WO2021179879A1 - 一种光载无线通信系统和非线性补偿方法 - Google Patents

一种光载无线通信系统和非线性补偿方法 Download PDF

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Publication number
WO2021179879A1
WO2021179879A1 PCT/CN2021/076209 CN2021076209W WO2021179879A1 WO 2021179879 A1 WO2021179879 A1 WO 2021179879A1 CN 2021076209 W CN2021076209 W CN 2021076209W WO 2021179879 A1 WO2021179879 A1 WO 2021179879A1
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dpd
signal
temperature
optical
nonlinear
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PCT/CN2021/076209
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English (en)
French (fr)
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吕毅博
李旭
王天祥
张伟伟
余荣道
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华为技术有限公司
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Publication of WO2021179879A1 publication Critical patent/WO2021179879A1/zh
Priority to US17/942,278 priority Critical patent/US12057883B2/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
    • H04B10/25—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
    • H04B10/25753—Distribution optical network, e.g. between a base station and a plurality of remote units
    • 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
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • 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
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • 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
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2543—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to fibre non-linearities, e.g. Kerr effect
    • 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
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2543—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to fibre non-linearities, e.g. Kerr effect
    • H04B10/2563—Four-wave mixing [FWM]
    • 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
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
    • 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
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • 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
    • 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
    • H04B10/505—Laser transmitters using external modulation
    • H04B10/5057—Laser transmitters using external modulation using a feedback signal generated by analysing the optical output

Definitions

  • This application relates to the field of wireless communication, and in particular to an optical-borne wireless communication system and a nonlinear compensation method.
  • the radio over Fiber (RoF) technology can improve the data transmission rate.
  • it effectively simplifies the hardware structure of the radio remote unit (RRU) and the baseband processing unit (Building Baseband Unit, BBU) in the access network.
  • RRU radio remote unit
  • BBU Building Baseband Unit
  • the analog RoF system can support technologies such as subcarrier modulation, Wavelength Division Multiplexing (WDM), and polarization multiplexing, and can realize multi-band and multi-communication signals (such as baseband digital signals, Long Term Evolution
  • WDM Wavelength Division Multiplexing
  • UMTS Universal Mobile Telecommunications System
  • Wi-Fi Wireless Fidelity
  • millimeter wave signals etc.
  • C-RAN Cloud-Radio Access Network
  • the distortion module determines the nonlinear characteristics of the downlink according to the input signal of the downlink and the feedback signal transmitted back by the feedback link, and then performs Digital Pre-Distortion (DPD) on the downlink to compensate for the downlink The nonlinear distortion.
  • DPD Digital Pre-Distortion
  • the feedback signal and the uplink data generally share the same transmission link. Therefore, it is necessary to add a control circuit on the RRU side to switch between the uplink data and the feedback information; in addition, to realize the feedback signal From the remote RRU back to the BBU, the feedback link must introduce new non-linear components such as E/O, O/E, and PA.
  • E/O, O/E, and PA new non-linear components
  • the introduction of control circuits, new E/O, O/E, PA and other devices will bring additional nonlinear distortion to the RoF system, resulting in the predistortion module not being able to obtain the correct nonlinear characteristics of the downlink, and the final predistortion
  • the module actually models and compensates for the nonlinearity of the entire uplink and downlink links. Therefore, the RoF system in the prior art still has the problem of poor linearization effect.
  • the embodiments of the present application provide a RoF system and a nonlinear compensation method to improve the linearization effect of the RoF system.
  • an embodiment of the present application provides a RoF system
  • the RoF system includes a BBU and an RRU, the RRU includes an electrical device, and the BBU includes a downlink and a feedback link;
  • the downlink is provided with A predistortion module and an optical device;
  • the input end of the feedback link is connected to the output end of the optical device, and the feedback link is used to feed back the nonlinear signal output by the optical device to the predistortion module;
  • the RoF system also includes a temperature detection module, which is used to detect the temperature value of the electrical device and transfer the temperature value to the predistortion module;
  • the predistortion module is used to: according to the temperature value and the The nonlinear signal performs digital predistortion DPD on the baseband signal.
  • the way of directly connecting the feedback link to the output end of the optical device can reduce the number of additional nonlinear components introduced by the feedback link, reduce the hardware complexity of the feedback link, and greatly reduce the Avoid the additional nonlinear distortion introduced by the feedback link.
  • the predistortion module performs DPD on the baseband signal based on the nonlinear signal fed back by the feedback link and the temperature value of the electrical device, which can ensure that the nonlinearity in the electrical and optical domains is compensated. In turn, the linearization effect of the RoF system is improved as a whole.
  • the predistortion module is specifically configured to: perform a first DPD on the original baseband signal according to the temperature value to compensate for the nonlinear distortion caused by the electrical device;
  • the baseband signal of the first DPD performs the second DPD to compensate for the nonlinear distortion caused by the optical device.
  • This embodiment on the one hand, based on the way that the feedback link is directly connected to the output end of the optical device 12, can reduce the number of additional nonlinear components introduced by the feedback link, reduce the hardware complexity of the feedback link, and thereby greatly reduce It even avoids the additional nonlinear distortion introduced by the feedback link, and improves the accuracy of the RoF system for nonlinear compensation in the optical domain; on the other hand, the method of remotely monitoring the temperature value of the electrical device 21 based on the predistortion module 11 can improve the RoF system The accuracy of nonlinear compensation in the electrical domain, while further simplifying the hardware complexity of RRU and BBU, and avoiding additional nonlinear distortion.
  • the corresponding relationship between the temperature of the electrical device and the DPD parameter is stored in the predistortion module; when the predistortion module performs the first DPD on the original baseband signal according to the temperature value, the specific The steps are: determining the DPD parameter corresponding to the temperature value according to the corresponding relationship; performing the first DPD on the original baseband signal according to the determined DPD parameter.
  • the efficiency of the predistortion module performing the first DPD on the original baseband signal can be improved, and the linearization effect of the RoF system can be further improved.
  • the temperature detection module is specifically configured to transmit the updated temperature value to the predistortion module when it is detected that the temperature value of the electrical device is updated.
  • the temperature detection module can be prevented from frequently sending temperature values to the predistortion module, and the power consumption of the system can be reduced.
  • the temperature detection module includes a thermistor, and the thermistor is arranged in the RRU and is arranged close to the electrical device.
  • the temperature detection module is realized by the thermistor, so that the temperature detection module is basically realized on the RRU side, which can save the calculation requirements on the BBU side.
  • the temperature detection module includes an induction optical fiber and a Raman optical time domain reflectometer; wherein the induction optical fiber is arranged in the RRU and is arranged close to the electrical device; the Raman The optical time domain reflectometer is installed in the BBU and connected to the predistortion module; the sensing fiber is used to sense the temperature of the electrical device to generate a Raman scattered light signal, and feed it back to the Raman light time Domain reflectometer; the Raman optical time domain reflectometer is used to determine the temperature of the electrical device according to the Raman scattered light signal.
  • the temperature detection module is basically implemented on the BBU side, which can save calculation requirements on the RRU side, and can simplify the system hardware complexity.
  • the predistortion module performs a second DPD on the baseband signal passing through the first DPD according to the nonlinear signal, specifically: using a preset algorithm to perform the second DPD on the baseband signal passing through the first DPD and the non-linear signal.
  • Linear signals are calculated to obtain DPD parameters; the DPD parameters are used to perform a second DPD on the baseband signal that has passed the first DPD;
  • the preset algorithm is a neural network model, Volterra polynomial, memory polynomial MP, Any one of the normalized memory polynomial GMP, Wiener-Hammerstein polynomial, cubic spline, regular piecewise linear equation CPWL.
  • the optical device includes an electro-optical modulator
  • the electrical device includes a power amplifier
  • the nonlinear distortion caused by the electro-optical modulator and the power amplifier can be compensated.
  • the optical device further includes a wavelength division multiplexer, and the input end of the wavelength division multiplexer is connected to the output end of the electro-optic modulator.
  • the input end of the feedback link is connected to the output end of the wavelength division multiplexer, so that the optical domain nonlinear distortion caused by the electro-optical modulator and the wavelength division multiplexer can be compensated as a whole, and the system performance can be further improved.
  • the input end of the feedback link is connected between the wavelength division multiplexer and the electro-optic modulator, so that the optical domain nonlinear distortion caused by the electro-optic modulator can be compensated without Taking into account the nonlinear distortion of the optical domain caused by the wavelength division multiplexer, the computational complexity of the predistortion module can be reduced.
  • an optical fiber is set between the BBU and the RRU; the temperature value and the uplink signal and downlink signal of the RoF system are transmitted through the optical fiber.
  • a first optical fiber and a second optical fiber are provided between the BBU and the RRU; the downlink signal of the RoF system and the temperature value are transmitted through the first optical fiber, and the RoF system
  • the uplink signal of the RoF system is transmitted through the second optical fiber; or, the downlink signal of the RoF system is transmitted through the first optical fiber, and the uplink signal of the RoF system or the temperature value is transmitted through the second optical fiber; or, The uplink signal and the downlink signal of the RoF system are transmitted through the first optical fiber, and the temperature value is transmitted through the second optical fiber.
  • the input end of the feedback link is connected to the output end of the optical device, including: the input end of the feedback link is directly connected to the output end of the optical device; or, the The input end of the feedback link and the output end of the optical device are indirectly connected through a linear element.
  • an embodiment of the present application provides a nonlinear compensation method, which is applied to a RoF system
  • the RoF system includes a base BBU and an RRU, the RRU includes an electrical device, and the BBU includes a downlink and a feedback link;
  • the downlink is provided with a predistortion module and an optical device;
  • the input end of the feedback link is connected to the output end of the optical device;
  • the RoF system further includes a temperature detection module;
  • the method includes: the feedback The link feeds back the non-linear signal output by the optical device to the predistortion module;
  • the temperature detection module detects the temperature value of the electrical device, and transmits the temperature value to the predistortion module;
  • the predistortion module performs digital predistortion DPD on the baseband signal according to the temperature value and the nonlinear signal.
  • the predistortion module performs digital predistortion DPD on the baseband signal according to the temperature value and the nonlinear signal, which specifically includes: the predistortion module performs digital predistortion DPD on the original baseband signal according to the temperature value.
  • the first digital predistortion DPD is used to compensate for the nonlinear distortion caused by the electrical device; the predistortion module performs a second DPD on the baseband signal passing through the first DPD according to the nonlinear signal to compensate for the optical device.
  • the nonlinear distortion is used to compensate for the nonlinear distortion caused by the electrical device.
  • the predistortion module stores the corresponding relationship between the temperature of the electrical device and the DPD parameter; the predistortion module performs the first digital predistortion DPD on the original baseband signal according to the temperature value, Specifically, it includes: the predistortion module determines the DPD parameter corresponding to the temperature value according to the corresponding relationship; the predistortion module performs the first DPD on the original baseband signal according to the determined DPD parameter.
  • the temperature detection module detects the temperature value of the electrical device and transmits the temperature value to the predistortion module, which specifically includes: the temperature detection module detects the electrical device When the temperature value of is updated, the updated temperature value is transmitted to the predistortion module.
  • the temperature detection module includes a thermistor, and the thermistor is arranged in the RRU and is arranged close to the electrical device.
  • the temperature detection module includes an induction optical fiber and a Raman optical time domain reflectometer; wherein the induction optical fiber is arranged in the RRU and is arranged close to the electrical device; the Raman The optical time domain reflectometer is arranged in the BBU and connected to the predistortion module; the temperature detection module detects the temperature value of the electrical device, including: the sensing fiber induces the temperature of the electrical device to generate a pull The Raman scattered light signal is fed back to the Raman optical time domain reflectometer; the Raman optical time domain reflectometer determines the temperature of the electrical device according to the Raman scattered light signal.
  • the predistortion module performs second DPD on the baseband signal passing through the first DPD according to the nonlinear signal, which specifically includes: the predistortion module uses a preset algorithm to perform the second DPD on the baseband signal passing through the first DPD.
  • the signal and the nonlinear signal are calculated to obtain DPD parameters; the predistortion module uses the DPD parameters to perform a second DPD on the baseband signal that has passed the first DPD; wherein, the preset algorithm is a neural network model , Volterra polynomial, memory polynomial MP, normalized memory polynomial GMP, Wiener-Hammerstein polynomial, cubic spline BBUbic spline, regular piecewise linear equation CPWL any one of the algorithms.
  • the preset algorithm is a neural network model , Volterra polynomial, memory polynomial MP, normalized memory polynomial GMP, Wiener-Hammerstein polynomial, cubic spline BBUbic spline, regular piecewise linear equation CPWL any one of the algorithms.
  • the optical device includes an electro-optical modulator
  • the electrical device includes a power amplifier
  • the optical device further includes a wavelength division multiplexer, and the input end of the wavelength division multiplexer is connected to the output end of the electro-optic modulator; the input end of the feedback link is connected to The output end of the wavelength division multiplexer; or, the input end of the feedback link is connected between the wavelength division multiplexer and the electro-optic modulator.
  • an optical fiber is set between the BBU and the RRU; the temperature value and the uplink signal and downlink signal of the RoF system are transmitted through the optical fiber.
  • a first optical fiber and a second optical fiber are provided between the BBU and the RRU; the downlink signal of the RoF system and the temperature value are transmitted through the first optical fiber, and the RoF system
  • the uplink signal of the RoF system is transmitted through the second optical fiber; or, the downlink signal of the RoF system is transmitted through the first optical fiber, and the uplink signal of the RoF system or the temperature value is transmitted through the second optical fiber; or, The uplink signal and the downlink signal of the RoF system are transmitted through the first optical fiber, and the temperature value is transmitted through the second optical fiber.
  • the input end of the feedback link is connected to the output end of the optical device, including: the input end of the feedback link is directly connected to the output end of the optical device; or, the The input end of the feedback link and the output end of the optical device are indirectly connected through a linear element.
  • an embodiment of the present application provides a method for generating a DPD lookup table.
  • the method includes: selecting a first temperature from a temperature set, wherein the temperature set includes the first aspect or the first Aspect at least one possible temperature of the electrical device described in any one of the possible designs, the first temperature is any temperature in the temperature set; the first non-zero temperature when the electrical device is at the first temperature is determined Linear model; generate a first baseband signal, and up-convert the baseband signal to obtain a radio frequency signal; input the radio frequency signal into the first non-linear model to generate a non-linear radio frequency signal; perform processing on the non-linear radio frequency signal Down-conversion and low-pass filtering are used to obtain a nonlinear baseband signal; the first DPD parameter corresponding to the first temperature is determined according to the first baseband signal and the nonlinear baseband signal. Traverse all the temperatures in the temperature set and repeat the above steps to obtain the DPD parameter corresponding to each temperature in the temperature set; generate a DPD
  • determining the first DPD parameter corresponding to the first temperature according to the first baseband signal and the nonlinear baseband signal specifically includes: using a neural network model, Volterra polynomial, and memory polynomial MP , Normalized memory polynomial GMP, Wiener-Hammerstein polynomial, cubic spline cubic spline, regular piecewise linear equation CPWL any one of the algorithms for the first baseband signal and the nonlinear baseband The signal is calculated to obtain the first DPD parameter corresponding to the first temperature.
