WO2021018121A1 - 一种基于卫星载荷平台的旁路网络导引方法 - Google Patents

一种基于卫星载荷平台的旁路网络导引方法 Download PDF

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WO2021018121A1
WO2021018121A1 PCT/CN2020/105099 CN2020105099W WO2021018121A1 WO 2021018121 A1 WO2021018121 A1 WO 2021018121A1 CN 2020105099 W CN2020105099 W CN 2020105099W WO 2021018121 A1 WO2021018121 A1 WO 2021018121A1
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satellite
pilot signal
information
network
signal
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PCT/CN2020/105099
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English (en)
French (fr)
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金野
吕国成
刘爱民
王宝吉
何涛
董明科
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北京大学
北京鑫星卫通科技有限公司
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Priority to US17/630,522 priority Critical patent/US20220247482A1/en
Publication of WO2021018121A1 publication Critical patent/WO2021018121A1/zh

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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
    • H04B7/1851—Systems using a satellite or space-based relay
    • 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
    • H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
    • H04B7/18586—Arrangements for data transporting, e.g. for an end to end data transport or check
    • 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
    • H04B7/204—Multiple access
    • H04B7/2041—Spot beam multiple access
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • 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 present invention relates to the technical field of satellite communication, in particular to a bypass network guidance method based on a satellite load platform.
  • Satellite communication technology is a communication between two or more earth stations that uses artificial earth satellites as relay stations to forward radio waves. Since the 1990s, the rapid development of satellite mobile communications has promoted the advancement of antenna technology. Satellite communication has many advantages such as wide coverage, large communication capacity, good transmission quality, convenient and rapid networking, and easy realization of global seamless links. It is considered to be an important means indispensable for establishing global personal communications.
  • the satellite communication system is composed of a communication satellite and an earth station connected by the satellite.
  • Geostationary communication satellites are currently the most commonly used stars in global satellite communication systems. They are launched to an altitude of 35860 kilometers above the equator, so that the satellite's rotation direction is consistent with the earth's rotation, and the satellite's rotation period is exactly equal to the earth's rotation Period (24 hours), so that the satellite always maintains a synchronized operation state. Therefore, geostationary satellites are also called synchronous orbit satellites.
  • Synchronous orbit satellites periodically orbit the earth at high speed.
  • the distance between the satellite and each ground receiving station will continue to change, resulting in a phase difference between the satellite clock and the ground receiving station clock, and the satellite
  • Doppler frequency shift will be caused, which will cause the signal frequency distortion of the signal received by the ground receiving station, which will result in an offset between the ground receiving station clock and the satellite clock, resulting in the clock synchronization between the satellite ground stations .
  • the distance difference between different beams and user stations is larger, and the Doppler frequency shift of the satellite relative to the user stations in different beams is more significant, resulting in larger clock deviations between user stations in different beams.
  • Additional base station for clock synchronization is added to the Doppler frequency shift of the satellite relative to the user stations in different beams.
  • the method of using satellite navigation to modify the local clock to obtain a high-precision clock and to achieve time synchronization through time transfer technology has been deeply studied at home and abroad.
  • a high-precision external reference clock or high-precision clock source is required.
  • the technical problem to be solved by the present invention is to provide a bypass network guidance method based on a satellite load platform, which can reduce the influence of the distance change and Doppler frequency shift of satellite ground stations in the entire network. Unification, to achieve precise quasi-synchronization between the clock of the entire network and the clock of the satellite.
  • the technical scheme of the present invention is: this bypass network guidance method based on satellite load platform,
  • the bypass pilot signal is sent, and the pilot signal is sent to all down-satellite beams to provide guidance for all satellite stations covered by the satellite signal.
  • the present invention is based on a satellite load platform, based on a satellite-borne high-stability clock source, to send bypass guidance signals, which are sent to all down-satellite beams, and provide guidance signals for all satellite stations covered by the satellite.
  • the influence of the distance change and Doppler frequency shift of the satellite ground stations of the entire network is unified, and the clock of the entire network is accurately quasi-synchronized with the clock of the satellite.
  • Fig. 1 shows a flowchart of a preferred embodiment of a bypass network guidance method based on a satellite payload platform according to the present invention.
