WO2011103767A1 - 一种数字预失真处理方法及设备 - Google Patents

一种数字预失真处理方法及设备 Download PDF

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Publication number
WO2011103767A1
WO2011103767A1 PCT/CN2011/000242 CN2011000242W WO2011103767A1 WO 2011103767 A1 WO2011103767 A1 WO 2011103767A1 CN 2011000242 W CN2011000242 W CN 2011000242W WO 2011103767 A1 WO2011103767 A1 WO 2011103767A1
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Prior art keywords
signal
training signal
training
dpd
module
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PCT/CN2011/000242
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English (en)
French (fr)
Inventor
陈东
蔡月民
康绍莉
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电信科学技术研究院
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Priority to EP11746809.0A priority Critical patent/EP2530832A4/en
Priority to US13/581,070 priority patent/US8526537B2/en
Publication of WO2011103767A1 publication Critical patent/WO2011103767A1/zh

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
    • H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
    • H03F1/3247—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits using feedback acting on predistortion circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
    • H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/32—Modifications of amplifiers to reduce non-linear distortion
    • H03F1/3241—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits
    • H03F1/3258—Modifications of amplifiers to reduce non-linear distortion using predistortion circuits based on polynomial terms
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B1/0475—Circuits with means for limiting noise, interference or distortion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/36—Modulator circuits; Transmitter circuits
    • H04L27/366—Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator
    • H04L27/367—Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator using predistortion
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/336—A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/451—Indexing scheme relating to amplifiers the amplifier being a radio frequency amplifier
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2201/00—Indexing scheme relating to details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements covered by H03F1/00
    • H03F2201/32—Indexing scheme relating to modifications of amplifiers to reduce non-linear distortion
    • H03F2201/3233—Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/354—Adjacent channel leakage power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B2001/0408—Circuits with power amplifiers
    • H04B2001/0425—Circuits with power amplifiers with linearisation using predistortion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H04L27/2623—Reduction thereof by clipping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/242—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account path loss
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H04W52/246—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters where the output power of a terminal is based on a path parameter calculated in said terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/30—TPC using constraints in the total amount of available transmission power
    • H04W52/32—TPC of broadcast or control channels
    • H04W52/325—Power control of control or pilot channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/30—TPC using constraints in the total amount of available transmission power
    • H04W52/36—TPC using constraints in the total amount of available transmission power with a discrete range or set of values, e.g. step size, ramping or offsets
    • H04W52/367—Power values between minimum and maximum limits, e.g. dynamic range

Definitions

  • the present invention relates to wireless communication technologies, and in particular, to a digital predistortion processing method and device. Background technique
  • the high transmission power causes the linearity of the broadband power amplifier to deteriorate seriously, which directly leads to the deterioration of the in-band signal EVM (Error Vector Magnitude) and the out-of-band interference.
  • EVM Error Vector Magnitude
  • the current test shows that the 2010MHz-2025MHz band is at the rated power of 43dBm.
  • the adjacent channel interference power is close to OdBm
  • the ACLR Adjacent Channel Leakage power Ratio
  • the 3GPP the 3rd Generation Partnership Project, 3rd Generation Partnership Project
  • the required secondary signal indicator 45dBc is far from the same and cannot meet the requirements of 3GPP.
  • Multi-carrier applications (9 carriers, 12 carriers, or even more carriers) make the bandwidth of the signal increasingly stronger ⁇ , plus the application of various complex modulation methods, such as: 16QAM (Quadature Amplitude Modulation) , 64QAM, OFDM (Orthogonal Frequency Division Multiplex), etc.
  • the peak-to-average ratio of the transmitted signal is very high
  • TD-SCDMA Time Division-Synchronous Code Division Multiple Access, Time Division Synchronous CDMA (Code Division Multiple Access) In)
  • system 12 plant application peak-to-average ratio of up to 16-17dB, even if phase rotation is limited to only 9.5 dB
  • LTE-TDD Long Term Evolution - Time Division Duplex, long-term evolution - time division multiplexing
  • the ratio is about 10dB.
  • the efficiency of the power amplifier will be very low, usually below 10%. If it is not retracted, it will introduce a large nonlinear distortion. The receiver will not be able to demodulate the signal. 3.
  • the requirements for power amplifier efficiency of green base stations have increased from less than 10% in the past to over 30%, and the efficiency of the whole machine is also above 20%. At present, research on technologies such as envelope tracking shows that >40% of the overall efficiency is possible.
  • DPD Digital PreDistortion
  • FIG 1 is a schematic diagram of a general digital pre-distortion scheme.
  • the current general DPD scheme is shown in Figure 1.
  • Input I/Q Inphase/Quadrature, in-phase/quadrature M-words are subjected to DUC (Digital UpConverter), multi-carrier combination, CFR (Crest Factor Reduction), peak factor reduction, peak factor is equal to The square root of the peak-to-average ratio), then pre-distort the transmitted signal, and enter the PA (Power Amplifier) through the DAC (Digital-to-Analogue Converter) and carrier modulation, and obtain the power amplifier through coupling.
  • the output signal is transmitted back to the digital predistortion module via the feedback channel.
  • the bit width and sample bandwidth of the ADC (Analogue-to-Digital Converter) on the feedback channel have a great influence on the predistortion performance.
  • the distortion module always counts the signal characteristics until the appropriate signal is found to start the coefficient training.
  • the reference of the selection signal can be the signal dynamic range, PAPR (Peak Average Power Ratio), power, amplitude, phase and other signal characteristics; It is also possible to jointly consider the characteristics of the frame structure (such as including special time slots); or a specific transmission design.
  • the time domain characteristics of the signal are irregular.
  • a fixed segment signal can be periodically used for parameter estimation.
  • the operation of the statistical signal is not required, but an external trigger signal is used to trigger the data acquisition.
  • TDD Time Division Duplex, WiMAX ( Worldwide Interoperability over Microwave Access) based on OFDM (Orthogonal Frequency Divi on Multiplex) technology.
  • Time division duplexing In the frame structure, it is determined that the power of the Preamble (preamble) code portion is higher, and after the CFR has a larger signal range, it can be used as a good choice for estimating the sample. If the signal does not have such time domain characteristics, the sample is randomly collected, and signal determination is performed, and the sample that meets the requirements is collected until the parameter estimation is performed to ensure the accuracy of the estimated parameter.
  • the prior art mainly implements digital pre-distortion based on dynamic tracking signal changes. This method shows good performance for single-antenna applications, because the DPD coefficient training module is dedicated to the channel and can track signal changes in real time, so it can be timely Compensates for distortion caused by nonlinearity of the power amplifier.
  • the shortcomings of this method are at least the following two points: First, it needs to run in real time, because it is not known whether the signal can be used for coefficient training, so it is necessary to keep track of the change of the signal and compare it with the signal template for long-term statistics to trigger the training.
  • the digital IF resources that are already tight are one more constraint; the second is that if multiple antenna applications are needed, the corresponding DPD feedback channel and coefficient training module need to be separately configured for each antenna, which will greatly increase with the increase of the number of antennas. Increasing the size and cost of the device is not achievable from a product perspective.
  • the downlink Preamble signal has a large transmission power, since the data area supports the carrier power boost, the power of the real transmit signal Preamble is not necessarily the maximum; and the Preamble peak-to-average ratio is very low. , less than 5dB, which does not meet the requirements of the digital predistortion training signal; TD-SCDMA broadcast channel and DwPTS (Downlink Pilot Time Slot) signals do not meet the required training signal characteristics, so must also consider What kind of signal can be used for DPD coefficient training. Summary of the invention
  • a digital predistortion processing method is provided in the embodiment of the present invention, including the following steps: sending a training signal to at least one radio frequency front-end device according to requirements;
  • a digital predistortion processing device is provided in the embodiment of the present invention, including:
  • the training signal module is configured to send the training signal to the at least one RF front-end device according to the requirement;
  • the acquisition module is configured to collect the output training signal training module of the RF front-end device through the feedback channel as needed, and use the DPD coefficient of the RF front-end device according to the requirement Training; an update module for updating the DPD coefficients of the corresponding RF front-end equipment as needed after the coefficient training is completed.
  • the training signal since the training signal is specially generated for DPD coefficient training, it may be transmitted as needed, or may be periodic or non-periodic transmission, so that real-time operation is not required, and it is not necessary to track signals all the time. Change and compare with long-term statistical signal templates to trigger training;
  • the training signal is sent to at least one RF front-end device as needed, and the RF front-end device can be collected through the feedback channel as needed.
  • the output training signal can update the DPD coefficient of each channel of the corresponding RF front-end device as needed after training the DPD coefficient of the RF front-end device, so that the multi-antenna application can be satisfied, and it is not necessary to separately configure each antenna separately.
  • the DPD feedback channel and coefficient training module will not increase the size and cost of the device when the antenna is increased. From the perspective of productization, the achievability is good.