  • an embodiment of the present application provides a computer-readable storage medium, the computer-readable storage medium stores a computer program, and the computer program includes program instructions that, when executed by a computer, cause the The computer executes the method described in any possible design of the second aspect or the second aspect or any possible design of the third aspect or the third aspect of the embodiments of the present application.
  • an embodiment of the present application provides a computer program product, the computer program product includes: computer program code, when the computer program code runs on a computer, the computer executes the second aspect or the first aspect of the embodiments of the present application The method described in any possible design of the second aspect or the third or any possible design of the third aspect.
  • an embodiment of the present application provides a processing device, including: at least one processor; and, a memory communicatively connected with the at least one processor; The executed instructions, the at least one processor executes the instructions stored in the memory to make any possible design of the second aspect or the second aspect or any possible design of the third aspect or the third aspect of the embodiments of the present application The method described in the design is executed.
  • an embodiment of the present application provides a chip, which is coupled with a memory, and is configured to read and execute program instructions stored in the memory to implement the second aspect or any of the second aspects of the embodiments of the present application Possible design or the method described in the third aspect or any one of the possible designs of the third aspect.
  • Figure 1 is a schematic diagram of an analog predistortion scheme
  • Figure 2 is a schematic diagram of a digital predistortion scheme
  • Figure 3 is a schematic diagram of a WDM-based multi-wavelength RoF system linearization scheme
  • FIG. 4 is a schematic structural diagram of a RoF system provided by the implementation of this application.
  • FIG. 5 is a flowchart of a nonlinear compensation method provided by the implementation of this application.
  • 6A and 6B are schematic diagrams of feedback links provided by the implementation of this application.
  • FIG. 7A and 7B are schematic diagrams of the temperature detection module 22 provided by the implementation of this application.
  • FIG. 8 is a flowchart of a method for generating a DPD lookup table provided by an embodiment of the application.
  • Figure 9A is a schematic diagram of DPD technical parameter estimation based on the direct learning architecture
  • Figure 9B is a schematic diagram of DPD technical parameter estimation based on indirect learning architecture
  • FIG. 10 is a flowchart of a method for processing downlink signals provided by the implementation of this application.
  • FIG. 11A is a schematic structural diagram of another possible RoF system provided by an embodiment of this application.
  • FIG. 11B is a schematic structural diagram of another possible RoF system provided by an embodiment of this application.
  • 11C is a schematic structural diagram of another possible RoF system provided by an embodiment of this application.
  • 11D is a schematic structural diagram of another possible RoF system provided by an embodiment of this application.
  • 11E is a schematic structural diagram of another possible RoF system provided by an embodiment of this application.
  • FIG. 12 is a schematic structural diagram of a processing device provided by an embodiment of this application.
  • FIG. 13 is a schematic structural diagram of another processing device provided by an embodiment of the application.
  • Solution one analog pre-distortion solution.
  • FIG. 1 is a schematic diagram of an analog predistortion scheme.
  • the core of this scheme is the light wave dispersion model induced by optical fiber and other optical devices.
  • Theoretical analysis shows that the dispersion distortion caused by the transmission of the optical signal in the RoF system is a function of the input laser source current. Therefore, corresponding analog predistortion processing is performed on the current of the input laser source, and the effect of compensating the optical domain dispersion can be completed.
  • this solution can only compensate for the optical domain dispersion distortion caused by the optical devices in the RoF system, and does not take into account the nonlinear distortion caused by the electrical devices in the RoF system, nor the nonlinear distortion caused by the memory characteristics of the devices. ;
  • the compensation scheme is sensitive to other parameters such as the wavelength of the transmitted light wave, the length of the optical fiber, and the operating temperature of the device, so its universality and robustness are poor. Therefore, the linearization effect of the RoF system is still very poor.
  • FIG 2 is a schematic diagram of a digital predistortion scheme.
  • a feedback link is set from the antenna on the RRU side to the BBU, so that the downlink signal of the RRU is sent out through the antenna all the way, and all the way back to the BBU via the feedback link.
  • the RRU side is equipped with a digital predistortion module (Digi predis).
  • the digital predistortion module can model the nonlinear characteristics of the downlink according to the input signal of the downlink and the feedback signal transmitted by the feedback link, and then the downlink Do digital predistortion to compensate for the nonlinear distortion of the downlink.
  • Solution three DPD solution based on wavelength division multiplexer (WDM).
  • WDM wavelength division multiplexer
  • FIG 3 is a schematic diagram of a WDM-based multi-wavelength RoF system linearization scheme.
  • a single fiber can be used to transmit signals of different wavelengths, so that the system can use different wavelengths to complete the transmission of uplink and downlink and feedback information. For example, use 1550nm to transmit downlink data signals while using 1310nm. The wavelength of the transmission of uplink data and feedback information.
  • This solution also performs digital compensation in the electrical domain for the non-linearity of the full link of the RoF system. Since the nonlinear performance of the RoF link is directly proportional to the intensity of the transmitted signal, and the intensity of the signal light is directly related to the intensity of the laser source access signal, this solution usually adds an adjustable attenuator to the feedback link. By adjusting the strength of the feedback signal, this action can only reduce the additional nonlinear distortion introduced by the E/O on the feedback link, but there is still additional distortion introduced on the actual feedback link (the signal power is attenuated by the long feedback fiber, Dispersion, etc.).
  • embodiments of the present application provide a RoF system and a nonlinear compensation method, which are used to improve the linearization effect of the RoF system.
  • the RoF system and nonlinear compensation method provided by the embodiments of this application can be applied to various communication systems, such as: long term evolution (LTE) system, fifth generation (5th generation, 5G) system, such as NR, and the following A generation of communication systems, such as 6G systems, etc.
  • LTE long term evolution
  • 5G fifth generation
  • 6G systems such as 6G systems
  • the technical solutions of the embodiments of the present application can also be applied to other communication systems, such as satellite communication systems, car networking communication systems, and so on.
  • the RoF system includes a baseband unit (Building Baseband Unit, BBU) 01 and a remote radio unit (RRU) 02.
  • BBU01 and RRU02 are connected by optical fiber; among them, RRU02 includes electrical components 21, and BBU01 includes downlink and feedback Link, the downlink is provided with a predistortion module 11 and an optical device 12, the input end of the feedback link is connected to the output end of the optical device 12, and the output end of the feedback link is connected to the predistortion module 11.
  • the RoF system also includes a temperature detection module 22.
  • the temperature detection module 22 can be set in RRU02, or in BBU01, or partly in BBU01 and partly in RRU02, and there is no limitation here. In FIG. 4, the temperature detection module 22 is set in the RRU02 as an example.
  • connection may include both direct connection and indirect connection.
  • the input end of the feedback link can be directly connected to the output end of the optical device 12, and the input end of the feedback link and the output end of the optical device 12 can also be indirectly connected through other linear elements, such as the input end of the feedback link and the optical device 12.
  • Components that have little or no effect on nonlinear distortion, such as resistors and capacitors, can also be arranged between the output ends of the device 12.
  • the output end of the feedback link and the predistortion module can also be connected directly or indirectly, which will not be repeated here.
  • the specific hardware implementation of the predistortion module 11 can be achieved through field-programmable gate array (FPGA), application specific integrated circuit (ASIC), system chip (System on Chip, SoC), and central processing unit. (Central Processor Unit, CPU), Network Processor (Network Processor, NP), Digital Signal Processing Circuit (Digital Signal Processor, DSP), Micro Controller (Micro Controller Unit, MCU), Programmable Controller (Programmable Logic Device, PLD) or other integrated chips.
  • the predistortion module 11 can store and run the software or program corresponding to the nonlinear compensation method provided in the embodiment of the present application, so as to realize the nonlinear compensation method provided in the embodiment of the present application.
  • Fig. 5 is a specific method for the RoF system shown in Fig. 4 to perform nonlinear compensation on the downlink signal, including:
  • S501 The feedback link feeds back the nonlinear signal output by the optical device 12 to the predistortion module 11; the temperature detection module 22 detects the temperature value of the electrical device 21, and sends the temperature value to the predistortion module 11.
  • the predistortion module 11 performs a DPD operation on the baseband signal according to the temperature value and the nonlinear signal.
  • the predistortion module 11 can separately model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain:
  • the predistortion module 11 performs the first DPD on the original baseband signal according to the temperature value to realize the compensation of the nonlinear distortion caused by the electrical device 21 (ie, electrical domain compensation);
  • the predistortion module 11 performs a second DPD on the baseband signal passing through the first DPD according to the output signal of the feedback link (that is, the nonlinear signal output by the optical device 12) to realize the compensation of the nonlinear distortion caused by the optical device 12 (That is, optical domain compensation).
  • the predistortion module 11 in the RoF system performs modeling and compensation for optical domain nonlinearity and electrical domain nonlinearity respectively.
  • the predistortion module 11 based on the way that the feedback link is directly connected to the output end of the optical device 12, Reduce the number of additional nonlinear components introduced by the feedback link, reduce the hardware complexity of the feedback link, and greatly reduce or even avoid the additional nonlinear distortion introduced by the feedback link, and improve the accuracy of the RoF system for nonlinear compensation in the optical domain
  • the predistortion module 11 based on the predistortion module 11 to remotely monitor the temperature value of the electrical device 21, the accuracy of the RoF system for nonlinear compensation in the electrical domain can be improved, while further simplifying the RRU and BBU hardware complexity and avoiding additional introduction Non-linear distortion.
  • the embodiments of the present application can improve the linearization effect of the RoF system and reduce the hardware complexity of the RoF system.
  • optical device 12 and the electrical device 21 in the embodiments of the present application are introduced.
  • the optical device 12 includes an electro-optical modulator (E/O), and the electrical device 21 includes a power amplifier (PA).
  • E/O electro-optical modulator
  • PA power amplifier
  • the electro-optic modulator has the greatest nonlinear impact on the RoF system. Therefore, by feeding back the nonlinear signal output by the electro-optic modulator to the predistortion module 11, the predistortion module 11 can more accurately compensate the electro-optic modulation
  • the optical domain nonlinear distortion caused by the amplifier, and on the RRU side, the PA is the main component that causes the electrical domain nonlinearity. Therefore, the temperature value of the PA is fed back to the predistortion module 11, so that the predistortion module 11 can more accurately compensate for the PA caused by the PA.
  • the nonlinear distortion of the electrical domain is realized, and the nonlinear compensation of the optical domain and the electrical domain is realized.
  • the optical device 12 may include a wavelength division multiplexer (WDM) in addition to the electro-optical modulator.
  • WDM wavelength division multiplexer
  • the input end of the wavelength division multiplexer and The output terminal of the electro-optical modulator is connected (directly or indirectly).
  • the feedback link can be designed in the following two ways:
  • the input end of the feedback link is connected to the output end of the wavelength division multiplexer.
  • the feedback signal obtained by the predistortion module can reflect the non-linear characteristics caused by the electro-optic modulator and the wavelength division multiplexer as a whole, so the predistortion module 11 can simultaneously treat the non-linear characteristics caused by the electro-optic modulator and the wavelength division multiplexer. Compensation is performed linearly, so that the downstream signal has a better linearization effect.
  • the input end of the feedback link is connected between the wavelength division multiplexer and the electro-optic modulator.
  • the feedback signal obtained by the predistortion module can reflect the nonlinear characteristics caused by the electro-optic modulator. Therefore, the predistortion module 11 can compensate for the nonlinearity caused by the electro-optic modulator without considering the nonlinear distortion caused by WDM.
  • the calculation amount and complexity of the predistortion module 11 can be reduced, and the calculation efficiency can be improved.
  • the electrical device 21 may also include an attenuator, an opto-electronic converter, etc.
  • the optical device 12 may also include an electro-optical converter, an optical domain amplifier, an optical splitter, and the like.
  • the input end of the feedback link can be connected to the output end of the last optical device, so that the feedback signal can reflect the non-linear characteristics of all optical devices 12, thereby making the predistortion module 11
  • the overall optical domain nonlinear distortion of the downlink can be compensated.
  • the temperature of each electrical device can be monitored separately, and the temperature of each electrical device can be compensated for the nonlinear distortion caused by the electrical device.
  • the temperature detection module 22 in the embodiment of the present application may be implemented by a thermistor.
  • the thermistor can be arranged in the RRU02 and arranged close to the electric device 21.
  • the temperature of the PA can be determined according to the voltage difference-temperature value correspondence table.
  • the temperature detection module 22 may be realized by an optical fiber sensor and a Raman optical time domain reflectometer.
  • the temperature detection module 22 includes a Raman optical time domain reflectometer 221 and a sensing fiber 222, wherein the sensing fiber 222 is arranged in the RRU02 and is close to the electrical device 21 (in FIG. 7B, PA is taken as an example, the sensing fiber The optical fiber 222 is arranged around the PA).
  • the Raman optical time domain reflectometer 221 includes a de-wavelength division multiplexer, a photodetector (PD), an analog-to-digital converter (ADC), and a comparison circuit.
  • the Raman optical time domain reflectometer is installed in the BBU01 and connected to the predistortion module 11.
  • the sensing fiber can sense the temperature of the electric device 21 to generate a Raman scattered light signal and feed it back to the Raman optical time domain reflectometer; the Raman optical time domain reflectometer determines the temperature of the electric device 21 according to the Raman scattered light signal.
  • Raman scattering is related to the thermal vibration of fiber molecules, so it is sensitive to temperature and can be used for temperature measurement.
  • Raman scattered light includes light of two frequencies: Stokes light and Anti-Stokes light. Their frequencies are distributed on both sides of the incident light frequency and propagate in the opposite direction. Because Anti-Stokes scattered light is sensitive to temperature, its intensity is modulated by temperature, while Stokes scattered light is basically independent of temperature, so the ratio of the two light intensities is only related to the temperature of the optical fiber, so the optical fiber can be used for temperature sensing.
  • thermoelectric module 22 is merely examples of the temperature detection module 22 and are not limited, and may also be implemented in other ways during specific implementation, which is not limited in the embodiment of the present application.
  • the following describes a specific implementation manner of the predistortion module 11 performing the first DPD on the original baseband signal according to the temperature value.
  • the predistortion module 11 may pre-store the corresponding relationship between the temperature of the electrical device 21 and the DPD parameter.