  • Fig. 2 shows a schematic diagram of transmission of a pilot signal on a satellite according to the present invention, where the pilot signal does not include indication information.
  • Fig. 3 shows a schematic diagram of the transmission of a pilot signal on a satellite according to the present invention, where the pilot signal includes indication information, and the indication information is generated by a ground network management satellite station.
  • Fig. 4 shows a schematic diagram of the transmission of the pilot signal on the satellite according to the present invention, where the pilot signal includes indication information, and the indication information of the ground system part is generated by one or more ground network management satellite stations.
  • Figure 5 shows a schematic diagram of a pilot frame structure according to a preferred embodiment of the present invention.
  • the bypass pilot signal is sent, and the pilot signal is sent to all down-satellite beams to provide guidance for all satellite stations covered by the satellite signal.
  • the present invention is based on a satellite load platform, based on a satellite-borne high-stability clock source, to send bypass guidance signals, which are sent to all down-satellite beams, and provide guidance signals for all satellite stations covered by the satellite.
  • the influence of the distance change and Doppler frequency shift of the satellite ground stations of the entire network is unified, and the clock of the entire network is accurately quasi-synchronized with the clock of the satellite.
  • each lower satellite beam all or part of the frequency band of the lower satellite channel is occupied for transmission, and all or part of the frequency band occupied by the pilot signal in the lower satellite channel is the pilot frequency band.
  • the signal power accounts for 0.1 ⁇ -1% of the total power of the pilot band.
  • the pilot signal is sent, it is spread by spreading code and superimposed on the communication signal in the pilot band in a noise-like low power spectrum signal mode. , The influence on the signal-to-noise ratio of satellite station signal reception is lower than the influence of the background thermal noise at the receiving end of the satellite station;
  • the pilot signal provides guidance, carrier and clock synchronization, standard timing and indication information for multiple types of terminal stations in the channel to build networks and communicate with each other.
  • the present invention selects a satellite in the open wireless channel as a reference, and sends a pilot signal.
  • the pilot signal occupies all or part of the frequency band of the open wireless channel for transmission.
  • the pilot signal occupies all or part of the frequency band in the open wireless channel.
  • the pilot signal power accounts for 0.1 ⁇ -1% of the total power in the pilot band, so the power of the pilot signal is much lower than the other signals, so there is no need to insert redundant measurement data in the service data.
  • each earth station in the open wireless network when the pilot signal is sent, it is spread by spreading code, and superimposed on the communication signal in the pilot frequency band in a noise-like low power spectrum signal mode to receive the signal at the receiving end
  • the influence of the signal-to-noise ratio is lower than that of the background thermal noise of the receiving end, and does not affect the receiving performance of other signals; in the network, the user receiving station monitors the pilot signal of the satellite, and completes the user receiving station and the satellite by receiving the pilot signal
  • the clock synchronization of the clock can unify the influence of the distance change and Doppler frequency shift of the satellite ground stations of the whole network, and realize the accurate quasi-synchronization of the clock of the whole network and the clock of the satellite.
  • the pilot signal includes: a frame header, a frame sequence number, and an indication information data body;
  • the frame header includes a synchronization header, a pilot, the synchronization header is used for the pilot signal frame timing and carrier recovery, and the pilot field is used for eliminating the pilot.
  • the frequency offset of the pilot signal frame is the identification of the cycle sequence of the pilot signal frame;
  • the indication information data body field carries indication information, which is used to indicate satellite load status, satellite channel status, network operation status and management information;
  • the satellite station receives the guidance signal sent by the satellite, and completes the clock synchronization between the satellite station and the satellite load platform by receiving the guidance signal.
  • the guidance signal is generated by the satellite (as shown in Figure 2), and the indication information data body contains the status information and operation information of the satellite, and the information of the ground network that cannot be directly obtained by the satellite platform.
  • the earth station collects the relevant instruction information to the satellite platform (as shown in Figure 3), after demodulation and reception by the satellite platform, and sorting, it is broadcasted to all satellite stations in the beams of all satellites through the instruction information data frame in the pilot signal .
  • the information of the ground network that cannot be directly obtained by the satellite platform includes: satellite ground network status, satellite station access status, satellite station operation status, and resource allocation status.
  • the guidance signal is generated by the satellite, and the instruction information is collected on the satellite platform, and the satellite platform becomes the management and guidance information center of the entire satellite system.
