WO2021109812A1 - 中心单元、拉远单元、小站系统及通信方法 - Google Patents

中心单元、拉远单元、小站系统及通信方法 Download PDF

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Publication number
WO2021109812A1
WO2021109812A1 PCT/CN2020/127966 CN2020127966W WO2021109812A1 WO 2021109812 A1 WO2021109812 A1 WO 2021109812A1 CN 2020127966 W CN2020127966 W CN 2020127966W WO 2021109812 A1 WO2021109812 A1 WO 2021109812A1
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Prior art keywords
signal
optical
electrical signal
analog electrical
central unit
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PCT/CN2020/127966
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English (en)
French (fr)
Inventor
李旭
王天祥
余荣道
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华为技术有限公司
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Publication of WO2021109812A1 publication Critical patent/WO2021109812A1/zh
Priority to US17/832,825 priority Critical patent/US20220303020A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/614—Coherent receivers comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
    • H04B10/25759—Details of the reception of RF signal or the optical conversion before the optical fibre
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/506—Multiwavelength transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/572—Wavelength control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • 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

  • This application relates to communication technology, in particular to a central unit, a remote unit, a small station system and a communication method.
  • MIMO Multiple-input multiple-output
  • MIMO technology can make full use of space resources and effectively increase system channel capacity without increasing spectrum resources and antenna transmission power, it is regarded as an important technology in the communications field.
  • the embodiments of the present application provide a central unit, a remote unit, a small station system, and a communication method to construct a small station that can implement distributed MIMO functions more easily, and improve the communication quality of the small station system.
  • an embodiment of the present application provides a central unit including: a digital-to-analog conversion DAC module, an analog-to-digital conversion ADC module, a first electro-optical conversion module, and a first photoelectric conversion module.
  • the DAC module is used to convert the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero-frequency signal, an intermediate frequency signal or a radio frequency signal; the first electrical-to-optical conversion module is used to convert the first analog electrical signal into a first
  • the optical signal is output to the remote unit; the first photoelectric conversion module is used to convert the second optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal ;
  • the ADC module is used to convert the second analog electrical signal into a digital signal.
  • the digital-to-analog conversion DAC module and the analog-to-digital conversion ADC module are arranged in the central unit, so that the central unit transmits the analog optical signal to the remote unit, and the analog optical signal is transmitted to the multiple remote units in the central unit.
  • the processing delay of analog devices in analog transmission is usually in the order of nanoseconds, and the total delay formed by the path transmission delay fluctuates little or even fixed, it is relatively easy to achieve multiple calibrations in the central unit.
  • the synchronization of the remote unit makes it possible to easily implement the distributed MIMO function.
  • the central unit also includes a middle radio frequency module; the middle radio frequency module is used to convert the first analog electrical signal into an electrical signal at the first frequency; the first electro-optical conversion module is specifically used to convert the first frequency The electrical signal of the second frequency point is converted into the first optical signal and output to the remote unit; and/or, the second analog electrical signal is converted into the electrical signal of the second frequency point; the ADC module is specifically used to simulate the second frequency point The electrical signal is converted into a digital signal.
  • the middle radio frequency module is used to convert the first analog electrical signal into an electrical signal at the first frequency
  • the first electro-optical conversion module is specifically used to convert the first frequency
  • the electrical signal of the second frequency point is converted into the first optical signal and output to the remote unit
  • the second analog electrical signal is converted into the electrical signal of the second frequency point
  • the ADC module is specifically used to simulate the second frequency point
  • the electrical signal is converted into a digital signal.
  • the first electro-optical conversion module is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1; first The photoelectric conversion module is specifically configured to convert N second optical signals received from the remote unit into N second analog electrical signals; N is an integer greater than or equal to 1.
  • the processing delay of the analog device in the analog transmission is usually on the order of nanoseconds, and it is compared with the total delay fluctuation formed by the path transmission delay. Small or even fixed, so it is easier to synchronize multiple remote units through calibration in the central unit, which makes it possible to implement distributed MIMO functions more easily.
  • the central unit also includes at least one of the following: a first wavelength division multiplexer MUX, or a first demultiplexer DEMUX; the first MUX is used to combine M channels of first optical signals And output to the remote unit; the first DEMUX is used to separate N second optical signals, and output the separated second optical signals to the first photoelectric conversion module. Because the first MUX and the first DEMUX are set in the central unit, when the central unit transmits signals to the convergence unit, the sending link or the receiving link can be realized through an optical fiber, and the communication link between the central unit and the convergence unit is relatively simple.
  • the central unit is also used to input an optical power control signal to the first electro-optical conversion module; the first electro-optical conversion module is also used to output optical power related to the optical power control signal, and the optical power is used to control the pull The magnification of the amplifier in the far unit.
  • the first electro-optical conversion module includes a directly modulated laser source, and the optical power control signal is a DC bias current; the central unit is also used to input a DC bias current to the directly modulated laser source.
  • the remote unit may not include the ADC module, DAC module, and digital processing module. Therefore, the remote unit may not be able to realize the amplification of the amplifier through its own numerical control, etc. Therefore, in practical applications, if the amplifier's magnification needs to be adjusted, the central unit can control the amplifier's magnification.
  • the first electro-optical conversion module includes an indirect modulator and a laser source; the optical power control signal is a DC bias current, and the central unit is also used to input a DC bias current to the laser source; or, optical power control The signal is the bias voltage, and the central unit is also used to input the bias voltage to the indirect modulator.
  • an embodiment of the present application provides a remote unit, including: a second photoelectric conversion module, a second electro-optical conversion module, and an amplifier.
  • the second photoelectric conversion module is used to convert the third optical signal received from the central unit into a third analog electrical signal;
  • the third optical signal is the optical signal obtained by converting the analog electrical signal;
  • the third analog electrical signal is zero frequency Signal, intermediate frequency signal or radio frequency signal;
  • the amplifier is used to amplify the third analog electrical signal;
  • the second electro-optical conversion module is used to convert the fourth analog electrical signal into a fourth optical signal and output to the central unit;
  • the fourth analog electrical signal is zero Frequency signal, intermediate frequency signal or radio frequency signal.
  • the structure of the remote unit is relatively simple and can include fewer modules. Therefore, the remote unit can be conveniently set up in the small station system.
  • the second photoelectric conversion module is also used to convert the optical power related to the optical power control signal into a direct current; the amplifier is also used to amplify the third analog electrical signal with an amplification factor related to the direct current.
  • the remote unit also includes an up-mixing module and a down-mixing module; the up-mixing module is used to convert the third analog electrical signal into an electrical signal at the third frequency; the amplifier is specifically used to amplify The electrical signal at the third frequency point; the down-mixing module is used to convert the fourth analog electrical signal into an electrical signal at the fourth frequency point; the second electro-optical conversion module is specifically used to convert the electrical signal at the fourth frequency point into a fourth frequency point.
  • the optical signal is output to the central unit.
  • an embodiment of the present application provides a small station system, including: a central unit of any possible design such as the first aspect or the first aspect, and any possible design of the second aspect or the second aspect The design of the remote unit.
  • the small station system further includes a convergence unit; the central unit and one or more remote units are connected by the convergence unit.
  • the convergence unit includes a second demultiplexer MUX and a second demultiplexer DEMUX; the second DEMUX is used to split the optical signal combined by the first MUX of the central unit, and The branched optical signal is output to one or more remote units; the second MUX is used to combine multiple optical signals received from one or more remote units, and transmit the combined optical signals to the central unit The first DEMUX.
  • the small station system also includes an optical fiber transmission link; the central unit and one or more remote units are connected through the optical fiber transmission link.
  • the optical fiber transmission link includes one or more third wavelength division multiplexers MUX and one or more third demultiplexers DEMUX; any third DEMUX is used in the central unit Separate the target optical signal related to the remote unit connected to any third DEMUX from the optical signal combined with the first MUX, and output the target optical signal to the remote unit connected to any third DEMUX; The third MUX is used to combine the optical signals received from the remote unit connected to any third MUX, and output the combined optical signals to the first DEMUX of the central unit.
  • an embodiment of the present application provides a communication method applied to a central unit, including:
  • the baseband signal Convert the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero-frequency signal, an intermediate frequency signal or a radio frequency signal; convert the first analog electrical signal into a first optical signal and output it to the remote unit;
  • the second optical signal of the remote unit is converted into a second analog electrical signal;
  • the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal;
  • the second analog electrical signal is converted into a digital signal.
  • it further includes: converting the first analog electrical signal into an electrical signal at a first frequency; converting the first analog electrical signal into a first optical signal and outputting it to the remote unit includes: The electrical signal at the frequency point is converted into a first optical signal and output to the remote unit; the second analog electrical signal is converted into an electrical signal at the second frequency point; and the second analog electrical signal is converted into a digital signal including: The analog electrical signal of the point is converted into a digital signal.
  • converting the first analog electrical signal into a first optical signal and outputting to the remote unit includes: converting M first analog electrical signals into M first optical signals and outputting to the remote unit Unit; M is an integer greater than or equal to 1; converting the second optical signal received from the remote unit into a second analog electrical signal includes: converting N second optical signals received from the remote unit into N second optical signals Analog electrical signal; N is an integer greater than or equal to 1.
  • converting the M first analog electrical signals into M first optical signals and outputting them to the remote unit includes: combining the M first optical signals and outputting them to the remote unit; Converting N channels of second optical signals received from the remote unit into N channels of second analog electrical signals includes: separating N channels of second optical signals, and converting the separated second optical signals into N channels of second analog electrical signals signal.
  • it further includes: inputting an optical power control signal to the first electro-optical conversion module; outputting optical power related to the optical power control signal, and the optical power is used to control the amplification factor of the amplifier in the remote unit.
  • the first electro-optical conversion module includes a directly modulated laser source, and the optical power control signal is a DC bias current; inputting the optical power control signal to the first electro-optical conversion module includes: inputting a direct current to the directly modulated laser source Bias current.
  • the first electro-optical conversion module includes an indirect modulator and a laser source; the optical power control signal is a DC bias current, and inputting the optical power control signal to the first electro-optical conversion module includes: inputting a DC to the laser source Bias current; or, the optical power control signal is a bias voltage, and inputting the optical power control signal to the first electro-optical conversion module includes: inputting the bias voltage to the indirect modulator.
  • an embodiment of the present application provides a communication method applied to a remote unit, including: converting a third optical signal received from a central unit into a third analog electrical signal; the third optical signal is a conversion to an analog electrical signal The obtained optical signal; the third analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal; the third analog electrical signal is amplified; the fourth analog electrical signal is converted into a fourth optical signal and output to the central unit; the fourth analog electrical signal The signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the method further includes: converting the optical power related to the optical power control signal into a direct current; amplifying the third analog electrical signal includes: amplifying the third analog electrical signal by using an amplification factor related to the direct current.
  • it further includes: converting the third analog electrical signal into an electrical signal at a third frequency; amplifying the third analog electrical signal includes: amplifying the electrical signal at the third frequency; and converting the fourth analog electrical signal
  • the conversion into the electrical signal of the fourth frequency point; the conversion of the fourth analog electrical signal into the fourth optical signal and output to the central unit includes: the electrical signal of the fourth frequency point is converted into the fourth optical signal and output to the central unit.
  • an embodiment of the present application provides a communication method applied to a small station system, including: a central unit converts a baseband signal into a first analog electrical signal; the first analog electrical signal is a zero frequency signal, an intermediate frequency signal, or a radio frequency signal ; The central unit converts the first analog electrical signal into a first optical signal and outputs it to the remote unit; the remote unit converts the first optical signal received from the central unit into a third analog electrical signal; the third analog electrical signal is zero Frequency signal, intermediate frequency signal or radio frequency signal; the remote unit amplifies the third analog electrical signal; the remote unit converts the fourth analog electrical signal into a fourth optical signal and outputs it to the central unit; the fourth analog electrical signal is a zero frequency signal, Intermediate frequency signal or radio frequency signal; the central unit converts the fourth optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, intermediate frequency signal or radio frequency signal; the central unit converts the second analog electrical signal The signal is converted to a digital
  • an embodiment of the present application provides a central unit including: a digital-to-analog conversion DAC circuit, an analog-to-digital conversion ADC circuit, a first electro-optical conversion circuit, and a first photoelectric conversion circuit.
  • the DAC circuit is used to convert the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero-frequency signal, an intermediate frequency signal or a radio frequency signal; the first electro-optical conversion circuit is used to convert the first analog electrical signal into a first The optical signal is output to the remote unit; the first photoelectric conversion circuit is used to convert the second optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal ; ADC circuit is used to convert the second analog electrical signal into a digital signal.
  • the digital-to-analog conversion DAC circuit and the analog-to-digital conversion ADC circuit are arranged in the central unit, so that the central unit transmits the analog optical signal to the remote unit, and transmits the analog optical signal to the multiple remote units in the central unit.
  • the central unit transmits the analog optical signal to the remote unit, and transmits the analog optical signal to the multiple remote units in the central unit.
  • the processing delay of analog devices in analog transmission is usually in the order of nanoseconds, and the total delay formed by the path transmission delay fluctuates little or even fixed, it is relatively easy to achieve multiple calibrations in the central unit.
  • the synchronization of the remote unit makes it possible to easily implement the distributed MIMO function.
  • the central unit also includes an intermediate radio frequency circuit; the intermediate radio frequency circuit is used to convert the first analog electrical signal into an electrical signal at the first frequency; the first electro-optical conversion circuit is specifically used to convert the first frequency The electrical signal of the second frequency point is converted into the first optical signal and output to the remote unit; and/or, the second analog electrical signal is converted into the electrical signal of the second frequency point; the ADC circuit is specifically used to simulate the second frequency point The electrical signal is converted into a digital signal.
  • the harmonic interval of the electrical signal is larger and it is easier to filter out, and the signal quality is better.
  • the first electrical-optical conversion circuit is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1; first The photoelectric conversion circuit is specifically configured to convert N second optical signals received from the remote unit into N second analog electrical signals; N is an integer greater than or equal to 1.
  • the processing delay of the analog device in the analog transmission is usually on the order of nanoseconds, and it is compared with the total delay fluctuation formed by the path transmission delay. Small or even fixed, so it is easier to synchronize multiple remote units through calibration in the central unit, which makes it possible to implement distributed MIMO functions more easily.
  • the central unit also includes at least one of the following: a first wavelength division multiplexer MUX, or a first demultiplexer DEMUX; the first MUX is used to combine M channels of first optical signals And output to the remote unit; the first DEMUX is used to separate N second optical signals, and output the separated second optical signals to the first photoelectric conversion circuit. Because the first MUX and the first DEMUX are set in the central unit, when the central unit transmits signals to the convergence unit, the sending link or the receiving link can be realized through an optical fiber, and the communication link between the central unit and the convergence unit is relatively simple.
  • the central unit is also used to input an optical power control signal to the first electro-optical conversion circuit; the first electro-optical conversion circuit is also used to output optical power related to the optical power control signal, and the optical power is used to control the pull The magnification of the amplifier in the far unit.
  • the first electro-optical conversion circuit includes a directly modulated laser source, and the optical power control signal is a DC bias current; the central unit is also used to input a DC bias current to the directly modulated laser source.
  • the remote unit may not include ADC circuits, DAC circuits, and digital processing circuits. Therefore, the remote unit may not be able to achieve amplification of the amplifier through its own numerical control, etc. Therefore, in practical applications, if the amplifier's magnification needs to be adjusted, the central unit can control the amplifier's magnification.
  • the first electro-optical conversion circuit includes an indirect modulator and a laser source; the optical power control signal is a DC bias current, and the central unit is also used to input a DC bias current to the laser source; or, optical power control The signal is the bias voltage, and the central unit is also used to input the bias voltage to the indirect modulator.
  • an embodiment of the present application provides a remote unit, including: a second photoelectric conversion circuit, a second electro-optical conversion circuit, and an amplifier.
  • the second photoelectric conversion circuit is used to convert the third optical signal received from the central unit into a third analog electrical signal;
  • the third optical signal is the optical signal obtained by converting the analog electrical signal;
  • the third analog electrical signal is zero frequency Signal, intermediate frequency signal or radio frequency signal;
  • the amplifier is used to amplify the third analog electrical signal;
  • the second electro-optical conversion circuit is used to convert the fourth analog electrical signal into a fourth optical signal and output to the central unit;
  • the fourth analog electrical signal is zero Frequency signal, intermediate frequency signal or radio frequency signal.
