WO2024119562A1 - Procédé et système pour établir rapidement une liaison de communication entre un satellite et le sol - Google Patents

Procédé et système pour établir rapidement une liaison de communication entre un satellite et le sol Download PDF

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Publication number
WO2024119562A1
WO2024119562A1 PCT/CN2022/143226 CN2022143226W WO2024119562A1 WO 2024119562 A1 WO2024119562 A1 WO 2024119562A1 CN 2022143226 W CN2022143226 W CN 2022143226W WO 2024119562 A1 WO2024119562 A1 WO 2024119562A1
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low
orbit satellite
communication
time
uplink signal
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PCT/CN2022/143226
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English (en)
Chinese (zh)
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吴琼
蒋林
李奇奋
朱富颖
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北京遥测技术研究所
航天长征火箭技术有限公司
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Publication of WO2024119562A1 publication Critical patent/WO2024119562A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18523—Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service
    • H04B7/18526—Arrangements for data linking, networking or transporting, or for controlling an end to end session
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the invention relates to a method and system for quickly establishing a communication link between a satellite and an earth, belonging to the technical field of satellite communications.
  • some low-orbit satellites and communication terminals use long codes with a period of several days for communication.
  • the Doppler and code phase of the low-orbit long code signal are unknown, it is difficult for the low-orbit satellite and the communication terminal to establish a connection.
  • the code phase of the low-orbit long code signal requires the calculation of the propagation delay between the two.
  • the current method of calculating the propagation delay requires the known low-orbit satellite system time, and then combined with the low-orbit satellite ephemeris and the terminal position, the propagation delay can be calculated; in addition, Doppler compensation requires the known communication terminal clock drift.
  • the common means of obtaining the low-orbit navigation system time and clock drift can be obtained by receiving satellite navigation signals and positioning.
  • This method requires the communication terminal to have the ability to receive satellite navigation signals and locate, and after obtaining, the satellite navigation system time is converted to the low-orbit satellite system time; or the communication terminal has the ability to be timed and keep time, but the communication terminal clock drift cannot be obtained. This makes the design of the communication terminal more complicated, and it needs to have additional navigation and positioning capabilities.
  • the technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a method and system for quickly establishing a communication link between the satellite and the ground, to simply compensate for the low-orbit long code signal, without the need for navigation timing or terminal clock drift, so that the low-orbit satellite and the communication terminal can quickly establish a connection.
  • the technical solution of the present invention is: a method for quickly establishing a communication link between a satellite and a ground, which is applied to a communication terminal, and the method comprises the following steps:
  • the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris.
  • the control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
  • step S1-4 taking the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delaying for a period of time, and obtaining the communication uplink signal transmission time t3 ;
  • step S1-6 configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
  • Another technical solution provided by the present invention is: a method for quickly establishing a communication link between a satellite and an earth, which is applied to a low-orbit satellite, and the method comprises the following steps:
  • the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
  • the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
  • the communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
  • the communication uplink signal is obtained by the communication terminal through the following method:
  • step S2-2-3 using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal reaches the low-orbit satellite at the next full second of the low-orbit satellite;
  • step S2-2-5 Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
  • the next full second time t2 of the low-orbit satellite is:
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
  • ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite
  • ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
  • the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1- ⁇ , wherein ⁇ is the delay to the next full second.
  • the communication terminal adopts an atomic clock.
  • the communication uplink signal Doppler f dop is:
  • k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier;
  • f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
  • the broadcast downlink signal adopts spread spectrum BPSK modulation.
  • the broadcast downlink signal pseudo code is a Gold code.
  • a technical solution of the present invention is: a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
  • a low-orbit satellite sends a broadcast downlink signal to a communication terminal, wherein a control data frame is modulated in the broadcast downlink signal, a start time of a frame header of the control data frame is aligned with an integer second time of the low-orbit satellite, the control data frame includes an integer second time corresponding to a current frame header, control information, and an ephemeris of the low-orbit satellite, and the control information includes an initial phase information of a pseudo-random code used for an uplink signal and a downlink signal when the low-orbit satellite communicates with the communication terminal; and according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next integer second of the low-orbit satellite system time;
  • the communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time.
  • the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication
  • the period of time is 1-2 ⁇ .
  • the method provided by the present invention can use the low-orbit satellite system time at the current frame header moment obtained from the received downlink signal to calculate the next full second launch time of the low-orbit satellite system.
  • the error of this time is only the propagation delay of the low-orbit satellite.
  • the Doppler and code phase accuracy required by the dynamic requirements of the low-orbit satellite fully meet its timing accuracy.
  • the present invention does not need to obtain the communication terminal clock drift, and the Doppler calculation method is simple. Since the communication terminal uses an atomic clock, the clock drift error between the payload and the communication terminal is less than the compensation accuracy requirement of the uplink signal Doppler and can be ignored. The compensation Doppler can be calculated only by tracking the Doppler obtained by the downlink signal.
