i ＝ρ i +Δt 0i
wherein the main satellite S 0 Is the sum eta of the clock differences and the signal transmission delays 0 Is eta 0 ＝ρ 0 。
4. The multi-star collaborative ground communication method of claim 1, wherein the random phase disturbance δ i Obeys uniform distribution delta i ～uniform(-π/3,π/3)。
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