  • the structure of the remote unit is relatively simple and can include fewer circuits. Therefore, the remote unit can be conveniently set up in the small station system.
  • the second photoelectric conversion circuit is also used to convert the optical power related to the optical power control signal into a direct current; the amplifier is also used to amplify the third analog electrical signal with an amplification factor related to the direct current.
  • the remote unit also includes an up-mixing circuit and a down-mixing circuit; the up-mixing circuit is used to convert the third analog electrical signal into an electrical signal at the third frequency; the amplifier is specifically used to amplify The electrical signal at the third frequency point; the down-mixing circuit is used to convert the fourth analog electrical signal into an electrical signal at the fourth frequency point; the second electro-optical conversion circuit is specifically used to convert the electrical signal at the fourth frequency point into a fourth frequency point The optical signal is output to the central unit.
  • the up-mixing circuit is used to convert the third analog electrical signal into an electrical signal at the third frequency
  • the amplifier is specifically used to amplify The electrical signal at the third frequency point
  • the down-mixing circuit is used to convert the fourth analog electrical signal into an electrical signal at the fourth frequency point
  • the second electro-optical conversion circuit is specifically used to convert the electrical signal at the fourth frequency point into a fourth frequency point
  • the optical signal is output to the central unit.
  • an embodiment of the present application provides a small station system, including: a central unit of any possible design such as the seventh aspect or the seventh aspect, and any possible design of the eighth aspect or the eighth aspect The design of the remote unit.
  • the small station system further includes a convergence unit; the central unit and one or more remote units are connected by the convergence unit.
  • the convergence unit includes a second demultiplexer MUX and a second demultiplexer DEMUX; the second DEMUX is used to split the optical signal combined by the first MUX of the central unit, and The branched optical signal is output to one or more remote units; the second MUX is used to combine multiple optical signals received from one or more remote units, and transmit the combined optical signals to the central unit The first DEMUX.
  • the small station system also includes an optical fiber transmission link; the central unit and one or more remote units are connected through the optical fiber transmission link.
  • the optical fiber transmission link includes one or more third wavelength division multiplexers MUX and one or more third demultiplexers DEMUX; any third DEMUX is used in the central unit Separate the target optical signal related to the remote unit connected to any third DEMUX from the optical signal combined with the first MUX, and output the target optical signal to the remote unit connected to any third DEMUX; The third MUX is used to combine the optical signals received from the remote unit connected to any third MUX, and output the combined optical signals to the first DEMUX of the central unit.
  • Figure 1 is a schematic diagram of an existing small station system structure
  • Figure 2 is a schematic diagram of another existing small station system structure
  • FIG. 3 is a schematic diagram of a central unit structure according to an embodiment of the application.
  • FIG. 4 is a schematic structural diagram of a remote unit according to an embodiment of the application.
  • FIG. 5 is a schematic structural diagram of a small station system according to an embodiment of the application.
  • FIG. 6 is a schematic structural diagram of an electro-optical conversion module according to an embodiment of the application.
  • FIG. 7 is a schematic structural diagram of another electro-optical conversion module according to an embodiment of the application.
  • FIG. 8 is a schematic structural diagram of another electro-optical conversion module according to an embodiment of the application.
  • FIG. 9 is a schematic diagram of a specific small station system structure according to an embodiment of the application.
  • FIG. 10 is a schematic diagram of another specific small station system structure according to an embodiment of the application.
  • FIG. 11 is a schematic diagram of another specific small station system structure according to an embodiment of the application.
  • FIG. 12 is a schematic diagram of another specific small station system structure according to an embodiment of the application.
  • FIG. 13 is a schematic flowchart of a communication method according to an embodiment of this application.
  • FIG. 14 is a schematic flowchart of another communication method according to an embodiment of the application.
  • FIG. 15 is a schematic flowchart of another communication method according to an embodiment of this application.
  • LTE long term evolution
  • 5G fifth generation mobile communication
  • module described in the embodiments of this application may be a circuit built by a circuit, or may be a functional module realized by a software program, or may be a module realized by a circuit and a software program. There is no specific restriction on this.
  • each module may be an integrated module or an independent module, which is not specifically limited in the embodiment of the present application.
  • a small station system can include three parts: a central unit, a convergence unit, and a remote unit.
  • the distance between the central unit and the convergence unit can be in the order of kilometers
  • the distance between the convergence unit and the remote unit can be in the order of 100 meters
  • the common public radio interface (CPRI) can be used between the central unit and the convergence unit in the optical fiber.
  • the digital signal is transmitted on.
  • the CPRI interface can be used to transmit digital signals between the convergence unit and the remote unit, or intermediate frequency analog signals can be transmitted on the cable.
  • the central unit includes a baseband processing module.
  • the convergence unit includes an interface protocol digital processing unit module.
  • the remote unit includes a digital processing module, an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC), a middle radio frequency module, a duplexer and an antenna.
  • ADC analog-to-digital converter
  • DAC digital-to-analog converter
  • the central unit includes the baseband processing module; the convergence unit includes the interface protocol digital processing unit part, ADC and DAC, and the intermediate radio frequency module.
  • the remote unit includes a middle radio frequency module, a duplexer and an antenna.
  • the Dot system moves the digital processing modules, ADC and DAC modules of the remote units in the Lampsite system and the Qcell system down to the convergence unit, reducing the functional modules of the remote unit.
  • the functional module of the convergence unit has been added.
  • the central unit outputs digital signals to the remote unit. Due to possible retransmission or buffering during digital signal transmission, the central unit interacts with multiple When the remote units are connected, the remote units are usually not synchronized, which makes it difficult for the small station system of the prior art to realize the distributed MIMO function.
  • Fig. 1 shows a traditional Lampsite system or Qcell system.
  • the central unit includes a baseband processing module; the convergence unit includes an interface protocol digital processing module; the remote unit includes a digital processing module, ADC and DAC, mid-range radio frequency module, duplexer and antenna.
  • the baseband processing module of the central unit can generate baseband signals; the baseband signal stream is transmitted to the convergence unit through the fiber CPRI interface; the interface protocol digital processing module of the convergence unit receives the signal, and transmits the signal to the remote through the fiber CPRI interface Unit; remote unit digital processing module demodulates the signal; the demodulated signal is converted into an analog signal through the DAC; the analog signal is converted to the radio frequency signal of the corresponding frequency through the middle radio frequency module; the radio frequency signal is transmitted through the duplexer and the antenna.
  • the remote unit antenna receives the signal; the received signal passes through the duplexer to the receiving link; the received signal is converted to the baseband or intermediate frequency signal of the corresponding frequency through the intermediate radio frequency; the signal is converted into a digital signal by the ADC; digital processing module The digital signal is transmitted to the convergence unit through the optical fiber CPRI interface; the interface protocol digital processing module of the convergence unit receives the signal and transmits the received signal to the central unit through the optical fiber CPRI interface; the central unit baseband processing module realizes the demodulation of the signal.
  • Fig. 2 shows a conventional Dot system.
  • the central unit of the small station system includes a baseband processing module; the convergence unit includes an interface protocol digital processing module, ADC and DAC, and a middle radio frequency module; the remote unit includes a middle radio frequency module, a duplexer and an antenna.
  • the baseband processing module of the central unit In the transmission link, the baseband processing module of the central unit generates the baseband signal; the baseband signal stream is transmitted to the convergence unit through the optical fiber CPRI interface; the interface protocol digital processing module of the convergence unit receives the signal; the signal is converted into an analog signal by the DAC; the analog signal is passed through the intermediate frequency The module converts to the intermediate frequency signal of the corresponding frequency point; the intermediate frequency signal is transmitted to the remote unit through the cable; the remote unit radio frequency module is converted to the radio frequency signal of the corresponding frequency point through the signal; the radio frequency signal is transmitted through the duplexer and the antenna.
  • the remote unit antenna receives the signal; the received signal passes through the duplexer to the receiving link; the received signal is converted to the intermediate frequency signal of the corresponding frequency through the radio frequency module; the signal is transmitted to the convergence unit through the cable; the intermediate frequency module of the convergence unit The signal is converted to the baseband signal of the corresponding frequency point; the signal is converted into a digital signal by ADC; the interface protocol digital processing module of the convergence unit receives the signal, and transmits the signal to the central unit through the optical fiber CPRI interface; the central unit baseband processing module realizes the signal correction Demodulation.
  • the remote unit and the convergence unit have complex structures, resulting in large volumes, weight, and power consumption of the remote unit and the convergence unit.
  • the central unit transmits digital signals to the remote unit. Due to possible retransmission or buffering in the digital signal transmission, when the central unit is connected to multiple remote units, the remote units are usually not synchronized, resulting in the existing The technological small station system is difficult to realize the distributed MIMO function.
  • the small station system provided by the embodiment of the present application sets the DAC module and the ADC module in the central unit, so that the central unit transmits the analog optical signal to the remote unit, and transmits the analog optical signal to the multiple remote units in the central unit.
  • the processing delay of analog devices in analog transmission is usually in the order of nanoseconds, and the total delay formed by the path transmission delay fluctuates little or even fixed, it can be easily achieved through calibration in the central unit.
  • the synchronization of two remote units makes it possible to implement distributed MIMO functions easily.
  • the DAC module and ADC module are moved down to the central unit, so that a very simple remote unit can be set in the small station system, and an optional convergent unit with a very simple setting can be set remotely.
  • the volume, weight and power consumption of the unit and the convergence unit can all be small, which can further improve the performance of the remote unit and the convergence unit.
  • the small station system involved in the embodiments of the present application may follow the name of the original small station system in specific applications, for example, it may be defined as a Lampsite system, a Qcell system, or a Dot system. It can be understood that the small station system in the embodiment of the present application may also be adaptively named in other ways, such as naming the A system, the B system, etc., which is not specifically limited in the embodiment of the present application.
  • the central unit of the embodiment of this application can correspond to the baseband processing module (building base band unit, BBU) part of the Lampsite system, and the convergence unit can correspond to the indoor of the Lampsite system.
  • BBU building base band unit
  • the remote unit can correspond to the indoor radio frequency remote unit (pRRU) part of the Lampsite system.
  • FIG. 3 is a schematic structural diagram of a central unit 300 provided by an embodiment of the application.
  • the central unit 300 includes: a digital-to-analog conversion DAC module 31, an analog-to-digital conversion ADC module 34, a first electro-optical conversion module 32 and a first photoelectric conversion module 33.
  • the DAC module 31 is used to convert the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the first electrical-optical conversion module 32 is configured to convert the first analog electrical signal into a first optical signal and output it to the remote unit.
  • the first photoelectric conversion module 33 is used for converting the second optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the ADC module 34 is used to convert the second analog electrical signal into a digital signal.
  • the baseband signal may be generated by the central unit 300, or may be received from other devices in the central unit.
  • the central unit 300 may further include a baseband processing module, and the baseband processing module may generate a baseband signal.
  • the baseband signal may be a digital signal, and the specific content of the baseband signal may vary according to different application scenarios, and the embodiment of the present application does not specifically limit the baseband signal.
  • the baseband signal can be used as the input of the DAC module 31.
  • the DAC module 31 After the DAC module 31 performs analog-to-digital conversion on the baseband signal, it can output the first analog electrical signal.
  • the first analog electrical signal may be a zero frequency signal, an intermediate frequency signal or a radio frequency signal, which is not specifically limited in the embodiment of the present application.
  • the first analog electrical signal can be used as the input of the first electro-optical conversion module 32.
  • the first electro-optical conversion module 32 can be an electro-optical conversion module for converting analog signals. After the first electro-optical conversion module converts the first analog electrical signal, it can output The first optical signal to the remote unit.
  • the output end of the first electro-optical conversion module 32 can communicate with the remote unit through an optical fiber or a converging unit, and the first optical signal can be transmitted to the remote unit through the optical fiber or the converging unit.
  • the process of outputting the first optical signal to the remote unit will be described in detail, which will not be repeated here.
  • the first optical signal in the embodiment of the present application may be output to one or more remote units, that is, the number of remote units may be determined according to actual application scenarios, which is not specifically limited in the embodiment of the present application.
  • the processing delay of an analog device in analog transmission is usually on the order of nanoseconds, and the total delay fluctuation caused by the path transmission delay is small. Even fixed, so it is easier to synchronize multiple remote units through calibration in the central unit, thereby making it possible to implement distributed MIMO functions more easily.
  • the first photoelectric conversion module 33 can receive the second optical signal from the remote unit.
  • the remote unit may receive the signal sent by the terminal device from the terminal device through an antenna, etc., and then convert the signal sent by the terminal device into a second optical signal, and transmit it to the second optical signal of the central unit 300 through an optical fiber or a converging unit.
  • a photoelectric conversion module 33 may be used to convert the signal sent by the terminal device into a second optical signal, and transmit it to the second optical signal of the central unit 300 through an optical fiber or a converging unit.
  • the first photoelectric conversion module 33 converts the second optical signal, it outputs a second analog electrical signal.
  • the second analog electrical signal may be a zero frequency signal, an intermediate frequency signal, or a radio frequency signal, which is not specifically limited in the embodiment of the present application.
  • the second analog electrical signal can be used as the input of the ADC module 34. After the ADC module 34 performs photoelectric conversion of the second analog signal, an output digital signal can be obtained. The central unit can then process the digital signal according to actual needs. There is no specific restriction on this.
  • the central unit transmits digital signals to the remote unit. Due to possible retransmission or buffering in the digital signal transmission, the central unit is connected to multiple remote units. When the remote units are usually not synchronized, it is difficult for the small station system of the prior art to realize the MIMO function.
  • the digital-to-analog conversion DAC module and the analog-to-digital conversion ADC module are arranged in the central unit, so that the central unit transmits analog optical signals to the remote unit, and the central unit transmits the analog optical signal to the multiple remote units.
  • FIG. 4 is a schematic structural diagram of a remote unit 400 provided by an embodiment of the application.
  • the remote unit 400 includes: a second photoelectric conversion module 41, a second electro-optical conversion module 43 and an amplifier 42.
  • the second photoelectric conversion module 41 is used to convert the third optical signal received from the central unit into a third analog electrical signal; the third optical signal is an optical signal obtained by converting the analog electrical signal; the third analog electrical signal is zero Frequency signal, intermediate frequency signal or radio frequency signal.
  • the amplifier 42 is used to amplify the third analog electrical signal.
  • the second electrical-optical conversion module 43 is used to convert the fourth analog electrical signal into a fourth optical signal and output it to the central unit; the fourth analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the remote unit 400 may receive the third optical signal from the central unit.
  • the third optical signal may be output through the first electro-optical conversion module of the embodiment shown in FIG. 3, which will not be repeated here.
  • the second photoelectric conversion module 41 photoelectrically converts the third optical signal, and then outputs a third analog electrical signal.
  • the third analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal, which is not specifically limited in the embodiment of the present application.
  • the third analog electrical signal can be used as the input of an amplifier (or a power amplifier (PA)) 42, and the amplifier 42 can amplify the third analog electrical signal.
  • the amplification factor of the amplifier 42 can be a fixed value or an adjustable value. Yes, it can be flexibly adjusted according to actual needs, which is not specifically limited in the embodiment of the present application.
  • the remote unit may not include the ADC module, DAC module, and digital processing module. Therefore, the remote unit may not be implemented by its own numerical control, etc.
  • the control of the amplification factor of the amplifier 42 Therefore, in practical applications, if the amplification factor of the amplifier 42 needs to be adjusted, the central unit can control the amplification factor of the amplifier 42. This will be described in detail in the subsequent embodiments and will not be repeated here.
  • the analog electrical signal amplified by the amplifier 42 may be further transmitted through an antenna or the like, which is not specifically limited in the embodiment of the present application.
  • the fourth analog electrical signal may be an analog electrical signal received by the remote unit 500 through an antenna or the like.
  • the fourth analog electrical signal may be a zero frequency signal, an intermediate frequency signal or a radio frequency signal, which is not specifically limited in the embodiment of the present application.
  • the fourth analog electrical signal can be used as the input of the second electrical-optical conversion module 43.
  • the second electrical-optical conversion module 43 converts the fourth analog electrical signal into electrical-optical form and then outputs a fourth optical signal.
  • the fourth optical signal can be further passed through an optical fiber or converged. The unit and the like are transmitted to the central unit, and subsequent embodiments will describe in detail the specific implementation of outputting the fourth optical signal to the central unit, which will not be repeated here.