  • FIG1 is a flow chart of a method according to an embodiment of the present invention.
  • the satellite payload has high accuracy requirements on the Doppler and code phase of the low-orbit long code signal, and the communication terminal needs to accurately compensate for the Doppler and code phase of the uplink transmission signal.
  • the present invention does not require the communication terminal to have navigation timing capability, nor does it need to provide positioning clock drift.
  • the low-orbit satellite system time at the current frame header moment is obtained from the downlink signal, and the propagation delay is ignored, so that the transmission time of the next full second can be obtained to calculate the propagation delay; then the relationship between the broadcast downlink signal Doppler and the communication uplink signal Doppler is used, and the characteristics of the atomic clock with small clock drift are combined to realize the compensation of the uplink transmission signal Doppler and code phase.
  • the method is simple and the accuracy meets the compensation requirements.
  • the core idea of the present invention is to obtain the low-orbit satellite system time of the current frame header moment from the broadcast downlink signal. This time plus one is the low-orbit satellite system launch moment of the next full second. However, there is a propagation delay error. As long as the error meets the timing accuracy and the communication terminal receives the pseudo-random code phase much more than 10ms in advance of the next full second, it will be sufficient.
  • the error between the moment when the communication terminal receives the frame header of the broadcast downlink signal and the full second moment of the low-orbit satellite is in the millisecond level.
  • the maximum acceleration of the low-orbit satellite is about 400Hz/s, and the maximum pseudo-range change rate is about 6000m/s.
  • the maximum propagation delay does not exceed 10ms.
  • the pseudo-range change within 10ms does not exceed 60m/s.
  • the 60m error meets the phase accuracy requirement of the transmission compensation; in addition, the communication terminal will receive the pseudo-random code phase in advance of the next full second, and the advance time is much greater than 10ms. Therefore, even if there is a propagation delay, the next full second moment obtained from the broadcast downlink signal can be used as the uplink signal transmission time, and its timing accuracy is acceptable.
  • Doppler compensation since the terminal uses an atomic clock, its clock drift can be ignored. It is only necessary to calculate the communication uplink signal Doppler based on the broadcast downlink signal Doppler at the time of transmission.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the present invention provides a method for quickly establishing a communication link between a satellite and a ground, and the method is applied to a communication terminal and comprises the following steps:
  • the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris.
  • the control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
  • step S1-4 using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t3 ; the period of time is 1-2 ⁇ .
  • step S1-6 configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • a method for quickly establishing a communication link between a satellite and an earth comprising the following steps:
  • the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
  • the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
  • the communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
  • the communication uplink signal is obtained by the communication terminal through the following method:
  • step S2-2-3 Based on the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1, a delay of 2 ⁇ is performed to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal arrives at the low-orbit satellite at the next full second of the low-orbit satellite, wherein ⁇ is the propagation delay between the low-orbit satellite and the communication terminal; and the period of time is 1-2 ⁇ .
  • step S2-2-5 Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
  • t 2 , t 1 , and ⁇ t represent the low-orbit satellite system time of the next full second, the low-orbit satellite system time corresponding to the current frame header moment, and the propagation delay error, respectively.
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
  • ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite
  • ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
  • the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1- ⁇ , where ⁇ is the delay to the next full second.
  • the signal Doppler has the following relationship:
  • f track f SV + f D - f R
  • f dop -k ⁇ (f track + 2 ⁇ f R - f sv )
  • f track is the broadcast downlink signal tracking frequency
  • f D is the motion-induced Doppler
  • f SV is the corresponding clock drift of the broadcast downlink signal, in Hz
  • f R is the corresponding clock drift of the broadcast downlink frequency of the communication terminal
  • k is the nominal carrier frequency of the communication uplink signal/nominal carrier frequency of the broadcast downlink signal
  • f dop is the Doppler of the communication uplink signal. Since the communication terminal uses an atomic clock and the payload clock drift is also small, its error is less than the compensation accuracy requirement of the uplink signal Doppler, so f R and f SV can be ignored. Therefore, when the communication terminal uses an atomic clock, the communication uplink signal Doppler f dop is:
  • k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier;
  • f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
  • the broadcast downlink signal adopts spread spectrum BPSK modulation
  • the broadcast downlink signal pseudo code is Gold code
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • This embodiment provides a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
  • the low-orbit satellite sends a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the full second time of the low-orbit satellite, and the control data frame includes the full second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, wherein the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal; according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next full second of the low-orbit satellite system time;
  • the communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time.
  • the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the frequency of the broadcast downlink signal is 1176.45MHz
  • the second pulse can be obtained through frame synchronization, and the low-orbit satellite time corresponding to the control data frame header can be obtained through the telegram, and the Doppler f track of the 1176.45MHz frequency point can be tracked.
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite t 2 is calculated to be 0.003329609 seconds; the low-orbit satellite system time corresponding to its launch time should be:
  • f track -436