  • the satellite generates instruction information, which is combined with the guidance signal and broadcast.
  • the pilot signal is sent by the management center station in the earth station, and the satellite is demodulated and regenerated, and then broadcast to multiple beams.
  • the satellite is demodulated and regenerated, and then broadcast to multiple beams.
  • one of the earth stations sends instruction information to the satellite, and the satellite receives the instruction information and combines it with the pilot signal and broadcasts it.
  • the satellite generates instruction information, which is combined with the guidance signal and broadcast.
  • the indication information in the satellite platform guidance signal includes: guidance frame number, satellite operation information, satellite status information, network operation of all ground stations under multiple beams, network management information, operation information of all satellite stations under multiple beams , Satellite channel status information, satellite channel resource allocation information, system business information, and system security information.
  • Adding instruction information to the data body allows the pilot signal to have network management capabilities in addition to achieving precise clock synchronization.
  • the network management center station can add instruction information to the data body to broadcast the entire network through the pilot signal. After the user stations in the entire network receive it, they can get the instruction information from the network management center station, so as to achieve the capabilities of network information synchronization, network resource management and scheduling, and network state awareness.
  • the pilot signal includes: a frame header, a frame sequence number, and an indication information data body;
  • the frame header includes a synchronization header, a pilot, the synchronization header is used for the pilot signal frame timing and carrier recovery, and the pilot field is used for eliminating the pilot.
  • the frequency offset of the pilot signal frame is an identifier for the cycle sequence of the pilot signal frame;
  • the indication information data body field carries indication information, which is used to indicate the channel, network status and management information;
  • Each terminal station demodulates and receives the pilot signal, extracts the carrier and clock information, identifies the base station sending the pilot information according to the instruction information in the pilot signal, and completes the reception of other instruction information.
  • the pilot signal includes: a header (Header), a pilot (Pilot), a frame number (ID) and a data body (Data Frame).
  • the frame header is used for pilot signal frame timing and carrier recovery, the length is 16-128bit; the pilot field is all 0 fields, the length is more than 60bit, used to eliminate the frequency deviation of the pilot signal frame; the frame sequence number field is more than 8bit It is used to measure the absolute distance of the earth station; the data body field carries network management information, and is used to manage and maintain satellite network information with other stations in the network.
  • the length is 256 to 1008 bits.
  • the frame header is a 64-bit differential M sequence (the m sequence is the most basic PN sequence used in the CDMA system and is the abbreviation of the longest linear feedback shift register sequence), and the pilot
  • the field is a sequence of all "0"s with a length of 520 bits, the frame sequence number is an 8-bit sequence number, used to indicate (0-255), and the data body uses 1008-bit length, 1/2 code rate LDPC code for channel coding;
  • the frame header is a 32-bit differential Gold code
  • the pilot is a 200-bit all-“0” sequence
  • the frame sequence number is a 10-bit sequence number to indicate (0 ⁇ 1023)
  • the frame header is a 16-bit differential M sequence
  • the pilot is a 100-bit all-zero sequence
  • the frame sequence number is a 12-bit sequence number to indicate (0 ⁇ 4095)
  • the body uses 512-length Turbo coding for channel coding.
  • the period of the signal frame is fixed and the frame number is identified in the signal frame as the basic unit and calibration of the clock; the period of the signal frame ranges from 1ms to 1000ms, and the pilot signal adopts binary phase shift keying BPSK mode Cyclic modulation, keep sending continuously or intermittently.
  • the ground receiving station continuously receives the pilot signal, and can distinguish each frame in the received pilot signal according to the frame structure. As the pilot signal, the length of each frame is fixed, and the information rate of each frame is fixed.
  • the time represented by the frame is also fixed, so the ground receiving station can determine the time interval through the interval between the pilot signal frames, and the interval between the signal frames (that is, the signal frame period) as the basic unit of the clock, through different serial numbers
  • the time difference between frames is used to complete the time calibration. If the time interval count of the two frames before and after is not equal to the pilot signal frame period, the clock of the ground receiving station needs to be adjusted.
  • the period of the signal frame ranges from 50ms to 250ms.
  • the signal frame period is an integral multiple of 50ms, 100ms, 150ms, 200ms, 250ms, the basic unit of the clock and the calibration effect are best.