  • FIG. 1 is a schematic diagram of a general digital predistortion scheme in the background art
  • FIG. 2 is a schematic flowchart of implementing a digital predistortion processing method according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of a signal flow of a DPD algorithm according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a digital pre-distortion processing scheme based on a training sequence according to an embodiment of the present invention
  • FIG. 5 is a schematic flowchart of a digital pre-distortion processing implementation process according to Embodiment 1 of the present invention
  • FIG. 6 is a schematic flowchart of an implementation process of digital pre-distortion processing according to Embodiment 2 of the present invention
  • Figure ⁇ is a schematic flowchart of generating a training signal in a TD-SCDMA system according to an embodiment of the present invention
  • FIG. 8 is a schematic diagram of a DPD training sequence generation principle in a TD-SCDMA system according to an embodiment of the present invention
  • FIG. 9 is a schematic flowchart of generating a training signal in an LTE-TDD system according to an embodiment of the present invention
  • FIG. 11 is a schematic structural diagram of a digital predistortion processing apparatus according to an embodiment of the present invention.
  • FIG. 12 is a schematic structural diagram of a training signal module in a TD-SCDMA system according to an embodiment of the present invention
  • FIG. 13 is a schematic structural diagram of a training signal module in an LTE-TDD system according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of the implementation process of the digital pre-distortion processing method. As shown in the figure, the digital pre-distortion processing process may include the following steps:
  • Step 201 Send a training signal to the at least one radio frequency front end device according to the requirement;
  • the radio front-end equipment can adopt an RRU (Radio Remote Unit), but the RRU is defined based on the architecture of the current commercial base station, and is a commonly used concept in the industry.
  • the RRU is only one of the RF front-end devices, because the RF front-end device can be a single RF channel, a collection of multiple RF channels, a collection of multiple RRUs, and the like.
  • RRU Radio Remote Unit
  • each RF channel may include a power amplifier device.
  • the training signal may be a training signal that is generated in advance and stored in the communication system, and may also be transmitted after being generated as needed.
  • the training signal when it is sent, it may be sent as needed, or periodically, or sent aperiodically.
  • Step 202 Collect an output training signal of the RF front-end device through the feedback channel according to the requirement;
  • Step 203 Train the DPD coefficient of the RF front-end device as needed;
  • Step 204 After the coefficient training is completed, update each channel of the corresponding RF front-end device as needed. DPD coefficient.
  • implementation may further include:
  • Step 205 Perform pre-distortion processing on the transmit signal on the radio frequency front-end device according to the updated DPD coefficient as needed.
  • the method may further include:
  • Pre-distortion processing that is, the transmitted training signal is subjected to initial pre-distortion processing and then transmitted to at least one radio frequency front-end device.
  • the training signal when the training signal is sent to the at least one RF front-end device, the output training signal of the RF front-end device is collected, the DPD coefficient of the RF front-end device is trained, and the DPD coefficient of each channel of the corresponding RF front-end device is updated,
  • Implementation is due to the fact that in some cases certain RF front-end devices (eg RRUs) do not require training. For example, in the case of a high degree of product quality control, some R Us can directly give usable estimation coefficients based on other RRU configurations.
  • the power amplifiers have good consistency, there will be some RUs Training, and even the entire product, only need to customize the coefficients corresponding to different application scenarios at the factory. Therefore, in the implementation, the RF front-end equipment that needs to be implemented can be processed according to the needs of the practice.
  • GaN gallium nitride
  • MEMS MicroElectron-mechanical System
  • Figure 3 is a schematic diagram of the signal flow of the DPD algorithm. As shown in the figure, if the training sequence length is ⁇ , the memory depth is Q, and the intermodulation order is K, then:
  • the feedback signal In order to maintain the power balance, the feedback signal ") needs to eliminate the rated linear gain of the power amplifier G to obtain the signal 3 ⁇ 4 ⁇ ):
  • FIG. 4 is a schematic diagram of a digital pre-distortion processing scheme based on a training sequence, which shows two channels (antennas) suitable for TD-SCDMA or LTE-TDD (Long Term Evolution-Time Division Duplex).
  • the principle of the DPD solution is obvious. Obviously, the scheme can be extended to any antenna configuration. As shown in the figure, the brief description is as follows:
  • the DPD-dedicated training signal in step 201 is generated; then, after the DUC and the CFR, the pre-distortion of the RRU-A and the RRU-B are respectively entered.
  • DPD-A and DPD-B then entering the power amplifier after DAC and carrier modulation, obtaining the power amplifier output signal through coupling, and transmitting through RRU-A and RRU-B respectively, ie step 201; then passing through feedback channel and feedback capture respectively.
  • the DPD-dedicated training signal is extracted, that is, step 202; the DPD training of step 203 is started, and the LUT (Look Up Table) is updated after the coefficient is updated, and then the DPD coefficients of the corresponding RRU channels are updated, that is, step 204.
  • the DPD coefficients of RRU-A and RRU-B can be updated in sequence, or they can be updated at the same time, as needed.
  • the training signal is generated after the enable signal is triggered, and the second embodiment is pre-generated and stored in the communication system.
  • FIG. 5 is a schematic diagram of the implementation process of the digital pre-distortion processing in the first embodiment, as shown in the figure, which may include:
  • Step 501 The system is powered on.
  • Step 502 Wait for the clock to trigger the DPD coefficient update.
  • Step 503 Generate a maximum carrier supported by the system, a maximum user, and a training signal at the highest order modulation.
  • Step 504 The CFR module limits the peak-to-average ratio of the signal to the target PAPR.
  • Step 505 Send a DPD dedicated training signal using a DwPTS time slot or any other downlink time slot. That is, the training signal processed through step 504 is transmitted.
  • Step 506 After the initial pre-distortion of the DPD, that is, after the initial pre-distortion processing, adjust the transmit signal level to meet the maximum configured power requirement, and enable the transmit signal to enter the RRU.
  • Step 507 Set an RF (Radio Frequency) switch, and collect an output dedicated training signal of the RRU-A through a feedback channel.
  • RF Radio Frequency
  • Step 508 Adjust the level of the feedback signal so that it maintains the same level as the transmitted signal.
  • Step 509 Start DPD coefficient training.
  • Step 510 Set an RF switch, and collect an output dedicated training signal of the RRU-B through the feedback channel.
  • Step 511 Adjust the level of the feedback signal so that it maintains the same level as the transmitted signal.
  • Step 512 Start DPD coefficient training.
  • step 507 to step 509 are repeated, and the DPD coefficient training can be started by setting the RF switch and collecting the output dedicated training signals of other RRUs through the feedback channel.
  • Step 513 After the coefficient training is completed, the DPD coefficients of the A and B channels are updated respectively.
  • Step 514 Close the feedback channel and the DPD training module and return to step 502.
  • Step 515 Perform predistortion processing on the transmitted signal.
  • FIG. 6 is a schematic diagram of a digital pre-distortion processing implementation process in Embodiment 2, as shown in the figure, Includes:
  • Step 601 Pre-generate and store the training signal in the system.
  • Step 602 The system is powered on.
  • Step 603 Wait for the clock to trigger the DPD coefficient update function.
  • Step 604 Call a pre-stored training signal.
  • Step 605 The CFR module limits the peak-to-average ratio of the signal to the target PAPR. If the pre-stored training signal is a signal processed in step 605, this step can be skipped.
  • Step 606 Send a DPD-dedicated training signal using a DwPTS time slot or any other downlink time slot. That is, the training signal obtained after the processing of step 605 is transmitted.
  • Step 607 After the initial pre-distortion of the DPD, that is, after the initial pre-distortion processing, adjust the transmit signal level to meet the maximum configured power requirement, and enable the transmit signal to enter the RRU.
  • Step 608 Set an RF switch, and collect an output dedicated training signal of the RRU-A through the feedback channel.
  • Step 609 Adjust the level of the feedback signal to keep the same level as the transmitted signal.
  • Step 610 Start DPD coefficient training.
  • Step 611 Set an RF switch, and collect an output dedicated training signal of the RRU-B through the feedback channel.
  • Step 612 Adjust the level of the feedback signal so that it maintains the same level as the transmitted signal.
  • Step 613 starting DPD coefficient training.
  • step 608 to step 610 are repeated, and the DPD coefficient training can be started by setting the RF switch to collect the output dedicated training signals of other RRUs through the feedback channel.
  • Step 614 After the coefficient training is completed, the DPD coefficients of the A and B channels are updated respectively.
  • Step 615 Close the feedback channel and the DPD training module and return to step 603.
  • Step 616 Perform predistortion processing on the transmitted signal.
  • the DPD training signal can further meet the following requirements: 1.
  • the training signal is a signal with a large transmission power. Since the DPD improves the power efficiency of the RF front-end equipment by compensating for the nonlinearity of the power amplifier, the feedback signal (RF PA output) must be able to reflect the nonlinearity of the power amplifier well. This requires that the power of the transmitted signal used for training must be sufficiently large, the peak power is less than or equal to the PldB power point, or less than or equal to the P3dB power point, even close to the saturation point of the power amplifier, which can be adjusted according to the power amplifier efficiency requirement.
  • the training signal is a signal with a high peak-to-average ratio.