  • the structure of the remote unit is relatively simple and can include fewer modules. Therefore, the remote unit can be conveniently set up in the small station system.
  • FIG. 5 is a schematic structural diagram of a small station system provided by an embodiment of this application. As shown in FIG. 5, the small station system includes: a central unit 510 and a remote unit 520.
  • the DAC module 511, ADC module 514, first electro-optical conversion module 512, and first photoelectric conversion module 513 in the central unit 510 can refer to the description of the embodiment corresponding to FIG. 3, and the second photoelectric conversion module 521 in the remote unit 520
  • the second electro-optical conversion module 523 and the amplifier 522 can refer to the description of the embodiment corresponding to FIG. 4, which will not be repeated here.
  • the central unit 510 and the remote unit 520 may be connected by an optical fiber transmission link, that is, the small station system 500 in the embodiment of the present application may not include an aggregation unit, so that the device types in the small station system can be reduced.
  • the central unit 510 and the remote unit 520 may be connected through the convergence unit 530, so as to realize convenient access to the remote unit through the convergence unit 530 that is closer to the remote unit.
  • 100 optical fibers may be set between the central unit 510 and the convergence unit 530.
  • the central unit further includes a middle radio frequency module 515.
  • the intermediate radio frequency module 515 is used to convert the first analog electrical signal into an electrical signal at the first frequency; the first electrical-to-optical conversion module 512 is specifically used to convert the electrical signal at the first frequency into a first optical signal and output it to the remote unit.
  • the intermediate radio frequency module 515 can convert the first analog electrical signal in the transmission link into an electrical signal at the first frequency point.
  • the first frequency point may include 2.4 GHz, 3 GHz, 5 GHz, or the like.
  • the first frequency point can be determined according to actual application scenarios. For example, when the value of the first frequency point is higher, the harmonic interval of the electrical signal is larger and it is easier to filter out, and the signal quality is better, but the first frequency point When the value of the dot is higher, the performance requirement of the first electro-optical conversion module 512 is higher, which will increase the cost of the first electro-optical conversion module 512. When the value of the first frequency point is low, the performance requirements of the first electro-optical conversion module 512 are lower, and the cost of the first electro-optical conversion module 512 is not increased, but the harmonic interval of the electrical signal is small, which is likely to cause interference, and the signal quality Poor.
  • the intermediate radio frequency module 515 can convert the second analog electrical signal into an electrical signal at the second frequency point; the ADC module 514 is specifically used to convert the analog electrical signal at the second frequency point into a digital signal.
  • the second frequency point may be the same as the first frequency point, or may be different from the first frequency point.
  • the specific value of the second frequency point can be adaptively set according to the performance of the ADC module 514 and the like, which is not specifically limited in the embodiment of the present application.
  • the remote unit 520 further includes an up-mixing module 524 and a down-mixing module 525.
  • the up-mixing module 524 may be used to convert the third analog electrical signal into the electrical signal of the third frequency point; the amplifier 522 is specifically used to amplify the third frequency point Electrical signal.
  • the third frequency point can be adaptively set according to the frequency point actually required when the remote unit sends an electrical signal, which is not specifically limited in the embodiment of this application.
  • the down-mixing module 525 is used to convert the fourth analog electrical signal into an electrical signal at the fourth frequency point; the second electrical-to-optical conversion module 523 is specifically used to convert the electrical signal at the fourth frequency point into a fourth optical signal and output it to the center unit.
  • the fourth frequency point may include 2.4 GHz, 3 GHz, 5 GHz, or the like.
  • the fourth frequency point can be determined according to actual application scenarios. For example, when the value of the fourth frequency point is higher, the harmonic interval of the electrical signal is larger and it is easier to filter out, and the signal quality is better, but the fourth frequency point When the value of the dot is higher, the performance requirement of the second electro-optical conversion module 523 is higher, which will increase the cost of the second electro-optical conversion module 523. When the value of the fourth frequency point is low, the performance requirements of the second electro-optical conversion module 523 are lower, and the cost of the second electro-optical conversion module 523 will not increase, but the harmonic interval of the electrical signal is small, which is likely to cause interference, and the signal quality Poor.
  • the values of the third frequency point and the fourth frequency point may be the same or different, which is not specifically limited in the embodiment of the present application.
  • the intermediate radio frequency module 515, the up-mixing module 524, and the down-mixing module 525 can all be set or not set according to actual application scenarios. This is not specifically limited.
  • the central unit has no RF module in the central unit, and an up-mixing module in the remote unit; for example, the DAC output frequency range of the central unit is 0.20-0.22 GHz, and the up-mixing module of the remote unit will The signal is converted to 2.4-2.42GHz.
  • the central unit has a middle radio frequency module, and the remote unit does not have an up-mixing module; for example, the DAC output frequency range of the central unit is 0.20-0.22GHz, and the middle radio frequency module of the central unit converts the signal to 2.4-2.42 GHz.
  • the central unit has a middle radio frequency module
  • the remote unit has an up-mixing module; for example, the DAC output frequency range of the central unit is 0.20-0.22GHz, and the middle radio frequency module of the central unit converts the signal to 1.4-1.42GHz , The up-mixing module of the remote unit converts the signal to 2.4-2.42GHz.
  • the central unit is also used to input an optical power control signal to the first electro-optical conversion module 512.
  • the first electro-optical conversion module 512 is also used to output optical power related to the optical power control signal, and the optical power is used to control the amplification factor of the amplifier in the remote unit.
  • the central unit can change the output DC of the second photoelectric conversion module 521 of the remote unit by controlling the output optical power of the first electro-optical conversion module 512, and then use the DC to control the amplification factor of the PA in the remote unit.
  • the remote unit may not be able to control the PA amplification factor, and the remote unit can be controlled based on the optical power control signal output by the central unit.
  • the control of the amplifier may be generated by the baseband processing module in the central unit.
  • the first electro-optical conversion module 512 includes a directly modulated laser source 5121, and the optical power control signal is a DC bias current; the central unit is also used to input a DC bias current to the directly modulated laser source.
  • the first electro-optical conversion module adopts a method of directly modulating a laser.
  • the optical power control signal is for adjusting the DC bias current of the directly modulated laser source, and the output optical power of the first electro-optical conversion module can be adjusted based on the DC bias current.
  • the first electro-optical conversion module 512 includes an indirect modulator 5122 and a laser source 5123.
  • the optical power control signal is a DC bias current, and the central unit is also used to input a DC bias current to the laser source;
  • the first electro-optical conversion module adopts a laser source and an indirect modulator.
  • the optical power control signal is the DC bias current of the laser source. Based on the DC bias current, the output optical power of the first electro-optical conversion module can be adjusted, thereby realizing the adjustment of the output optical power of the indirect modulator.
  • the first electro-optical conversion module 512 includes an indirect modulator 5124 and a laser source 5125.
  • the optical power control signal is the bias voltage, and the central unit is also used to input the bias voltage to the indirect modulator.
  • the first electro-optical conversion module adopts a laser source and an indirect modulator.
  • the optical power control signal is for adjusting the bias voltage of the indirect modulator, and the output optical power of the first electro-optical conversion module can be adjusted based on the bias voltage.
  • the second photoelectric conversion module 521 is also used to convert the optical power related to the optical power control signal into a direct current; the amplifier 522 is also used to amplify the third analog circuit with an amplification factor related to the direct current signal.
  • a digital signal transmission link can also be established between the central unit 510 and the remote unit 520, and the transmission link can be used to transmit the digital signal that controls the amplification factor of the amplifier 522, so as to realize the remote unit
  • the control of the magnification of the middle amplifier is not specifically limited in the embodiment of the present application.
  • the signal processing process can be as follows:
  • the baseband processing module In the central unit, the baseband processing module generates baseband signals.
  • the baseband signal is converted into an analog electrical signal through the DAC module.
  • the analog electrical signal is converted into a zero frequency, intermediate frequency or radio frequency electrical signal through an optional intermediate radio frequency module.
  • the intermediate frequency or radio frequency electrical signal is converted to the optical domain through the first electrical-optical conversion module to obtain the optical signal.
  • the optical signal is transmitted through the optical fiber, and then transmitted to the remote unit through the optional convergence unit.
  • the second photoelectric conversion module converts the optical signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency through an optional up-mixer module.
  • the analog electrical signal is amplified by the PA, and the amplified signal is transmitted through the duplexer and the antenna.
  • the baseband processing module sends an optical power control signal to control the output optical power of the first electro-optical conversion module.
  • the DC output of the second photoelectric conversion module is used to control the PA's gain.
  • the antenna receives the analog electric signal.
  • the analog electrical signal enters the receiving link through the duplexer.
  • the analog electrical signal passes through the optional down-mixer module to a designated frequency point; the analog electrical signal is converted to the optical domain through the second electrical-optical conversion module to obtain the optical signal.
  • the optical signal is transmitted through the optical fiber, and then transmitted to the central unit through the optional convergence unit.
  • the first photoelectric conversion module converts the optical signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency point through an optional RF module.
  • the analog electrical signal is converted into a digital signal through the ADC module.
  • the digital signal is demodulated by the baseband processing module.
  • the small station system may include multiple remote units.
  • FIGS. 9 to 12 show four exemplary structural schematic diagrams including multiple remote units in the small station system.
  • the baseband processing module in the central unit may be called a baseband processing unit, which is not specifically limited in the embodiment of the present application.
  • FIG. 9 shows a schematic structural diagram of a specific small station system according to an embodiment of the present application.
  • the small station system includes a central unit, an aggregation unit and M remote units.
  • the first electro-optical conversion module is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1.
  • the first photoelectric conversion module is specifically configured to convert N channels of second optical signals received from the remote unit into N channels of second analog electrical signals; N is an integer greater than or equal to 1.
  • M and K can be set according to actual application scenarios, which are not specifically limited in the embodiment of the present application.
  • M and N may be the same or different.
  • M and N are the same as an example, and the values of M and N are not limited.
  • the central unit further includes a first wavelength division multiplexer (multiplexer, MUX), and the first MUX is used to combine the first optical signals of M channels and output them to the remote unit.
  • a first wavelength division multiplexer multiplexer, MUX
  • MUX wavelength division multiplexer
  • the central unit further includes a first demultiplexer (demultiplexer, DEMUX).
  • DEMUX demultiplexer
  • the first DEMUX is used to separate N channels of second optical signals and output the separated second optical signals to the first photoelectric conversion module.
  • the convergence unit includes a second demultiplexer MUX and a second demultiplexer DEMUX; the second DEMUX is used to split the optical signal combined by the first MUX of the central unit, and split the split optical signal.
  • the signal is output to one or more remote units.
  • the sending link or receiving The link can be realized by an optical fiber, and the communication link between the central unit and the convergence unit is relatively simple.
  • the signal processing process can be:
  • the baseband processing module In the central unit, the baseband processing module generates M-channel baseband signals. M-channel baseband signals are converted into M-channel analog electrical signals through the DAC module. M-channel analog electrical signals are converted into zero-frequency, intermediate-frequency or radio-frequency electrical signals through an optional intermediate radio frequency module. M channels of zero-frequency, intermediate-frequency or radio frequency electrical signals pass through the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, and are converted to optical domain signals of different wavelengths. M channels of optical domain signals are combined through MUX. The combined optical domain signal is transmitted to the convergence unit through the optical fiber.
  • DEMUX separates the optical domain signals of different wavelengths into M channels.
  • the separated M channels of optical domain signals enter the remote unit 1, the remote unit 2...the remote unit M respectively.
  • the photoelectric conversion module converts the received optical domain signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency through an optional up-mixer module.
  • the analog electrical signal is amplified by PA.
  • the amplified signal is transmitted through the duplexer and antenna.
  • the baseband processing module sends M optical power control signals, and the M optical power control signals respectively control the output optical power of the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, each In the remote unit, the photoelectric conversion module controls the amplification factor of the PA based on the DC output of the optical power control signal.
  • the antenna receives analog electrical signals.
  • the analog electrical signal enters the receiving link through the duplexer.
  • the analog electrical signal is converted to a specified frequency through an optional down-mixer module.
  • the analog electrical signal is converted into an optical domain signal through the electrical-optical conversion module.
  • the optical domain signal is transmitted to the convergence unit through the optical fiber.
  • M channels of optical domain signals are combined through MUX.
  • the combined optical domain signal reaches the central unit through the optical fiber.
  • DEMUX separates the optical domain signals of different wavelengths into M channels.
  • the photoelectric conversion module 21, the photoelectric conversion module 22...and the photoelectric conversion module convert the optical signal into an analog electric signal; the analog electric signal is converted to a specified frequency through an optional intermediate radio frequency module; the analog electric signal is converted into a digital signal through the ADC module signal.
  • the digital signal is demodulated by the baseband processing module.
  • the MIMO function may be supported.
  • the analog electrical signal includes 0.4-0.6GHz and 0.8-1GHz
  • the 0.4-0.6GHz signal can be converted into 2.4GHz and transmitted to 4 antennas
  • the 0.8-1GHz signal can be converted into 3.5GHz And it is transmitted to 2 antennas; so as to realize the MIMO function.
  • FIG. 10 shows a schematic structural diagram of another specific small station system according to an embodiment of the present application.
  • the small station system includes a central unit, an aggregation unit and M remote units.
  • the first electro-optical conversion module is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1.
  • the first photoelectric conversion module is specifically configured to convert N channels of second optical signals received from the remote unit into N channels of second analog electrical signals; N is an integer greater than or equal to 1.
  • M and K can be set according to actual application scenarios, which are not specifically limited in the embodiment of the present application.
  • M and N may be the same or different.
  • M and N are the same as an example, and the values of M and N are not limited.
  • the electro-optical conversion module of the central unit and the remote unit are connected based on optical fiber. Therefore, the M electro-optical conversion modules may have electro-optical conversion modules with the same output wavelength, and the performance requirements of the electro-optical conversion modules are lower, so It can reduce the cost and overhead caused by setting different wavelength electro-optical conversion modules.
  • the optical fiber may be a multi-core optical fiber or an optical cable.
  • a multi-core optical fiber refers to multiple cores in the same optical fiber; an optical cable refers to a combination of multiple optical fibers into an optical cable, thereby reducing the complexity of line layout.
  • the N photoelectric conversion modules may have photoelectric conversion modules with the same output wavelength, which has lower requirements on the performance of the photoelectric conversion module, so that the cost and expenditure caused by the installation of different wavelength photoelectric conversion modules can be reduced.
  • the signal processing process can be:
  • the baseband processing module In the central unit, the baseband processing module generates M-channel baseband signals. M-channel baseband signals are converted into M-channel analog electrical signals through the DAC module. M-channel analog electrical signals are converted into zero-frequency, intermediate-frequency or radio-frequency electrical signals through an optional intermediate radio frequency module. M channels of zero frequency, intermediate frequency or radio frequency electrical signals are converted into optical domain signals through the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M. The M-channel optical domain signal is transmitted to the convergence unit through the optical fiber.
  • M optical fibers are separated, that is, M optical domain signals, and the M optical domain signals enter the remote unit 1, the remote unit 2... and the remote unit M respectively.
  • the photoelectric conversion module converts the received optical domain signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency through an optional up-mixer module.
  • the analog electrical signal is amplified by PA.
  • the amplified signal is transmitted through the duplexer and antenna.
  • the baseband processing module sends M optical power control signals, and the M optical power control signals respectively control the output optical power of the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, each In the remote unit, the photoelectric conversion module controls the amplification factor of the PA based on the DC output of the optical power control signal.
  • the antenna receives analog electrical signals.
  • the analog electrical signal enters the receiving link through the duplexer.
  • the analog electrical signal is converted to a specified frequency through an optional down-mixer module.
  • the analog electrical signal is converted into an optical domain signal through the electrical-optical conversion module.
  • the optical domain signal is transmitted to the convergence unit through the optical fiber.
  • the M-channel optical domain signal reaches the central unit through the optical fiber.
  • the photoelectric conversion module 21, the photoelectric conversion module 22...and the photoelectric conversion module 2M convert the optical signal into an analog electric signal; the analog electric signal is converted to a specified frequency through an optional RF module; the analog electric signal is converted into an analog electric signal through the ADC module Digital signal.
  • the digital signal is demodulated by the baseband processing module.
  • the MIMO function may be supported.