  • spread spectrum communication is performed by using a spread spectrum code with a length of 64 to 65536 bits; the spread spectrum code adopts M sequence, Gold code, OVSF code or C/A code.
  • the best use range of spread spectrum code is 1024 ⁇ 4096, in this range, the effect of spectrum expansion in spread spectrum communication is the best.
  • the spreading code here is for the data body.
  • the spreading code uses M sequence (M sequence), Gold code (Gold code is a pseudo-random code derived from m sequence, which has pseudo-random properties similar to m sequence, but its length is different. The number is more than m sequence), OVSF code (Orthogonal Variable Spreading Factor. OVSF code is mainly used for orthogonal spreading. The rate of the traffic channel is different, and the length of the OVSF code used is also different) or C/A code (Coarse Acquisition Code. A pseudo-random code issued by GPS satellites for coarse ranging and acquisition of GPS satellites. It is actually a Gold code, which is composed of two 10-level feedback shift registers. The formed G code is generated).
  • M sequence M sequence
  • Gold code is a pseudo-random code derived from m sequence, which has pseudo-random properties similar to m sequence, but its length is different. The number is more than m sequence
  • OVSF code Orthogonal Variable Spreading Factor. OVSF code is mainly used for orthogonal spreading
  • the M sequence is generated first, and then the M sequence is differentially encoded to eliminate the influence of frequency offset, and the differentially encoded sequence is used as the frame header; the spreading code uses the M sequence with a length of 12 to 128 bits as the basic time sequence.
  • the spread spectrum method here is for the frame header of the pilot signal.
  • the spreading code uses an M sequence with a length of 12 to 128 bits as the basic time sequence.
  • the differential M sequence with a length of 64 bits is used as the frame header of the pilot signal, and the fast synchronization capture performance is the best.
  • channel coding is used to encode the indication information.
  • the channel coding uses LDPC (Low-density Parity-check, low-density parity-check) coding, Polar coding, and RS coding (Reed-Solomon codes, Reed-Solomon codes), convolutional codes or Turbo codes (also known as parallel concatenated convolutional codes).
  • LDPC Low-density Parity-check, low-density parity-check
  • Polar coding Polar coding
  • RS coding Random-Solomon codes, Reed-Solomon codes
  • convolutional codes also known as parallel concatenated convolutional codes.
  • the change in the absolute distance between the satellite and the earth station is obtained through the phase difference between the sending end and the receiving end.
  • the satellite In the process of the management center station continuously sending the guidance signal, the satellite will continuously move around the earth and move with the "8" trajectory relative to the sub-satellite point. Therefore, the distance between the satellite and the management center station is constantly changing.
  • the path delay of the pilot signal will continue to change, but the movement of the satellite presents a certain regularity, changing from far to near and then from near to far, so the path delay changes also show a certain regularity.
  • the path delay change of the link sent to the satellite is consistent with the path delay change of the link path received from the satellite signal, so at the pilot signal receiving end and the pilot signal sending end
  • the phase delay between the two is equivalent to the double satellite-to-ground path delay variation. Therefore, when the receiver of spread spectrum communication detects that the maximum correlation peak moves in a certain direction, it can track the maximum correlation peak while obtaining Phase delay, half of the phase delay is the path delay.
  • the path delay is multiplied by the speed of light to get the absolute distance change between the satellite and the earth station.
  • the earth receiving station continuously receives the pilot signal, and uses the fixed-length period of the pilot signal to calibrate the time, and uses the number of received frames to calculate the time, so as to achieve accurate clocks between the ground receiving station and the management center station Real-time synchronization to achieve precise real-time synchronization of clocks across the entire network.
  • the pilot signal is sent intermittently, the earth receiving station receives the pilot signal intermittently, and adds absolute time information to the pilot signal to complete ground reception
  • the clocks of the station and the management center station are synchronized to achieve quasi-synchronization of the clocks of the entire network.