  • the peak-to-average ratio of the signal is required to be consistent with the peak-to-average ratio of the power amplifier selection.
  • the signal should take into account the variation of the sampling rate of the digital intermediate frequency part. To avoid the spike signal generated by the CFR leakage of the training signal, a signal with a high peak-to-average ratio should be selected as the training signal.
  • Predistortion is for all transmitted signals rather than for transmitting large signals.
  • the coefficients are applied to the entire dynamic range of the transmitted signal, so the dynamic range of the training signal needs to match the dynamic range of the transmitted signal.
  • the power fluctuation of the transmitted training signal caused by DPD should be eliminated as much as possible.
  • the ADC input signal level should be matched to maintain sufficient accuracy.
  • the feedback signal of the DPD training signal is calibrated to synchronize with the transmitted signal and eliminate the amplitude and phase distortion caused by the nonlinearity of the feedback RF channel.
  • the feedback signal of the DPD training needs to be calibrated accordingly, it should be ensured that it is synchronized with the transmitted signal and eliminates the amplitude and phase distortion caused by the nonlinearity of the feedback RF channel.
  • the DwPTS time slot when sending the training signal, can be used or used exclusively.
  • the training signal is transmitted in part or all of the downlink time slots in which the training signal is transmitted.
  • the time slot for transmitting the training signal may include a DwPTS and a GAP (protection) time slot, or part or all of the downlink time slots dedicated to transmitting the training signal;
  • the specific time slot may include a special time slot DwPTS and a GAP time slot or a part or all of the downlink time slots dedicated to transmitting the reference signal;
  • the time slot in which the training signal is transmitted may include a DwPTS and a GAP time slot, or a part or all of the downlink time slots dedicated to transmitting the training signal.
  • the specific time slot may include a special time slot DwPTS and a GAP time slot or a portion or all of the downlink time slots dedicated to transmitting the reference signal.
  • the same feedback channel can be used for multi-channel time division multiplexing.
  • Embodiments 1 and 2 For details, refer to the embodiments in Embodiments 1 and 2. It can also be seen from the schematic diagram of FIG. The following is an example of the generation of dedicated training signals in the TD-SCDMA system and the LTE-TDD system.
  • FIG. 7 is a schematic flowchart of generating a training signal in a TD-SCDMA system.
  • the training signal when the training signal is generated, the training signal may include:
  • Step 701 Generate a random number obeying a normal distribution to simulate a multi-user merged source, and the data length is determined according to a DPD coefficient training requirement;
  • Step 702 Perform coding, modulation, and spreading on the same channel coding, modulation, and spreading mode for each user.
  • Step 703 Perform gain adjustment on the coded, modulated, and spread-spectrum signals, where “the gain adjustment factor for combining the multi-user signals is determined according to the number of users and the number of code channels;
  • Step 704 Combine multiple user signals sent on the same carrier.
  • Step 705 Generate a multi-carrier digital intermediate frequency signal by performing digital up-conversion (DUC) and peak-to-average ratio suppression CFR (peak factor reduction) on the combined user signal;
  • DUC digital up-conversion
  • CFR peak-to-average ratio suppression
  • Step 706 The multi-carrier digital intermediate frequency signal is used as the training signal.
  • the training signal can generate training signals according to the maximum carrier supported by the communication system, the maximum user, and the highest order of modulation.
  • FIG. 8 is a schematic diagram showing the principle of generating a DPD training sequence in a TD-SCDMA system.
  • DBB Digital BaseBand, Digital Base Band, also called BB
  • the random sequence generator generates a random number 0/1 that follows a normal distribution to simulate a multi-user merged source, data length. Determined according to DPI) training requirements; each user/code channel uses the same channel coding, modulation, and spreading mode; ⁇ is the multi-user/code channel signal combining gain adjustment factor, depending on the number of users/code channels;
  • DBB Digital BaseBand, Digital Base Band
  • BB Digital Baseband, Digital Base Band
  • ⁇ is the maximum number of carriers.
  • the rotational phase of the completion of the main ⁇ different users transmit signals to reduce peak to average power ratio signal represents a carrier angular frequency representation corresponding to "represents a sampling point: ⁇ represents a sampling interval.
  • the maximum number of carriers may be used, such as 9/12;
  • the maximum number of code channels that may be transmitted such as 16 code channels;
  • the highest modulation level possible such as 64QAM;
  • the length of the signal depends on the algorithm design, in principle, as long as it contains enough points to describe the PA distortion.
  • the power of the transmitted digital signal should be maximized in the actual application.
  • the signal conversion relationship from the baseband to the antenna port will be determined when the RF front-end equipment determines, and the final RF output power must be the maximum.
  • the training signal can be repeated, so the training signal generating portion shown by the broken line in FIG. 8 can be run offline to generate the required signal, and the A-point multi-carrier merged Both the signal and the B-point digital intermediate frequency signal can be used as the DPD training signal.
  • Which signal can be selected according to the system implementation, and can be stored in the ROM (Read Only Memory) of the DFE unit.
  • FIG. 9 is a schematic flowchart of generating a training signal in an LTE-TDD system.
  • the training signal may include:
  • Step 901 The random sequence is modulated by an OFDM (Orthogonal Frequency Division Multiplex) compliant with 3GPP specifications to generate a baseband transmit signal.
  • OFDM Orthogonal Frequency Division Multiplex
  • Step 902 Use the generated baseband transmit signal as a training signal.
  • Step 903 The digital intermediate frequency signal is generated after the baseband transmit signal is subjected to digital up-conversion (DUC) and peak-to-average ratio suppression (CFR) modules;
  • DUC digital up-conversion
  • CFR peak-to-average ratio suppression
  • Step 904 Use the generated digital intermediate frequency signal as a training signal.
  • FIG. 10 is a schematic diagram of a DPD training sequence generation principle in an LTE-TDD system.
  • the random sequence is subjected to OFDM modulation conforming to the 3GPP specifications to generate a standard baseband transmission signal (point A) having the following characteristics, and then digitally upconverted (DUC) and peak-to-average ratio suppression (CFR) modules to generate numbers.
  • IF signal point B
  • Both the A and B signals can be used as DPD training signals. Which signal can be selected according to the system implementation, because DPD training can be done offline, so it can be stored in the ROM of the DFE unit in the specific implementation.
  • PRBs Physical Resource Blocks
  • a digital pre-distortion processing device is also provided in the embodiment of the present invention. Since the principle of solving the problem is similar to a digital pre-distortion processing method, the implementation of the device can be implemented by referring to the method. It will not be repeated here.
  • the device may include: a training signal module 1101, configured to send a training signal to enter at least one radio frequency front-end device according to requirements;
  • the acquisition module 1103 is configured to collect the output training of the RF front-end device through the feedback channel as needed.
  • Practice signal
  • the training module 1104 is configured to train the DPD coefficients of the RF front-end equipment according to requirements; and the update module 1105 is configured to update the DPD coefficients of the corresponding RF front-end equipment as needed after the coefficient training is completed.
  • the implementation may further include a pre-distortion module 1102, configured to send the training signal to the at least one radio frequency front end device after the initial predistortion processing.
  • a pre-distortion module 1102 configured to send the training signal to the at least one radio frequency front end device after the initial predistortion processing.
  • the training signal module can be further used to employ training signals that are pre-generated and stored in the communication system.
  • the training signal module may further be used to send, or send periodically, or periodically, when the training signal is sent.
  • the RF front-end device may also include a single RF channel, or multiple RF channels, or a collection of multiple RRUs.
  • each RF channel can also include a power amplifier device.
  • the training signal module can be further used to use a signal with a large transmission power and a high peak-to-average ratio as a training signal.
  • the training signal module may be further configured to transmit a training signal by using a DwPTS time slot or a part or all of the downlink time slots dedicated to transmitting the training signal when transmitting the training signal.
  • the training signal module may include a first sending unit and/or a second sending unit, where: the first sending unit is configured to include a DwPTS and a GAP time slot in the TD-SCDMA system, or is specifically used for transmitting Transmitting the training signal to a time slot of part or all of the downlink time slot of the training signal;
  • a second sending unit configured to, in the LTE-TDD system, transmit the training signal in a time slot including a DwPTS and a GAP time slot, or a part or all of a downlink time slot dedicated to transmitting the training signal.
  • the device may further include one or a combination of the following modules:
  • a matching module configured to match a dynamic range of the training signal with a dynamic range of the transmitted signal
  • a power adjustment module configured to perform power adjustment on the DPD training signal, to eliminate the DPD caused by The power fluctuation of the transmitted training signal
  • a feedback signal power adjustment module for performing power adjustment on a feedback signal of the DPD training signal to match a requirement of an ADC input signal level
  • a calibration module that calibrates the feedback signal of the DPD training signal to synchronize with the transmitted signal and eliminates amplitude and phase distortion caused by nonlinearity of the feedback RF channel.