  • the predistortion module 11 performs the first DPD on the original baseband signal according to the temperature value, it directly according to the corresponding relationship Determine the DPD parameter corresponding to the temperature value, and then perform the first DPD on the original baseband signal according to the determined DPD parameter.
  • g is the small signal amplification gain
  • r is the amplitude of the input signal
  • L is the maximum amplitude of the signal amplification
  • s is the smoothing parameter
  • a is the phase change gradient value of the PA during linear operation
  • b is the phase when the PA is in saturation.
  • c is the initial phase value when PA has no signal input
  • d is the phase correction value when PA is in saturation.
  • the look-up table can be addressed through the PA temperature to obtain different temperature values The corresponding DPD parameter value.
  • a method for generating a DPD lookup table includes:
  • S803 Generate a first baseband signal, and up-convert the baseband signal to obtain a radio frequency signal;
  • S805 Perform down-conversion and low-pass filtering on the nonlinear radio frequency signal to obtain a nonlinear baseband signal
  • S806 Determine a first DPD parameter corresponding to the first temperature according to the first baseband signal and the nonlinear baseband signal.
  • neural network models Volterra polynomials, memory polynomials (MP), generalized memory polynomials (GMP), and Wiener-Hammerstein (Wiener-Hammerstein) can be used here.
  • Any one of polynomial, cubic spline, Canonical piecewise-linear (CPWL) and other algorithms calculates the first baseband signal and the nonlinear baseband signal to obtain the first temperature correspondence The first DPD parameter.
  • CPWL Canonical piecewise-linear
  • step S807 Determine whether to traverse all the temperatures in the temperature set; if yes, perform step S808; otherwise, go back to step S801, adjust the temperature value and repeat steps S802-S806 until all temperatures in the temperature set are traversed.
  • S808 Generate a DPD look-up table according to each temperature in the temperature set and the DPD parameter corresponding to each temperature.
  • the operator can store the DPD look-up table in the predistortion module 11 in advance. In this way, when the RoF system processes the downlink signal, the predistortion module 11 can directly read the DPD look-up table to perform nonlinearity on the downlink signal. compensate.
  • the operator can also store the algorithm shown in FIG. 8 in the predistortion module 11, and the predistortion module 11 can directly run the algorithm to generate the DPD lookup table, or run the algorithm to update the original DPD lookup table.
  • the temperature detection module 22 may only transmit the updated temperature value to the predistortion module 11 when it detects that the temperature value of the electrical device 21 is updated (changed); or, the temperature detection module 22 is configured according to the design
  • the temperature value is periodically sent to the predistortion module 11 at a predetermined time interval, which is not limited in the embodiment of the present application. In this way, the temperature detection module 22 can be prevented from frequently sending temperature values to the predistortion module, and the power consumption of the system can be reduced.
  • the temperature detection module 22 determines that the temperature value is updated in a specific implementation manner: the temperature detection module 22 determines that the difference between the current temperature and the temperature sent last time reaches a set threshold, and then determines that the temperature value of the electrical device 21 is updated.
  • the set threshold may be related to the distribution of temperature values in the DPD look-up table.
  • the temperature value distribution in the DPD lookup table ranges from 0°C to 100°C, and the interval between adjacent temperature values is 1°C, that is, "0°C, 1°C, 2°C, 3°C,..., 98°C, 99°C, 100°C"
  • the set threshold can be set to 1°C or an integer multiple of 1°C, so as to ensure that the temperature value sent by the temperature measurement module 22 to the predistortion module 11 has corresponding DPD parameters in the DPD look-up table, and further Ensure the reliability of electrical domain nonlinear compensation.
  • the predistortion module 11 may use a preset algorithm to calculate the baseband signal and the nonlinear signal that have passed through the first DPD to obtain DPD parameters; and then use the DPD parameters to perform the second DPD on the baseband signal that has passed through the first DPD.
  • the preset algorithms include but are not limited to the following machine learning algorithms: neural network model, Volterra polynomial, memory polynomial (MP), normalized memory polynomial (GMP), Wiener- Wiener-Hammerstein polynomials, cubic splines, Canonical piecewise-linear equations (CPWL), etc.
  • the nonlinearity of the downlink signal can be expressed by the following formula:
  • a km represents the k-th order, and the parameter of the nonlinear term when the memory depth is m.
  • the parameter vector W [w 11 , w 12 ,...w km ,...] is obtained, and the parameter W can be used as a DPD parameter for DPD operation.
  • the direct learning architecture uses the feedback signal Y(n) and the downlink signal X(n+k) before DPD operation to estimate the DPD parameters.
  • a delay k is required for the downlink signal, that is, X(n) is transformed into X(n+k)
  • indirect learning In the architecture, the feedback signal Y(n) and the downlink signal U(n) after DPD operation (that is, the input signal of the predistortion module 11) are used to estimate the DPD parameters.
  • the solution formula (Eq.7) may adopt algorithms such as least square method, least mean square method, or singular value decomposition method, which is not limited in the embodiment of the present application.
  • one or more optical fibers can be set between BBU01 and RRU02 to transmit signals between BBU01 and RRU02.
  • two optical fibers can be set between BBU01 and RRU02, such as the first optical fiber and the second optical fiber; then the signal transmission between BBU01 and RRU02 can include the following distribution methods: 1) RoF system downstream signal and temperature The value is transmitted through the first optical fiber, and the uplink signal of the RoF system is transmitted through the second optical fiber; 2) the downlink signal of the RoF system is transmitted through the first optical fiber, and the uplink signal or temperature value of the RoF system is transmitted through the second optical fiber; 3) the RoF system The upstream signal and the downstream signal are transmitted through the first optical fiber, and the temperature value is transmitted through the second optical fiber.
  • step S1002 Determine whether the temperature of the PA needs to be updated. If it needs to be updated, perform step S1015 (execute the optimized static nonlinear model and update the static DPD parameters according to the temperature of the PA), otherwise continue to step S1002;
  • step S1003. Perform a static DPD operation on the downlink signal according to the DPD parameters determined in step S1016 (that is, the first DPD mentioned above);
  • step S1004 Perform a dynamic DPD operation, that is, the second DPD above.
  • the parameters of the dynamic DPD are obtained in step S1014 (de-multiplexing the feedback signal, photoelectric conversion, down-conversion, filtering, digital-to-analog conversion, etc., to obtain nonlinear Digital baseband signal, based on the original baseband signal and nonlinear baseband signal to obtain dynamic DPD parameters);
  • step S1008 Obtain the downlink output on the BBU side, determine whether the dynamic DPD parameters need to be updated, and if necessary, execute step S1015, otherwise continue to execute step S1009;
  • the RRU side also needs to perform a multi-wavelength optical signal de-wavelength division multiplexing operation
  • S1012 Perform a power amplification operation on the electrical signal to obtain a radio frequency signal
  • the downlink signal with good linearization can be sent out through the antenna.
  • FIG. 11A is a schematic structural diagram of another possible RoF system provided in an embodiment of this application.
  • A1 Baseband resource pool. It is responsible for generating downlink baseband data and receiving uplink baseband data.
  • A2 Predistortion module. It includes a quasi-static-dynamic cascaded DPD module, a corresponding parameter estimation module, and a quasi-static PA model lookup table.
  • A3 Digital-to-analog converter (DAC). Used to convert digital baseband signals into baseband analog signals.
  • DAC Digital-to-analog converter
  • A4 Mixer. Used to realize up-down frequency conversion operation.
  • A5 Local oscillator. Provide radio frequency carrier.
  • A6 Band pass filter.
  • A7 Low noise amplifier.
  • A8 Electro-optical modulation (E/O) module. Convert radio frequency signals into optical signals. It may be a direct modulator or an external modulator.
  • A9 Optical splitter. It divides an optical signal into two optical signals. The power ratio between the two optical signals is determined by the selected splitter. In the present invention, we use a power ratio of 9:1. The downlink signal from the BBU to the RRU accounts for 90% of the power, and 10% of the optical signals are used as local feedback.
  • A10 Optical fiber.
  • the length of the fiber in the local feedback link does not exceed 10m, and the length of the fiber between the BBU and the RRU is 5-50km.
  • A11 Wavelength division multiplexer. Used to achieve the convergence of multiple wavelength optical signals.
  • A12 Optical switch. Select the desired wavelength to pass the signal.
  • A13 Photodetector (PD, O/E). Convert optical signals into electrical signals.
  • A14 Gain adjustable amplifier.
  • A15 Low-pass filter.
  • A16 Analog-to-digital converter (ADC). Convert baseband analog signal to baseband digital signal.
  • A17 De-wavelength division multiplexer. Distribute multiple wavelength signals transmitted on one optical fiber to different ports for output one by one.
  • Attenuator it can be a fixed attenuator or an adjustable attenuator.
  • A19 Power amplifier (PA).
  • A20 Antenna.
  • A21 Induction fiber. It is coiled around the PA on the AAU side to sense the temperature of the PA.
  • A22 Raman Optical Time Domain Reflectometer (ROTDR). Used to determine the temperature of the remote sensing fiber.
  • ROTDR Raman Optical Time Domain Reflectometer
  • A23 Optical domain amplifier.
  • the RoF system in this example includes at least one uplink and downlink and one local feedback link.
  • the optical splitter divides the optical signal passing through the wavelength division multiplexer into two, one of which transmits downlink data, and the other is used for local feedback.
  • the local feedback optical signal is first divided into multiple signals according to the wavelength by the de-wavelength division multiplexer, and then the optical switch is used to sequentially send the optical signals of different wavelengths to the local PD according to the time division multiplexing method.
  • the downlink cooperates with the electric switch to choose to receive the local feedback data signal or the uplink signal.
  • the uplink signal here can be either an uplink data signal or a Raman scattered light wave used to monitor temperature.
  • the sensing fiber is arranged around the PA.
  • the received optical information passes through the optical splitter, one beam leads to the radio frequency link, and the other beam is sent to the induction fiber.
  • the BBU side uses ROTDR to remotely monitor the PA temperature.
  • Local feedback signal combined with remote PA temperature information, using polynomial method, static/quasi-static model and neural network and other parameter estimation methods can be used for the parameters required for DPD operation.
  • this example adopts a multi-channel double-layer cascaded DPD architecture to model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain respectively.
  • the electrical domain nonlinear modeling and compensation are realized by remotely monitoring the PA temperature on the BBU side.
  • the system hardware complexity can be simplified.
  • the BBU side introduces the PA temperature information
  • Non-linear modeling and compensation can avoid the additional non-linearity introduced by the prior art through the design of detecting the complex feedback link from the RRU side to the BBU side.
  • Optical domain nonlinear modeling and compensation are realized by establishing a signal feedback link locally in the BBU, because the link contains a variety of optical devices, such as electro-optical converters, wavelength division multiplexers, de-wavelength division multiplexers and possible Therefore, the DPD technology in this solution can uniformly compensate the nonlinear distortion generated by a variety of optical devices (considering the introduction of four-wave mixing and adjacent wavelength crosstalk in many optical devices), it can improve the optical domain The accuracy of nonlinear compensation.
  • the optical fiber temperature measurement method has high accuracy and is not susceptible to electromagnetic interference.
  • FIG. 11B is a schematic structural diagram of another possible RoF system provided in an embodiment of this application.
  • the RoF system in this example includes at least one uplink and downlink and one local feedback link.
  • the optical splitter is used to split the output optical signal of the E/O module into two, one of which transmits the downstream data, and the other is used for local feedback.
  • the BBU side uses an optical switch to sequentially send optical signals of different wavelengths to the local PD according to the time-division multiplexing mode. Cooperate with the electric switch to choose to receive the local feedback data signal or the uplink signal.
  • the uplink signal here can be either an uplink data signal or a Raman scattered light wave used to monitor temperature.
  • the sensing fiber is arranged around the PA.
  • the received optical information is sent to the induction fiber through a bundle of optical splitters leading to a radio frequency link.
  • the BBU side uses ROTDR to remotely monitor the PA temperature.
  • the local feedback signal is combined with the remote PA temperature information obtained, using polynomial method, static/quasi-static model and neural network and other parameter estimation methods to obtain the parameters required for the cascaded DPD operation.
  • this example also adopts a multi-channel double-layer cascaded DPD architecture to model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain respectively.
  • the electrical domain nonlinear modeling and compensation are realized by remotely monitoring the PA temperature on the BBU side, which can simplify the system hardware complexity and avoid the introduction of the existing technology through the design of the RRU side to the BBU side to detect the complex feedback link Additional non-linearity.
  • Optical domain nonlinear modeling and compensation are realized by establishing a signal feedback link locally in the BBU, which can uniformly compensate the nonlinear distortion generated by a variety of optical devices (taking into account the four-wave mixing and adjacent wavelength crosstalk introduced by many optical devices Etc.).
  • the feedback link in this example is set before the wavelength division multiplexer, which can further simplify the system hardware complexity.
  • FIG. 11C is a schematic structural diagram of another possible RoF system provided in an embodiment of this application.
  • the RoF system in this example includes at least one uplink and downlink and one local feedback link.
  • the optical splitter is used to split the output optical signal of the E/O module into two, one of which transmits the downstream data, and the other is used for local feedback.
  • the optical splitter corresponds to the E/O module one to one.
  • An optical switch is used on the BBU side to sequentially send optical signals of different wavelengths to the local PD according to the time-division multiplexing mode.
  • Uplink data is transmitted using an independent WDM-RoF link.
  • the Raman scattered light wave and the local feedback optical signal are connected to the same optical switch and cooperate with the electric switch to complete the reception of the feedback signal and the scattered signal respectively.
  • the sensing fiber is arranged around the PA.
  • the received downstream optical information passes through the optical splitter, one beam leads to the radio frequency link and the other beam is sent to the induction fiber.
  • the BBU side uses ROTDR to remotely monitor the PA temperature.
  • the local feedback signal is combined with the remote PA temperature information obtained, using polynomial method, static/quasi-static model and neural network and other parameter estimation methods to obtain the parameters required for the cascaded DPD operation.
  • this example also adopts a multi-channel double-layer cascaded DPD architecture to model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain respectively.
  • the electrical domain nonlinear modeling and compensation are realized by remotely monitoring the PA temperature on the BBU side, which can simplify the system hardware complexity and avoid the introduction of the existing technology through the design of the RRU side to the BBU side to detect the complex feedback link Additional non-linearity.
  • Optical domain nonlinear modeling and compensation are realized by establishing a signal feedback link locally in the BBU, which can uniformly compensate the nonlinear distortion generated by a variety of optical devices (taking into account the four-wave mixing and adjacent wavelength crosstalk introduced by many optical devices Etc.).
  • the temperature monitoring in this example adopts a separate link for transmission, which can avoid the problem of interference between uplink data and temperature information transmission, and further improve the accuracy of the nonlinear compensation of the RoF system.