  • the analog electrical signal includes 0.4-0.6GHz and 0.8-1GHz
  • the 0.4-0.6GHz signal can be converted into 2.4GHz and transmitted to 4 antennas
  • the 0.8-1GHz signal can be converted into 3.5GHz And it is transmitted to 2 antennas; so as to realize the MIMO function.
  • FIG. 11 shows a schematic structural diagram of another specific small station system according to an embodiment of the present application.
  • the small station system includes a central unit and M remote units.
  • the first electro-optical conversion module is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1.
  • the first photoelectric conversion module is specifically configured to convert N channels of second optical signals received from the remote unit into N channels of second analog electrical signals; N is an integer greater than or equal to 1.
  • M and K can be set according to actual application scenarios, which are not specifically limited in the embodiment of the present application.
  • M and N may be the same or different.
  • M and N are the same as an example, and the values of M and N are not limited.
  • the central unit and M remote units are connected by optical fiber transmission links.
  • the central unit further includes a first wavelength division multiplexer MUX, and the first MUX is used to combine M channels of first optical signals and output them to the remote unit.
  • a first wavelength division multiplexer MUX the first MUX is used to combine M channels of first optical signals and output them to the remote unit.
  • the central unit further includes a first demultiplexer DEMUX, and the first DEMUX is used to separate N channels of second optical signals and output the separated second optical signals to the first photoelectric conversion module.
  • a first demultiplexer DEMUX the first DEMUX is used to separate N channels of second optical signals and output the separated second optical signals to the first photoelectric conversion module.
  • the optical fiber transmission link includes M third wavelength division multiplexers MUX and M third demultiplexers DEMUX; any third DEMUX is used for the optical signal combined through the first MUX of the central unit Separate the target optical signal related to the remote unit connected to any third DEMUX, and output the target optical signal to the remote unit connected to any third DEMUX; any third MUX is used to The optical signal received by a remote unit connected to a third MUX is combined, and the combined optical signal is output to the first DEMUX of the central unit.
  • the central unit is provided with the first MUX and the first DEMUX, and the optical fiber transmission link is provided with M third MUXs and M third DEMUXs, the central unit transmits signals to the remote unit
  • the transmission link or the receiving link can be realized by an optical fiber, the communication link between the central unit and the remote unit is relatively simple.
  • the signal processing process can be:
  • the baseband processing module In the central unit, the baseband processing module generates M-channel baseband signals. M-channel baseband signals are converted into M-channel analog electrical signals through the DAC module. M-channel analog electrical signals are converted into zero-frequency, intermediate-frequency or radio-frequency electrical signals through an optional intermediate radio frequency module. M channels of zero-frequency, intermediate-frequency or radio frequency electrical signals pass through the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, and are converted to optical domain signals of different wavelengths. M channels of optical domain signals are combined through MUX. The combined optical domain signal is transmitted through the optical fiber.
  • each DEMUX module separates the optical domain signal corresponding to the wavelength of the remote unit.
  • the optical domain signals separated in sequence enter the remote unit 1, the remote unit 2...the remote unit M respectively.
  • the photoelectric conversion module converts the received optical domain signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency through an optional up-mixer module.
  • the analog electrical signal is amplified by PA.
  • the amplified signal is transmitted through the duplexer and antenna.
  • the baseband processing module sends M optical power control signals, and the M optical power control signals respectively control the output optical power of the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, each In the remote unit, the photoelectric conversion module controls the amplification factor of the PA based on the DC output of the optical power control signal.
  • the antenna receives analog electrical signals.
  • the analog electrical signal enters the receiving link through the duplexer.
  • the analog electrical signal is converted to a specified frequency through an optional down-mixer module.
  • the analog electrical signal is converted into an optical domain signal through the electro-optical conversion module.
  • the optical domain signals of different wavelengths are combined through the corresponding MUX in turn.
  • the combined optical domain signal reaches the central unit through the optical fiber.
  • DEMUX separates the optical domain signals of different wavelengths into M channels.
  • the photoelectric conversion module 21, the photoelectric conversion module 22...and the photoelectric conversion module 2M convert the optical signal into an analog electric signal; the analog electric signal is converted to a specified frequency by an optional intermediate radio frequency module; the analog electric signal is converted into an analog electric signal by the ADC module Digital signal.
  • the digital signal is demodulated by the baseband processing module.
  • the MIMO function may be supported.
  • the analog electrical signal includes 0.4-0.6GHz and 0.8-1GHz
  • the 0.4-0.6GHz signal can be converted into 2.4GHz and transmitted to 4 antennas
  • the 0.8-1GHz signal can be converted into 3.5GHz And it is transmitted to 2 antennas; so as to realize the MIMO function.
  • FIG. 12 shows a schematic structural diagram of another specific small station system according to an embodiment of the present application.
  • the small station system includes a central unit and M remote units.
  • the first electro-optical conversion module is specifically configured to convert M first analog electrical signals into M first optical signals and output them to the remote unit; M is an integer greater than or equal to 1.
  • the first photoelectric conversion module is specifically configured to convert N channels of second optical signals received from the remote unit into N channels of second analog electrical signals; N is an integer greater than or equal to 1.
  • M and K can be set according to actual application scenarios, which are not specifically limited in the embodiment of the present application.
  • M and N may be the same or different.
  • M and N are the same as an example, and the values of M and N are not limited.
  • the electro-optical conversion module of the central unit and the remote unit are connected based on optical fiber. Therefore, the M electro-optical conversion modules may have electro-optical conversion modules with the same output wavelength, and the performance requirements of the electro-optical conversion modules are lower, so It can reduce the cost and overhead caused by setting different wavelength electro-optical conversion modules.
  • the optical fiber may be a multi-core optical fiber or an optical cable.
  • a multi-core optical fiber refers to multiple cores in the same optical fiber; an optical cable refers to a combination of multiple optical fibers into an optical cable, thereby reducing the complexity of line layout.
  • the N photoelectric conversion modules may have photoelectric conversion modules with the same output wavelength, which has lower requirements on the performance of the photoelectric conversion module, thereby reducing the cost and expenditure caused by installing photoelectric conversion modules with different wavelengths.
  • the signal processing process can be:
  • the baseband processing module In the central unit, the baseband processing module generates M-channel baseband signals. M-channel baseband signals are converted into M-channel analog electrical signals through the DAC module. M-channel analog electrical signals are converted into zero-frequency, intermediate-frequency or radio-frequency electrical signals through an optional intermediate radio frequency module. M channels of zero frequency, intermediate frequency or radio frequency electrical signals are converted into optical domain signals through the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M. The M-channel optical domain signal is transmitted through the optical fiber transmission link.
  • M optical fibers are sequentially separated, that is, M optical domain signals, and M optical domain signals enter remote unit 1, remote unit 2, ... remote unit M, respectively.
  • the photoelectric conversion module converts the received optical domain signal into an analog electric signal.
  • the analog electrical signal is converted to a specified frequency through an optional up-mixer module.
  • the analog electrical signal is amplified by PA.
  • the amplified signal is transmitted through the duplexer and antenna.
  • the baseband processing module sends M optical power control signals, and the M optical power control signals respectively control the output optical power of the electro-optical conversion module 11, the electro-optical conversion module 12... and the electro-optical conversion module 1M, each In the remote unit, the photoelectric conversion module controls the amplification factor of the PA based on the DC output of the optical power control signal.
  • the antenna receives analog electrical signals.
  • the analog electrical signal enters the receiving link through the duplexer.
  • the analog electrical signal passes through the optional down-mixer module to the specified frequency point.
  • the analog electrical signal is converted into an optical domain signal through the electrical-optical conversion module.
  • the optical domain signal is transmitted through the optical fiber transmission link.
  • the M-channel optical domain signal reaches the central unit through the optical fiber.
  • the photoelectric conversion module 21, the photoelectric conversion module 22...and the photoelectric conversion module 2M convert the optical signal into an analog electric signal; the analog electric signal is converted to a specified frequency through an optional RF module; the analog electric signal is converted into an analog electric signal through the ADC module Digital signal.
  • the digital signal is demodulated by the baseband processing module.
  • the MIMO function may be supported.
  • the analog electrical signal includes 0.4-0.6GHz and 0.8-1GHz
  • the 0.4-0.6GHz signal can be converted into 2.4GHz and transmitted to 4 antennas
  • the 0.8-1GHz signal can be converted into 3.5GHz And it is transmitted to 2 antennas; so as to realize the MIMO function.
  • FIG. 9 to FIG. 12 can be used independently or cross-multiplexed, which is not specifically limited in this application.
  • a central unit is connected to multiple remote units, and multiple remote units form a distributed MIMO system.
  • Fig. 13 shows a schematic flow chart of a communication method. As shown in Fig. 13, applied to the central unit of any of the above embodiments, the method includes:
  • S1301 Convert the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • S13902 Convert the first analog electrical signal into a first optical signal and output it to the remote unit.
  • S1303 Convert the second optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • it further includes: converting the first analog electrical signal into an electrical signal at a first frequency; converting the first analog electrical signal into a first optical signal and outputting it to the remote unit includes: The electrical signal at the frequency point is converted into a first optical signal and output to the remote unit; the second analog electrical signal is converted into an electrical signal at the second frequency point; and the second analog electrical signal is converted into a digital signal including: The analog electrical signal of the point is converted into a digital signal.
  • converting the first analog electrical signal into a first optical signal and outputting to the remote unit includes: converting M first analog electrical signals into M first optical signals and outputting to the remote unit Unit; M is an integer greater than or equal to 1; converting the second optical signal received from the remote unit into a second analog electrical signal includes: converting N second optical signals received from the remote unit into N second optical signals Analog electrical signal; N is an integer greater than or equal to 1.
  • converting the M first analog electrical signals into M first optical signals and outputting them to the remote unit includes: combining the M first optical signals and outputting them to the remote unit; Converting N channels of second optical signals received from the remote unit into N channels of second analog electrical signals includes: separating N channels of second optical signals, and converting the separated second optical signals into N channels of second analog electrical signals signal.
  • the method further includes: inputting an optical power control signal to the first electro-optical conversion module; outputting optical power related to the optical power control signal, and the optical power is used to control the amplification factor of the amplifier in the remote unit.
  • the first electro-optical conversion module includes a directly modulated laser source, and the optical power control signal is a DC bias current; inputting the optical power control signal to the first electro-optical conversion module includes: inputting a direct current to the directly modulated laser source Bias current.
  • the first electro-optical conversion module includes an indirect modulator and a laser source; the optical power control signal is a DC bias current, and inputting the optical power control signal to the first electro-optical conversion module includes: inputting a DC to the laser source Bias current; or, the optical power control signal is a bias voltage, and inputting the optical power control signal to the first electro-optical conversion module includes: inputting the bias voltage to the indirect modulator.
  • the execution subject of the method on the central unit side may be the central unit or the device in the central unit (it should be noted that the central unit is described as an example in the embodiments provided in this application) .
  • the device in the central unit may be a chip system, a circuit, or a module, etc., which is not limited in this application.
  • the method in this embodiment can correspondingly be used to execute the steps executed by the central unit in the above device embodiment, and its implementation principles and technical effects are similar, and will not be repeated here.
  • Fig. 14 shows a schematic flow chart of a communication method. As shown in Fig. 14, applied to the remote unit of any of the above embodiments, the method includes:
  • S1401 Convert the third optical signal received from the central unit into a third analog electrical signal; the third optical signal is an optical signal obtained by converting an analog electrical signal; the third analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal .
  • S1402 Amplify the third analog electrical signal.
  • S1403 Convert the fourth analog electrical signal into a fourth optical signal and output it to the central unit; the fourth analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the method further includes: converting the optical power related to the optical power control signal into a direct current; amplifying the third analog electrical signal includes: amplifying the third analog electrical signal by using an amplification factor related to the direct current.
  • it further includes: converting the third analog electrical signal into an electrical signal at a third frequency; amplifying the third analog electrical signal includes: amplifying the electrical signal at the third frequency; and converting the fourth analog electrical signal
  • the conversion into the electrical signal of the fourth frequency point; the conversion of the fourth analog electrical signal into the fourth optical signal and output to the central unit includes: the electrical signal of the fourth frequency point is converted into the fourth optical signal and output to the central unit.
  • the execution subject of the central unit-side method can be the remote unit or the device in the remote unit (it should be noted that in the embodiment provided in this application, the remote unit is taken as an example. describe).
  • the device in the remote unit may be a chip system, a circuit, or a module, etc., which is not limited in this application.
  • the method in this embodiment can correspondingly be used to execute the steps executed by the remote unit in the above-mentioned device embodiment, and its implementation principles and technical effects are similar, and will not be repeated here.
  • FIG. 15 shows a schematic flowchart of a communication method. As shown in FIG. 15, it is applied to the small station system of any of the above embodiments, and the method includes:
  • the central unit converts the baseband signal into a first analog electrical signal; the first analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the central unit converts the first analog electrical signal into a first optical signal and outputs it to the remote unit.
  • the remote unit converts the first optical signal received from the central unit into a third analog electrical signal; the third analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the remote unit converts the fourth analog electrical signal into a fourth optical signal and outputs it to the central unit; the fourth analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • the central unit converts the fourth optical signal received from the remote unit into a second analog electrical signal; the second analog electrical signal is a zero frequency signal, an intermediate frequency signal or a radio frequency signal.
  • S1507 The central unit converts the second analog electrical signal into a digital signal.
  • the method in this embodiment can correspondingly be used to execute the steps performed by each device in the small station system in the above device embodiment, and the implementation principles and technical effects are similar, and will not be repeated here.
  • the disclosed device and method may be implemented in other ways.
  • the device embodiments described above are only illustrative.
  • the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components may be combined or It can be integrated into another system, or some features can be ignored or not implemented.
  • the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.
  • the functional units in the various embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit.
  • the above-mentioned integrated unit may be implemented in the form of hardware, or may be implemented in the form of hardware plus software functional units.
  • the above-mentioned integrated unit implemented in the form of a software functional unit may be stored in a computer readable storage medium.
  • the above-mentioned software functional unit is stored in a storage medium, and includes several instructions to enable a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor to execute the method described in each embodiment of the present application. Part of the steps.
  • the aforementioned storage media include: U disk, mobile hard disk, read-only memory (read-only memory, ROM), random access memory (random access memory, RAM), magnetic disk or optical disk and other media that can store program code .