  • FIG. 12 is a schematic structural diagram of a training signal module in a TD-SCDMA system. As shown in the figure, when the training signal module generates the training signal in the TD-SCDMA system, the method may include:
  • the first random sequence generator 1201 is configured to generate a random number obeying a normal distribution to simulate a multi-user merged source, and the data length is determined according to a DPD coefficient training requirement;
  • a coded modulation and spreading unit 1202 configured to encode, modulate, and spread the same channel coding, modulation, and spreading mode for each user;
  • the gain unit 1203 is configured to perform gain adjustment on the encoded, modulated, and spread-spectrum signals, where “the gain adjustment factor for combining the multi-user signals is determined according to the number of users and the number of code channels;
  • the merging unit 1204 is configured to combine the multiple user signals sent on the same carrier.
  • the first DUC-CFR unit 1205 is configured to generate the multi-carrier digital number after the combined user signals are digitally up-converted and peak-to-average ratio suppressed. IF signal;
  • the first selecting unit 1206 is configured to use the multi-carrier digital intermediate frequency signal as the training signal.
  • the training signal module may be further configured to generate a training signal according to a maximum carrier supported by the communication system, a maximum user, and a highest order of modulation.
  • FIG. 13 is a schematic structural diagram of a training signal module in an LTE-TDD system. As shown in the figure, when the training signal module generates the training signal in the LTE-TDD system, the training signal module may include:
  • a second random sequence generator 1301, configured to generate a random sequence
  • the baseband modulation unit 1302 is configured to generate a baseband transmit signal after the random sequence is modulated by OFDM according to the 3GPP specifications, and use the generated baseband transmit signal as a training signal;
  • a second DUC-CFR unit 1303, configured to generate a digital intermediate frequency signal after passing the baseband transmit signal through the DUC and CFR;
  • the second selecting unit 1304 is configured to use the generated digital intermediate frequency signal as the training signal.
  • the collection module 1103 can be further configured to: when the output training signal of the RF front-end device is collected through the feedback channel as needed, if the RF front-end device includes multiple RF channels, the same feedback channel can be used for multiple channel time division multiplexing. .
  • the predistortion module 1102 can be further configured to perform predistortion processing on the transmit signal on the radio frequency front end device according to the updated DPD coefficient as needed.
  • a specific training signal is periodically transmitted to perform digital pre-distortion coefficient training; since the training signal is periodic transmission, real-time operation is not required, and it is not necessary to constantly track the change of the signal and Signal templates for long-term statistics are compared to trigger training.
  • a time slot for transmitting a training signal in the TD-SCDMA system and the LTE-TDD system is provided, that is, a training signal is transmitted in a specific time slot in the TD-SCDMA system, and the specific time slot includes a special time slot DwPTS and GAP. a time slot or part or all of a downlink time slot dedicated to transmitting the reference signal; transmitting a training signal in a specific time slot in the LTE-TDD system, the specific time slot containing a special time slot DwPTS and a GAP time slot or dedicated to transmitting Part or all of the downlink time slot of the reference signal.
  • the specific reference signal has the following distinct features: a large transmission power and a high peak-to-average ratio;
  • the same feedback channel can be multi-channel time division multiplexed for digital predistortion coefficient training.
  • DPD training signal features of the DPD training signal are also provided for ease of implementation.
  • the technical solution provided by the present invention has at least one or more of the following advantages: (1) Simple implementation and good performance;
  • the technical solution provided in the embodiment of the present invention can also support multiple radio front-end devices (such as RRU, etc.) in various forms.