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Abstract

La présente invention concerne un procédé et un système pour établir rapidement une liaison de communication entre un satellite et le sol, lorsqu'un système de code long est utilisé en communication avec un satellite à faible orbite, un terminal de communication est nécessaire pour compenser avec précision le Doppler et une phase de code d'un signal de transmission de liaison montante. Dans le procédé, tout d'abord, un temps de système de satellite à orbite basse à un moment d'en-tête de trame d'une trame de données de commande est acquis à partir d'un signal descendant de diffusion, la différence de retard temporel du moment pouvant être ignorée selon une garantie de conception de système et dynamique de signal d'orbite basse, et le moment de transmission d'un signal montant de communication qui est reçu par un satellite à orbite basse à l'ensemble de la seconde étant obtenu, de façon à calculer une phase de code ; puis, en utilisant une relation entre le Doppler du signal descendant de diffusion et le Doppler du signal montant de transmission de communication combiné à la caractéristique d'une horloge atomique possédant une faible dérive d'horloge, une compensation pour la phase Doppler et de code du signal montant de transmission est réalisée.
PCT/CN2022/143226 2022-12-09 2022-12-29 Procédé et système pour établir rapidement une liaison de communication entre un satellite et le sol WO2024119562A1 (fr)

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CN202211584671.8A CN116346191A (zh) 2022-12-09 2022-12-09 一种星地快速建立通信链接的方法和系统
CN202211584671.8 2022-12-09

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6058306A (en) * 1998-11-02 2000-05-02 Hughes Electronics Corporation Compensation of dynamic doppler frequency of large range in satellite communication systems
CN104297765A (zh) * 2014-09-25 2015-01-21 上海欧科微航天科技有限公司 一种用于低轨卫星准同步通信系统的地面终端模拟器
CN104702547A (zh) * 2014-09-25 2015-06-10 上海欧科微航天科技有限公司 一种联合导频信息和卫星星历的多普勒频移估计与补偿方法
CN108919312A (zh) * 2018-05-03 2018-11-30 武汉大学 基于低轨卫星的自主导航信号增强方法
CN110545247A (zh) * 2019-07-31 2019-12-06 成都天奥集团有限公司 低轨卫星多载波通信系统下行链路载波频偏估计与补偿方法
CN113422639A (zh) * 2021-07-02 2021-09-21 东方红卫星移动通信有限公司 低轨卫星通信系统基于位置和星历的同步方法和系统

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6058306A (en) * 1998-11-02 2000-05-02 Hughes Electronics Corporation Compensation of dynamic doppler frequency of large range in satellite communication systems
CN104297765A (zh) * 2014-09-25 2015-01-21 上海欧科微航天科技有限公司 一种用于低轨卫星准同步通信系统的地面终端模拟器
CN104702547A (zh) * 2014-09-25 2015-06-10 上海欧科微航天科技有限公司 一种联合导频信息和卫星星历的多普勒频移估计与补偿方法
CN108919312A (zh) * 2018-05-03 2018-11-30 武汉大学 基于低轨卫星的自主导航信号增强方法
CN110545247A (zh) * 2019-07-31 2019-12-06 成都天奥集团有限公司 低轨卫星多载波通信系统下行链路载波频偏估计与补偿方法
CN113422639A (zh) * 2021-07-02 2021-09-21 东方红卫星移动通信有限公司 低轨卫星通信系统基于位置和星历的同步方法和系统

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