  • FIG. 11D is a schematic structural diagram of another possible RoF system provided in an embodiment of this application.
  • the RoF system in this example uses the electrical domain temperature monitoring method.
  • the PA temperature monitoring and control circuit A25 realizes the observation of the PA temperature and determines the temperature value return scheme.
  • this module can control the attenuation value of the attenuator.
  • the RoF system in this example includes at least one uplink and downlink and one local feedback link, without the need for a signal feedback link on the remote RRU side.
  • the BBU side uses an optical splitter to divide the optical signal sent by the E/O module into two, one beam transmits data downstream, and the other beam performs local feedback.
  • an optical switch is required, and the feedback signals of different wavelengths are sequentially sent to the local PD in a time-division multiplexing manner.
  • the temperature of the PA is monitored by the thermistor and the look-up table.
  • the value of the attenuator can be spontaneously adjusted on the RRU side to ensure that the transmitted signal power is in the PA amplification linear region; frequency-shift keying (FSK) modulation or other modulation methods can also be used to combine the temperature information , Passed back to the BBU via the uplink.
  • FSK frequency-shift keying
  • This information can use time division multiplexing to share the transmission link with the uplink information, or additional time slot resources can be opened up in the uplink data frame structure.
  • the local feedback signal is combined with the remote PA temperature information obtained, and the parameters required for the cascaded predistortion operation are trained by polynomial methods, static/quasi-static models, and neural networks.
  • this example also adopts a multi-channel double-layer cascaded DPD architecture to model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain respectively.
  • the electrical domain nonlinear modeling and compensation are realized by remotely monitoring the PA temperature on the BBU side, which can simplify the system hardware complexity and avoid the introduction of the existing technology through the design of the RRU side to the BBU side to detect the complex feedback link Additional non-linearity.
  • Optical domain nonlinear modeling and compensation are realized by establishing a signal feedback link locally in the BBU, which can uniformly compensate the nonlinear distortion generated by a variety of optical devices (taking into account the four-wave mixing and adjacent wavelength crosstalk introduced by many optical devices Etc.).
  • this example adopts the electrical domain temperature monitoring method, and the control circuit adopts adjusting the value of the adjustable attenuator or the bias voltage value of the PA, so that the linear amplification of the radio frequency signal can be realized, which can further save Computing requirements on the BBU side.
  • FIG. 11E is a schematic structural diagram of another possible RoF system provided in an embodiment of this application.
  • the RoF system in this example uses the electrical domain temperature monitoring method.
  • the RoF system includes at least one uplink and downlink and one local feedback link, without the need for a signal feedback link on the remote RRU side.
  • the BBU side uses an optical splitter to divide the E/O module and the optional optical signal through the optical domain amplifier into two, one beam transmits data downstream, and the other beam performs local feedback.
  • the temperature of the PA is monitored by the thermistor and the look-up table.
  • the value of the attenuator can be adjusted spontaneously at the RRU end to ensure that the transmitted signal power is in the PA amplification linear region; FSK modulation or other modulation methods can also be used to transmit the temperature information back to the BBU via the uplink.
  • This information can use time division multiplexing to share the transmission link with the uplink information, or additional time slot resources can be opened up in the uplink data frame structure.
  • the local feedback signal is combined with the remote PA temperature information obtained, and the parameters required for the cascaded predistortion operation are trained by polynomial methods, static/quasi-static models, and neural networks.
  • this example also adopts a multi-channel double-layer cascaded DPD architecture to model and compensate for the nonlinearity in the optical domain and the nonlinearity in the electrical domain respectively.
  • the electrical domain nonlinear modeling and compensation are realized by remotely monitoring the PA temperature on the BBU side, which can simplify the system hardware complexity and avoid the introduction of the existing technology through the design of the RRU side to the BBU side to detect the complex feedback link Additional non-linearity.
  • Optical domain nonlinear modeling and compensation are realized by establishing a signal feedback link locally in the BBU, which can uniformly compensate the nonlinear distortion generated by a variety of optical devices (taking into account the four-wave mixing and adjacent wavelength crosstalk introduced by many optical devices Etc.).
  • this example uses a single wavelength to transmit the downlink data, so WDM can be omitted, which can avoid the nonlinearity caused by WDM to the RoF system, and can further save the calculation on the BBU side. need.
  • the embodiments of the present application also provide a computer-readable storage medium, the computer-readable storage medium stores a computer program, and the computer program includes program instructions that, when executed by a computer, cause The computer executes the nonlinear compensation method provided in the foregoing embodiment.
  • the embodiments of the present application also provide a computer-readable storage medium, the computer-readable storage medium stores a computer program, and the computer program includes program instructions that, when executed by a computer, cause The computer executes the method for generating the DPD lookup table provided in the above-mentioned embodiment.
  • the embodiments of the present application also provide a computer program product, the computer program product includes: computer program code, when the computer program code is run on a computer, the computer executes the non-transmission method provided in the above-mentioned embodiments. Linear compensation method.
  • the embodiments of the present application also provide a computer program product, the computer program product includes: computer program code, when the computer program code runs on a computer, the computer executes the generation provided in the above embodiments DPD lookup table method.
  • an embodiment of the present application further provides a processing device, including: at least one processor 1201; and, a memory 1202 communicatively connected to the at least one processor; Instructions executed by the at least one processor 1201, the at least one processor 1201 executes the instructions stored in the memory 1202, so that the nonlinear compensation method provided in the foregoing embodiment is executed.
  • processor 1201 and the memory 1202 may be coupled through an interface circuit, or may be integrated together, which is not limited here.
  • the specific connection medium between the foregoing processor 1201 and the memory 1202 is not limited in the embodiment of the present application.
  • the memory 1202 and the processor 1201 are connected by a bus 1203 in FIG. 12, and the bus is represented by a thick line in FIG. To be limited.
  • the bus can be divided into an address bus, a data bus, a control bus, and so on. For ease of presentation, only one thick line is used in FIG. 12 to represent it, but it does not mean that there is only one bus or one type of bus.
  • an embodiment of the present application further provides a processing device, including: at least one processor 1301; and a memory 1302 communicatively connected to the at least one processor 1301; the processor 1301 and The memories 1302 can be coupled through an interface circuit or can be integrated together.