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Abstract

本申请实施例提供一种中心单元、拉远单元、小站系统及通信方法，将数模转换DAC模块和模数转换ADC模块设置在中心单元中，使得中心单元向拉远单元传输模拟的光信号，在中心单元向多个拉远单元传输该模拟的光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。

Description

中心单元、拉远单元、小站系统及通信方法
本申请要求于2019年12月06日提交中国专利局、申请号为201911243332.1、申请名称为“中心单元、拉远单元、小站系统及通信方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信技术，尤其涉及中心单元、拉远单元、小站系统及通信方法。
背景技术
多输入多输出技术(multiple-input multiple-output，MIMO)是指在发射端和接收端分别使用多个发射天线和接收天线，使信号通过发射端与接收端的多个天线传送和接收，从而改善通信质量。因为MIMO技术能充分利用空间资源，在不增加频谱资源和天线发射功率的情况下，有效提高系统信道容量，因此被视为通信领域的重要技术。
现有技术中，为了满足园区、机场、停车场、办公室等区域的无线覆盖需求，逐渐发展了小站产品。示例性的，业界主流小站产品包括华为的Lampsite系统，中兴的Qcell系统和爱立信的Dot系统。
但是，现有技术的小站系统中，难以实现分布式MIMO功能，严重制约了小站技术的发展。
发明内容
本申请实施例提供一种中心单元、拉远单元、小站系统及通信方法，以构建可以较容易的实现分布式MIMO功能的小站，提升小站系统的通信质量。
第一方面，本申请实施例提供一种中心单元，包括：数模转换DAC模块、模数转换ADC模块、第一电光转换模块和第一光电转换模块。
其中，DAC模块用于将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号；第一电光转换模块用于将第一模拟电信号转换为第一光信号并输出至拉远单元；第一光电转换模块用于将接收自拉远单元的第二光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号；ADC模块用于将第二模拟电信号转换为数字信号。本申请实施例中，将数模转换DAC模块和模数转换ADC模块设置在中心单元中，使得中心单元向拉远单元传输模拟的光信号，在中心单元向多个拉远单元传输该模拟的光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
在一种可能的设计中，中心单元还包括中射频模块；中射频模块用于将第一模拟电信号转换为第一频点的电信号；第一电光转换模块具体用于将第一频点的电信号转 换为第一光信号并输出至拉远单元；和/或，用于将第二模拟电信号转换为第二频点的电信号；ADC模块具体用于将第二频点的模拟电信号转换为数字信号。第一频点的值较高时，电信号的谐波间隔较大容易滤除，信号质量较好。
在一种可能的设计中，第一电光转换模块具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；第一光电转换模块具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。这样，在中心单元向多个拉远单元传输该模拟的第一光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
在一种可能的设计中，中心单元还包括下列至少一种：第一波分复用器MUX，或第一解复用器DEMUX；第一MUX用于将M路第一光信号进行合路并输出至拉远单元；第一DEMUX用于将N路第二光信号分离，并将分离的第二光信号输出至第一光电转换模块。因为中心单元中设置了第一MUX和第一DEMUX，在中心单元向汇聚单元传输信号时，发送链路或接收链路可以通过一根光纤实现，中心单元和汇聚单元之间的通信链路较为简单。
在一种可能的设计中，中心单元还用于向第一电光转换模块输入光功率控制信号；第一电光转换模块还用于输出与光功率控制信号有关的光功率，光功率用于控制拉远单元中的放大器的放大倍数。
在一种可能的设计中，第一电光转换模块包括直接调制激光源，光功率控制信号为直流偏置电流；中心单元还用于向直接调制激光源输入直流偏置电流。因为本申请实施例中构建了较简单的拉远单元，拉远单元中可以不包括ADC模块、DAC模块和数字处理模块，因此，拉远单元可能无法通过自身的数控等实现对放大器的放大倍数的控制，因此，实际应用中，如果放大器的放大倍数需要调整，可以通过中心单元控制放大器的放大倍数。
在一种可能的设计中，第一电光转换模块包括间接调制器和激光源；光功率控制信号为直流偏置电流，中心单元还用于向激光源输入直流偏置电流；或，光功率控制信号为偏置电压，中心单元还用于向间接调制器输入偏置电压。
第二方面，本申请实施例提供一种拉远单元，包括：第二光电转换模块、第二电光转换模块和放大器。
其中，第二光电转换模块用于将接收自中心单元的第三光信号转换为第三模拟电信号；第三光信号为对模拟电信号转换得到的光信号；第三模拟电信号为零频信号、中频信号或射频信号；放大器用于放大第三模拟电信号；第二电光转换模块用于将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。本申请实施例中，拉远单元的结构较为简单，可以包括较少的模块，因此在小站系统中可以方便的设置拉远单元。
在一种可能的设计中，第二光电转换模块还用于将与光功率控制信号有关的光功率转换为直流电流；放大器还用于采用与直流电流有关的放大倍数放大第三模拟电信号。
在一种可能的设计中，拉远单元还包括上混频模块和下混频模块；上混频模块用于将第三模拟电信号转换为第三频点的电信号；放大器具体用于放大第三频点的电信号；下混频模块用于将第四模拟电信号转换为第四频点的电信号；第二电光转换模块具体用于将第四频点的电信号转换为第四光信号并输出至中心单元。
第三方面，本申请实施例提供一种小站系统，包括：如第一方面或第一方面的任一种可能的设计的中心单元，以及如第二方面或第二方面的任一种可能的设计的拉远单元。
在一种可能的设计中，小站系统还包括汇聚单元；中心单元和一个或多个拉远单元通过汇聚单元连接。
在一种可能的设计中，汇聚单元包括第二分复用器MUX和第二解复用器DEMUX；第二DEMUX用于将经中心单元的第一MUX合路的光信号分路，并将分路的光信号输出至一个或多个拉远单元；第二MUX用于将从一个或多个拉远单元接收的多路光信号合路，并将合路的光信号传输给中心单元的第一DEMUX。
在一种可能的设计中，小站系统还包括光纤传输链路；中心单元和一个或多个拉远单元通过光纤传输链路连接。
在一种可能的设计中，光纤传输链路包括一个或多个第三波分复用器MUX，和一个或多个第三解复用器DEMUX；任意一个第三DEMUX用于在经中心单元的第一MUX合路的光信号中，分离与任意一个第三DEMUX连接的拉远单元相关的目标光信号，并将目标光信号输出至与任意一个第三DEMUX连接的拉远单元；任意一个第三MUX用于将从与任意一个第三MUX连接的拉远单元接收的光信号合路，并将合路的光信号输出至中心单元的第一DEMUX。
第四方面，本申请实施例提供一种通信方法，应用于中心单元，包括：
将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号；将第一模拟电信号转换为第一光信号并输出至拉远单元；将接收自拉远单元的第二光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号；将第二模拟电信号转换为数字信号。
在一种可能的设计中，还包括：将第一模拟电信号转换为第一频点的电信号；将第一模拟电信号转换为第一光信号并输出至拉远单元包括：将第一频点的电信号转换为第一光信号并输出至拉远单元；将第二模拟电信号转换为第二频点的电信号；将第二模拟电信号转换为数字信号包括：将第二频点的模拟电信号转换为数字信号。
在一种可能的设计中，将第一模拟电信号转换为第一光信号并输出至拉远单元，包括：将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；将接收自拉远单元的第二光信号转换为第二模拟电信号包括：将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
在一种可能的设计中，将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元，包括：将M路第一光信号进行合路并输出至拉远单元；将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号，包括：将N路第二光信号分离，并将分离的第二光信号转换为N路第二模拟电信号。
在一种可能的设计中，还包括：向第一电光转换模块输入光功率控制信号；输出 与光功率控制信号有关的光功率，光功率用于控制拉远单元中的放大器的放大倍数。
在一种可能的设计中，第一电光转换模块包括直接调制激光源，光功率控制信号为直流偏置电流；向第一电光转换模块输入光功率控制信号，包括：向直接调制激光源输入直流偏置电流。
在一种可能的设计中，第一电光转换模块包括间接调制器和激光源；光功率控制信号为直流偏置电流，向第一电光转换模块输入光功率控制信号，包括：向激光源输入直流偏置电流；或，光功率控制信号为偏置电压，向第一电光转换模块输入光功率控制信号，包括：向间接调制器输入偏置电压。
第五方面，本申请实施例提供一种通信方法，应用于拉远单元，包括：将接收自中心单元的第三光信号转换为第三模拟电信号；第三光信号为对模拟电信号转换得到的光信号；第三模拟电信号为零频信号、中频信号或射频信号；放大第三模拟电信号；将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。
在一种可能的设计中，还包括：将与光功率控制信号有关的光功率转换为直流电流；放大第三模拟电信号包括：采用与直流电流有关的放大倍数放大第三模拟电信号。
在一种可能的设计中，还包括：将第三模拟电信号转换为第三频点的电信号；放大第三模拟电信号包括：放大第三频点的电信号；将第四模拟电信号转换为第四频点的电信号；将第四模拟电信号转换为第四光信号并输出至中心单元包括：将第四频点的电信号转换为第四光信号并输出至中心单元。
第六方面，本申请实施例提供一种通信方法，应用于小站系统，包括：中心单元将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号；中心单元将第一模拟电信号转换为第一光信号并输出至拉远单元；拉远单元将接收自中心单元的第一光信号转换为第三模拟电信号；第三模拟电信号为零频信号、中频信号或射频信号；拉远单元放大第三模拟电信号；拉远单元将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号；中心单元将接收自拉远单元的第四光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号；中心单元将第二模拟电信号转换为数字信号。
第七方面，本申请实施例提供一种中心单元，包括：数模转换DAC电路、模数转换ADC电路、第一电光转换电路和第一光电转换电路。
其中，DAC电路用于将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号；第一电光转换电路用于将第一模拟电信号转换为第一光信号并输出至拉远单元；第一光电转换电路用于将接收自拉远单元的第二光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号；ADC电路用于将第二模拟电信号转换为数字信号。本申请实施例中，将数模转换DAC电路和模数转换ADC电路设置在中心单元中，使得中心单元向拉远单元传输模拟的光信号，在中心单元向多个拉远单元传输该模拟的光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
在一种可能的设计中，中心单元还包括中射频电路；中射频电路用于将第一模拟电信号转换为第一频点的电信号；第一电光转换电路具体用于将第一频点的电信号转换为第一光信号并输出至拉远单元；和/或，用于将第二模拟电信号转换为第二频点的电信号；ADC电路具体用于将第二频点的模拟电信号转换为数字信号。第一频点的值较高时，电信号的谐波间隔较大容易滤除，信号质量较好。
在一种可能的设计中，第一电光转换电路具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；第一光电转换电路具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。这样，在中心单元向多个拉远单元传输该模拟的第一光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
在一种可能的设计中，中心单元还包括下列至少一种：第一波分复用器MUX，或第一解复用器DEMUX；第一MUX用于将M路第一光信号进行合路并输出至拉远单元；第一DEMUX用于将N路第二光信号分离，并将分离的第二光信号输出至第一光电转换电路。因为中心单元中设置了第一MUX和第一DEMUX，在中心单元向汇聚单元传输信号时，发送链路或接收链路可以通过一根光纤实现，中心单元和汇聚单元之间的通信链路较为简单。
在一种可能的设计中，中心单元还用于向第一电光转换电路输入光功率控制信号；第一电光转换电路还用于输出与光功率控制信号有关的光功率，光功率用于控制拉远单元中的放大器的放大倍数。
在一种可能的设计中，第一电光转换电路包括直接调制激光源，光功率控制信号为直流偏置电流；中心单元还用于向直接调制激光源输入直流偏置电流。因为本申请实施例中构建了较简单的拉远单元，拉远单元中可以不包括ADC电路、DAC电路和数字处理电路，因此，拉远单元可能无法通过自身的数控等实现对放大器的放大倍数的控制，因此，实际应用中，如果放大器的放大倍数需要调整，可以通过中心单元控制放大器的放大倍数。
在一种可能的设计中，第一电光转换电路包括间接调制器和激光源；光功率控制信号为直流偏置电流，中心单元还用于向激光源输入直流偏置电流；或，光功率控制信号为偏置电压，中心单元还用于向间接调制器输入偏置电压。
第八方面，本申请实施例提供一种拉远单元，包括：第二光电转换电路、第二电光转换电路和放大器。
其中，第二光电转换电路用于将接收自中心单元的第三光信号转换为第三模拟电信号；第三光信号为对模拟电信号转换得到的光信号；第三模拟电信号为零频信号、中频信号或射频信号；放大器用于放大第三模拟电信号；第二电光转换电路用于将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。本申请实施例中，拉远单元的结构较为简单，可以包括较少的电路，因此在小站系统中可以方便的设置拉远单元。
在一种可能的设计中，第二光电转换电路还用于将与光功率控制信号有关的光功 率转换为直流电流；放大器还用于采用与直流电流有关的放大倍数放大第三模拟电信号。
在一种可能的设计中，拉远单元还包括上混频电路和下混频电路；上混频电路用于将第三模拟电信号转换为第三频点的电信号；放大器具体用于放大第三频点的电信号；下混频电路用于将第四模拟电信号转换为第四频点的电信号；第二电光转换电路具体用于将第四频点的电信号转换为第四光信号并输出至中心单元。
第九方面，本申请实施例提供一种小站系统，包括：如第七方面或第七方面的任一种可能的设计的中心单元，以及如第八方面或第八方面的任一种可能的设计的拉远单元。
在一种可能的设计中，小站系统还包括汇聚单元；中心单元和一个或多个拉远单元通过汇聚单元连接。
在一种可能的设计中，汇聚单元包括第二分复用器MUX和第二解复用器DEMUX；第二DEMUX用于将经中心单元的第一MUX合路的光信号分路，并将分路的光信号输出至一个或多个拉远单元；第二MUX用于将从一个或多个拉远单元接收的多路光信号合路，并将合路的光信号传输给中心单元的第一DEMUX。
在一种可能的设计中，小站系统还包括光纤传输链路；中心单元和一个或多个拉远单元通过光纤传输链路连接。
在一种可能的设计中，光纤传输链路包括一个或多个第三波分复用器MUX，和一个或多个第三解复用器DEMUX；任意一个第三DEMUX用于在经中心单元的第一MUX合路的光信号中，分离与任意一个第三DEMUX连接的拉远单元相关的目标光信号，并将目标光信号输出至与任意一个第三DEMUX连接的拉远单元；任意一个第三MUX用于将从与任意一个第三MUX连接的拉远单元接收的光信号合路，并将合路的光信号输出至中心单元的第一DEMUX。
应当理解的是，本申请的第二方面至第九方面与本申请的第一方面的技术方案相对应，各方面及对应的可行实施方式所取得的有益效果相似，不再赘述。
附图说明
图1为现有的一种小站系统结构示意图；
图2为现有的另一种小站系统结构示意图；
图3为本申请实施例的一种中心单元结构示意图；
图4为本申请实施例的一种拉远单元结构示意图；
图5为本申请实施例的一种小站系统结构示意图；
图6为本申请实施例的一种电光转换模块结构示意图；
图7为本申请实施例的另一种电光转换模块结构示意图；
图8为本申请实施例的又一种电光转换模块结构示意图；
图9为本申请实施例的一种具体小站系统结构示意图；
图10为本申请实施例的另一种具体小站系统结构示意图；
图11为本申请实施例的又一种具体小站系统结构示意图；
图12为本申请实施例的再一种具体小站系统结构示意图；
图13为本申请实施例的一种通信方法的流程示意图；
图14为本申请实施例的另一种通信方法的流程示意图；
图15为本申请实施例的又一种通信方法的流程示意图。
具体实施方式