  • Concatenated application scenarios (such as star, chain, or ring) simplify the system implementation of DPD applications.
  • embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.
  • computer-usable storage media including but not limited to disk storage, CD-ROM, optical storage, etc.
  • the computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device.
  • the apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.
  • These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. Instructions are provided for implementation in the flowchart The steps of a process or a plurality of processes and/or block diagrams of a function specified in a block or blocks.

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Description

一种数字预失真处理方法及设备 技术领域
本发明涉及无线通信技术， 特别涉及一种数字预失真处理方法及设备。 背景技术
由于器件及环境的影响， 绝大多数功放的非线性响应都不理想， 会造成 带内带外信号幅度和相位的失真。 特别是目前正大力研发并准备投入商用的 宽帶多载波无线通信系统对射频功率放大器的线性度和效率较之窄带单载波 系统有更高的需求。 下面是目前 3G、 4G技术发展带来的功放应用问题。
1、高发射功率导致宽带功放的线性度严重恶化，直接导致带内信号 EVM ( Error Vector Magnitude， 矢量误差幅度 )的恶化， 以及带外干扰加剧， 目前 测试表明 2010MHz-2025MHz频段在发射额定功率 43dBm时导致临道干扰功 率接近 OdBm,邻道和次临道的 ACLR( Adjacent Channel Leakage power Ratio, 邻道泄漏功率比）约为 35dBc，和 3GPP ( the 3rd Generation Partnership Project, 第 3代移动通信合作项目）要求的次临道指标 45dBc指标相差甚远， 无法满 足 3GPP的规定。
2、 多载波应用 （9载波、 12载波， 甚至更多载波）使得信号的带宽日益 增力 σ，再加上各种复杂调制方式的应用，例如： 16QAM ( Quadrature Amplitude Modulation, 正交幅度调制）、 64QAM、 OFDM ( Orthogonal Frequency Division Multiplex, 正交频分复用）等， 发射信号的峰均比很高， TD-SCDMA ( Time Division-Synchronous Code Division Multiple Access, 时分同步 CDMA (码分 多址接入））系统 12栽应用峰均比可达 16-17dB， 即使采用相位旋转也仅仅限 制在 9.5 dB左右， LTE-TDD ( Long Term Evolution - Time Division Duplex, 长 期演进-时分复用 ) 的峰均比也达 10dB左右， 如果仅靠功率回退技术来保证 功放的线性特性， 会使得功放的效率非常低， 通常在百分之十以下， 如果不 回退则会引入很大的非线性失真， 接收机将无法解调信号。 3、 绿色基站对功放效率的要求已经由过去的不到 10%提高到 30%以上， 整机效率也在 20%以上， 目前如包络跟踪等技术的研究表明 >40%的整机效率 是可能的。
上述问题激发了提高功率效率技术的需求， 而功放的线性和效率本身就 是一对矛盾， 如果仅仅寄希望于通过功放技术及工艺的改进来解决上述问题， 目前的器件还很难满足。 因此， 在现有功放技术的基础上， 保证效率的同时 如何提升功放线性特性则非常关键。 DPD ( Digital PreDistortion, 数字预失真） 技术是解决该矛盾最有效的功放线性化技术之一， 它有效的借助现有强大的 信号处理技术在数字域来补偿功放的非线性， 在减小设备体积、 功耗、 成本 的同时提高更大功率的输出信号。
图 1为通用数字预失真方案的示意图，目前通用的 DPD方案如图 1所示。 输入 I/Q ( Inphase/Quadrature,同相 /正交 M言号经过 DUC( Digital UpConverter, 数字上变频）， 多载波合并后进行峰均比抑制 CFR ( Crest Factor Reduction, 峰值因子减小， 峰值因子等于峰均比的开平方）， 然后对发射信号作预失真处 理， 并经过 DAC ( Digital-to-Analogue Converter, 数模转换器）及载波调制后 进入 PA ( Power Amplifier, 功放）， 通过耦合获得功放输出信号并经过反馈通 道回传到数字预失真模块，反馈通道上的 ADC( Analogue-to-Digital Converter, 模数转换器） 的位宽和釆样带宽对预失真性能有很大影响， 数字预失真模块 一直在统计信号特性， 直到找到合适的信号才开始系数训练。 选择信号的基 准可以是信号的动态范围、 PAPR ( Peak Average Power Ratio, 峰均比）、 功 率、 幅度、相位等信号特征； 也可以联合考虑帧结构特点（如包含特殊时隙）； 或者特定的传输设计。
某些情况下， 信号的时域特性艮有规律， 那么就可以周期地采用某固定 段信号进行参数估计， 此时， 将不需要统计信号的操作， 而是用一个外部触 发信号触发数据的采集， 例如， 基于 OFDM ( Orthogonal Frequency Divi on Multiplex, 正交频分复用 )技术的 WiMAX ( Worldwide interoperability over Microwave Access, 全球 :波接入互通技术 ) 的 TDD ( Time Division Duplex, 时分双工） 帧结构中， 确定 Preamble (前导）码部分的功率较高， CFR之后 具有较大的信号范围， 就可以作为参数估计样本的上好选择。 如果信号不具 备这样的时域特性， 则随机的采集样本， 并进行信号判定， 一直采集到符合 要求的样本， 才进行参数估计， 以保证所估计参数的准确性。
现有技术主要是基于动态跟踪信号变化来实现数字预失真， 该方法对于 单天线应用表现出很好的性能， 因为 DPD系数训练模块是该通道专用的， 可 以实时跟踪信号的变化， 所以可以及时补偿功放非线性导致的失真。
但是该方法的缺点至少有如下两点： 一是需要实时运行， 因为不知道信 号是否可以用于系数训练， 所以必须一直跟踪信号的变化并和长时间统计的 信号模版进行比较以触发训练， 这给本来就紧张的数字中频资源又多了一道 约束； 二是如需满足多天线应用， 则需要给每路天线单独配置相应的 DPD反 馈通道和系数训练模块， 随着天线数的增加这将大大增加设备的体积和成本， 从产品化角度来看， 可实现性差。
进一步的， 对于基于 OFDM技术的 WiMAX系统， 虽然下行 Preamble信 号发射功率大， 但是由于数据区支持栽波功率提升， 所以真正的发射信号 Preamble的功率并不一定是最大； 此外 Preamble峰均比很低， 小于 5dB, 这 不满足数字预失真训练信号的要求； TD-SCDMA 的广播信道和 DwPTS ( Downlink Pilot Time Slot, 下行导频时隙）信号也均不满足需要的训练信号 特性， 所以还必须考虑什么样的信号可用于 DPD系数训练。 发明内容
本发明所解决的技术问题在于提供了一种数字预失真处理方法及设备。 本发明实施例中提供了一种数字预失真处理方法， 包括如下步骤： 根据需要发送训练信号进入至少一个射频前端设备；
根据需要通过反馈通道采集射频前端设备的输出训练信号；
根据需要对射频前端设备的 DPD系数进行训练；
系数训练完成后， 根据需要更新相应射频前端设备的 DPD系数。 本发明实施例中提供了一种数字预失真处理设备， 包括：
训练信号模块， 用于根据需要发送训练信号进入至少一个射频前端设备； 采集模块， 用于根据需要通过反馈通道采集射频前端设备的输出训练信 训练模块， 用于根据需要对射频前端设备的 DPD系数进行训练； 更新模块， 用于在系数训练完成后， 根据需要更新相应的射频前端设备 的 DPD系数。
本发明有益效杲如下：
在本发明提供的技术方案中， 由于训练信号专门为了 DPD系数训练生成 的， 其可以按需要进行发射， 也可以是周期性或者非周期性的发射， 所以不 需要实时运行， 不必一直跟踪信号的变化并和长时统计的信号模版进行比较 以触发训练；
由于射频前端设备通常都可以包含单个射频通道、 或者多个射频通道、 或者多个 RRU的集合， 而训练信号是根据需要发送进入至少一个射频前端设 备， 并可以根据需要通过反馈通道采集射频前端设备的输出训练信号， 从而 在对射频前端设备的 DPD系数进行训练后能根据需要更新相应的射频前端设 备各通道的 DPD系数， 因此能够满足多天线应用， 且不需要给每路天线单独 配置相应的 DPD反馈通道和系数训练模块， 在天线增加时也不会增加设备的 体积和成本， 从产品化角度来看， 可实现性好。 附图说明
图 1为背景技术中通用数字预失真方案示意图；
图 2为本发明实施例中数字预失真处理方法实施流程示意图；
图 3为本发明实施例中 DPD算法信号流程示意图；
图 4为本发明实施例中基于训练序列的数字预失真处理方案原理示意图； 图 5为本发明实施例一中的数字预失真处理实施流程示意图；
图 6为本发明实施例二中的数字预失真处理实施流程示意图； 图 Ί为本发明实施例中在 TD-SCDMA 系统中生成训练信号的流程示意 图；
图 8为本发明实施例中 TD-SCDMA系统 DPD训练序列生成原理示意图； 图 9为本发明实施例中在 LTE-TDD系统中生成训练信号的流程示意图； 图 10为本发明实施例中 LTE-TDD系统 DPD训练序列生成原理示意图； 图 11为本发明实施例中数字预失真处理设备结构示意图；
