WO2012037822A1

WO2012037822A1 - Digital predistortion system and digital predistortion processing method

Info

Publication number: WO2012037822A1
Application number: PCT/CN2011/075792
Authority: WO
Inventors: 张烈
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-09-21
Filing date: 2011-06-16
Publication date: 2012-03-29
Also published as: CN102413084A

Abstract

The present invention discloses a digital predistortion system and a digital predistortion processing method, wherein the digital predistortion system includes: a baseband system, which is set for sending service data and power level information corresponding to the service data to a radio frequency system; the radio frequency system, which is set for obtaining the predistortion coefficient corresponding to the power level information and performing a digital predistortion processing on the service data with the predistortion coefficient. The present invention can perform the digital predistortion processing on the current service data with the power level information corresponding to the current service data in real time, save resources and improve the efficiency and accuracy of the digital predistortion processing.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a digital pre-distortion (DPD) system and a digital pre-distortion processing method. BACKGROUND OF THE INVENTION With the rapid development of mobile communication technologies, wireless communication bands become more and more crowded, and frequency band resources are becoming more and more tense. In order to change this situation and achieve more communication channels in a limited spectrum range, it is necessary to improve the spectrum efficiency of the existing frequency bands. For this reason, many new broadband digital transmission technologies (such as OFDM (Orthogonal Frequency Division Multiplexing) have been applied. , Orthogonal Frequency Division Multiplexing) and WCDMA (Wideband Code Division Multiple Access), and high-frequency modulation (such as QPSK (Quadature Phase Shift Keying)) And M~QAM (Quadature Amplitude Modulation); etc., in order to achieve higher spectral utilization density and wider channel space allocation. These highly efficient digital modulation transmission techniques are almost always based on non-constant envelopes. However, with the reduction of the channel width and the improvement of the spectrum utilization rate, the consequent problem is an increase in out-of-band radiation, which causes an increase in the adjacent channel. The main reason for this problem is that in many wireless communication systems, in order to provide high enough output power and maximum output, the power amplifier usually works in a non-linear region, even in the vicinity of the saturation region, at which point the power amplifier appears. Very strong nonlinear characteristics. To solve such problems, digital predistortion techniques and analog feedforward techniques are widely used to compensate for the nonlinear characteristics of power amplifiers. Digital predistortion has become the mainstream power amplifier linearization technology with its good low hardware complexity, high stability and high efficiency. In the digital predistortion system, since the power amplifier has different excitation distortions for signals of different power levels, it is necessary to extract different predistortion coefficients for signals of different power levels to perform digital predistortion processing on the service data using the predistortion coefficients. At present, the power level determination in the predistortion system of the related art is performed in the radio frequency system, that is, the radio system needs to calculate the power level of the service data according to the service data sent by the baseband system, so that the service data needs to be extended. When calculating, the data of the latter moment is digitally predistorted according to the power level of the data at the previous moment, thereby causing a predistortion processing error. In addition, Moreover, since the number of points for calculating the average power must be able to effectively distinguish the power level in a certain number, the delay time is long, which will occupy a large amount of FPGA resources. SUMMARY OF THE INVENTION A primary object of the present invention is to provide a digital predistortion system and a digital predistortion processing method to at least solve the above-described power level calculation of service data by a radio frequency system such that the calculated power level lags behind the service data, thereby causing the digital pre- The problem of distortion processing errors. According to an aspect of the present invention, a digital predistortion system is provided, comprising: a baseband system configured to transmit service data and corresponding power level information to a radio frequency system; and an RF system configured to obtain the power level information The pre-distortion coefficient, and the pre-distortion coefficient is used to perform digital pre-distortion processing on the service data. The baseband system includes: a media access control layer module, configured to send service scheduling information to the physical layer module, where the service scheduling information includes power level information corresponding to the service data; and the physical layer module is configured to configure the power of the service data to The power indicated by the power level information, and the configured service data and power level information are sent to the radio frequency system. The physical layer module includes: an analyzing unit, configured to analyze power level information of each time domain segment from the service scheduling information, where the power level information includes power level information of the service data in different time domain segments; It is configured to configure the power of the service data sent in each time domain segment as the power indicated by the power level information of the time domain segment. The radio frequency system includes: a lookup module configured to find a pre-distortion coefficient corresponding to the received power level information from the radio frequency system; and a processing module configured to multiply the service data by the found pre-distortion coefficient to complete the service Digital