  • the memory 1302 stores instructions that can be executed by the at least one processor 1301, and the at least one processor 1301 executes the instructions stored in the memory 1302 to execute the method for generating a DPD look-up table provided in the foregoing embodiment. .
  • processor 1301 and the memory 1302 may be coupled through an interface circuit, or may be integrated together, which is not limited here.
  • the specific connection medium between the foregoing processor 1301 and the memory 1302 is not limited in the embodiment of the present application.
  • the memory 1302 and the processor 1301 are connected by a bus 1303 in FIG. 13, and the bus is represented by a thick line in FIG. To be limited.
  • the bus can be divided into an address bus, a data bus, a control bus, and so on. For ease of presentation, only one thick line is used in FIG. 13, but it does not mean that there is only one bus or one type of bus.
  • the embodiments of the present application also provide a chip, the chip may be coupled with a memory, or the memory may be integrated inside the chip, which is not limited here.
  • the chip can read and execute the program instructions stored in the memory to implement the nonlinear compensation method provided in the above-mentioned embodiments.
  • the embodiments of the present application also provide a chip, the chip may be coupled with a memory, or the memory may be integrated inside the chip, which is not limited here.
  • the chip can read and execute the program instructions stored in the memory to implement the method for generating the DPD look-up table provided in the foregoing embodiment.
  • the processor mentioned in the embodiments of the present application may be implemented by hardware or software.
  • the processor When implemented by hardware, the processor may be a logic circuit, an integrated circuit, or the like.
  • the processor When implemented by software, the processor may be a general-purpose processor, which is implemented by reading software codes stored in the memory.
  • the processor may be a central processing unit (central processing unit, CPU), or other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), and Application Specific Integrated Circuit (ASIC) , Ready-made programmable gate array (Field Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc.
  • the general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.
  • the memory mentioned in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memory.
  • the non-volatile memory can be read-only memory (Read-Only Memory, ROM), programmable read-only memory (Programmable ROM, PROM), erasable programmable read-only memory (Erasable PROM, EPROM), and electrically available Erase programmable read-only memory (Electrically EPROM, EEPROM) or flash memory.
  • the volatile memory may be a random access memory (Random Access Memory, RAM), which is used as an external cache.
  • RAM random access memory
  • SRAM static random access memory
  • DRAM dynamic random access memory
  • DRAM synchronous dynamic random access memory
  • SDRAM double data rate synchronous dynamic random access memory
  • Double Data Eate SDRAM, DDR SDRAM enhanced synchronous dynamic random access memory
  • Enhanced SDRAM, ESDRAM synchronous connection dynamic random access memory
  • Synchlink DRAM, SLDRAM synchronous connection dynamic random access memory
  • DR RAM Direct Rambus RAM
  • the processor is a general-purpose processor, DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component
  • the memory storage module
  • this application can be provided as methods, systems, or computer program products. Therefore, this application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, this application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.
  • computer-usable storage media including but not limited to disk storage, CD-ROM, optical storage, etc.
  • These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing equipment to work in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including the instruction device.
  • the device implements the functions specified in one process or multiple processes in the flowchart and/or one block or multiple blocks in the block diagram.
  • These computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of steps are executed on the computer or other programmable equipment to produce computer-implemented processing, thereby executing instructions on the computer or other programmable equipment Provides steps for realizing the functions specified in one process or multiple processes in the flowchart and/or one block or multiple blocks in the block diagram.

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Abstract

本申请实施例提供一种光载无线通信系统和非线性补偿方法，用以提高RoF系统的线性化效果。其中，所述RoF系统包括BBU和RRU，所述RRU包括电器件，所述BBU包括下行链路和反馈链路；所述下行链路上设置有预失真模块和光器件；所述反馈链路的输入端与所述光器件的输出端连接，所述反馈链路用于将所述光器件输出的非线性信号反馈给所述预失真模块；所述RoF系统还包括温度检测模块，用于检测所述电器件的温度值，并将所述温度值传递给所述预失真模块；所述预失真模块用于：根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD。

Description

一种光载无线通信系统和非线性补偿方法
相关申请的交叉引用
本申请要求在2020年03月11日提交中国专利局、申请号为202010167908.7、申请名称为“一种光载无线通信系统和非线性补偿方法”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
本申请涉及无线通信领域，尤其涉及一种光载无线通信系统和非线性补偿方法。
背景技术
与数字通用公共无线电接口(Common Public Radio Interface，CPRI)/增强型CPRI(Enhanced-CPRI，eCPRI)拉远技术相比，光载无线通信(Radio over Fiber，RoF)技术可以在提升数据传输速率的同时，有效地简化接入网中射频拉远单元(Radio Remote Unit，RRU)和基带处理单元(Building Base band Unit，BBU)的硬件结构。同时，模拟RoF系统能够支持副载波调制、波分复用(Wavelength Division Multiplexing，WDM)以及偏振复用等技术，可以实现多频带、多通信制式信号(如基带数字信号、长期演进(Long Term Evolution、LTE)信号、移动通信系统(Universal Mobile Telecommunications System，UMTS)信号、无线网络(Wi-Fi)信号、毫米波信号等)的共存共传，可进一步提升中心接入网(Cloud-Radio Access Network，C-RAN)在兼容性、接入用户数量以及吞入量等方面的表现。
但是，RoF系统中，下行链路上存在大量非线性元件，例如光电转换(Optical-Electro，O/E)器件、电光转换(Electro-Optical，E/O)器件以及功率放大器(Power Amplifier，PA)等，导致下行信号产生非线性失真。现有技术为了补偿下行链路上的非线性失真，通常从RRU侧设置反馈链路到BBU侧，通过反馈链路将RRU侧的下行信号反馈至BBU，同时在RRU侧设置预失真模块，预失真模块根据下行链路的输入信号和反馈链路传输回来的反馈信号确定下行链路的非线性特性，进而对下行链路做数字预失真(Digital Pre-Distortion，DPD)，以补偿下行链路的非线性失真。
现有技术中，为了降低硬件复杂度，反馈信号和上行数据一般共享同一条传输链路，因此需要在RRU侧添加控制电路，实现上行数据与反馈信息之间的切换；另外，为实现反馈信号从远端RRU传回BBU，反馈链路必须引入了新的E/O、O/E、PA等非线性元件。而控制电路、新的E/O、O/E、PA等器件的引入会给RoF系统带来额外的非线性失真，导致预失真模块不能得到正确的下行链路的非线性特性，最终预失真模块实际是对上下行全链路的非线性进行了建模与补偿。所以，现有技术中的RoF系统仍存在线性化效果差的问题。
发明内容
本申请实施例提供一种RoF系统和非线性补偿方法，用以提高RoF系统的线性化效果。
第一方面，本申请实施例提供一种RoF系统，所述RoF系统包括BBU和RRU，所述RRU包括电器件，所述BBU包括下行链路和反馈链路；所述下行链路上设置有预失真模块和光器件；所述反馈链路的输入端与所述光器件的输出端连接，所述反馈链路用于将所述光器件输出的非线性信号反馈给所述预失真模块；所述RoF系统还包括温度检测模块，用于检测所述电器件的温度值，并将所述温度值传递给所述预失真模块；所述预失真模块用于：根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD。
在本申请实施例中，将反馈链路直接连接至光器件的输出端的方式，可以减少反馈链路额外引入的非线性元器件数量，降低反馈链路的硬件复杂度，进而大幅度地降低甚至避免反馈链路额外引入的非线性失真，同时预失真模块基于反馈链路反馈的非线性信号以及电器件的温度值对基带信号进行DPD，可以保证对电域和光域的非线性均进行补偿，进而从整体上提高RoF系统的线性化效果。
在一个可能的设计中，所述预失真模块具体用于：根据所述温度值对原始基带信号进行第一DPD，以补偿所述电器件引起的非线性失真；根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，以补偿所述光器件引起的非线性失真。
本实施方式，一方面，基于反馈链路直接连接至光器件12的输出端的方式，可以减少反馈链路额外引入的非线性元器件数量，降低反馈链路的硬件复杂度，进而大幅度地降低甚至避免反馈链路额外引入的非线性失真，提高RoF系统对光域非线性补偿的准确性；另一方面，基于预失真模块11远程监控电器件的21的温度值的方式，可以提高RoF系统对电域非线性补偿的准确性，同时进一步简化RRU和BBU硬件复杂度，避免额外引入的非线性失真。
在一个可能的设计中，所述预失真模块中存储有所述电器件的温度和DPD参数的对应关系；所述预失真模块在根据所述温度值对原始基带信号进行第一DPD时，具体为：根据所述对应关系确定出与所述温度值相对应的DPD参数；根据确定出的DPD参数对原始基带信号进行第一DPD。
通过本实施方式，能够提高预失真模块对原始基带信号进行第一DPD的效率，进一步提高RoF系统的线性化效果。
在一个可能的设计中，所述温度检测模块具体用于：在检测到所述电器件的温度值更新时，将更新的温度值传递给所述预失真模块。
通过本实施方式，可以避免温度检测模块频繁地向预失真模块发送温度值，可以降低系统的功耗。
在一个可能的设计中，所述温度检测模块包括热敏电阻，所述热敏电阻设置在所述RRU中，且紧贴所述电器件设置。
本实施方式，温度检测模块通过热敏电阻实现，使得温度检测模块基本在RRU侧实现，可以节省BBU侧的计算需求。
在一个可能的设计中，所述温度检测模块包括感应光纤和拉曼光时域反射计；其中，所述感应光纤设置在所述RRU中，且紧贴所述电器件设置；所述拉曼光时域反射计设置在所述BBU中，且与所述预失真模块连接；所述感应光纤用于感应所述电器件的温度生成拉曼散射光信号，并反馈给所述拉曼光时域反射计；所述拉曼光时域反射计用于根据所述拉曼散射光信号确定所述电器件的温度。
通过本实施方式，温度检测模块基本在BBU侧实现，可以节省RRU侧的计算需求， 可以简化系统硬件复杂度。
在一个可能的设计中，所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，具体为：使用预设算法对经过第一DPD的基带信号和所述非线性信号进行计算，获得DPD参数；使用所述DPD参数对所述经过第一DPD的基带信号进行第二DPD；其中，所述预设算法为神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条cubic spline、正则分段线性方程CPWL中的任意一种算法。
通过本实施方式，可以进一步提高RoF系统对光域非线性补偿的准确性。
在一个可能的设计中，所述光器件包括电光调制器，所述电器件包括功率放大器。
通过本实施方式，可以对电光调制器和功率放大器引起的非线性失真进行补偿。
在一个可能的设计中，所述光器件还包括波分复用器，所述波分复用器的输入端与所述电光调制器的输出端连接。其中，所述反馈链路的输入端连接在所述波分复用器的输出端，这样可以对电光调制器和波分复用器引起的光域非线性失真进行整体补偿，进一步提高系统的线性化效果；或者，所述反馈链路的输入端连接在所述波分复用器和所述电光调制器之间，这样可以对电光调制器引起的光域非线性失真进行补偿，而不考虑波分复用器引起的光域非线性失真，可以降低预失真模块的计算复杂度。
在一个可能的设计中，所述BBU和所述RRU之间设置一条光纤；所述温度值以及所述RoF系统的上行信号、下行信号通过所述光纤传输。
通过本实施方式，可以降低光纤部署成本。