图 12为本发明实施例中 TD-SCDMA系统中的训练信号模块结构示意图； 图 13为本发明实施例中 LTE-TDD系统中的训练信号模块结构示意图。 具体实施方式
下面结合附图对本发明的具体实施方式进行说明。
图 2 为数字预失真处理方法实施流程示意图， 如图所示， 在数字预失真 处理过程中可以包括如下步骤：
步骤 201、 根据需要发送训练信号进入至少一个射频前端设备；
具体实施中， 射频前端设备可以采用 RRU ( Radio Remote Unit, 射频拉 远单元）， 但是 RRU是基于现在商用基站的架构来定义的， 是业内常用概念。 RRU仅是射频前端设备中的一种， 因为射频前端设备可以为单个射频通道、 多个射频通道的集合、 多个 RRU的集合等。 为便于理解， 下面的实施方式中 主要以 RRU为例子来进行说明； 进一步的， 每个射频通道可以包含一个功率 放大器设备。
具体实施中， 训练信号可以采用预先生成并存储在通信系统中的训练信 号， 当然也可以按照需要生成后即发射。
具体实施中， 在发送训练信号时， 可以按需发送， 或者周期性发送， 或 者非周期性发送。
步骤 202、 根据需要通过反馈通道采集射频前端设备的输出训练信号； 步骤 203、 根据需要对射频前端设备的 DPD系数进行训练；
步骤 204、在系数训练完成后，根据需要更新相应的射频前端设备各通道 的 DPD系数。
进一步的， 在实施中还可以包括：
步骤 205、 根据需要根据更新后的 DPD系数对射频前端设备上的发射信 号进行预失真处理。
在上述实施中， 在步骤 201中， 还可以进一步包括：
预失真处理， 即对发送出的训练信号经过初始预失真处理后再发送进入 至少一个射频前端设备。
实施中， 在发送训练信号进入至少一个射频前端设备、 在采集射频前端 设备的输出训练信号、 对射频前端设备的 DPD系数进行训练、 更新相应的射 频前端设备各通道的 DPD系数时， 可以根据需要进行实施， 这是由于在某些 情况下会出现某些射频前端设备（如： RRU )无需训练的情况。 例如在产品 质量控制程度比较高的情况下， 某些 R U可以根据其他 RRU配置情况， 直 接给出可用的估计系数。 再比如因为随着 GaN (氮化镓）及新的半导体工艺， 甚至 MEMS ( MicroElectron-mechanicalSystem , 微机电系统）技术的应用， 使 得功放有很好的一致性的情况下， 会存在某些 R U无需训练， 甚至整个产品 都只需在出厂时定制好相应于不同应用场景的系数即可。 因此， 实施中可以 根据实践的需要对需要实施的射频前端设备实施相应的处理。
在更新相应的射频前端设备各通道的 DPD 系数时， 可以参见以下 DPD 算法信号执行流程。
图 3为 DPD算法信号流程示意图， 如图所示， 假定训练序列长度为 Ν， 记忆深度为 Q， 交调阶数为 K， 则有：
( 1 )、 发射信号 χ(")经过预失真处理后的信号 ζ(")和功放输出信号 （反 馈信号）之间有如下关系：
K Q k l
z{n) =
k=2l-\ X ∑< (" - ）| " - )|一
¾r=0
/=l,2，...,L(K+l)/2」 C 1 ) (2)、 为了保持功率平衡， 反馈信号 "）需消除功放额定线性增益 G 得到信号¾ ^)：
Figure imgf000009_0001
Figure imgf000009_0003
(3)、 上述信号的矩阵表示如下:
反馈信号：
U = Lu10， U K0, U -u (0)，... (N-1)]
(3) 参考信号： z = Ua， z = [z(0),.-.,2(N-i)]
(4) 目标 DPD系数：
Figure imgf000009_0002
( 4 )、 估计出的目标 DPD系数 a的最小二乘解表示如下： a二 (U"U)— 1 VH
(6)
(5)、 通过 Cholesky (乔里斯基）分解获得 'νΗν ，令 R = U"U
'-1
' k=\
0,
(7) 令 g" = ， 为 G的第 z'行第 列元素， 为 R的第 行第 列元素: 假设 Β = ( ， 有
Figure imgf000010_0001
一 kj i > j
0
( 8 ) 为 B的第 行第 列元素， 则有: R 1 = BHB
( 9 ) 代入（ 7 ) 式即可得到估计的目标 DPD系数 a。
图 4为基于训练序列的数字预失真处理方案原理示意图， 图中给出了适 用于 TD-SCDMA或者 LTE-TDD ( Long Term Evolution-Time Division Duplex, 长期演进 -时分双工） 的两通道（天线） DPD解决方案原理示意， 显然， 该方 案可以扩展到任意天线配置， 则如图所示， 简要说明如下：
当需要开始进行数字预失真处理时，通过 DPD使能触发信号触发开始后， 生成步骤 201中的 DPD专用的训练信号； 然后经过 DUC和 CFR后， 分别进 入 RRU-A和 RRU-B的预失真处理 DPD-A和 DPD-B, 然后经过 DAC和载波 调制后进入功放， 通过耦合获得功放输出信号， 并分别经 RRU-A和 RRU-B 发送， 即步骤 201 ; 然后分别经过反馈通道和反馈捕获后抽取 DPD专用训练 信号， 即步骤 202; 开始步骤 203的 DPD训练， 分别在系数更新后进行 LUT ( LookUp Table,查找表）的更新，然后更新相应的 RRU各通道的 DPD系数， 即步骤 204。 在系数更新过程中， 可以依次更新 RRU-A和 RRU-B的 DPD系 数， 也可以同时更新， 视需要采用。
为了更好的理解如何实施本发明， 下面提供实例结合图 4进行说明， 实 施例一中训练信号是在使能信号触发后生成的， 实施例二是预先生成并存储 在通信系统中的。
实施例一 图 5 为实施例一中的数字预失真处理实施流程示意图， 如图所示， 可以 包括：
步骤 501、 系统上电。
步骤 502、 等待时钟触发 DPD系数更新。
步骤 503、 生成系统支持的最大栽波， 最多用户， 最高阶调制时的训练信 号。
步骤 504、 经过 CFR模块限制信号峰均比为目标 PAPR。
步骤 505、 使用 DwPTS时隙或者其他任何下行时隙发射 DPD专用训练 信号。 即发射经过步骤 504处理的训练信号。
步骤 506、 经过 DPD初始预失真后， 即初始预失真处理后， 调整发射信 号电平， 使其满足最大配置功率要求， 并使发射信号进入 RRU。
步骤 507、 设置 RF ( Radio Frequency, 射频）开关， 通过反馈通道采集 RRU-A的输出专用训练信号。
步骤 508、 调整反馈信号电平， 使其保持和发射信号电平相同。
步骤 509、 开始 DPD系数训练。
步骤 510、 设置 RF开关， 通过反馈通道采集 RRU-B的输出专用训练信 号。
步骤 511、 调整反馈信号电平， 使其保持和发射信号电平相同。
步骤 512、 开始 DPD系数训练。
在多天线配置时， 即如两通道 RRU-A和 RRU-B时， 重复步骤 507至步 骤 509， 通过设置 RF开关， 通过反馈通道采集其它 RRU的输出专用训练信 号后开始 DPD系数训练即可。
步骤 513、 系数训练完成后分别更新 A和 B通道的 DPD系数。
步骤 514、 关闭反馈通道和 DPD训练模块并返回步骤 502。
步骤 515、 对发射信号进行预失真处理。
实施例二
图 6 为实施例二中的数字预失真处理实施流程示意图， 如图所示， 可以 包括：
步骤 601、 预生成并存储训练信号在系统中。
步骤 602、 系统上电。
步骤 603、 等待时钟触发 DPD系数更新功能。
步骤 604、 调用预存储的训练信号。
步骤 605、经过 CFR模块限制信号峰均比为目标 PAPR。如果预存的训练 信号是经过步骤 605处理的信号， 则可跳过此步。
步骤 606、 使用 DwPTS时隙或者其他任何下行时隙发射 DPD专用训练 信号。 即发射步骤 605处理后得到的训练信号。
步骤 607、 经过 DPD初始预失真后， 即初始预失真处理后， 调整发射信 号电平， 使其满足最大配置功率要求， 并使发射信号进入 RRU。
步骤 608、 设置 RF开关， 通过反馈通道采集 RRU-A的输出专用训练信 步骤 609、 调整反馈信号电平， 使其保持和发射信号电平相同。
步骤 610、 开始 DPD系数训练。
步骤 611、 设置 RF开关， 通过反馈通道采集 RRU-B的输出专用训练信 号。
步骤 612、 调整反馈信号电平， 使其保持和发射信号电平相同。
步骤 613、 开始 DPD系数训练。
在多天线配置时， 即如两通道 RRU-A和 RRU-B时， 重复步骤 608至步 骤 610， 通过设置 RF开关来通过反馈通道采集其它 RRU的输出专用训练信 号后开始 DPD系数训练即可。
步骤 614、 系数训练完成后分别更新 A和 B通道 DPD系数。
步骤 615、 关闭反馈通道和 DPD训练模块并返回步骤 603。
步骤 616、 对发射信号进行预失真处理。
实施中， 为了获得更好的效果， DPD训练信号可以进一步作如下要求： 1、 训练信号是发射功率大的信号。 由于 DPD是通过补偿功放非线性来提高射频前端设备功率效率的， 所以 反馈信号（RF PA输出） 必须能够很好反应功放的非线性。 这就要求用于训 练的发射信号的功率必须足够大， 峰值功率小于等于 PldB功率点， 或者小于 等于 P3dB功率点， 甚至接近功放的饱和点， 可根据功放效率要求调节。
2、 训练信号是峰均比高的信号。
由于用于训练的反馈信号需要反应功放的非线性， 这要求信号的峰均比 要和功放选型的峰均比要求一致，有足够多的失真信号点经历功放非线性失 真， 这要求选择训练信号要考虑到数字中频部分采样率的变化， 要避免训练 信号包含 CFR漏消产生的尖峰信号， 尽可能选择峰均比高的一段信号作为训 练信号。
3、 使训练信号的动态范围与发射信号的动态范围匹配。
预失真针对的是所有的发射信号而不是发射的大信号， 系数要适用于发 射信号的整个动态范围， 所以训练信号的动态范围需要和发射信号的动态范 围匹配。
4、 对 DPD训练信号进行功率调整， 消除 DPD引起的发射训练信号的功 率波动。
由于 DPD训练信号需要进行相应的功率调整，因此应该尽可能消除 DPD 引起的发射训练信号功率波动。
5、 对 DPD训练信号的反馈信号进行功率调整， 匹配 ADC输入信号电平 的要求。
由于 DPD训练信号的反馈信号必须进行相应的功率调整， 因此应该匹配 ADC输入信号电平的要求， 以保持足够的精度。