本申请实施例的方案可以应用在长期演进(long term evolution，LTE)中，也可以应用在第五代移动通信(5 Generation，5G)系统中，或者未来的移动通信系统。
其中，在本申请实施例的描述中，除非另有说明，“/”表示或的意思，例如，A/B可以表示A或B；本文中的“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。并且，在本申请实施例的描述中，除非另有说明，“多个”是指两个或多于两个。另外，为了便于清楚描述本申请的技术方案，在本申请的实施例中，采用了“第一”、“第二”等字样对功能和作用基本相同的相同项或相似项进行区分。本领域技术人员可以理解“第一”、“第二”等字样并不对数量和执行次序进行限定，并且“第一”、“第二”等字样也并不限定一定不同。
需要说明的是，本申请实施例中所描述的“模块”，可以是电路搭建的电路，或者可以是软件程序实现的功能模块，或者可以是电路与软件程序共同实现的模块，本申请实施例对此不作具体限定。
可以理解，各模块可以是集成模块，也可以是独立的模块，本申请实施例对此不作具体限定。
通常的，小站系统可以包括三个部分：中心单元、汇聚单元和拉远单元。中心单元与汇聚单元间距离可以为千米量级，汇聚单元与拉远单元间距离可以为百米量级，中心单元与汇聚单元间可以采用公共无线电接口(common public radio Interface，CPRI)在光纤上传输数字信号。汇聚单元与拉远单元间可以采用CPRI接口传输数字信号，或者可以在电缆传输中频模拟信号。
比如，传统的Lampsite系统和Qcell系统中，中心单元包括基带处理模块。汇聚单元包括接口协议数字处理单元模块。拉远单元包括数字处理模块，模拟数字转换器(analog to digital converter，ADC)及数字模拟转换器(digital to analog converter，DAC)，中射频模块，双工器和天线。
传统的Dot系统中，中心单元包括基带处理模块；汇聚单元包括接口协议数字处理单元部分、ADC及DAC、中射频模块。拉远单元包括中射频模块，双工器和天线。
可见，上述三种传统的小站系统中，Dot系统将Lampsite系统和Qcell系统中拉远单元的数字处理模块及ADC和DAC模块，下移至汇聚单元，减小了拉远单元的功能模块，增加了汇聚单元的功能模块。
但是，上述三种传统的小站系统中，具有共同的特点，即中心单元向拉远单元输出的是数字信号，由于数字信号传输中可能的重传或缓存等原因，在中心单元与多个拉远单元连接时，各拉远单元通常不同步，导致现有技术的小站系统难以实现分布式MIMO功能。
示例性的，图1示出了一种传统的Lampsite系统或Qcell系统。
在该小站系统中，中心单元包括基带处理模块；汇聚单元包括接口协议数字处理模块；拉远单元包括数字处理模块，ADC及DAC，中射频模块，双工器和天线。
发送链路中，中心单元的基带处理模块可以产生基带信号；基带信号流经过光纤CPRI接口传输至汇聚单元；汇聚单元的接口协议数字处理模块接收信号，并将信号经过光纤CPRI接口传输至拉远单元；拉远单元数字处理模块解调信号；解调后的信号经过DAC转换为模拟信号；模拟信号经过中射频模块转换至对应频点的射频信号；射频信号经过双工器及天线发射出去。
接收链路中，拉远单元天线接收信号；接收信号经过双工器至接收链路；接收信号经过中射频转换至对应频点的基带或中频信号；信号经ADC转换为数字信号；数字处理模块将数字信号经过光纤CPRI接口传输至汇聚单元；汇聚单元的接口协议数字处理模块接收信号，并将接收的信号经过光纤CPRI接口传输至中心单元；中心单元基带处理模块实现对信号的解调。
示例性的，图2示出了一种传统的Dot系统。
小站系统中心单元包括基带处理模块；汇聚单元包括接口协议数字处理模块，ADC及DAC，中射频模块；拉远单元包括中射频模块，双工器和天线。
发送链路中，中心单元的基带处理模块产生基带信号；基带信号流经过光纤CPRI接口传输至汇聚单元；汇聚单元的接口协议数字处理模块接收信号；信号经过DAC转换为模拟信号；模拟信号经过中频模块转换至对应频点的中频信号；中频信号经过电缆传输至拉远单元；拉远单元射频模块经信号转换至对应频点的射频信号；射频信号经过双工器及天线发射出去。
接收链路中，拉远单元天线接收信号；接收信号经过双工器至接收链路；接收信号经过射频模块转换至对应频点的中频信号；信号经电缆传输至汇聚单元；汇聚单元的中频模块将信号转换至对应频点的基带信号；信号经ADC转换为数字信号；汇聚单元的接口协议数字处理模块接收信号，并将信号经过光纤CPRI接口传输至中心单元；中心单元基带处理模块实现对信号的解调。
可见，如图1或图2所示的传统小站系统中，一方面，拉远单元及汇聚单元结构复杂，导致拉远单元及汇聚单元体积、重量和功耗等均较大，另一方面，中心单元向拉远单元传输的是数字信号，由于数字信号传输中可能的重传或缓存等原因，在中心单元与多个拉远单元连接时，各拉远单元通常不同步，导致现有技术的小站系统难以实现分布式MIMO功能。
基于此，本申请实施例提供的小站系统，将DAC模块和ADC模块设置在中心单元中，使得中心单元向拉远单元传输模拟的光信号，在中心单元向多个拉远单元传输该模拟的光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
可以理解，因为本申请实施例中，将DAC模块和ADC模块下移中心单元中，使得小站系统中可以设置非常简单的拉远单元，以及可选的设置非常简单的汇聚单元，使得拉远单元和汇聚单元的体积、重量和功耗等均可以较小，可以进一步改善拉远单元和汇聚单元的性能。
本申请实施例所涉及的小站系统，具体应用中，可以沿用原有的小站系统的命名，例如可以定义为Lampsite系统、Qcell系统或Dot系统。可以理解，本申请实施例的 小站系统还可以采用其他方式适应性命名，例如命名为A系统、B系统等，本申请实施例对此不作具体限定。
以本申请实施例的小站系统对应于传统Lampsite系统为例，本申请实施例的中心单元可以对应Lampsite系统的基带处理模块(building base band unit，BBU)部分，汇聚单元可以对应Lampsite系统的室内型设备(radio hub，RHub)部分，拉远单元可以对应Lampsite系统的室内型射频拉远单元(pico remote radio unit，pRRU)部分。
下面以具体地实施例对本申请的技术方案以及本申请的技术方案如何解决上述技术问题进行详细说明。下面这几个具体的实施例可以独立实现，也可以相互结合，对于相同或相似的概念或过程可能在某些实施例中不再赘述。
图3为本申请实施例提供的一种中心单元300的结构示意图。如图3所示，中心单元300包括：数模转换DAC模块31、模数转换ADC模块34、第一电光转换模块32和第一光电转换模块33。
其中，DAC模块31用于将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号。第一电光转换模块32用于将第一模拟电信号转换为第一光信号并输出至拉远单元。第一光电转换模块33用于将接收自拉远单元的第二光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号。ADC模块34用于将第二模拟电信号转换为数字信号。
本申请实施例中，基带信号可以是中心单元300产生的，也可以是在中心单元从其他设备接收的。示例性的，中心单元300中还可以包括基带处理模块，基带处理模块可以产生基带信号。
基带信号可以为数字信号，基带信号的具体内容可以依据应用场景的不同而不同，本申请实施例对基带信号不作具体限定。
在中心单元的发送链路中，基带信号可以作为DAC模块31的输入，DAC模块31对基带信号进行模数转换后，可以输出第一模拟电信号。第一模拟电信号可以零频信号、中频信号或射频信号，本申请实施例对此不作具体限定。
第一模拟电信号可以作为第一电光转换模块32的输入，第一电光转换模块32可以是用于转换模拟信号的电光转换模块，第一电光转换模块对第一模拟电信号转换后，可以输出第一光信号至拉远单元。
可以理解，在实际应用中，第一电光转换模块32的输出端可以通过光纤或汇聚单元等与拉远单元实现通信，则第一光信号可以通过光纤或汇聚单元传输至拉远单元。后续的实施例中将详细说明第一光信号输出至拉远单元的过程，在此不再赘述。
需要说明的是，本申请实施例中第一光信号可以输出至一个或多个拉远单元，即拉远单元的数量可以根据实际的应用场景确定，本申请实施例对此不作具体限定。
且，因为第一电光转换模块32输出的是模拟电信号转换的光信号，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
在中心单元的接收链路中，第一光电转换模块33可以从拉远单元接收第二光信号。示例性的，拉远单元可以通过天线等从终端设备中接收终端设备发送的信号，进而将 该终端设备发送的信号转换为第二光信号，并通过光纤或汇聚单元传输至中心单元300的第一光电转换模块33。
第一光电转换模块33将第二光信号转换后，输出第二模拟电信号。第二模拟电信号可以为零频信号、中频信号或射频信号，本申请实施例对此不作具体限定。
第二模拟电信号可以作为ADC模块34的输入，ADC模块34将第二模拟信号进行光电转换后，可以得到输出数字信号，中心单元进而可以根据实际需求适应的处理该数字信号，本申请实施例对此不作具体限定。
综上所述，现有技术的小站系统中，中心单元向拉远单元传输的是数字信号，由于数字信号传输中可能的重传或缓存等原因，在中心单元与多个拉远单元连接时，各拉远单元通常不同步，导致现有技术的小站系统难以实现MIMO功能。本申请实施例的小站系统中，将数模转换DAC模块和模数转换ADC模块设置在中心单元中，使得中心单元向拉远单元传输模拟的光信号，在中心单元向多个拉远单元传输该模拟的光信号时，由于模拟传输中模拟器件的处理时延通常为纳秒级别，且与路径传输时延构成的总时延波动较小甚至固定，因此可以较为容易的在中心单元通过校准实现多个拉远单元的同步，从而为较为容易的实现分布式MIMO功能提供了可能。
图4为本申请实施例提供的一种拉远单元400的结构示意图。如图4所示，拉远单元400包括：第二光电转换模块41、第二电光转换模块43和放大器42。
其中，第二光电转换模块41用于将接收自中心单元的第三光信号转换为第三模拟电信号；第三光信号为对模拟电信号转换得到的光信号；第三模拟电信号为零频信号、中频信号或射频信号。放大器42用于放大第三模拟电信号。第二电光转换模块43用于将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。
本申请实施例中，拉远单元400可以从中心单元接收第三光信号。示例性的，第三光信号可以是通过如图3的实施例的第一电光转换模块输出的，在此不再赘述。
第二光电转换模块41将第三光信号进行光电转换后，输出第三模拟电信号。第三模拟电信号为零频信号、中频信号或射频信号，本申请实施例对此不作具体限定。
第三模拟电信号可以作为放大器(也可以成为功率放大器(power amplifier，PA))42的输入，放大器42可以放大第三模拟电信号，放大器42的放大倍数可以为固定值，也可以是可调的，进而可以根据实际的需求灵活调整，本申请实施例对此不作具体限定。
需要说明的是，因为本申请实施例中构建了较简单的拉远单元，拉远单元中可以不包括ADC模块、DAC模块和数字处理模块，因此，拉远单元可能无法通过自身的数控等实现对放大器42的放大倍数的控制，因此，实际应用中，如果放大器42的放大倍数需要调整，可以通过中心单元控制放大器42的放大倍数，后续实施例中将详细说明，在此不再赘述。
可选的，经放大器42放大后的模拟电信号可以进一步通过天线等进行发射，本申请实施例对此不作具体限定。
第四模拟电信号可以是拉远单元500通过天线等接收的模拟电信号。第四模拟电信号可以为零频信号、中频信号或射频信号，本申请实施例对此不作具体限定。
第四模拟电信号可以作为第二电光转换模块43的输入，第二电光转换模块43将第四模拟电信号进行电光转换后，输出第四光信号，进一步的第四光信号可以通过光纤或汇聚单元等传输至中心单元，后续实施例将详细说明第四光信号输出至中心单元的具体实现，在此不再赘述。
本申请实施例中，拉远单元的结构较为简单，可以包括较少的模块，因此在小站系统中可以方便的设置拉远单元。
图5为本申请实施例提供的一种小站系统的结构示意图。如图5所示，小站系统包括：中心单元510和拉远单元520。
其中，中心单元510中DAC模块511、ADC模块514、第一电光转换模块512和第一光电转换模块513可以参照图3对应的实施例的描述，拉远单元520中的第二光电转换模块521、第二电光转换模块523和放大器522可以参照图4对应的实施例的描述，在此不再赘述。
可选的，中心单元510和拉远单元520可以通过光纤传输链路连接，即本申请实施例的小站系统500可以不包括汇聚单元，从而可以减少小站系统中的设备类型。
或者，中心单元510和拉远单元520可以通过汇聚单元530连接，以通过距离拉远单元较近的汇聚单元530实现方便的拉远单元接入等。示例性的，可以在中心单元510和汇聚单元530之间设置100根光纤，实际应用中，可能只存在30个拉远单元，则汇聚单元中在连接该30个拉远单元后，汇聚单元中存在70根光纤的预留，则在后续需要增加拉远单元时，可以在汇聚单元中适应接入，不需要对中心单元510进行调整。
可选的，如图5所示，中心单元还包括中射频模块515。
中射频模块515用于将第一模拟电信号转换为第一频点的电信号；第一电光转换模块512具体用于将第一频点的电信号转换为第一光信号并输出至拉远单元。
本申请实施例中，中射频模块515可以将发送链路中的第一模拟电信号转换为第一频点的电信号。示例性的，第一频点可以包括2.4GHz、3GHz或5GHz等。
可以理解，第一频点可以根据实际的应用场景确定，示例性的，第一频点的值较高时，电信号的谐波间隔较大容易滤除，信号质量较好，但第一频点的值较高时，对第一电光转换模块512的性能要求较高，会增加第一电光转换模块512的成本。第一频点的值较低时，对第一电光转换模块512的性能要求较低，不会增加第一电光转换模块512的成本，但是电信号的谐波间隔较小容易产生干扰，信号质量较差。
在接收链路中，中射频模块515可以将第二模拟电信号转换为第二频点的电信号；ADC模块514具体用于将第二频点的模拟电信号转换为数字信号。
本申请实施例中，第二频点可以与第一频点相同，也可以与第一频点不同。第二频点的具体值可以根据ADC模块514的性能等适应设定，本申请实施例对此不作具体限定。
可选的，拉远单元520还包括上混频模块524和下混频模块525。
本申请实施例中，在小站系统的发送链路中，上混频模块524可以用于将第三模拟电信号转换为第三频点的电信号；放大器522具体用于放大第三频点的电信号。
本申请实施例中，第三频点可以根据拉远单元发送电信号时实际需求的频点适应 设定，本申请实施例对此不作具体限定。
下混频模块525用于将第四模拟电信号转换为第四频点的电信号；第二电光转换模块523具体用于将第四频点的电信号转换为第四光信号并输出至中心单元。示例性的，第四频点可以包括2.4GHz、3GHz或5GHz等。
可以理解，第四频点可以根据实际的应用场景确定，示例性的，第四频点的值较高时，电信号的谐波间隔较大容易滤除，信号质量较好，但第四频点的值较高时，对第二电光转换模块523的性能要求较高，会增加第二电光转换模块523的成本。第四频点的值较低时，对第二电光转换模块523的性能要求较低，不会增加第二电光转换模块523的成本，但是电信号的谐波间隔较小容易产生干扰，信号质量较差。
第三频点与第四频点的值可以相同，也可以不同，本申请实施例对此不作具体限定。
需要说明的是，本申请实施例中，小站系统中，中射频模块515、上混频模块524和下混频模块525都可以根据实际的应用场景适应设置或不设置，本申请实施例对此不作具体限定。
示例性的，一种场景中，中心单元中无中射频模块，拉远单元中有上混频模块；如中心单元的DAC输出频率范围为0.20-0.22GHz，拉远单元的上混频模块将信号变频至2.4-2.42GHz。另一种场景中，中心单元有中射频模块，拉远单元中无上混频模块；如中心单元的DAC输出频率范围为0.20-0.22GHz，中心单元的中射频模块将信号变频至2.4-2.42GHz。又一种场景中，中心单元有中射频模块，拉远单元有上混频模块；如中心单元的DAC输出频率范围为0.20-0.22GHz，中心单元的中射频模块将信号变频至1.4-1.42GHz，拉远单元的上混频模块将信号变频至2.4-2.42GHz。
可选的，中心单元还用于向第一电光转换模块512输入光功率控制信号。第一电光转换模块512还用于输出与光功率控制信号有关的光功率，光功率用于控制拉远单元中的放大器的放大倍数。
本申请实施例中，中心单元可以通过控制第一电光转换模块512的输出光功率，改变拉远单元的第二光电转换模块521的输出直流，进而利用直流控制拉远单元中PA的放大倍数。
本申请实施例中，因为可以构建不包含数字处理模块的拉远单元，因此拉远单元可能无法实现对PA的放大倍数的控制，则可以基于中心单元输出的光功率控制信号实现对拉远单元中的放大器的控制。示例性的，光功率控制信号可以由中心单元中的基带处理模块产生。
示例性的，如图6所示，第一电光转换模块512包括直接调制激光源5121，光功率控制信号为直流偏置电流；中心单元还用于向直接调制激光源输入直流偏置电流。
本申请实施例中，第一电光转换模块采用直接调制激光器的方式。光功率控制信号为调整直接调制激光源的直流偏置电流，基于直流偏置电流可以调整第一电光转换模块的输出光功率。
示例性的，如图7所示，第一电光转换模块512包括间接调制器5122和激光源5123。光功率控制信号为直流偏置电流，中心单元还用于向激光源输入直流偏置电流；
本申请实施例中，第一电光转换模块采用激光源与间接调制器的方式。光功率控 制信号为激光源的直流偏置电流，基于直流偏置电流可以调整第一电光转换模块的输出光功率，进而实现调整间接调制器的输出光功率。