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Abstract

公开一种基于卫星载荷平台的旁路网络导引方法，其能够将全网卫星地面站距离变化和多普勒频移的影响统一化，实现全网的时钟与卫星的时钟精确准同步。这种基于卫星载荷平台的旁路网络导引方法，在卫星通信系统中，基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号。

Description

一种基于卫星载荷平台的旁路网络导引方法 技术领域
本发明涉及卫星通信的技术领域，尤其涉及一种基于卫星载荷平台的旁路网络导引方法。
背景技术
卫星通信技术(Satellite communication technology)是一种利用人造地球卫星作为中继站来转发无线电波而进行的两个或多个地球站之间的通信。自20世纪90年代以来，卫星移动通信的迅猛发展推动了天线技术的进步。卫星通信具有覆盖范围广、通信容量大、传输质量好、组网方便迅速、便于实现全球无缝链接等众多优点，被认为是建立全球个人通信必不可少的一种重要手段。
卫星通信系统是由通信卫星和经该卫星连通的地球站两部分组成。静止通信卫星是目前全球卫星通信系统中最常用的星体，是将通信卫星发射到赤道上空35860公里的高度上，使卫星运转方向与地球自转方向一致，并使卫星的运转周期正好等于地球的自转周期(24小时)，从而使卫星始终保持同步运行状态。故静止卫星也称为同步轨道卫星。
同步轨道卫星周期性环绕地球高速运动，在卫星高速运动的过程中，卫星距离各个地面接收站之间的距离会不断发生变化，从而导致 卫星时钟与地面接收站时钟之间存在相位差，并且卫星高速运动下，会引发多普勒频移，导致地面接收站收到的信号发生信号频率的畸变，从而导致地面接收站时钟和卫星时钟之间存在偏移，导致卫星地面站之间时钟不同步。
多波束情况下，不同波束间，用户站之间的距离差更大，卫星相对不同波束中用户站的多普勒频移影响更显著，导致不同波束的用户站之间时钟偏差较大，需要额外的基准站来进行时钟同步。
利用卫星导航授时修正本地时钟获得高精度时钟和通过时间传递技术实现时间同步的方法国内外已经进行了深入的研究。利用GPS时钟长期稳定度较好的特性或芯片级原子钟短期稳定度较好的优点实现GPS驯服晶振。在传统方法中，都需要一个高精度的外部基准时钟或高精度的时钟源。
发明内容
为克服现有技术的缺陷，本发明要解决的技术问题是提供了一种基于卫星载荷平台的旁路网络导引方法，其能够将全网卫星地面站距离变化和多普勒频移的影响统一化，实现全网的时钟与卫星的时钟精确准同步。
本发明的技术方案是：这种基于卫星载荷平台的旁路网络导引方法，
在卫星通信系统中，基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号。
本发明基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号，因此能够将全网卫星地面站距离变化和多普勒频移的影响统一化，实现全网的时钟与卫星的时钟精确准同步。
附图说明
图1示出了根据本发明的基于卫星载荷平台的旁路网络导引方法的一个优选实施例的流程图。
图2示出了根据本发明的卫星上的导引信号的传输示意图，其中导引信号不包括指示信息。
图3示出了根据本发明的卫星上的导引信号的传输示意图，其中导引信号包括指示信息，指示信息是由一个地面网络管理卫星站生成的。
图4示出了根据本发明的卫星上的导引信号的传输示意图，其中导引信号包括指示信息，地面系统部分的指示信息是由一个或多个地面网络管理卫星站生成的。
图5示出了根据本发明的一个优选实施例的导频帧结构的示意图。
具体实施方式
这种基于卫星载荷平台的旁路网络导引方法，
在卫星通信系统中，基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号。
本发明基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号，因此能够将全网卫星地面站距离变化和多普勒频移的影响统一化，实现全网的时钟与卫星的时钟精确准同步。
优选地，如图1所示，在每个下星波束内，占用下星信道的全部频带或部分频带发送，导引信号在下星信道中占用的全部频带或部分频带为导引频带，导引信号功率占导引频带全部功率的比例范围为0.1‰-1％，导引信号发送时通过扩频码进行扩频，以类噪声的低功率谱信号模式叠加在导引频带内的通信信号上，对卫星站信号接收信噪比的影响低于卫星站接收端本底热噪声的影响；