在一个可能的设计中，所述BBU和所述RRU之间设置有第一光纤和第二光纤；所述RoF系统的下行信号和所述温度值通过所述第一光纤传输，所述RoF系统的上行信号通过所述第二光纤传输；或者，所述RoF系统的下行信号通过所述第一光纤传输，所述RoF系统的上行信号或所述温度值通过所述第二光纤传输；或者，所述RoF系统的上行信号和下行信号通过所述第一光纤传输，所述温度值通过所述第二光纤传输。
通过本实施方式，可以提高RoF系统部署的灵活性。
在一个可能的设计中，所述反馈链路的输入端与所述光器件的输出端连接，包括：所述反馈链路的输入端与所述光器件的输出端直接连接；或者，所述反馈链路的输入端与所述光器件的输出端通过线性元件间接连接。
通过本实施方式，可以提高RoF系统部署的灵活性，提高方案的适用性。
第二方面，本申请实施例提供一种非线性补偿方法，应用于RoF系统，所述RoF系统包括基BBU和RRU，所述RRU包括电器件，所述BBU包括下行链路和反馈链路；所述下行链路上设置有预失真模块和光器件；所述反馈链路的输入端与所述光器件的输出端连接；所述RoF系统还包括温度检测模块；所述方法包括：所述反馈链路将所述光器件输出的非线性信号反馈给所述预失真模块；所述温度检测模块检测所述电器件的温度值，并将所述温度值传递给所述预失真模块；所述预失真模块根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD。
在一个可能的设计中，所述预失真模块根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD，具体包括：所述预失真模块根据所述温度值对原始基带信号进行第一数字预失真DPD，以补偿所述电器件引起的非线性失真；所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，以补偿所述光器件引起的非线性失真。
在一个可能的设计中，所述预失真模块中存储有所述电器件的温度和DPD参数的对应关系；所述预失真模块根据所述温度值对原始基带信号进行第一数字预失真DPD，具体包括：所述预失真模块根据所述对应关系确定出与所述温度值相对应的DPD参数；所述预失真模块根据确定出的DPD参数对原始基带信号进行第一DPD。
在一个可能的设计中，所述温度检测模块检测所述电器件的温度值，并将所述温度值传递给所述预失真模块，具体包括：所述温度检测模块在检测到所述电器件的温度值更新时，将更新的温度值传递给所述预失真模块。
在一个可能的设计中，所述温度检测模块包括热敏电阻，所述热敏电阻设置在所述RRU中，且紧贴所述电器件设置。
在一个可能的设计中，所述温度检测模块包括感应光纤和拉曼光时域反射计；其中，所述感应光纤设置在所述RRU中，且紧贴所述电器件设置；所述拉曼光时域反射计设置在所述BBU中，且与所述预失真模块连接；所述温度检测模块检测所述电器件的温度值，包括：所述感应光纤感应所述电器件的温度生成拉曼散射光信号，并反馈给所述拉曼光时域反射计；所述拉曼光时域反射计根据所述拉曼散射光信号确定所述电器件的温度。
在一个可能的设计中，所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，具体包括：所述预失真模块使用预设算法对经过第一DPD的基带信号和所述非线性信号进行计算，获得DPD参数；所述预失真模块使用所述DPD参数对所述经过第一DPD的基带信号进行第二DPD；其中，所述预设算法为神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条BBUbic spline、正则分段线性方程CPWL中的任意一种算法。
在一个可能的设计中，所述光器件包括电光调制器，所述电器件包括功率放大器。
在一个可能的设计中，所述光器件还包括波分复用器，所述波分复用器的输入端与所述电光调制器的输出端连接；所述反馈链路的输入端连接在所述波分复用器的输出端；或者，所述反馈链路的输入端连接在所述波分复用器和所述电光调制器之间。
在一个可能的设计中，所述BBU和所述RRU之间设置一条光纤；所述温度值以及所述RoF系统的上行信号、下行信号通过所述光纤传输。
在一个可能的设计中，所述BBU和所述RRU之间设置有第一光纤和第二光纤；所述RoF系统的下行信号和所述温度值通过所述第一光纤传输，所述RoF系统的上行信号通过所述第二光纤传输；或者，所述RoF系统的下行信号通过所述第一光纤传输，所述RoF系统的上行信号或所述温度值通过所述第二光纤传输；或者，所述RoF系统的上行信号和下行信号通过所述第一光纤传输，所述温度值通过所述第二光纤传输。
在一个可能的设计中，所述反馈链路的输入端与所述光器件的输出端连接，包括：所述反馈链路的输入端与所述光器件的输出端直接连接；或者，所述反馈链路的输入端与所述光器件的输出端通过线性元件间接连接。
第三方面，本申请实施例提供一种生成DPD查找表的方法，所述方法包括：从温度集合中选择第一温度，其中所述温度集合中包括如本申请实施例第一方面或第一方面任一种可能的设计中所述的电器件的至少一个可能的温度，所述第一温度为所述温度集合中的任一温度；确定所述电器件处于第一温度时的第一非线性模型；生成第一基带信号，并对所述基带信号上变频，获得射频信号；将所述射频信号输入所述第一非线性模型，生成非 线性射频信号；对所述非线性射频信号进行下变频、低通滤波，获得非线性基带信号；根据所述第一基带信号和所述非线性基带信号确定所述第一温度对应的第一DPD参数。遍历所述温度集合中的所有温度，重复以上步骤，得到所述温度集合中的各个温度对应的DPD参数；根据所述温度集合中的各个温度以及与各个温度对应的DPD参数生成DPD查找表。
在一个可能的设计中，根据所述第一基带信号和所述非线性基带信号确定所述第一温度对应的第一DPD参数，具体包括：采用神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条cubic spline、正则分段线性方程CPWL中的任意一种算法对所述第一基带信号和所述非线性基带信号进行计算，获得所述第一温度对应的第一DPD参数。
第四方面，本申请实施例提供一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序包括程序指令，所述程序指令在被计算机执行时，使所述计算机执行如本申请实施例第二方面或第二方面任一种可能的设计或第三方面或第三方面任一种可能的设计中所述的方法。
第五方面，本申请实施例提供一种计算机程序产品，所述计算机程序产品包括：计算机程序代码，当所述计算机程序代码在计算机上运行时，使得计算机执行本申请实施例第二方面或第二方面任一种可能的设计或第三方面或第三方面任一种可能的设计中所述的方法。
第六方面，本申请实施例提供一种处理装置，包括：至少一个处理器；以及，与所述至少一个处理器通信连接的存储器；其中，所述存储器存储有可被所述至少一个处理器执行的指令，所述至少一个处理器通过执行所述存储器存储的指令，使得本申请实施例第二方面或第二方面任一种可能的设计或第三方面或第三方面任一种可能的设计中所述的方法被执行。
第七方面，本申请实施例提供一种芯片，所述芯片与存储器耦合，用于读取并执行所述存储器中存储的程序指令，实现本申请实施例第二方面或第二方面任一种可能的设计或第三方面或第三方面任一种可能的设计中所述的方法。
附图说明
图1为模拟预失真方案的示意图；
图2为数字预失真方案的示意图；
图3为基于WDM的多波长RoF系统线性化方案的示意图；
图4为本申请实施提供的一种RoF系统的结构示意图；
图5为本申请实施提供的一种非线性补偿方法的流程图；
图6A、图6B为本申请实施提供的反馈链路的示意图；
图7A、图7B为本申请实施提供的温度检测模块22的示意图；
图8为本申请实施例提供的一种生成DPD查找表的方法的流程图；
图9A为基于直接学习架构的DPD技术参数估计原理图；
图9B为基于间接学习架构的DPD技术参数估计原理图；
图10为本申请实施提供的一种处理下行信号的方法的流程图；
图11A为本申请实施例提供的另一种可能的RoF系统的结构示意图；
图11B为本申请实施例提供的另一种可能的RoF系统的结构示意图；
图11C为本申请实施例提供的另一种可能的RoF系统的结构示意图；
图11D为本申请实施例提供的另一种可能的RoF系统的结构示意图；
图11E为本申请实施例提供的另一种可能的RoF系统的结构示意图；
图12为本申请实施例提供的一种处理装置的结构示意图；
图13为本申请实施例提供的另一种处理装置的结构示意图。
具体实施方式
目前，RoF系统预失真方案主要有三种：
方案一、模拟预失真方案。
参见图1，为模拟预失真方案的示意图。该方案的核心是光纤以及其他光器件引发的光波色散模型。理论分析表明，光信号在RoF系统中传输时引发的色散失真，是关于输入激光源电流的函数。因此对输入激光源的电流进行相应的模拟预失真处理，可以完成对光域色散的补偿效果。
具体的，设P out(t)为RoF系统光检测器(PD)的输出功率，P In(t)是激光源射频信号输入功率，τ(λ)为光信号传输的时延，是一个与光信号波长λ相关的函数，令α表示整个RoF链路的衰减，则有如下公式(Eq.1)成立：
Figure PCTCN2021076209-appb-000001
其中，
Figure PCTCN2021076209-appb-000002
表示色散斜率。公式(Eq.1)表现了RoF系统的色散情况。根据功率计算公式P＝I 2R可知，RoF系统输入输出功率都可以表示为关于激光源输入电流I的函数。因此，通过对输入电流I进行模拟预失真，可以补偿因为RoF系统色散引起的失真。
但是，该方案仅能对RoF系统中的光器件引发的光域色散失真进行了补偿，并没有考虑到RoF系统中电器件引起的非线性失真，也没有考虑到器件记忆特性引起的非线性失真；同时，该补偿方案对传输光波的波长，光纤的长度，器件工作的温度等其他参数敏感，因此普适性与鲁棒性较差。所以，RoF系统的线性化效果仍然很差。
方案二、数字预失真(DPD)方案。
参见图2，为数字预失真方案的示意图。该方案从RRU侧的天线处设置反馈链路至BBU，使得RRU的下行信号一路通过天线发送出去，一路通过反馈链路回到BBU。RRU侧设置数字预失真模块(Digi predis)，数字预失真模块根据下行链路的输入信号和反馈链路传输回来的反馈信号可以对下行链路的非线性特性进行建模，进而对下行链路做数字预失真，以补偿下行链路的非线性失真。
从图2可以看出，该方案需要建立从RRU侧到BBU侧的反馈链路。为了降低硬件复杂度，该方案中反馈信号和上行数据共享同一条链路，但此举需要在RRU侧添加控制电路，以实现上行信号与反馈信号在反馈链路上的切换。并且，反馈链路中引入了新的非线性器件，例如EO/OE模块、光纤以及功率放大器(PA)等，它们的存在也给RoF系统带来了额外的非线性失真，使得预失真模块最终执行的DPD操作实际是对上下行全链路的非线性进行了建模与补偿，并非我们实际需要的仅对下行链路非线性进行建模与补偿。所以，RoF系统的线性化效果仍然很差。
方案三、基于波分复用器(WDM)的DPD方案。
参见图3，是基于WDM的多波长RoF系统线性化方案示意图。在该方案中，由于WDM器件的引入，可以实现一根光纤传递不同波长的信号，这样该系统可以用不同波长完成上下行以及反馈信息的传递，比如用1550nm的波长传递下行数据信号而用1310nm的波长传递上行数据和反馈信息。
该方案同样对RoF系统全链路的非线性进行电域数字补偿。由于RoF链路的非线性表现与发送信号光强成正比关系，而信号光强的强度又与激光源接入信号的强度直接相关，所以该方案通常在反馈链路上增加可调衰减器，以调整反馈信号强度的方式，此举仅能降低反馈链路上E/O引入的额外非线性失真，但实际反馈链路上仍有额外失真的引入(长反馈光纤带来信号功率的衰减，色散等)。另外，多波长并行传递下行数据时，WDM的引入还会导致四波混频、光域串扰以及多个电域信号之间产生交调等问题，会额外引入更多的非线性，导致DPD参数学习更复杂。此外该方案采用离线DPD参数估计方法，距离实际场景化应用仍具有一定差距。
为了解决上述一个或多个技术问题，本申请实施例提供一种RoF系统和非线性补偿方法，用于提高RoF系统的线性化效果。本申请实施例提供的RoF系统和非线性补偿方法可以适用于各种通信系统，例如：长期演进(long term evolution，LTE)系统、第五代(5th generation，5G)系统，如NR，以及下一代的通信系统，如6G系统等。当然，本申请实施例的技术方案也可以应用于其它的通信系统，例如卫星通信系统、车联网通信系统等等。
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整的描述。
参见图4，为本申请实施提供的一种RoF系统的结构示意图。RoF系统包括基带单元(Building Base band Unit，BBU)01和远端射频单元(Remote Radio Unit，RRU)02，BBU01和RRU02通过光纤连接；其中，RRU02包括电器件21，BBU01包括下行链路和反馈链路，下行链路上设置有预失真模块11和光器件12，反馈链路的输入端与光器件12的输出端连接，反馈链路的输出端与预失真模块11连接。RoF系统还包括温度检测模块22，温度检测模块22可以设置在RRU02，或者设置在BBU01，或者部分设置在BBU01、部分设置在RRU02，这里不做限制。图4中是以温度检测模块22设置在RRU02为例。
应理解，本文中所涉及的“连接”，除非有特别说明之外，均可以包括直接连接和间接连接两种情况。例如，反馈链路的输入端可以与光器件12的输出端直接相连，反馈链路的输入端与光器件12的输出端也可以通过其它线性元件间接连接，例如反馈链路的输入端与光器件12的输出端之间还可以设置电阻、电容等对非线性失真影响较小或者没有影响的元器件。同理，反馈链路的输出端与预失真模块连接也可以直接连接和间接连接两种情况，这里不再赘述。
预失真模块11的具体硬件实现可以通过现场可编程门阵列(field-programmable gate array，FPGA)，专用集成芯片(Application Specific Integrated Circuit，ASIC)，系统芯片(System on Chip，SoC)，中央处理器(Central Processor Unit，CPU)，网络处理器(Network Processor，NP)，数字信号处理电路(Digital Signal Processor，DSP)，微控制器(Micro Controller Unit，MCU)、可编程控制器(Programmable Logic Device，PLD)或其他集成芯片等来实现。预失真模块11可以存储并运行本申请实施例提供的非线性补偿方法所对应的软件或程序，进而实现本申请实施例提供的非线性补偿方法。
参见图5，为图4所示RoF系统对下行信号进行非线性补偿的具体方法，包括：
S501、反馈链路将光器件12输出的非线性信号反馈给预失真模块11；温度检测模块22检测电器件21的温度值，并将温度值发送给预失真模块11。
S502、预失真模块11根据温度值和非线性信号对基带信号进行DPD操作。
具体的，预失真模块11可以针对光域非线性和电域非线性分别建模并进行补偿：
1)预失真模块11根据温度值对原始基带信号进行第一DPD，实现对电器件21引起的非线性失真的补偿(即电域补偿)；
2)预失真模块11根据反馈链路的输出信号(即光器件12输出的非线性信号)对经过第一DPD的基带信号进行第二DPD，实现对光器件12引起的非线性失真的补偿(即光域补偿)。
本申请实施例中，RoF系统中的预失真模块11针对光域非线性和电域非线性分别进行建模和补偿，一方面，基于反馈链路直接连接至光器件12的输出端的方式，可以减少反馈链路额外引入的非线性元器件数量，降低反馈链路的硬件复杂度，进而大幅度地降低甚至避免反馈链路额外引入的非线性失真，提高RoF系统对光域非线性补偿的准确性；另一方面，基于预失真模块11远程监控电器件21的温度值的方式，可以提高RoF系统对电域非线性补偿的准确性，同时进一步简化RRU和BBU硬件复杂度，避免额外引入的非线性失真。综上，本申请实施例可以提高RoF系统的线性化效果并降低RoF系统的硬件复杂度。
下面，介绍本申请实施例中的光器件12和电器件21。
一种可能的设计中，光器件12包括电光调制器(E/O)，电器件21包括功率放大器(PA)。
一般而言，在BBU侧，电光调制器对RoF系统的非线性影响最大，所以通过将电光调制器输出的非线性信号反馈至预失真模块11，可以使得预失真模块11更加准确地补偿电光调制器引起的光域非线性失真，而在RRU侧，PA是引起电域非线性的主要器件，因此将PA的温度值反馈至预失真模块11，可以使得预失真模块11更加准确地补偿PA引起的电域非线性失真，进而实现光域和电域的非线性补偿。
一种可能的设计中，如果RoF系统是多波长RoF拉远系统，则光器件12除了电光调制器之外，还可以包括波分复用器(WDM)，波分复用器的输入端与电光调制器的输出端(直接或间接)连接。
在此设计中，反馈链路可以有以下两种设计方式：
方式1，参见图6A，反馈链路的输入端连接在波分复用器的输出端。这种方式下，预失真模块获得的反馈信号能够反映电光调制器和波分复用器整体引起的非线性特性，因此预失真模块11同时可以对电光调制器和波分复用器引起的非线性进行补偿，使得下行信号具有更好的线性化效果。
方式2，参见图6B，反馈链路的输入端连接在波分复用器和电光调制器之间。这种方式下，预失真模块获得的反馈信号能够反映电光调制器引起的非线性特性，因此预失真模块11可以对电光调制器引起的非线性进行补偿，而不考虑WDM引起的非线性失真，能够降低预失真模块11的计算量和复杂度，提高运算效率。
应理解，以上只是对本申请实施例可能涉及到的光器件12和电器件21的示例，并不能用来限定本申请实施例中光器件12和电器件21具体类型或数量。例如，在具体实施时，电器件21还可以包括衰减器、光电转换器等；光器件12还可以包括电光转换器、光域放大器、光分路器等。
进一步的，如果光器件12涉及多个，则可以将反馈链路的输入端连接至最后一个光器件的输出端，使得反馈信号能够体现所有光器件12的非线性特征，进而使得预失真模块11可以对下行链路整体的光域非线性失真进行补偿。
进一步的，如果电器件21设计多个，则可以分别对每个电器件进行温度监控，并对每个电器件的温度对该电器件引起的非线性失真进行补偿。
下面，介绍温度检测模块22的具体实现方式。
一种可能的设计中，本申请实施例中的温度检测模块22可以由热敏电阻来实现。具体的，热敏电阻可以设置在RRU02中，且紧贴电器件21设置。
参见图7A，为热敏电阻测温的一种可能的实现方式。首先，将热敏电阻Rx贴在目标电器件21(图7A中以功率放大器PA为例)上；然后，将热敏电阻Rx与其他三个电阻值已知的定值电阻(R1、R2、R3)联入惠斯通电桥中，且将惠斯通电桥连接直流电压源VCC(图6A中用电池表示电源，但是实际可以不仅限于电池，只要是电压稳定的直流电压源就行)。当PA温度发生变化时，热敏电阻阻值变化，从而惠斯通电桥两臂之间的电压值也将发生变化。其中，电压差值为：
Figure PCTCN2021076209-appb-000003
此时，根据电压差值-温度值对应表就可以确定出PA的温度。
另一种可能的设计中，温度检测模块22可以由感应光纤和拉曼光时域反射计实现。
具体的，参见图7B，温度检测模块22包括拉曼光时域反射计221和感应光纤222，其中感应光纤222设置在RRU02中，且紧贴电器件21(图7B中以PA为例，感应光纤222环绕在PA周围)设置。拉曼光时域反射计221包括解波分复用器、光检测器(PD)，模数转换器(ADC)以及比较电路。拉曼光时域反射计设置在BBU01中，且与预失真模块11连接。