示例性的，如图8所示，第一电光转换模块512包括间接调制器5124和激光源5125。光功率控制信号为偏置电压，中心单元还用于向间接调制器输入偏置电压。
本申请实施例中，第一电光转换模块采用激光源与间接调制器的方式。光功率控制信号为调整间接调制器的偏置电压，基于偏置电压可以调整第一电光转换模块的输出光功率。
适应的，拉远单元中，第二光电转换模块521还用于将与光功率控制信号有关的光功率转换为直流电流；放大器522还用于采用与直流电流有关的放大倍数放大第三模拟电信号。
可以理解，实际应用中，还可以在中心单元510与拉远单元520中建立数字信号传输链路，该传输链路可以用于传输控制放大器522的放大倍数的数字信号，从而实现对拉远单元中放大器的放大倍数的控制，本申请实施例对此不作具体限定。
以图5所示的包含可选的模块的小站系统为例，在该小站系统中，信号处理过程可以为：
发送链路中：
中心单元内，基带处理模块产生基带信号。基带信号经过DAC模块，转为模拟电信号。模拟电信号经过可选的中射频模块转换为零频、中频或者射频电信号。中频或者射频电信号经过第一电光转换模块转换至光域，得到光信号。
光信号经过光纤传输，经过可选的汇聚单元，传输至拉远单元。
拉远单元内，第二光电转换模块将光信号转换为模拟电信号。模拟电信号经过可选的上混频器模块变频至指定频点。
拉远单元内，模拟电信号经过PA进行放大，放大后的信号经过双工器和天线进行发射。
可选的，中心单元内，基带处理模块发送光功率控制信号，控制第一电光转换模块的输出光功率，适应的，拉远单元内，第二光电转换模块的直流输出，用来控制PA的放大倍数。
接收链路中：
拉远单元内，天线接收模拟电信号。模拟电信号经过双工器进入接收链路。模拟电信号经过可选的下混频器模块至指定频点；模拟电信号经过第二电光转换模块转换至光域，得到光信号。
光信号经过光纤传输，经过可选的汇聚单元，传输至中心单元。
中心单元内，第一光电转换模块将光信号转换为模拟电信号。模拟电信号经过可选的中射频模块变换至指定频点。模拟电信号经过ADC模块，转换为数字信号。数字信号由基带处理模块进行解调。
可选的，小站系统中可以包括多个拉远单元。示例性的，图9至图12示出了小站系统中包括多个拉远单元的四种示例性结构示意图。
需要说明的是，在实际应用中，中心单元中的基带处理模块可能称为基带处理单元，本申请实施例对此不作具体限定。
可选的，图9示出了本申请实施例的一种具体的小站系统的结构示意图。
如图9所示，小站系统中，包括中心单元、汇聚单元和M个拉远单元。
第一电光转换模块具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数。第一光电转换模块具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
本申请实施例中，第一电光转换模块可以是M个独立的电光转换模块，也可以是M个电光转换模块集成为一体的模块，还可以是M个电光转换模块即成为K个模块，如M为100，100个电光转换模块中，每4个集成到一起，则K＝25，M和K的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
本申请实施例中，第一光电转换模块可以是N个独立的光电转换模块，也可以是N个光电转换模块集成为一体的模块，还可以是N个电光转换模块即成为L个模块，如N为100，100个电光转换模块中，每4个集成到一起，则L＝25，N和L的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
需要说明的是，M和N可以相同也可以不同，图9中以M和N相同进行示例，并不限定M和N的取值。
可选的，中心单元还包括第一波分复用器(multiplexer，MUX)，第一MUX用于将M路第一光信号进行合路并输出至拉远单元。
可选的，中心单元还包括第一解复用器(demultiplexer，DEMUX)，第一DEMUX用于将N路第二光信号分离，并将分离的第二光信号输出至第一光电转换模块。
可选的，汇聚单元包括第二分复用器MUX和第二解复用器DEMUX；第二DEMUX用于将经中心单元的第一MUX合路的光信号分路，并将分路的光信号输出至一个或多个拉远单元。
本申请实施例中，因为中心单元中设置了第一MUX和第一DEMUX，汇聚单元中设置了第二MUX和第二DEMUX，因此，在中心单元向汇聚单元传输信号时，发送链路或接收链路可以通过一根光纤实现，中心单元和汇聚单元之间的通信链路较为简单。
以图9所示的小站系统为例，在该小站系统中，信号的处理过程可以为：
发送链路中：
中心单元内，基带处理模块产生M路基带信号。M路基带信号经过DAC模块，转为M路模拟电信号。M路模拟电信号经过可选的中射频模块转换为零频、中频或者射频电信号。M路零频、中频或者射频电信号经过电光转换模块11、电光转换模块12……和电光转换模块1M，转换至不同波长的光域信号。M路光域信号经过MUX进行合路。合路后的光域信号经过光纤传输至汇聚单元。
汇聚单元内，DEMUX将不同波长的光域信号分离成M路。分离后的M路光域信号，分别进入拉远单元1、拉远单元2……拉远单元M。
每个拉远单元内，光电转换模块将接收的光域信号转换为模拟电信号。模拟电信号经过可选的上混频器模块变频至指定频点。模拟电信号经过PA进行放大。放大后的信号经过双工器和天线进行发射。
可选的，中心单元内，基带处理模块发送M个光功率控制信号，M个光功率控制 信号分别控制电光转换模块11、电光转换模块12……和电光转换模块1M的输出光功率，每个拉远单元内，光电转换模块基于光功率控制信号的直流输出，控制PA的放大倍数。
接收链路中：
每个拉远单元内，天线接收模拟电信号。模拟电信号经过双工器进入接收链路。模拟电信号经过可选的下混频器模块变频至指定频点。模拟电信号经过电光转换模块转换为光域信号。光域信号经过光纤传输至汇聚单元。
汇聚单元内，M路光域信号经过MUX进行合路。合路后的光域信号经过光纤到达中心单元。
中心单元内，DEMUX将不同波长的光域信号分离成M路。光电转换模块21、光电转换模块22……和光电转换模块将光信号转换为模拟电信号；模拟电信号经过可选的中射频模块变换至指定频点；模拟电信号经过ADC模块，转换为数字信号。数字信号由基带处理模块进行解调。
本申请实施例中，可以支持MIMO功能。示例性的，例如发送链路中，模拟电信号包括0.4-0.6GHz及0.8-1GHz，可以将0.4-0.6GHz信号转换为2.4GHz且传输至4根天线，将0.8-1GHz信号转换为3.5GHz且传输至2根天线；从而实现MIMO功能。
需要说明的是，在本申请实施例中，由于采用了波分复用器，因此，中心单元中的各电光转换模块的波长需要不同，从而实现合路后的信号能够正确的分路。
可选的，图10示出了本申请实施例的另一种具体的小站系统的结构示意图。
如图10所示，小站系统中，包括中心单元、汇聚单元和M个拉远单元。
第一电光转换模块具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数。第一光电转换模块具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
本申请实施例中，第一电光转换模块可以是M个独立的电光转换模块，也可以是M个电光转换模块集成为一体的模块，还可以是M个电光转换模块即成为K个模块，如M为100，100个电光转换模块中，每4个集成到一起，则K＝25，M和K的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
本申请实施例中，第一光电转换模块可以是N个独立的光电转换模块，也可以是N个光电转换模块集成为一体的模块，还可以是N个电光转换模块即成为L个模块，如N为100，100个电光转换模块中，每4个集成到一起，则L＝25，N和L的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
需要说明的是，M和N可以相同也可以不同，图10中以M和N相同进行示例，并不限定M和N的取值。
本申请实施例中，中心单元的电光转换模块与拉远单元之间基于光纤连接，因此，M个电光转换模块可以存在输出波长相同的电光转换模块，对电光转换模块性能的要求较低，从而可以降低设置不同波长电光转换模块带来的成本开销。
可选的，光纤可以是多芯光纤或光缆等，具体的，多芯光纤指同一根光纤内有多个纤芯；光缆指将多根光纤组合成光缆，从而可以降低线路布置的复杂性。
N个光电转换模块可以存在输出波长相同的光电转换模块，对光电转换模块性能 的要求较低，从而可以降低设置不同波长光电转换模块带来的成本开销。
以图10所示的小站系统为例，在该小站系统中，信号的处理过程可以为：
发送链路中：
中心单元内，基带处理模块产生M路基带信号。M路基带信号经过DAC模块，转为M路模拟电信号。M路模拟电信号经过可选的中射频模块转换为零频、中频或者射频电信号。M路零频、中频或者射频电信号经过电光转换模块11、电光转换模块12……和电光转换模块1M，转换为光域信号。M路光域信号经过光纤传输至汇聚单元。
汇聚单元内，分离出M根光纤，即M路光域信号，M路光域信号分别进入拉远单元1、拉远单元2……和拉远单元M。
每个拉远单元内，光电转换模将接收的光域信号转换为模拟电信号。模拟电信号经过可选的上混频器模块变频至指定频点。模拟电信号经过PA进行放大。放大后的信号经过双工器和天线进行发射。
可选的，中心单元内，基带处理模块发送M个光功率控制信号，M个光功率控制信号分别控制电光转换模块11、电光转换模块12……和电光转换模块1M的输出光功率，每个拉远单元内，光电转换模块基于光功率控制信号的直流输出，控制PA的放大倍数。
接收链路中：
每个拉远单元内，天线接收模拟电信号。模拟电信号经过双工器进入接收链路。模拟电信号经过可选的下混频器模块变频至指定频点。模拟电信号经过电光转换模块转换为光域信号。光域信号经过光纤传输至汇聚单元。
汇聚单元内，M路光域信号经过光纤到达中心单元。
中心单元内分离出M路光信号。光电转换模块21、光电转换模块22……和光电转换模块2M将光信号转换为模拟电信号；模拟电信号经过可选的中射频模块变换至指定频点；模拟电信号经过ADC模块，转换为数字信号。数字信号由基带处理模块进行解调。
本申请实施例中，可以支持MIMO功能。示例性的，例如发送链路中，模拟电信号包括0.4-0.6GHz及0.8-1GHz，可以将0.4-0.6GHz信号转换为2.4GHz且传输至4根天线，将0.8-1GHz信号转换为3.5GHz且传输至2根天线；从而实现MIMO功能。
可选的，图11示出了本申请实施例的又一种具体的小站系统的结构示意图。
如图11所示，小站系统中，包括中心单元和M个拉远单元。
第一电光转换模块具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数。第一光电转换模块具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
本申请实施例中，第一电光转换模块可以是M个独立的电光转换模块，也可以是M个电光转换模块集成为一体的模块，还可以是M个电光转换模块即成为K个模块，如M为100，100个电光转换模块中，每4个集成到一起，则K＝25，M和K的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
本申请实施例中，第一光电转换模块可以是N个独立的光电转换模块，也可以是 N个光电转换模块集成为一体的模块，还可以是N个电光转换模块即成为L个模块，如N为100，100个电光转换模块中，每4个集成到一起，则L＝25，N和L的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
需要说明的是，M和N可以相同也可以不同，图11中以M和N相同进行示例，并不限定M和N的取值。
中心单元和M个拉远单元通过光纤传输链路连接。
可选的，中心单元还包括第一波分复用器MUX，第一MUX用于将M路第一光信号进行合路并输出至拉远单元。
可选的，中心单元还包括第一解复用器DEMUX，第一DEMUX用于将N路第二光信号分离，并将分离的第二光信号输出至第一光电转换模块。
可选的，光纤传输链路包括M个第三波分复用器MUX和M个第三解复用器DEMUX；任意一个第三DEMUX用于在经中心单元的第一MUX合路的光信号中，分离与任意一个第三DEMUX连接的拉远单元相关的目标光信号，并将目标光信号输出至与任意一个第三DEMUX连接的拉远单元；任意一个第三MUX用于将从与任意一个第三MUX连接的拉远单元接收的光信号合路，并将合路的光信号输出至中心单元的第一DEMUX。
本申请实施例中，因为中心单元中设置了第一MUX和第一DEMUX，光纤传输链路中设置了M个第三MUX和M个第三DEMUX，因此，在中心单元向拉远单元传输信号时，发送链路或接收链路可以通过一根光纤实现，中心单元和拉远单元之间的通信链路较为简单。
以图11所示的小站系统为例，在该小站系统中，信号的处理过程可以为：
发送链路中：
中心单元内，基带处理模块产生M路基带信号。M路基带信号经过DAC模块，转为M路模拟电信号。M路模拟电信号经过可选的中射频模块转换为零频、中频或者射频电信号。M路零频、中频或者射频电信号经过电光转换模块11、电光转换模块12……和电光转换模块1M，转换至不同波长的光域信号。M路光域信号经过MUX进行合路。合路后的光域信号经过光纤传输。
光纤传输链路中，每个DEMUX模块分离对应拉远单元的波长的光域信号。依次分离的光域信号，分别进入拉远单元1、拉远单元2……拉远单元M。
每个拉远单元内，光电转换模将接收的光域信号转换为模拟电信号。模拟电信号经过可选的上混频器模块变频至指定频点。模拟电信号经过PA进行放大。放大后的信号经过双工器和天线进行发射。
可选的，中心单元内，基带处理模块发送M个光功率控制信号，M个光功率控制信号分别控制电光转换模块11、电光转换模块12……和电光转换模块1M的输出光功率，每个拉远单元内，光电转换模块基于光功率控制信号的直流输出，控制PA的放大倍数。
接收链路中：
每个拉远单元内，天线接收模拟电信号。模拟电信号经过双工器进入接收链路。模拟电信号经过可选的下混频器模块变频至指定频点。模拟电信号经过电光转换模块 转换为光域信号。
光纤传输链路中，不同波长的光域信号依次经过对应的MUX进行合路。合路后的光域信号经过光纤到达中心单元。
中心单元内，DEMUX将不同波长的光域信号分离成M路。光电转换模块21、光电转换模块22……和光电转换模块2M将光信号转换为模拟电信号；模拟电信号经过可选的中射频模块变频至指定频点；模拟电信号经过ADC模块，转换为数字信号。数字信号由基带处理模块进行解调。
本申请实施例中，可以支持MIMO功能。示例性的，例如发送链路中，模拟电信号包括0.4-0.6GHz及0.8-1GHz，可以将0.4-0.6GHz信号转换为2.4GHz且传输至4根天线，将0.8-1GHz信号转换为3.5GHz且传输至2根天线；从而实现MIMO功能。
可选的，图12示出了本申请实施例的另一种具体的小站系统的结构示意图。
如图12所示，小站系统中，包括中心单元和M个拉远单元。
第一电光转换模块具体用于将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数。第一光电转换模块具体用于将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
本申请实施例中，第一电光转换模块可以是M个独立的电光转换模块，也可以是M个电光转换模块集成为一体的模块，还可以是M个电光转换模块即成为K个模块，如M为100，100个电光转换模块中，每4个集成到一起，则K＝25，M和K的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
本申请实施例中，第一光电转换模块可以是N个独立的光电转换模块，也可以是N个光电转换模块集成为一体的模块，还可以是N个电光转换模块即成为L个模块，如N为100，100个电光转换模块中，每4个集成到一起，则L＝25，N和L的具体值可以根据实际的应用场景设定，本申请实施例对此不作具体限定。
需要说明的是，M和N可以相同也可以不同，图12中以M和N相同进行示例，并不限定M和N的取值。
本申请实施例中，中心单元的电光转换模块与拉远单元之间基于光纤连接，因此，M个电光转换模块可以存在输出波长相同的电光转换模块，对电光转换模块性能的要求较低，从而可以降低设置不同波长电光转换模块带来的成本开销。
可选的，光纤可以是多芯光纤或光缆等，具体的，多芯光纤指同一根光纤内有多个纤芯；光缆指将多根光纤组合成光缆，从而可以降低线路布置的复杂性。
N个光电转换模块可以存在输出波长相同的光电转换模块，对光电转换模块性能的要求较低，从而可以降低设置不同波长光电转换模块带来的成本开销。
以图12所示的小站系统为例，在该小站系统中，信号的处理过程可以为：
发送链路中：
中心单元内，基带处理模块产生M路基带信号。M路基带信号经过DAC模块，转为M路模拟电信号。M路模拟电信号经过可选的中射频模块转换为零频、中频或者射频电信号。M路零频、中频或者射频电信号经过电光转换模块11、电光转换模块12……和电光转换模块1M，转换为光域信号。M路光域信号经过光纤传输链路传输。
光纤传输链路中，依次分离出M根光纤，即M路光域信号，M路光域信号分别 进入拉远单元1、拉远单元2……拉远单元M。
每个拉远单元内，光电转换模将接收的光域信号转换为模拟电信号。模拟电信号经过可选的上混频器模块变频至指定频点。模拟电信号经过PA进行放大。放大后的信号经过双工器和天线进行发射。
可选的，中心单元内，基带处理模块发送M个光功率控制信号，M个光功率控制信号分别控制电光转换模块11、电光转换模块12……和电光转换模块1M的输出光功率，每个拉远单元内，光电转换模块基于光功率控制信号的直流输出，控制PA的放大倍数。