6、 对 DPD训练信号的反馈信号进行校准， 使其与发射信号同步且消除 反馈射频通道非线性引起的幅度和相位失真。
由于 DPD训练的反馈信号需要进行相应的校准， 因此应该确保与发射信 号同步且消除反馈射频通道非线性引起的幅度和相位失真。
另外， 具体实施中， 发送训练信号时， 可以使用 DwPTS时隙或者专门用 于发射该训练信号的部分或者全部下行时隙发射训练信号。
具体的， 在 TD-SCDMA系统中， 发射训练信号的时隙可以包括 DwPTS 和 GAP (保护） 时隙， 或者是专门用于发射该训练信号的部分或者全部下行 时隙；
即， 在 TD-SCDMA系统中的特定时隙发射训练信号时， 该特定时隙可以 包含特殊时隙 DwPTS和 GAP时隙或者专门用于发射该参考信号的部分或者 全部下行时隙；
或者， 在 LTE-TDD系统中， 发射所述训练信号的时隙可以包括 DwPTS 和 GAP时隙， 或者是专门用于发射该训练信号的部分或者全部下行时隙。
即， 在 LTE-TDD系统中的特定时隙发射训练信号时， 该特定时隙可以包 含特殊时隙 DwPTS和 GAP时隙或者专门用于发射该参考信号的部分或者全 部下行时隙。
实施中， 根据需要通过反馈通道采集射频前端设备的输出训练信号时， 如果射频前端设备包含多个通道， 则可以多通道时分复用同一反馈通道进行 采集。
具体可以参见实施例一、 二中的实施方式， 也可以从图 4的示意图看出。 下面以 TD-SCDMA系统与 LTE-TDD系统中对专用训练信号的生成为例 进行说明。
1、 TD-SCDMA系统 DPD训练信号生成„
图 7为在 TD-SCDMA系统中生成训练信号的流程示意图， 如图所示， 在 TD-SCDMA系统中， 训练信号在生成时， 可以包括：
步骤 701、产生服从正态分布的随机数用以模拟多用户合并后的信源，数 据长度根据 DPD系数训练要求确定；
步骤 702、 对每个用户采用相同的信道编码、 调制和扩频模式进行编码、 调制、 扩频；
步骤 703、 对编码、 调制、 扩频后的信号进行增益调整， 其中， "为多用 户信号合并的增益调整因子， 根据用户数和码道数进行确定； 步骤 704、 对同一载波上发送的多个用户信号进行合并；
步骤 705、 将合并后的用户信号经过数字上变频 （DUC )和峰均比抑制 CFR (峰值因子减小）后生成多栽波数字中频信号；
步骤 706、 采用上述多载波数字中频信号作为训练信号。
实施中， 训练信号可以根据通信系统支持的最大载波、 最多用户、 调制 的最高阶生成训练信号。
图 8为 TD-SCDMA系统 DPD训练序列生成原理示意图。 如图所示， 在 DBB ( Digital BaseBand, 数字基带， 也可以称为 BB ) 中， 随机序列生成器产 生服从正态分布的随机数 0/1 用以模拟多用户合并后的信源， 数据长度根据 DPI)训练要求来确定；每个用户 /码道采用相同的信道编码、调制和扩频模式； α为多用户 /码道信号合并的增益调整因子， 取决于用户 /码道数； 在 DFE ( Digital Front-End, 数字前端） 中， 不同载波采用相同的基带信源。 其中， ejw'nTs 、
Figure imgf000015_0001
.. e 中， κ为最大载波数。 其中， ^^^主要完成对不同 用户信号的相位旋转以降低发射信号的峰均功率比， 表示第 1个载波对应 的角频率表示形式， "表示采样点， ： ^表示采样间隔。
实施中可以采用具有如下特征的训练信号：
可能用到最大载波数， 如 9/12载；
可能发射的最多码道数， 如 16码道；
可能使用的最高调制级， 如 64QAM;
信号长度取决于算法设计，原则上只要包含足够多能描述 PA失真的点就 可以。
满足这些条件， 则发送数字信号功率应该在实际应用时达到最大， 射频 前端设备确定时从基带到天线口的信号变换关系将确定，最终 RF输出功率一 定也是最大。
因为 DPD训练可以离线完成， 训练信号可以重复， 所以图 8中虚线所示 的训练信号生成部分可以离线运行生成所需要的信号， A点多载波合并后的 信号和 B点数字中频信号均可作为 DPD训练信号，采用哪个信号可根据系统 实现来选择， 具体实施中可以存储在 DFE单元的 ROM ( Read Only Memory, 只读存储器） 中。
2、 LTE-TDD系统 DPD训练信号生成
图 9为在 LTE-TDD 系统中生成训练信号的流程示意图， 如图所示， 在 LTIi-TDD系统中， 训练信号在生成时， 可以包括：
步骤 901、 随机序列经过符合 3GPP规范的 OFDM ( Orthogonal Frequency Division Multiplex ， 正交频分复用）调制后生成基带发射信号；
步骤 902、 采用生成的基带发射信号作为训练信号；
步骤 903、将基带发射信号经过数字上变频（DUC )和峰均比抑制（CFR ) 模块后生成数字中频信号；
步骤 904、 采用生成的数字中频信号作为训练信号。
图 10为 LTE-TDD系统 DPD训练序列生成原理示意图。 如图所示， 随机 序列经过符合 3GPP规范的 OFDM调制后生成标准的具有如下特征的基带发 射信号（A点）， 然后经过数字上变频（DUC )和峰均比抑制 （CFR )模块后 生成数字中频信号 （B点）。 A点和 B点信号均可作为 DPD训练信号， 采用 哪个信号可根据系统实现来选择， 因为 DPD训练可以离线完成， 所以具体实 施中可以存储在 DFE单元的 ROM中。
特征为： 占用足够多的 PRB ( Physical Resource Block, 物理资源块）， 并 尽可能占用全部 PRB， 采用 QPSK或 16QAM或 64QAM调制方式。
基于同一发明构思， 本发明实施例中还提供了一种数字预失真处理设备， 由于该设备解决问题的原理与一种数字预失真处理方法相似， 因此该设备的 实施可以参见方法的实施， 重复之处不再赘述。
图 11为数字预失真处理设备结构示意图， 如图所示， 设备中可以包括： 训练信号模块 1101， 用于根据需要发送训练信号进入至少一个射频前端 设备；
采集模块 1103, 用于根据需要通过反馈通道采集射频前端设备的输出训 练信号；
训练模块 1104， 用于根据需要对射频前端设备的 DPD系数进行训练； 更新模块 1105， 用于在系数训练完成后， 根据需要更新相应的射频前端 设备的 DPD系数。
进一步的， 实施中还可以包括预失真模块 1102， 用于对训练信号经过初 始预失真处理后发送进入至少一个射频前端设备。
实施中， 训练信号模块还可以进一步用于采用预先生成并存储在通信系 统中的训练信号。
实施中， 训练信号模块还可以进一步用于在发送训练信号时， 按需发送， 或者周期性发送， 或者非周期性发送。
实施中， 射频前端设备还可以包含单个射频通道、 或者多个射频通道、 或者多个 RRU的集合。
实施中， 每个射频通道还可以包含一个功率放大器设备。
实施中， 训练信号模块还可以进一步用于采用发射功率大和峰均比高的 信号作为训练信号。
实施中，训练信号模块还可以进一步用于在发送训练信号时，使用 DwPTS 时隙或者专门用于发射该训练信号的部分或者全部下行时隙发射训练信号。
实施中，训练信号模块可以包括第一发送单元和 /或第二发送单元，其中： 第一发送单元，用于在 TD-SCDMA系统中，在包括 DwPTS和 GAP时隙， 或者是专门用于发射该训练信号的部分或者全部下行时隙的时隙发射所述训 练信号；
第二发送单元， 用于在 LTE-TDD系统中， 在包括 DwPTS和 GAP时隙， 或者是专门用于发射该训练信号的部分或者全部下行时隙的时隙发射所述训 练信号。
实施中， 设备中还可以进一步包括以下模块之一或者其组合：
匹配模块， 用于使训练信号的动态范围与发射信号的动态范围匹配； 功率调整模块， 用于对 DPD训练信号进行功率调整， 消除 DPD引起的 发射训练信号的功率波动；
反馈信号功率调整模块，用于对 DPD训练信号的反馈信号进行功率调整, 匹配 ADC输入信号电平的要求；
校准模块， 用于对 DPD训练信号的反馈信号进行校准， 使其与发射信号 同步且消除反馈射频通道非线性引起的幅度和相位失真。
图 12为 TD-SCDMA系统中的训练信号模块结构示意图， 如图所示， 训 练信号模块在 TD-SCDMA系统中生成所述训练信号时， 可以包括：
第一随机序列生成器 1201， 用于产生服从正态分布的随机数用以模拟多 用户合并后的信源， 数据长度根据 DPD系数训练要求确定；
编码调制扩频单元 1202， 用于对每个用户采用相同的信道编码、 调制和 扩频模式进行编码、 调制、 扩频；
增益单元 1203， 用于对编码、 调制、 扩频后的信号进行增益调整， 其中， "为多用户信号合并的增益调整因子， 根据用户数和码道数进行确定；
合并单元 1204， 用于对同一载波上发送的多个用户信号进行合并； 第一 DUC-CFR单元 1205， 用于将合并后的用户信号经过数字上变频和 峰均比抑制后生成多栽波数字中频信号；
第一选择单元 1206， 用于采用上述多载波数字中频信号作为训练信号。 实施中， 训练信号模块还可以进一步用于根据通信系统支持的最大载波、 最多用户、 调制的最高阶生成训练信号。
图 13为 LTE-TDD系统中的训练信号模块结构示意图， 如图所示， 训练 信号模块在 LTE-TDD系统中生成所述训练信号时， 可以包括：
第二随机序列生成器 1301， 用于生成随机序列；
基带调制单元 1302， 用于将随机序列在按 3GPP规范的 OFDM调制后生 成基带发射信号， 采用生成的基带发射信号作为训练信号；
第二 DUC-CFR单元 1303 , 用于将基带发射信号经过 DUC和 CFR后生 成数字中频信号；
第二选择单元 1304， 用于采用生成的数字中频信号作为训练信号。 实施中， 釆集模块 1103还可以进一步用于在根据需要通过反馈通道采集 射频前端设备的输出训练信号时， 如果射频前端设备包含多个射频通道， 则 可以多通道时分复用同一反馈通道进行采集。
实施中，预失真模块 1102还可以进一步用于根据需要根据更新后的 DPD 系数对射频前端设备上的发射信号进行预失真处理。
为了描述的方便， 以上所述装置的各部分以功能分为各种模块或单元分 别描述。 当然， 在实施本发明时可以把各模块或单元的功能在同一个或多个 软件或硬件中实现。
由上述实施方式可见， 在本发明提供的技术方案中， 周期发射特定训练 信号进行数字预失真系数训练； 由于训练信号是周期性的发射， 所以不需要 实时运行， 不必一直跟踪信号的变化并和长时统计的信号模版进行比较以触 发训练。