导引信号为信道中多类型的终端站构建网络和相互通信提供导引、载波与时钟同步、标准定时与指示信息。
本发明在开放无线信道中选定卫星作为基准，发送一路导引信号，导引信号占用开放无线信道的全部频带或部分频带发送，导引信号在开放无线信道中占用的全部频带或部分频带为导引频带，导引信号功率占为导引频带全部功率的比例范围为0.1‰-1％，所以导引信号的功率远远低于其余信号，不必在业务数据中额外插冗余测量数据，能够被开放无线网络内各个地球站接收到；导引信号发送时通过扩频码进 行扩频，以类噪声的低功率谱信号模式叠加在导引频带内的通信信号上，对接收端信号接收信噪比的影响低于接收端本底热噪声的影响，不影响其他信号的接收性能；在网络中，用户接收站监听卫星的导引信号，通过接收导引信号，完成用户接收站和卫星时钟的时钟同步，因此能够将全网卫星地面站距离变化和多普勒频移的影响统一化，实现全网的时钟与卫星的时钟精确准同步。
优选地，所述导引信号包括：帧头、帧序号和指示信息数据体；帧头包括同步头、导频，同步头用于导引信号帧定时及载波恢复，导频字段用于消除导引信号帧的频偏；帧序号字段是对导引信号帧循环顺序的标识；指示信息数据体字段承载指示信息，用于指示卫星载荷状态、卫星信道状态、网络运行状态和管理信息；
在网络中，卫星站接收卫星发送的导引信号，通过接收导引信号，完成卫星站和卫星载荷平台的时钟同步。
所述导引信号是卫星生成的(如图2所示)，而指示信息数据体包含卫星的状态信息、运行信息，而卫星平台无法直接获取的地面网络的信息，各个上星点波束内的地球站向卫星平台汇集相关指示信息(如图3所示)，经卫星平台解调接收并整理后，再通过导引信号中的指示信息数据帧广播到所有下星点波束内的所有卫星站。卫星平台无法直接获取的地面网络的信息包括：卫星地面网络状态、卫星站入网状态、卫星站运行状态、资源分配状态。
所述导引信号是卫星生成的，指示信息汇集到卫星平台，卫星平台成为整个卫星系统的管理与导引信息中心。
或者，卫星生成指示信息，并与导引信号合成后广播。
优选地，如图4所示，所述导引信号是由地球站中的管理中心站发送，卫星通过解调再生后，广播到多个波束。通过这种方式，可以实现跨波束的全网时钟精确同步。
更进一步地，如图4所示，地球站之一向卫星发送指示信息，卫星接收该指示信息，并与导引信号合成后广播。
或者，卫星生成指示信息，并与导引信号合成后广播。
优选地，卫星平台导引信号中的指示信息包括：导引帧序号、卫星运行信息、卫星状态信息、多个波束下所有地面站网络运行、网络管理信息、多个波束下所有卫星站运行信息、卫星信道状态信息、卫星信道资源分配信息、系统业务信息、系统安全信息。在数据体中加入指示信息，可以让导引信号在实现时钟精确同步之外，拥有网络管理的能力，网络管理中心站可以通过在数据体中加入指示信息，通过导引信号进行全网广播，全网内用户站接收到以后，可以得到来自网络管理中心站的指示信息，从而可以达到网络信息同步、网络资源管理调度、网络状态感知的能力。
优选地，所述导引信号包括：帧头、帧序号和指示信息数据体；帧头包括同步头、导频，同步头用于导引信号帧定时及载波恢复，导频字段用于消除导引信号帧的频偏；帧序号字段是对导引信号帧循环顺序的标识；指示信息数据体字段承载指示信息，用于指示信道、网络状态和管理信息；
各终端站对该导引信号进行解调接收，提取出载波、时钟信息， 根据导引信号中的指示信息对发送导引信息的基准站进行鉴别并完成其他指示信息的接收。
如图5所示，所述导引信号包括：帧头(Header)、导频(Pilot)、帧序号(ID)和数据体(Data Frame)。帧头用于导引信号帧定时及载波恢复，长度在16～128bit；导频字段为全0字段，长度在60bit以上，用于消除导引信号帧的频偏；帧序号字段长度在8bit以上，用于对地球站绝对距离进行测量；数据体字段承载网络管理信息，用于与网内其他站管理和维护卫星网络信息，长度在256～1008bit。例如，一种导引信号格式中，帧头为长度64位的差分M序列(m序列是CDMA系统中采用的最基本的PN序列，是最长线性反馈移位寄存器序列的简称)，导频字段为长度520位的全“0”序列，帧序号为8位序号，用来表示(0～255)，数据体使用1008位长度、1/2码率的LDPC编码进行信道编码；