接收链路中：
每个拉远单元内，天线接收模拟电信号。模拟电信号经过双工器进入接收链路。模拟电信号经过可选的下混频器模块至指定频点。模拟电信号经过电光转换模块转换为光域信号。光域信号经过光纤传输链路传输。
光纤传输链路中，M路光域信号经过光纤到达中心单元。
中心单元内分离出M路光信号。光电转换模块21、光电转换模块22……和光电转换模块2M将光信号转换为模拟电信号；模拟电信号经过可选的中射频模块变换至指定频点；模拟电信号经过ADC模块，转换为数字信号。数字信号由基带处理模块进行解调。
本申请实施例中，可以支持MIMO功能。示例性的，例如发送链路中，模拟电信号包括0.4-0.6GHz及0.8-1GHz，可以将0.4-0.6GHz信号转换为2.4GHz且传输至4根天线，将0.8-1GHz信号转换为3.5GHz且传输至2根天线；从而实现MIMO功能。
需要说明的是，图9至图12中的各实施例既可以独立使用，也可以交叉复用，本申请对此不作具体限定。
图9至图12中的各实施例中，基带信号与拉远单元之间没有一一对应的关联关系，示例性的，多路基带信号可能输入一个拉远单元中，则基带信号的数量大于拉远单元的数量，本申请实施例对此不作具体限定。
需要说明的是，本申请的上述实施例可以应用于宏站的分布式MIMO系统中，或者其他系统中。使得一个中心单元，连接多个拉远单元，多个拉远单元构成分布式MIMO系统。
图13示出了一种通信方法的流程示意图，如图13所示，应用于上述任一实施例的中心单元，该方法包括：
S1301：将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号。
S13902：将第一模拟电信号转换为第一光信号并输出至拉远单元。
S1303：将接收自拉远单元的第二光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号。
S1304：将第二模拟电信号转换为数字信号。
在一种可能的设计中，还包括：将第一模拟电信号转换为第一频点的电信号；将第一模拟电信号转换为第一光信号并输出至拉远单元包括：将第一频点的电信号转换 为第一光信号并输出至拉远单元；将第二模拟电信号转换为第二频点的电信号；将第二模拟电信号转换为数字信号包括：将第二频点的模拟电信号转换为数字信号。
在一种可能的设计中，将第一模拟电信号转换为第一光信号并输出至拉远单元，包括：将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；将接收自拉远单元的第二光信号转换为第二模拟电信号包括：将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
在一种可能的设计中，将M路第一模拟电信号转换为M路第一光信号并输出至拉远单元，包括：将M路第一光信号进行合路并输出至拉远单元；将接收自拉远单元的N路第二光信号转换为N路第二模拟电信号，包括：将N路第二光信号分离，并将分离的第二光信号转换为N路第二模拟电信号。
在一种可能的设计中，还包括：向第一电光转换模块输入光功率控制信号；输出与光功率控制信号有关的光功率，光功率用于控制拉远单元中的放大器的放大倍数。
在一种可能的设计中，第一电光转换模块包括直接调制激光源，光功率控制信号为直流偏置电流；向第一电光转换模块输入光功率控制信号，包括：向直接调制激光源输入直流偏置电流。
在一种可能的设计中，第一电光转换模块包括间接调制器和激光源；光功率控制信号为直流偏置电流，向第一电光转换模块输入光功率控制信号，包括：向激光源输入直流偏置电流；或，光功率控制信号为偏置电压，向第一电光转换模块输入光功率控制信号，包括：向间接调制器输入偏置电压。
本申请实施例中，执行中心单元侧方法的执行主体可以是中心单元，也可以是中心单元中的装置(需要说明的是，在本申请提供的实施例中以中心单元为例进行描述的)。示例性地，中心单元中的装置可以是芯片系统、电路或者模块等，本申请不作限制。
本实施例的方法对应地可用于执行上述装置实施例中中心单元执行的步骤，其实现原理和技术效果类似，此处不再赘述。
图14示出了一种通信方法的流程示意图，如图14所示，应用于上述任一实施例的拉远单元，该方法包括：
S1401：将接收自中心单元的第三光信号转换为第三模拟电信号；第三光信号为对模拟电信号转换得到的光信号；第三模拟电信号为零频信号、中频信号或射频信号。
S1402：放大第三模拟电信号。
S1403：将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。
在一种可能的设计中，还包括：将与光功率控制信号有关的光功率转换为直流电流；放大第三模拟电信号包括：采用与直流电流有关的放大倍数放大第三模拟电信号。
在一种可能的设计中，还包括：将第三模拟电信号转换为第三频点的电信号；放大第三模拟电信号包括：放大第三频点的电信号；将第四模拟电信号转换为第四频点的电信号；将第四模拟电信号转换为第四光信号并输出至中心单元包括：将第四频点的电信号转换为第四光信号并输出至中心单元。
本申请实施例中，执行中心单元侧方法的执行主体可以是拉远单元，也可以是拉 远单元中的装置(需要说明的是，在本申请提供的实施例中以拉远单元为例进行描述的)。示例性地，拉远单元中的装置可以是芯片系统、电路或者模块等，本申请不作限制。
本实施例的方法对应地可用于执行上述装置实施例中拉远单元执行的步骤，其实现原理和技术效果类似，此处不再赘述。
图15示出了一种通信方法的流程示意图，如图15所示，应用于上述任一实施例的小站系统，该方法包括：
S1501：中心单元将基带信号转换为第一模拟电信号；第一模拟电信号为零频信号、中频信号或射频信号。
S1502：中心单元将第一模拟电信号转换为第一光信号并输出至拉远单元。
S1503：拉远单元将接收自中心单元的第一光信号转换为第三模拟电信号；第三模拟电信号为零频信号、中频信号或射频信号。
S1504：拉远单元放大第三模拟电信号。
S1505：拉远单元将第四模拟电信号转换为第四光信号并输出至中心单元；第四模拟电信号为零频信号、中频信号或射频信号。
S1506：中心单元将接收自拉远单元的第四光信号转换为第二模拟电信号；第二模拟电信号为零频信号、中频信号或射频信号。
S1507：中心单元将第二模拟电信号转换为数字信号。
本实施例的方法对应地可用于执行上述装置实施例中小站系统中各装置执行的步骤，其实现原理和技术效果类似，此处不再赘述。在本申请所提供的几个实施例中，应该理解到，所揭露的装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。上述集成的单元既可以采用硬件的形式实现，也可以采用硬件加软件功能单元的形式实现。
上述以软件功能单元的形式实现的集成的单元，可以存储在一个计算机可读取存储介质中。上述软件功能单元存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)或处理器(processor)执行本申请各个实施例所述方法的部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(read-only memory，ROM)、随机存取存储器(random access memory，RAM)、磁碟或者光盘等各种可以存储程序代码的介质。

Claims (26)

  1. 一种中心单元，其特征在于，所述中心单元包括：
    数模转换DAC模块、模数转换ADC模块、第一电光转换模块和第一光电转换模块；
    其中，所述DAC模块用于将基带信号转换为第一模拟电信号；所述第一模拟电信号为零频信号、中频信号或射频信号；
    所述第一电光转换模块用于将所述第一模拟电信号转换为第一光信号并输出至拉远单元；
    所述第一光电转换模块用于将接收自所述拉远单元的第二光信号转换为第二模拟电信号；所述第二模拟电信号为零频信号、中频信号或射频信号；
    所述ADC模块用于将所述第二模拟电信号转换为数字信号。
  2. 根据权利要求1所述的中心单元，其特征在于，所述中心单元还包括中射频模块；
    所述中射频模块用于将所述第一模拟电信号转换为第一频点的电信号；所述第一电光转换模块具体用于将所述第一频点的电信号转换为第一光信号并输出至拉远单元；和/或，
    用于将所述第二模拟电信号转换为第二频点的电信号；所述ADC模块具体用于将所述第二频点的模拟电信号转换为数字信号。
  3. 根据权利要求1-2任一项所述的中心单元，其特征在于，所述第一电光转换模块具体用于将M路所述第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；
    所述第一光电转换模块具体用于将接收自所述拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
  4. 根据权利要求3所述的中心单元，其特征在于，所述中心单元还包括下列至少一种：第一波分复用器MUX，或第一解复用器DEMUX；
    所述第一MUX用于将所述M路第一光信号进行合路并输出至所述拉远单元；
    所述第一DEMUX用于将所述N路第二光信号分离，并将分离的第二光信号输出至所述第一光电转换模块。
  5. 根据权利要求1-4任一项所述的中心单元，其特征在于，所述中心单元还用于向所述第一电光转换模块输入光功率控制信号；
    所述第一电光转换模块还用于输出与所述光功率控制信号有关的光功率，所述光功率用于控制所述拉远单元中的放大器的放大倍数。
  6. 根据权利要求5所述的中心单元，其特征在于，所述第一电光转换模块包括直接调制激光源，所述光功率控制信号为直流偏置电流；
    所述中心单元还用于向所述直接调制激光源输入所述直流偏置电流。
  7. 根据权利要求5所述的中心单元，其特征在于，所述第一电光转换模块包括间接调制器和激光源；
    所述光功率控制信号为直流偏置电流，所述中心单元还用于向所述激光源输入所 述直流偏置电流；或，
    所述光功率控制信号为偏置电压，所述中心单元还用于向所述间接调制器输入所述偏置电压。
  8. 一种拉远单元，其特征在于，所述拉远单元包括：第二光电转换模块、第二电光转换模块和放大器；
    其中，所述第二光电转换模块用于将接收自中心单元的第三光信号转换为第三模拟电信号；所述第三光信号为对模拟电信号转换得到的光信号；所述第三模拟电信号为零频信号、中频信号或射频信号；
    所述放大器用于放大所述第三模拟电信号；
    所述第二电光转换模块用于将第四模拟电信号转换为第四光信号并输出至所述中心单元；所述第四模拟电信号为零频信号、中频信号或射频信号。
  9. 根据权利要求8所述的拉远单元，其特征在于，所述第二光电转换模块还用于将与所述光功率控制信号有关的光功率转换为直流电流；
    所述放大器还用于采用与所述直流电流有关的放大倍数放大所述第三模拟电信号。
  10. 根据权利要求8或9所述的拉远单元，其特征在于，所述拉远单元还包括上混频模块和下混频模块；
    所述上混频模块用于将所述第三模拟电信号转换为第三频点的电信号；所述放大器具体用于放大所述第三频点的电信号；
    所述下混频模块用于将所述第四模拟电信号转换为第四频点的电信号；所述第二电光转换模块具体用于将所述第四频点的电信号转换为第四光信号并输出至所述中心单元。
  11. 一种小站系统，其特征在于，所述小站系统包括如权利要求1-7任一项所述的中心单元和一个或多个如权利要求8-10任一项所述的拉远单元。
  12. 根据权利要求11所述的小站系统，其特征在于，所述小站系统还包括汇聚单元；
    所述中心单元和一个或多个所述拉远单元通过所述汇聚单元连接。
  13. 根据权利要求12所述的小站系统，其特征在于，所述汇聚单元包括第二分复用器MUX和第二解复用器DEMUX；
    所述第二DEMUX用于将经所述中心单元的第一MUX合路的光信号分路，并将分路的光信号输出至一个或多个所述拉远单元；
    所述第二MUX用于将从一个或多个所述拉远单元接收的多路光信号合路，并将合路的光信号传输给所述中心单元的第一DEMUX。
  14. 根据权利要求11所述的小站系统，其特征在于，所述小站系统还包括光纤传输链路；
    所述中心单元和一个或多个所述拉远单元通过所述光纤传输链路连接。
  15. 根据权利要求14所述的小站系统，其特征在于，所述光纤传输链路包括一个或多个第三波分复用器MUX，和一个或多个第三解复用器DEMUX；
    任意一个所述第三DEMUX用于在经所述中心单元的第一MUX合路的光信号中，分离与所述任意一个第三DEMUX连接的拉远单元相关的目标光信号，并将所述目标 光信号输出至与所述任意一个第三DEMUX连接的拉远单元；
    任意一个所述第三MUX用于将从与所述任意一个第三MUX连接的拉远单元接收的光信号合路，并将合路的光信号输出至所述中心单元的第一DEMUX。
  16. 一种通信方法，其特征在于，应用于中心单元，所述方法包括：
    将基带信号转换为第一模拟电信号；所述第一模拟电信号为零频信号、中频信号或射频信号；
    将所述第一模拟电信号转换为第一光信号并输出至拉远单元；
    将接收自所述拉远单元的第二光信号转换为第二模拟电信号；所述第二模拟电信号为零频信号、中频信号或射频信号；
    将所述第二模拟电信号转换为数字信号。
  17. 根据权利要求16所述的方法，其特征在于，还包括：
    将所述第一模拟电信号转换为第一频点的电信号；所述将所述第一模拟电信号转换为第一光信号并输出至拉远单元包括：将所述第一频点的电信号转换为第一光信号并输出至拉远单元；和/或，
    将所述第二模拟电信号转换为第二频点的电信号；所述将所述第二模拟电信号转换为数字信号包括：将所述第二频点的模拟电信号转换为数字信号。
  18. 根据权利要求16-17任一项所述的方法，其特征在于，所述将所述第一模拟电信号转换为第一光信号并输出至拉远单元，包括：将M路所述第一模拟电信号转换为M路第一光信号并输出至拉远单元；M为大于或等于1的整数；
    所述将接收自所述拉远单元的第二光信号转换为第二模拟电信号包括：将接收自所述拉远单元的N路第二光信号转换为N路第二模拟电信号；N为大于或等于1的整数。
  19. 根据权利要求18所述的方法，其特征在于，所述将M路所述第一模拟电信号转换为M路第一光信号并输出至拉远单元，包括：
    将所述M路第一光信号进行合路并输出至所述拉远单元；
    所述将接收自所述拉远单元的N路第二光信号转换为N路第二模拟电信号，包括：
    将所述N路第二光信号分离，并将分离的第二光信号转换为N路第二模拟电信号。
  20. 根据权利要求16-19任一项所述的方法，其特征在于，还包括：
    向第一电光转换模块输入光功率控制信号；
    输出与所述光功率控制信号有关的光功率，所述光功率用于控制所述拉远单元中的放大器的放大倍数。
  21. 根据权利要求20所述的方法，其特征在于，所述第一电光转换模块包括直接调制激光源，所述光功率控制信号为直流偏置电流；所述向第一电光转换模块输入光功率控制信号，包括：
    向所述直接调制激光源输入所述直流偏置电流。
  22. 根据权利要求20所述的中心单元，其特征在于，所述第一电光转换模块包括间接调制器和激光源；
    所述光功率控制信号为直流偏置电流，所述向第一电光转换模块输入光功率控制信号，包括：向所述激光源输入所述直流偏置电流；或，
    所述光功率控制信号为偏置电压，向第一电光转换模块输入光功率控制信号，包括：向所述间接调制器输入所述偏置电压。
  23. 一种通信方法，其特征在于，应用于拉远单元，所述方法包括：
    将接收自中心单元的第三光信号转换为第三模拟电信号；所述第三光信号为对模拟电信号转换得到的光信号；所述第三模拟电信号为零频信号、中频信号或射频信号；
    放大所述第三模拟电信号；
    将第四模拟电信号转换为第四光信号并输出至所述中心单元；所述第四模拟电信号为零频信号、中频信号或射频信号。
  24. 根据权利要求23所述的方法，其特征在于，还包括：
    将与所述光功率控制信号有关的光功率转换为直流电流；
    所述放大所述第三模拟电信号包括：采用与所述直流电流有关的放大倍数放大所述第三模拟电信号。
  25. 根据权利要求23或24所述的方法，其特征在于，还包括：
    将所述第三模拟电信号转换为第三频点的电信号；所述放大所述第三模拟电信号包括：放大所述第三频点的电信号；
    将所述第四模拟电信号转换为第四频点的电信号；所述将第四模拟电信号转换为第四光信号并输出至所述中心单元包括：将所述第四频点的电信号转换为第四光信号并输出至所述中心单元。
  26. 一种通信方法，其特征在于，应用于小站系统，所述方法包括：
    中心单元将基带信号转换为第一模拟电信号；所述第一模拟电信号为零频信号、中频信号或射频信号；
    所述中心单元将所述第一模拟电信号转换为第一光信号并输出至拉远单元；
    所述拉远单元将接收自中心单元的第一光信号转换为第三模拟电信号；所述第三模拟电信号为零频信号、中频信号或射频信号；
    所述拉远单元放大所述第三模拟电信号；
    所述拉远单元将第四模拟电信号转换为第四光信号并输出至所述中心单元；所述第四模拟电信号为零频信号、中频信号或射频信号；
    所述中心单元将接收自所述拉远单元的第四光信号转换为第二模拟电信号；所述第二模拟电信号为零频信号、中频信号或射频信号；
    所述中心单元将所述第二模拟电信号转换为数字信号。
PCT/CN2020/127966 2019-12-06 2020-11-11 中心单元、拉远单元、小站系统及通信方法 WO2021109812A1 (zh)

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