进一步的， 还提供了在 TD-SCDMA系统与 LTE-TDD系统中发射训练信 号的时隙， 即， 在 TD-SCDMA系统中特定时隙发射训练信号， 该特定时隙包 含特殊时隙 DwPTS和 GAP时隙或者专门用于发射该参考信号的部分或者全 部下行时隙； 在 LTE-TDD系统中特定时隙发射训练信号， 该特定时隙包含特 殊时隙 DwPTS和 GAP时隙或者专门用于发射该参考信号的部分或者全部下 行时隙。
进一步的， 还提供了选择训练信号的具体原则， 即， 特定参考信号具有 如下明显特征： 发射功率大， 峰均比高；
进一步的， 在采用多天线时， 可以多通道时分复用同一反馈通道进行数 字预失真系数训练。
进一步的， 还提供了 DPD训练信号的特征以便于实施。
综上所述， 可见本发明提供的技术方案至少有如下优点中的一个或多个： ( 1 ) 实现简单， 性能好；
( 2 )最佳训练序列可以才艮据系统特征定制；
( 3 )符合 TDD系统应用的特点； ( 4 )适合 TD-SCDMA或 LTE-TDD多天线应用；
( 5 )适合 TD-SCDMA多频段组网应用；
( 6 )适合 TD-SCDMA和 LTE-TDD共平台应用。
进一步的， 如果考虑未来 RoF ( Radio Over Fiber, 光栽无线通信）技术 引入无线通信系统， 则本发明实施例中提供的技术方案还能够支持多射频前 端设备（如： RRU等） 以各种形式（如星形、 链形或者环形等）级联的应用 场景， 从而简化 DPD应用的系统实现代价。
本领域内的技术人员应明白， 本发明的实施例可提供为方法、 系统、 或 计算机程序产品。 因此， 本发明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， 本发明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。
本发明是参照根据本发明实施例的方法、 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操作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。
尽管已描述了本发明的优选实施例， 但本领域内的技术人员一旦得知了 基本创造性概念， 则可对这些实施例作出另外的变更和修改。 所以， 所附权 利要求意欲解释为包括优选实施例以及落入本发明范围的所有变更和修改。 发明的精神和范围。 这样， 倘若本发明的这些修改和变型属于本发明权利要 求及其等同技术的范围之内， 则本发明也意图包含这些改动和变型在内。

Claims

权 利 要 求
1、 一种数字预失真 DPD处理方法， 其特征在于， 包括如下步骤： 发送训练信号进入至少一个射频前端设备；
通过反馈通道采集射频前端设备的输出训练信号；
对射频前端设备的 DPD系数进行训练；
系数训练完成后， 更新相应射频前端设备的 DPD系数。
2、 如权利要求 1所述的方法， 其特征在于， 所述训练信号是预先生成并 存储在通信系统中的。
3、 如权利要求 1所述的方法， 其特征在于， 在发送训练信号时， 按需发 送， 或者周期性发送， 或者非周期性发送。
4、 如权利要求 1或 2或 3所述的方法， 其特征在于， 进一步包括： 对训练信号经过初始预失真处理后再发送。
5、 如权利要求 1所述的方法， 其特征在于， 所述射频前端设备包含单个 射频通道、 或者多个射频通道的集合、 或者多个射频拉远单元 RRU的集合。
6、 如权利要求 5所述的方法， 其特征在于， 每个射频通道包含一个功率 放大器设备。
7、 如权利要求 1所述的方法， 其特征在于， 所述训练信号是发射功率大 和峰均比高的信号。
8、 如权利要求 1所述的方法， 其特征在于， 发送训练信号时， 使用下行 导频时隙 DwPTS 时隙或者专门用于发射该训练信号的部分或者全部下行时 隙发射训练信号。
9、如权利要求 8所述的方法，其特征在于，在时分同步 CDMA TD-SCDMA 系统中， 发射所述训练信号的时隙包括 DwPTS和保护 GAP时隙， 或者是专 门用于发射该训练信号的部分或者全部下行时隙；
或， 在长期演进-时分双工 LTE-TDD 系统中， 发射所述训练信号的时隙 包括 DwPTS和 GAP时隙， 或者是专门用于发射该训练信号的部分或者全部 下行时隙。
10、 如权利要求 1 所述的方法， 其特征在于， 进一步包括以下步骤之一 或者其组合：
使训练信号的动态范围与发射信号的动态范围匹配；
对 DPD训练信号进行功率调整， 消除 DPD引起的发射训练信号的功率 波动；
对 DPD训练信号的反馈信号进行功率调整， 匹配模数转换器 ADC输入 信号电平的要求；
对 DPD训练信号的反馈信号进行校准， 使其与发射信号同步且消除反馈 射频通道非线性引起的幅度和相位失真。
11、 如权利要求 1至 10任一所述的方法， 其特征在于， 在 TD-SCDMA 系统中， 所述训练信号在生成时， 包括：
产生服从正态分布的随机数用以模拟多用户合并后的信源， 数据长度根 据 DPI)系数训练要求确定；
对每个用户采用相同的信道编码、 调制和扩频模式进行编码、 调制、 扩 频；
对编码、 调制、 扩频后的信号进行增益调整；
对同一载波上发送的多个用户信号进行合并；
将合并后的用户信号经过数字上变频 DUC和峰均比抑制 CFR后生成多 载波数字中频信号；
采用上述多栽波数字中频信号作为训练信号。
12、 如权利要求 11所述的方法， 其特征在于， 根据通信系统支持的最大 载波、 最多用户、 调制的最高阶生成训练信号。
13、 如权利要求 1至 10任一所述的方法， 其特征在于， 在 LTE-TDD系 统中， 所述训练信号在生成时， 包括：
将随机序列按 3GPP规范的正交频分复用 OFDM调制后生成基带发射信 采用生成的基带发射信号作为训练信号；
基带发射信号经过 DUC和 CFR后生成数字中频信号；
采用生成的数字中频信号作为训练信号。
14、 如权利要求 1至 13任一所述的方法， 其特征在于， 通过反馈通道采 集射频前端设备的输出训练信号时， 如果射频前端设备包含多个通道， 则对 多通道时分复用同一反馈通道进行采集。
15、 如权利要求 1至 14任一所述的方法， 其特征在于， 进一步包括： 根据更新后的 DPD系数对射频前端设备上的发射信号进行预失真处理。
16、 一种数字预失真处理设备， 其特征在于， 包括：
训练信号模块， 用于发送训练信号进入至少一个射频前端设备； 采集模块， 用于通过反馈通道采集射频前端设备的输出训练信号； 训练模块， 用于对射频前端设备的 DPD系数进行训练；
更新模块， 用于在系数训练完成后， 更新相应的射频前端设备的 DPD系 数。
17、 如权利要求 16所述的设备， 其特征在于， 训练信号模块进一步用于 采用预先生成并存储在通信系统中的训练信号。
18、 如权利要求 16所述的设备， 其特征在于， 训练信号模块进一步用于 在发送训练信号时， 按需发送， 或者周期性发送， 或者非周期性发送。
19、 如权利要求 16或 17或 18所述的设备， 其特征在于， 进一步包括： 预失真模块， 用于对训练信号模块发送的训练信号经过初始预失真处理 后发送进入至少一个射频前端设备。
20、 如权利要求 16所述的设备， 其特征在于， 所述射频前端设备包含单 个射频通道、 或者多个射频通道、 或者多个 RRU的集合。
21、 如权利要求 20所述的设备， 其特征在于， 每个射频通道包含一个功 率放大器设备。
22、 如权利要求 16所述的设备， 其特征在于， 训练信号模块进一步用于 釆用发射功率大和峰均比高的信号作为训练信号。
23、 如权利要求 16所述的设备， 其特征在于， 训练信号模块进一步用于 在发送训练信号时，使用 DwPTS时隙或者专门用于发射该训练信号的部分或 者全部下行时隙发射训练信号。
24、 如权利要求 23所述的设备， 其特征在于， 训练信号模块包括第一发 送单元和 /或第二发送单元， 其中：
第一发送单元，用于在 TD-SCDMA系统中，在包括 DwPTS和 GAP时隙， 或者是专门用于发射该训练信号的部分或者全部下行时隙的时隙发射所述训 练信号；
第二发送单元， 用于在 LTE-TDD系统中， 在包括 DwPTS和 GAP时隙， 或者专门用于发射该训练信号的部分或者全部下行时隙的时隙中发射所述训 练信号。
25、 如权利要求 16所述的设备， 其特征在于， 进一步包括以下模块之一 或者其组合：
匹配模块， 用于使训练信号的动态范围与发射信号的动态范围匹配； 功率调整模块， 用于对 DPD训练信号进行功率调整；
反馈信号功率调整模块，用于对 DPD训练信号的反馈信号进行功率调整； 校准模块， 用于对 DPD训练信号的反馈信号进行校准。
26、 如权利要求 16至 25任一所述的设备， 其特征在于， 训练信号模块 在 TD-SCDMA系统中生成所述训练信号时， 包括：
第一随机序列生成器， 用于产生服从正态分布的随机数用以模拟多用.户 合并后的信源；
编码调制扩频单元， 用于对每个用户采用相同的信道编码、 调制和扩频 模式进行编码、 调制、 扩频；
增益单元， 用于对编码、 调制、 扩频后的信号进行增益调整；
合并单元， 用于对同一载波上发送的多个用户信号进行合并；
第一 DUC-CFR单元，用于将合并后的用户信号经过数字上变频和峰均比 抑制后生成多载波数字中频信号； 第一选择单元， 用于采用合并后的多载波数字中频信号作为训练信号。
27、 如权利要求 26所述的设备， 其特征在于， 训练信号模块进一步用于 根据通信系统支持的最大栽波、 最多用户、 调制的最高阶生成训练信号。
28、 如权利要求 16至 25任一所述的设备， 其特征在于， 训练信号模块 在 LTE-TDD系统中生成所述训练信号时， 包括：
第二随机序列生成器， 用于生成随机序列；
基带调制单元， 用于将随机序列在按 3GPP规范的 OFDM调制后生成基 带发射信号， 采用生成的基带发射信号作为训练信号；
第二 DUC-CFR单元，用于在基带发射信号经过 DUC和 CFR后生成数字 中频信号；
第二选择单元， 用于采用生成的数字中频信号作为训练信号。
29、 如权利要求 16至 28任一所述的设备， 其特征在于， 采集模块进一 步用于根据需要在通过反馈通道采集射频前端设备的输出训练信号时， 如果 射频前端设备包含多个射频通道， 则对多通道时分复用同一反馈通道进行采 集。
30、 如权利要求 16至 29任一所述的设备， 其特征在于， 预失真模块进 一步用于根据更新后的 DPD系数对射频前端设备上的发射信号进行预失真处 理。
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