另一种导引信号格式中，帧头为长度32位的差分Gold码，导频为长度200位的全“0”序列，帧序号为10位序号，用来表示(0～1023)，数据体使用1008长度、1/4码率的LDPC编码进行信道编码；
另一种导引信号格式中，帧头为长度16位的差分M序列，导频为长度100位的全“0”序列，帧序号为12位序号，用来表示(0～4095)，数据体使用512长度的Turbo编码进行信道编码。
更进一步地，通过固定信号帧的周期和在信号帧中标识帧序号，作为时钟的基本单位和标定；信号帧的周期范围在1ms～1000ms，所述导引信号采用二进制相移键控BPSK方式循环调制，连续或间歇地保持 发送。地面接收站连续接收导引信号，并且根据帧结构可以对接收导引信号中的每一帧进行区分，作为导引信号，每一帧的长度固定，每一帧的信息速率固定，因此每一帧所代表的时间也固定，因此地面接收站可以通过导引信号帧之间的间隔来确定时间间隔，将信号帧之间的间隔(即，信号帧周期)作为时钟的基本单位，通过不同序号帧之间的时间差来完成时间标定，如果前后两帧时间间隔计数不等于导引信号帧周期，则地面接收站时钟需要进行调整。
更进一步地，信号帧的周期范围在50ms～250ms。当信号帧周期为50ms、100ms、150ms、200ms、250ms这些50ms的整数倍时，作为时钟的基本单位和标定的效果最好。
优选地，通过使用长度为64～65536bit的扩频码进行扩频通信；扩频码采用M序列、Gold码、OVSF码或C/A码。扩频码最佳使用范围在1024～4096，在这个范围内，扩频通信中频谱扩展的效果最佳。此处的扩频码是针对数据体的。
更进一步地，扩频码采用M序列(M sequence)、Gold码(Gold码是由m序列派生出的一种伪随机码，它具有类似于m序列具有的伪随机性质，但其长度不同序列的数目比m序列多)、OVSF码(正交可变扩频因子，Orthogonal Variable Spreading Factor。OVSF码主要用于正交扩频。业务信道的速率不同，使用的OVSF码的长度也不同)或C/A码(粗捕获码，Coarse Acquisition Code。GPS卫星发出的一种伪随机码，用于粗测距和捕获GPS卫星，其实是一种Gold码，即由2个10级反馈移位寄存器构成的G码产生)。
优选地，首先生成M序列，然后对M序列进行差分编码，消除频偏的影响，将差分编码以后的序列作为帧头；扩频码采用了长度为12～128bit的M序列作为基本时间序列。此处的扩频方法是针对导引信号的帧头。
更进一步地，扩频码采用了长度为12～128bit的M序列作为基本时间序列。采用长度为64bit的差分M序列作为导引信号帧头，快速同步捕获性能最佳。
更进一步地，采用信道编码来对指示信息进行编码，信道编码采用LDPC(Low-density Parity-check，低密度奇偶校验)编码、Polar编码(极化码)、RS编码(Reed-Solomon codes，里德-所罗门码)、卷积码或Turbo码(又称为并行级联卷积码)。使用信道编码对数据体进行编码再进行传输，可以在导引信号的接收方显著提高数据体的接收信噪比，改善接收性能，让数据体在非最佳工作状态时也能正常接收，提高整个系统的鲁棒性。
优选地，通过发送端和接收端的相位差，得到卫星与地球站之间绝对距离的变化。
在管理中心站连续发送导引信号的过程中，卫星会围绕着地球不断移动，并且相对于星下点呈现“8”字轨迹移动，因此卫星与管理中心站之间的距离不断发生变化，因此导引信号的路径时延会不断变化，但卫星的移动呈现一定的规律性，都是由远到近再由近到远地进行变化，因此路径时延的变化也呈现一定的规律性。
对于管理中心站，通过自身接收导引信号，发送到卫星的链路路径时延变化和接收到来自卫星信号的链路路径时延变化一致，因此在导引信号接收端和导引信号发送端之间的相位时延等效于双倍的星地路径时延变化，因此当扩频通信的接收机，探测到最大相关峰向某个方向移动，即可在跟踪最大相关峰的同时，得到相位时延，相位时延的一半即为路径时延，路径时延乘以光速即可得到卫星与地球站之间的绝对距离变化。
优选地，地球接收站通过连续接收所述导引信号，并通过所述导引信号的定长周期来标定时间，利用接收帧数来计算时间，从而达到地面接收站与管理中心站的时钟精准实时同步，从而实现全网时钟精准实时同步。