感应光纤可以感应电器件21的温度生成拉曼散射光信号，并反馈给拉曼光时域反射计；拉曼光时域反射计根据拉曼散射光信号确定电器件21的温度。
具体的，当光信号在光纤中传递时，会有散射光生成。其中拉曼散射是与光纤分子的热振动相关联的，因而对温度有敏感，可以用来进行温度测量。拉曼散射光包含两个频率的光：斯托克斯(Stokes)光和反斯托克斯(Anti-Stokes)光。它们的频率分布在入射光频率的两侧且反向传输。因为Anti-Stokes散射光对温度敏感，其强度受温度调制，而Stokes散射光基本上与温度无关，所以两者光强的比值只与光纤的温度有关，因此可以用光纤进行温度感知。
应理解，以上热敏电阻和拉曼光时域反射计仅仅是作为温度检测模块22的示例而非限定，在具体实施时还可以采用其他方式实现，本申请实施例不做限制。
下面，介绍预失真模块11根据温度值对原始基带信号进行第一DPD的具体实现方式。
一种可能的设计中，预失真模块11中可以预先存储电器件21的温度和DPD参数的对应关系，当预失真模块11在根据温度值对原始基带信号进行第一DPD时，直接根据对应关系确定出与温度值相对应的DPD参数，然后根据确定出的DPD参数对原始基带信号进行第一DPD。
以电器件21为PA为例，假设模拟信号经过功率放大器PA后发生非线性放大，在不考虑PA的记忆特性时，对PA的非线性行为进行数学建模，可以得到放大输出信号幅值A(r) 与相位
Figure PCTCN2021076209-appb-000004
的计算公式：
Figure PCTCN2021076209-appb-000005
Figure PCTCN2021076209-appb-000006
Figure PCTCN2021076209-appb-000007
其中，g是小信号放大增益，r是输入信号的幅值，L是信号放大最大幅值，s是平滑参数，a是PA在线性工作时的相位变化梯度值，b是PA饱和状态时相位变化梯度值，c时PA无信号输入时初始相位值，d是PA饱和状态时相位修正值。根据PA实际测试得到的幅值-幅值(AM-AM)转化图以及相位-幅值(PM-AM)转化图，通过调整上述公式的参数值，可以实现PA非线性模型的拟合。当PA工作温度发生变化时，AM-AM曲线和PM-AM曲线会随之发生变化。此时需要细调上述公式中的参数一遍再次完成模型拟合。当将PA的无记忆模型与其工作温度进行耦合后，就得到了与温度相关的模型集合。
进一步的，根据不同的PA模型，进行DPD操作，并记录DPD参数形成查找表(存储电器件21的温度和DPD参数的对应关系)，则该查找表可以通过PA温度寻址，得到不同温度值对应的DPD参数值。
参见图8，为本申请实施例提供的一种生成DPD查找表的方法，包括：
S801、从温度集合中选择第一温度，其中温度集合中包括电器件21的至少一个可能的温度，第一温度为温度集合中的任一温度；
S802、确定电器件21处于第一温度时的第一非线性模型；
S803、生成第一基带信号，并对基带信号上变频，获得射频信号；
S804、将射频信号输入第一非线性模型，生成非线性射频信号；
S805、对非线性射频信号进行下变频、低通滤波，获得非线性基带信号；
S806、根据第一基带信号和非线性基带信号确定第一温度对应的第一DPD参数。
具体的，这里可以采用神经网络模型、沃尔特拉(Volterra)多项式、记忆多项式(Memory polynomial,MP)、归一化记忆多项式(Generalized memory polynomial,GMP)、维纳-哈默斯坦(Wiener-Hammerstein)多项式、立方样条(cubic spline)、正则分段线性方程(Canonical piecewise-linear,CPWL)等算法中的任意一种算法对第一基带信号和非线性基带信号进行计算，进而获得第一温度对应的第一DPD参数。
S807、判断是否遍历温度集合中的所有温度；若为是，则执行步骤S808，否则回到步骤S801，调整温度值并重复步骤S802-S806，直至温度集合中的所有温度被遍历。
S808、根据温度集合中的各个温度以及与各个温度对应的DPD参数生成DPD查找表。
在具体实施时，操作人员可以提前将DPD查找表存储在预失真模块11中，这样，RoF系统在处理下行信号时，预失真模块11可以直接读取该DPD查找表以对下行信号进行非线性补偿。另外，操作人员也可以将图8所示的算法存储在预失真模块11中，预失真模块 11可以直接运行该算法生成DPD查找表，或者是运行该算法更新原有的DPD查找表。
需要说明的是，具体实施时，除了根据电器件21的温度对RoF系统的电域非线性失真建模和补偿外，如果电器件21还有其他属性会影响电域非线性失真，则还可以根据该其他属性对RoF系统的电域非线性失真建模和补偿，例如PA的材料(砷化镓，氮化镓等)。
一种可能的设计中，温度检测模块22可以是在检测到电器件21的温度值更新(发生变化)时，才将更新的温度值传递给预失真模块11；或者，温度检测模块22按照设定的时间间隔，周期性地向预失真模块11是温度值，本申请实施例不做限制。这样，可以避免温度检测模块22频繁地向预失真模块发送温度值，可以降低系统的功耗。
温度检测模块22判断温度值更新的具体实现方式可以是：温度检测模块22确定当前温度和上一次发送的温度的差值达到设定的阈值，则确定电器件21的温度值发生更新。
其中，设定的阈值可以与DPD查找表中的温度值的分布相关。例如，DPD查找表中的温度值分布为0℃～100℃，相邻温度值的间隔为1℃，即“0℃，1℃,2℃,3℃，……，98℃,99℃，100℃”，那么该设定阈值可以设定为1℃或者1℃的整数倍，这样才能保证温度测量模块22发送给预失真模块11的温度值在DPD查找表中存在对应的DPD参数，进一步保证电域非线性补偿的可靠性。
下面，介绍预失真模块11根据反馈链路的输出信号对经过第一DPD的基带信号进行第二DPD的具体实现方式。
具体的，预失真模块11可以使用预设算法对经过第一DPD的基带信号和非线性信号进行计算，获得DPD参数；然后使用DPD参数对经过第一DPD的基带信号进行第二DPD。
其中，预设算法包括但不限于以下机器学习算法：神经网络模型、沃尔特拉(Volterra)多项式、记忆多项式(Memory polynomial,MP)、归一化记忆多项式(Generalized memory polynomial,GMP)、维纳-哈默斯坦(Wiener-Hammerstein)多项式、立方样条(cubic spline)、正则分段线性方程(Canonical piecewise-linear,CPWL)等。
以记忆多项式为例。假设输入信号(经过第一DPD的基带信号)为x(n)，下行链路的输出为y(n)(这是指BBU侧的输出)，则可以通过以下公式表示下行信号的非线性：
Figure PCTCN2021076209-appb-000008
其中，表示a km表示第k阶，记忆深度为m时的非线性项的参数。
然后，将非线性系统的输出信号进行反馈，与发送信号建立逆失真模型，即：
Figure PCTCN2021076209-appb-000009
通过求解公式(Eq.7)，得到参数向量W＝[w 11,w 12,…w km,…]，则该参数W便可以作为DPD参数用来进行DPD操作。
其中，DPD技术参数估计的架构可以有两种：1)如图9A所示，直接学习架构，使用反馈信号Y(n)和DPD操作前的下行信号X(n+k)进行DPD参数的估计(其中，为了将反馈信号和下行信号在时间上对齐，所以需要对下行信号做一个延迟k，即将X(n)变换成X(n+k))；2)如图9B所示，间接学习架构，使用反馈信号Y(n)和DPD操作后的下行信号U(n)(即预失真模块11的输入信号)进行DPD参数的估计。
求解公式(Eq.7)可以采用最小二乘法、最小均方值法或者奇异值分解法等算法，本申请实施例不做限制。
下面，介绍本申请实施例中，BBU01和RRU02之间光纤设置方式。
具体的，BBU01和RRU02之间可以设置一条或多条光纤用来传输BBU01和RRU02之间的信号。
示例性的，BBU01和RRU02之间设置一条光纤，那么温度值、上行信号、下行信号等均通过该条光纤传输。
示例性的，BBU01和RRU02之间可以设置两条光纤，如第一光纤和第二光纤；那么BBU01和RRU02之间的信号传输可以包括以下几种分配方式：1)RoF系统的下行信号和温度值通过第一光纤传输，RoF系统的上行信号通过第二光纤传输；2)RoF系统的下行信号通过第一光纤传输，RoF系统的上行信号或温度值通过第二光纤传输；3)RoF系统的上行信号和下行信号通过第一光纤传输，温度值通过第二光纤传输。
以上介绍了RoF系统中各个模块的具体实现方式，下面对RoF系统对下行信号处理的整体流程进行介绍。参见图10，包括：
S1001、生成数字基带信号；
S1002、确定是否需要更新PA的温度，如果需要更新，则执行步骤S1015(根据PA的温度，执行优化静态非线性模型，更新静态DPD参数)，否则继续步骤S1002；
S1003、根据步骤S1016确定出的DPD参数对下行信号执行静态DPD操作(即上文中的第一DPD)；
S1004、执行动态DPD操作，即上文中的第二DPD，动态DPD的参数由步骤S1014获得(对反馈信号解波分复用、光电转换、下变频、滤波、数模转换等，得到非线性的数字基带信号，根据原始基带信号和非线性基带信号获得动态DPD参数)；
S1005、对动态DPD后的信号进行数模转换、上变频、滤波等，生成射频信号；
S1006、对射频信号进行电光转换，生成光信号；
S1007、如果是多波长并行传递下行数据，则还需要执行多波长光信号波分复用操作；
S1008、获得BBU侧的下行输出，判断是否需要更新动态DPD参数，如果需要则执行步骤S1015，否则继续执行步骤S1009；
S1009、通过光纤将下行信号传递至RRU侧；
S1010、如果是多波长并行传递下行数据，则RRU侧还需要执行多波长光信号解波分复用操作；
S1011、将光信号转换为电信号；
S1012、对电信号进行功率放大操作，获得射频信号；
S1013、将射频信号通过天线发射。
通过上述过程，即可实现将线性化良好的下行信号通过天线发送出去。
本申请实施例所述的各实施方式可以相互结合，以实现不同的技术效果。下面，通过列举几个具体的示例来说明。
示例1
参见图11A，为本申请实施例提供的另一种可能的RoF系统的结构示意图。
以下，先对各元器件的标号进行统一说明。
A1：基带资源池。其负责产生下行基带数据以及接收上行基带数据。
A2：预失真模块。其包含准静态-动态级联DPD模块以及相应的参数估计模块，准静态PA模型查找表。
A3：数模转换器(DAC)。用来将数字基带信号转为基带模拟信号。
A4：混频器。用来实现上下变频操作。
A5：本振。提供射频载波。
A6：带通滤波器。
A7：低噪声放大器。
A8：电光调制(E/O)模块。将射频信号转化为光信号。它即可能是直接调制器，也可以是外部调制器。
A9：光分路器。它将一条光信号分为两路光信号。两路光信号之间的功率比根据选用的分路器决定。本发明中我们采用9:1的功率比。从BBU到RRU的下行信号占功率90％，有10％的光信号作为本地反馈。
A10：光纤。本地反馈链路中光纤长度不超过10m，BBU到RRU之间的光纤长度为5～50km。
A11：波分复用器。用来实现多个波长光信号的汇合。
A12：光开关。选择所需要的波长信号通过。
A13：光检测器(PD，O/E)。将光信号转化为电信号。
A14：增益可调放大器。
A15：低通滤波器。
A16：模数转换器(ADC)。将基带模拟信号转为基带数字信号。
A17：解波分复用器。将一路光纤上传输的多个波长信号一一分配到不同的端口输出。
A18：衰减器，可以是固定衰减器，也可以是可调衰减器。
A19：功率放大器(PA)。
A20：天线。
A21：感应光纤。盘绕在AAU侧PA的周围，用来感应PA温度。
A22：拉曼光时域反射计(ROTDR)。用于判定远端感应光纤的温度。
A23：光域放大器。
本示例中的RoF系统至少包含一条上下行链路以及一条本地反馈链路。光分路器将经过波分复用器的光信号一分为二，其中一束传递下行数据，另一束用于本地反馈。本地反馈光信号首先通过解波分复用器根据波长分为多路信号，再用光开关，根据分时复用的方式依次将不同波长光信号送入本地PD中。下行链路配合电开关选择接收本地反馈数据信号或者上行信号。这里的上行信号既可以是上行数据信号，也可以是用来监控温度的拉曼散射光波。远端RRU侧，将感应光纤围绕PA布置。接收到的光信息经过光分路器，一束通向射频链路，另一束送往感应光纤。BBU侧使用ROTDR远程监控PA温度。本地反馈信号结合远端PA温度信息，利用多项式方法，静态/准静态模型以及神经网络等参数估计方法就可以DPD操作所需要的参数。
与现有技术相比，本示例采用多路双层级联DPD架构，针对光域非线性和电域非线性分别建模并进行补偿。其中，电域非线性建模和补偿通过在BBU侧对PA温度进行远程监控实现，通过将监控操作和电路设置在BBU侧，可以简化系统硬件复杂度，同时BBU侧根据温度信息对PA引入的非线性进行建模和补偿，可以避免现有技术通过RRU侧至BBU侧检测复杂反馈链路的设计所引入的额外非线性。光域非线性建模和补偿通过在BBU本地建立信号反馈链路实现，因为该链路中包含多种光器件，如电光转换器，波分复用器， 解波分复用器以及可能存在的光放大器等，所以此方案中DPD技术可以对多种光器件产生的非线性失真进行统一补偿(考虑了诸多光器件存在引入的四波混频、邻波长串扰等情况)，可以提高光域非线性补偿的准确性。另外，采用光纤测温的方法，准确度高且不易受到电磁干扰。
示例2
参见图11B，为本申请实施例提供的另一种可能的RoF系统的结构示意图。
本示例中的RoF系统至少包含一条上下行链路以及一条本地反馈链路。同样利用光分路器将E/O模块的输出光信号一分为二，其中一束传递下行数据，另一束用于本地反馈。有多少个E/O模块则有多少个光分路器与之对应。BBU侧利用光开关，根据分时复用的方式依次将不同波长光信号送入本地PD中。配合电开关选择接收本地反馈数据信号，或者上行信号。这里的上行信号既可以是上行数据信号，也可以是用来监控温度的拉曼散射光波。远端RRU侧，将感应光纤围绕PA布置。接收到的光信息经过光分路器一束通向射频链路一束送往感应光纤。BBU侧利用ROTDR远程监控PA温度。本地反馈信号结合得到的远端PA温度信息，利用多项式方法，静态/准静态模型以及神经网络等参数估计方法，得到级联DPD操作所需要的参数。
与现有技术相比，本示例同样采用多路双层级联DPD架构，针对光域非线性和电域非线性分别建模并进行补偿。其中，电域非线性建模和补偿通过在BBU侧对PA温度进行远程监控实现，可以简化系统硬件复杂度，同时可以避免现有技术通过RRU侧至BBU侧检测复杂反馈链路的设计所引入的额外非线性。光域非线性建模和补偿通过在BBU本地建立信号反馈链路实现，可以对多种光器件产生的非线性失真进行统一补偿(考虑了诸多光器件存在引入的四波混频、邻波长串扰等情况)。与示例1不同的是，本示例反馈链路设置在波分复用器之前，可进一步简化系统硬件复杂度。
示例3
参见图11C，为本申请实施例提供的另一种可能的RoF系统的结构示意图。
本示例中的RoF系统至少包含一条上下行链路以及一条本地反馈链路。同样利用光分路器将E/O模块的输出光信号一分为二，其中一束传递下行数据，另一束用于本地反馈。光分路器与E/O模块一一对应。BBU侧用光开关，根据分时复用的方式依次将不同波长光信号送入本地PD中。上行数据利用独立的WDM-RoF链路进行传输。拉曼散射光波与本地反馈光信号接入同一个光开关并配合电开关，分别完成反馈信号以及散射信号的接收。远端RRU侧，将感应光纤围绕PA布置。接收到的下行光信息经过光分路器，一束通向射频链路另一束送往感应光纤。BBU侧利用ROTDR远程监控PA温度。本地反馈信号结合得到的远端PA温度信息，利用多项式方法，静态/准静态模型以及神经网络等参数估计方法，得到级联DPD操作所需要的参数。
与现有技术相比，本示例同样采用多路双层级联DPD架构，针对光域非线性和电域非线性分别建模并进行补偿。其中，电域非线性建模和补偿通过在BBU侧对PA温度进行远程监控实现，可以简化系统硬件复杂度，同时可以避免现有技术通过RRU侧至BBU侧检测复杂反馈链路的设计所引入的额外非线性。光域非线性建模和补偿通过在BBU本地建立信号反馈链路实现，可以对多种光器件产生的非线性失真进行统一补偿(考虑了诸多光器件存在引入的四波混频、邻波长串扰等情况)。与示例1、2不同的是，本示例中的温度监控采用单独的链路传输，可以避免上行数据和温度信息传输相干扰的问题，进一步提 高RoF系统的非线性补偿的准确性。
示例4
参见图11D，为本申请实施例提供的另一种可能的RoF系统的结构示意图。
本示例中的RoF系统采用电域温度监控方法。PA温度监控与控制电路A25，实现PA温度的观测，确定温度值回传方案。当衰减器为可调衰减器时，此模块可以控制衰减器的衰减值。
本示例中的RoF系统至少包含一条上下行链路以及一条本地反馈链路，而无需远端RRU侧的信号反馈链路。BBU侧用光分路器将E/O模块发出的光信号一分为二，一束下行传递数据，另一束进行本地反馈。考虑到有多个电光调制器存在，则需要光开关，采用分时复用的方式依次将不同波长的反馈信号送入本地PD中。远端RRU侧，利用热敏电阻配合查找表对PA的温度进行监控。根据PA的温度变化，可以在RRU侧自发调整衰减器的值，保证发送信号功率处于PA放大线性区；也可以采用移频键控(Frequency-shift keying，FSK)调制或其他调制方式将温度信息，通过上行链路传递回BBU。该信息可以采用时分复用方式与上行信息共享传输链路也可以在上行数据帧结构中额外开辟时隙资源。本地反馈信号结合得到的远端PA温度信息，利用多项式方法，静态/准静态模型以及神经网络等方法训练得到级联预失真操作所需要的参数。
与现有技术相比，本示例同样采用多路双层级联DPD架构，针对光域非线性和电域非线性分别建模并进行补偿。其中，电域非线性建模和补偿通过在BBU侧对PA温度进行远程监控实现，可以简化系统硬件复杂度，同时可以避免现有技术通过RRU侧至BBU侧检测复杂反馈链路的设计所引入的额外非线性。光域非线性建模和补偿通过在BBU本地建立信号反馈链路实现，可以对多种光器件产生的非线性失真进行统一补偿(考虑了诸多光器件存在引入的四波混频、邻波长串扰等情况)。与示例1、2、3不同的是，本示例采用电域温度监控方法，控制电路采用调整可调衰减器的值或者PA的偏置电压值，从而可以实现射频信号的线性放大，能够进一步节省BBU侧的计算需求。
示例5
参见图11E，为本申请实施例提供的另一种可能的RoF系统的结构示意图。
本示例中的RoF系统采用电域温度监控方法。RoF系统至少包含一条上下行链路以及一条本地反馈链路，而无需远端RRU侧的信号反馈链路。BBU侧用光分路器将E/O模块以及可选的经过光域放大器的光信号一分为二，一束下行传递数据，另一束进行本地反馈。远端RRU侧，利用热敏电阻配合查找表对PA的温度进行监控。根据PA的温度变化，可以在RRU端自发调整衰减器的值，保证发送信号功率处于PA放大线性区；也可以采用FSK调制或其他调制方式将温度信息，通过上行链路传递回BBU。该信息可以采用时分复用方式与上行信息共享传输链路也可以在上行数据帧结构中额外开辟时隙资源。本地反馈信号结合得到的远端PA温度信息，利用多项式方法，静态/准静态模型以及神经网络等方法训练得到级联预失真操作所需要的参数。