优选地，对于实时性要求精度不高的系统，所述导引信号间断进行发送，地球接收站通过间断接收所述导引信号，在所述导引信号中加入绝对时间信息，从而完成地面接收站和管理中心站时钟授时同步，从而实现全网时钟准同步。
以上所述，仅是本发明的较佳实施例，并非对本发明作任何形式上的限制，凡是依据本发明的技术实质对以上实施例所作的任何简单修改、等同变化与修饰，均仍属本发明技术方案的保护范围。

Claims (10)

  1. 一种基于卫星载荷平台的旁路网络导引方法，其特征在于：在卫星通信系统中，基于卫星载荷平台，以星载高稳定时钟源为基准，发送旁路导引信号，导引信号发送到所有下星波束，为该卫星所覆盖的所有卫星站提供导引信号。
  2. 根据权利要求1所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：在每个下星波束内，占用下星信道的全部频带或部分频带发送，导引信号在下星信道中占用的全部频带或部分频带为导引频带，导引信号功率占导引频带全部功率的比例范围为0.1‰-1％，导引信号发送时通过扩频码进行扩频，以类噪声的低功率谱信号模式叠加在导引频带内的通信信号上，对卫星站信号接收信噪比的影响低于卫星站接收端本底热噪声的影响；
    导引信号为信道中多类型的终端站构建网络和相互通信提供导引、载波与时钟同步、标准定时与指示信息。
  3. 根据权利要求1或2所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：所述导引信号包括：帧头、帧序号和指示信息数据体；帧头包括同步头、导频，同步头用于导引信号帧定时及载波恢复，导频字段用于消除导引信号帧的频偏；帧序号字段是对导引信号帧循环顺序的标识；指示信息数据体字段承载指示信息，用于指示卫星载荷状态、卫星信道状态、网络运行状态和管理信息；
    在网络中，卫星站接收卫星发送的导引信号，通过接收导引信号，完成卫星站和卫星载荷平台的时钟同步。
  4. 根据权利要求1所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：所述导引信号是卫星生成的，而指示信息数据体包含卫星的状态信息、运行信息，而卫星平台无法直接获取的地面网络的信息，经由各个上星点波束内的网络管理卫星站向卫星平台汇集相关指示信息，经卫星平台解调接收并整理后，再通过导引信号中的指示信息数据帧广播到所有下星点波束内的所有卫星站。
  5. 根据权利要求4所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：卫星平台无法直接获取的地面网络的信息包括：卫星地面网络状态、卫星站入网状态、卫星站运行状态、资源分配状态。
  6. 根据权利要求1所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：所述导引信号是卫星生成的，指示信息汇集到卫星平台，卫星平台成为整个卫星系统的导引与指示信息中心。
  7. 根据权利要求2-6任一项所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：卫星平台导引信号中的指示信息包括：卫星运行信息、卫星状态信息、多个波束下所有卫星地面站的网络运行和网络管理信息、多个波束下所有卫星站的运行 信息、卫星信道状态信息、卫星信道资源分配信息、系统业务信息、系统安全信息。
  8. 根据权利要求7所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：通过固定信号帧的周期和导引信号帧中的标识帧序号，作为基准定时的基本单位和标定；导引信号帧的周期范围在1ms～1000ms，所述导引信号采用二进制相移键控BPSK方式循环调制，连续或间隙地保持发送。
  9. 根据权利要求8所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：通过使用长度为64～65536bit的扩频码进行扩频通信；扩频码采用M序列、Gold码、OVSF码或C/A码。
  10. 根据权利要求9所述的基于卫星载荷平台的旁路网络导引方法，其特征在于：首先生成M序列，然后对M序列进行差分编码，消除频偏的影响，将差分编码以后的序列作为帧头；扩频码采用了长度为12～128bit的M序列作为基本时间序列。
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