与现有技术相比，本示例同样采用多路双层级联DPD架构，针对光域非线性和电域非线性分别建模并进行补偿。其中，电域非线性建模和补偿通过在BBU侧对PA温度进行远程监控实现，可以简化系统硬件复杂度，同时可以避免现有技术通过RRU侧至BBU侧检测复杂反馈链路的设计所引入的额外非线性。光域非线性建模和补偿通过在BBU本地建立信号反馈链路实现，可以对多种光器件产生的非线性失真进行统一补偿(考虑了诸多 光器件存在引入的四波混频、邻波长串扰等情况)。与示例1、2、3、4不同的是，本示例中采用单波长传递下行数据，因而可以不用设置WDM，进而可以避免WDM引入给RoF系统带来的非线性，能够进一步节省BBU侧的计算需求。
基于同一技术构思，本申请实施例还提供一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序包括程序指令，所述程序指令在被计算机执行时，使所述计算机执行如上述实施例提供的非线性补偿方法。
基于同一技术构思，本申请实施例还提供一种计算机可读存储介质，所述计算机可读存储介质存储有计算机程序，所述计算机程序包括程序指令，所述程序指令在被计算机执行时，使所述计算机执行如上述实施例提供的生成DPD查找表的方法。
基于同一技术构思，本申请实施例还提供一种计算机程序产品，所述计算机程序产品包括：计算机程序代码，当所述计算机程序代码在计算机上运行时，使得计算机执行如上述实施例提供的非线性补偿方法。
基于同一技术构思，本申请实施例还提供一种计算机程序产品，所述计算机程序产品包括：计算机程序代码，当所述计算机程序代码在计算机上运行时，使得计算机执行如上述实施例提供的生成DPD查找表的方法。
基于同一技术构思，参见图12，本申请实施例还提供一种处理装置，包括：至少一个处理器1201；以及，与所述至少一个处理器通信连接的存储器1202；所述存储器1202存储有可被所述至少一个处理器1201执行的指令，所述至少一个处理器1201通过执行所述存储器1202存储的指令，使得上述实施例提供的非线性补偿方法被执行。
其中，所述处理器1201和所述存储器1202可以通过接口电路耦合，也可以集成在一起，这里不做限制。
本申请实施例中不限定上述处理器1201以及存储器1202之间的具体连接介质。本申请实施例在图12中以存储器1202、处理器1201之间通过总线1203连接，总线在图12中以粗线表示，其它部件之间的连接方式，仅是进行示意性说明，并不引以为限。所述总线可以分为地址总线、数据总线、控制总线等。为便于表示，图12中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线。
基于同一技术构思，参见图13，本申请实施例还提供一种处理装置，包括：至少一个处理器1301；以及，与所述至少一个处理器1301通信连接的存储器1302；所述处理器1301和所述存储器1302可以通过接口电路耦合也可以集成在一起。所述存储器1302存储有可被所述至少一个处理器1301执行的指令，所述至少一个处理器1301通过执行所述存储器1302存储的指令，使得上述实施例提供的生成DPD查找表的方法被执行。
其中，所述处理器1301和所述存储器1302可以通过接口电路耦合，也可以集成在一起，这里不做限制。
本申请实施例中不限定上述处理器1301以及存储器1302之间的具体连接介质。本申请实施例在图13中以存储器1302、处理器1301之间通过总线1303连接，总线在图13中以粗线表示，其它部件之间的连接方式，仅是进行示意性说明，并不引以为限。所述总线可以分为地址总线、数据总线、控制总线等。为便于表示，图13中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线。
基于同一技术构思，本申请实施例还提供一种芯片，所述芯片可以与存储器耦合，或者所述存储器可以集成在所述芯片内部，这里不做限制。
所述芯片可以读取并执行所述存储器中存储的程序指令，实现上述实施例提供的非线性补偿方法。
基于同一技术构思，本申请实施例还提供一种芯片，所述芯片可以与存储器耦合，或者所述存储器可以集成在所述芯片内部，这里不做限制。
所述芯片可以读取并执行所述存储器中存储的程序指令，实现上述实施例提供的生成DPD查找表的方法。
应理解，本申请实施例中提及的处理器可以通过硬件实现也可以通过软件实现。当通过硬件实现时，该处理器可以是逻辑电路、集成电路等。当通过软件实现时，该处理器可以是一个通用处理器，通过读取存储器中存储的软件代码来实现。
示例性的，处理器可以是中央处理单元(central processing unit，CPU)，还可以是其他通用处理器、数字信号处理器(Digital Signal Processor，DSP)、专用集成电路(Application Specific Integrated Circuit，ASIC)、现成可编程门阵列(Field Programmable Gate Array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
应理解，本申请实施例中提及的存储器可以是易失性存储器或非易失性存储器，或可包括易失性和非易失性存储器两者。其中，非易失性存储器可以是只读存储器(Read-Only Memory，ROM)、可编程只读存储器(Programmable ROM，PROM)、可擦除可编程只读存储器(Erasable PROM，EPROM)、电可擦除可编程只读存储器(Electrically EPROM，EEPROM)或闪存。易失性存储器可以是随机存取存储器(Random Access Memory，RAM)，其用作外部高速缓存。通过示例性但不是限制性说明，许多形式的RAM可用，例如静态随机存取存储器(Static RAM，SRAM)、动态随机存取存储器(Dynamic RAM，DRAM)、同步动态随机存取存储器(Synchronous DRAM，SDRAM)、双倍数据速率同步动态随机存取存储器(Double Data Eate SDRAM，DDR SDRAM)、增强型同步动态随机存取存储器(Enhanced SDRAM，ESDRAM)、同步连接动态随机存取存储器(Synchlink DRAM，SLDRAM)和直接内存总线随机存取存储器(Direct Rambus RAM，DR RAM)。
需要说明的是，当处理器为通用处理器、DSP、ASIC、FPGA或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件时，存储器(存储模块)可以集成在处理器中。
应注意，本文描述的存储器旨在包括但不限于这些和任意其它适合类型的存储器。
本领域内的技术人员应明白，本申请的实施例可提供为方法、系统、或计算机程序产品。因此，本申请可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且，本申请可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程序产品的形式。
本申请是参照根据本申请的方法、设备(系统)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器，使得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。
这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中，使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品，该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。
这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上，使得在计算机或其他可编程设备上执行一系列步骤以产生计算机实现的处理，从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。
显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本申请的范围。这样，倘若本申请的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (28)

  1. 一种光载无线通信RoF系统，其特征在于，所述RoF系统包括基带单元BBU和远端射频单元RRU，所述RRU包括电器件，所述BBU包括下行链路和反馈链路；
    所述下行链路上设置有预失真模块和光器件；所述反馈链路的输入端与所述光器件的输出端连接，所述反馈链路用于将所述光器件输出的非线性信号反馈给所述预失真模块；
    所述RoF系统还包括温度检测模块，用于检测所述电器件的温度值，并将所述温度值传递给所述预失真模块；
    所述预失真模块用于：根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD。
  2. 如权利要求1所述的RoF系统，其特征在于，所述预失真模块具体用于：
    根据所述温度值对原始基带信号进行第一DPD，以补偿所述电器件引起的非线性失真；
    根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，以补偿所述光器件引起的非线性失真。
  3. 如权利要求2所述的RoF系统，其特征在于，所述预失真模块中存储有所述电器件的温度和DPD参数的对应关系；
    所述预失真模块在根据所述温度值对原始基带信号进行第一DPD时，具体为：根据所述对应关系确定出与所述温度值相对应的DPD参数；根据确定出的DPD参数对原始基带信号进行第一DPD。
  4. 如权利要求1-3任一项所述的RoF系统，其特征在于，所述温度检测模块具体用于：在检测到所述电器件的温度值更新时，将更新的温度值传递给所述预失真模块。
  5. 如权利要求1-4任一项所述的RoF系统，其特征在于，所述温度检测模块包括热敏电阻，所述热敏电阻设置在所述RRU中，且紧贴所述电器件设置。
  6. 如权利要求1-4任一项所述的RoF系统，其特征在于，所述温度检测模块包括感应光纤和拉曼光时域反射计；
    其中，所述感应光纤设置在所述RRU中，且紧贴所述电器件设置；所述拉曼光时域反射计设置在所述BBU中，且与所述预失真模块连接；
    所述感应光纤用于感应所述电器件的温度生成拉曼散射光信号，并反馈给所述拉曼光时域反射计；
    所述拉曼光时域反射计用于根据所述拉曼散射光信号确定所述电器件的温度。
  7. 如权利要求2所述的RoF系统，其特征在于，所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，具体为：
    使用预设算法对经过第一DPD的基带信号和所述非线性信号进行计算，获得DPD参数；
    使用所述DPD参数对所述经过第一DPD的基带信号进行第二DPD；
    其中，所述预设算法为神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条cubic spline、正则分段线性方程CPWL中的任意一种算法。
  8. 如权利要求1-7任一项所述的RoF系统，其特征在于，所述光器件包括电光调制器，所述电器件包括功率放大器。
  9. 如权利要求8所述的RoF系统，其特征在于，所述光器件还包括波分复用器，所述波分复用器的输入端与所述电光调制器的输出端连接；
    所述反馈链路的输入端连接在所述波分复用器的输出端；或者，所述反馈链路的输入端连接在所述波分复用器和所述电光调制器之间。
  10. 如权利要求1-9任一项所述的RoF系统，其特征在于，所述BBU和所述RRU之间设置至少一条光纤；所述温度值以及所述RoF系统的上行信号、下行信号通过所述光纤传输。
  11. 如权利要求1-10任一项所述的RoF系统，其特征在于，所述BBU和所述RRU之间设置有第一光纤和第二光纤；
    所述RoF系统的下行信号和所述温度值通过所述第一光纤传输，所述RoF系统的上行信号通过所述第二光纤传输；或者，所述RoF系统的下行信号通过所述第一光纤传输，所述RoF系统的上行信号或所述温度值通过所述第二光纤传输；或者，所述RoF系统的上行信号和下行信号通过所述第一光纤传输，所述温度值通过所述第二光纤传输。
  12. 如权利要求1-11任一项所述的RoF系统，其特征在于，所述反馈链路的输入端与所述光器件的输出端连接，包括：
    所述反馈链路的输入端与所述光器件的输出端直接连接；或者，
    所述反馈链路的输入端与所述光器件的输出端通过线性元件间接连接。
  13. 一种非线性补偿方法，其特征在于，应用于光载无线通信RoF系统，所述RoF系统包括基带单元BBU和远端射频单元RRU，所述RRU包括电器件，所述BBU包括下行链路和反馈链路；所述下行链路上设置有预失真模块和光器件；所述反馈链路的输入端与所述光器件的输出端连接；所述RoF系统还包括温度检测模块；
    所述方法包括：
    所述反馈链路将所述光器件输出的非线性信号反馈给所述预失真模块；
    所述温度检测模块检测所述电器件的温度值，并将所述温度值传递给所述预失真模块；
    所述预失真模块根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD。
  14. 如权利要求13所述的方法，其特征在于，所述预失真模块根据所述温度值和所述非线性信号对基带信号进行数字预失真DPD，具体包括：
    所述预失真模块根据所述温度值对原始基带信号进行第一数字预失真DPD，以补偿所述电器件引起的非线性失真；
    所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，以补偿所述光器件引起的非线性失真。
  15. 如权利要求14所述的方法，其特征在于，所述预失真模块中存储有所述电器件的温度和DPD参数的对应关系；
    所述预失真模块根据所述温度值对原始基带信号进行第一数字预失真DPD，具体包括：
    所述预失真模块根据所述对应关系确定出与所述温度值相对应的DPD参数；
    所述预失真模块根据确定出的DPD参数对原始基带信号进行第一DPD。
  16. 如权利要求13-15任一项所述的方法，其特征在于，所述温度检测模块检测所述电器件的温度值，并将所述温度值传递给所述预失真模块，具体包括：
    所述温度检测模块在检测到所述电器件的温度值更新时，将更新的温度值传递给所述预失真模块。
  17. 如权利要求13-16任一项所述的方法，其特征在于，所述温度检测模块包括热敏电阻，所述热敏电阻设置在所述RRU中，且紧贴所述电器件设置。
  18. 如权利要求13-16任一项所述的方法，其特征在于，所述温度检测模块包括感应光纤和拉曼光时域反射计；其中，所述感应光纤设置在所述RRU中，且紧贴所述电器件设置；所述拉曼光时域反射计设置在所述BBU中，且与所述预失真模块连接；
    所述温度检测模块检测所述电器件的温度值，包括：
    所述感应光纤感应所述电器件的温度生成拉曼散射光信号，并反馈给所述拉曼光时域反射计；
    所述拉曼光时域反射计根据所述拉曼散射光信号确定所述电器件的温度。
  19. 如权利要求14所述的方法，其特征在于，所述预失真模块根据所述非线性信号对经过第一DPD的基带信号进行第二DPD，具体包括：
    所述预失真模块使用预设算法对经过第一DPD的基带信号和所述非线性信号进行计算，获得DPD参数；
    所述预失真模块使用所述DPD参数对所述经过第一DPD的基带信号进行第二DPD；
    其中，所述预设算法为神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条BBUbic spline、正则分段线性方程CPWL中的任意一种算法。
  20. 如权利要求13-19任一项所述的方法，其特征在于，所述光器件包括电光调制器，所述电器件包括功率放大器。
  21. 如权利要求20所述的方法，其特征在于，所述光器件还包括波分复用器，所述波分复用器的输入端与所述电光调制器的输出端连接；
    所述反馈链路的输入端连接在所述波分复用器的输出端；或者，所述反馈链路的输入端连接在所述波分复用器和所述电光调制器之间。
  22. 如权利要求13-21任一项所述的方法，其特征在于，所述BBU和所述RRU之间设置至少一条光纤；所述温度值以及所述RoF系统的上行信号、下行信号通过所述光纤传输。
  23. 如权利要求13-22任一项所述的方法，其特征在于，所述BBU和所述RRU之间设置有第一光纤和第二光纤；
    所述RoF系统的下行信号和所述温度值通过所述第一光纤传输，所述RoF系统的上行信号通过所述第二光纤传输；或者，所述RoF系统的下行信号通过所述第一光纤传输，所述RoF系统的上行信号或所述温度值通过所述第二光纤传输；或者，所述RoF系统的上行信号和下行信号通过所述第一光纤传输，所述温度值通过所述第二光纤传输。
  24. 如权利要求13-23任一项所述的方法，其特征在于，所述反馈链路的输入端与所述光器件的输出端连接，包括：
    所述反馈链路的输入端与所述光器件的输出端直接连接；或者，
    所述反馈链路的输入端与所述光器件的输出端通过线性元件间接连接。
  25. 一种生成DPD查找表的方法，其特征在于，所述方法包括：
    从温度集合中选择第一温度，其中所述温度集合中包括权利要求1-12任一项中所述的电器件的至少一个可能的温度，所述第一温度为所述温度集合中的任一温度；
    确定所述电器件处于第一温度时的第一非线性模型；
    生成第一基带信号，并对所述基带信号上变频，获得射频信号；
    将所述射频信号输入所述第一非线性模型，生成非线性射频信号；
    对所述非线性射频信号进行下变频、低通滤波，获得非线性基带信号；
    根据所述第一基带信号和所述非线性基带信号确定所述第一温度对应的第一DPD参数；
    遍历所述温度集合中的所有温度，重复以上步骤，得到所述温度集合中的各个温度对应的DPD参数；根据所述温度集合中的各个温度以及与各个温度对应的DPD参数生成DPD查找表。
  26. 如权利要求25所述的方法，其特征在于，根据所述第一基带信号和所述非线性基带信号确定所述第一温度对应的第一DPD参数，具体包括：
    采用神经网络模型、沃尔特拉Volterra多项式、记忆多项式MP、归一化记忆多项式GMP、维纳-哈默斯坦Wiener-Hammerstein多项式、立方样条cubic spline、正则分段线性方程CPWL中的任意一种算法对所述第一基带信号和所述非线性基带信号进行计算，获得所述第一温度对应的第一DPD参数。
  27. 一种计算机可读存储介质，其特征在于，所述计算机可读存储介质存储有计算机程序，所述计算机程序包括程序指令，所述程序指令在被计算机执行时，使所述计算机执行如权利要求13-24或25-26中任一项所述的方法。
  28. 一种处理装置，其特征在于，包括：
    至少一个处理器；以及，
    与所述至少一个处理器通信连接的存储器；其中，所述存储器存储有可被所述至少一个处理器执行的指令，所述至少一个处理器通过执行所述存储器存储的指令，使得如权利要求13-24或25-26中任一项所述的方法被执行。
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