predistortion processing of data. The searching module includes: a searching unit configured to find a pre-distortion coefficient table corresponding to the power level information from a plurality of pre-distortion coefficient tables saved by the radio system; and an obtaining unit, configured to obtain from the found pre-distortion coefficient table Predistortion coefficient. The radio frequency system further includes: an update module configured to update the pre-distortion coefficients in the plurality of pre-distortion coefficient tables saved by the radio system. According to another aspect of the present invention, a digital predistortion processing method is provided, including: a baseband system transmitting service data and corresponding power level information to a radio frequency system; and obtaining, by the radio frequency system, the above function The pre-distortion coefficient corresponding to the rate level information, and the pre-distortion coefficient is used to perform digital pre-distortion processing on the service data. The baseband system sends the service data and the corresponding power level information to the radio frequency system. The media access control layer module of the baseband system sends the service scheduling information to the physical layer module of the baseband system, where the service scheduling information includes the service data corresponding to the service data. Power level information: The physical layer module configures the power of the service data as the power indicated by the power level information; the physical layer module sends the configured service data and power level information to the radio frequency system. The power level information includes power level information of the service data in different time domain segments; the physical layer module configures the power of the service data as the power indicated by the power level information, and the physical layer module analyzes and obtains each time domain segment from the service scheduling information. Power level information; The physical layer module configures the power of the service data sent in each time domain segment as the power indicated by the power level information of the time domain segment. The radio frequency system extracts the pre-distortion coefficient corresponding to the power level information, and performs digital pre-distortion processing on the service data by using the pre-distortion coefficient: the radio frequency system locally searches for the pre-distortion coefficient corresponding to the received power level information; The service data is multiplied by the found pre-distortion coefficient to complete the digital pre-distortion processing of the service data. According to the present invention, the baseband system transmits the service data and the power level information corresponding to the service data to the radio frequency system, so that the radio frequency system can directly use the power level information to perform digital predistortion processing on the service data, thereby eliminating the need for the radio frequency. The system calculates and judges the power level of the service data, and solves the problem that the computing power partition of the radio system has large occupied resources and pre-distortion errors in the related technology, so that the corresponding power level information can be used for the current service data in real time. Digital pre-distortion processing saves resources and improves the efficiency and accuracy of digital pre-distortion processing. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 is a schematic diagram of a digital predistortion system according to an embodiment of the present invention; FIG. 2 is a schematic structural diagram of a DPD system in an LTE TDD system according to a preferred embodiment of the present invention; FIG. 3 is a schematic diagram of a DPD system according to an embodiment of the present invention. Flow chart of digital predistortion processing method; 4 is a flow chart of digital predistortion processing performed by a DPD system in an LTE TDD system in accordance with a preferred embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. 1 is a schematic diagram of a digital pre-distortion (DPD) system according to an embodiment of the present invention, including: a Baseband System (BBU) 10 and a Radio Remote Unit (RRU) 20, which are provided below. The function and structure are described. The baseband system 10 is configured to send the service data and its corresponding power level information (also referred to as power bin information) to the radio frequency system 20; the radio frequency system 20 is configured to obtain a pre-distortion coefficient corresponding to the power level information, And using the predistortion coefficient to perform digital predistortion processing on the service data. In this embodiment, the baseband system sends the service data, and the power level information corresponding to the service data is also sent to the radio frequency system, so that the radio frequency system can directly use the power level information to perform digital pre-distortion processing on the service data, thereby eliminating the need for The radio frequency system calculates and judges the power level of the service data, and solves the problem that the power system of the radio system has a large occupied resource and a pre-distortion error in the related technology, so that the corresponding power level can be used for the current service data in real time. The information is digitally predistorted, which saves resources and improves the efficiency and accuracy of digital predistortion processing. As shown in FIG. 1, the baseband system 10 may include a media access control (MAC) layer module 102 and a physical (Physics, PHY) layer module 104, where: the medium access control layer module 102 is set to the physical layer. The module 104 sends the service scheduling information (equivalent to the configuration information), where the service scheduling information includes power level information corresponding to the service data (the service data can belong to different users); the physical layer module 104 is configured to use the power of the service data. The power indicated by the power level information is configured, and the configured service data and the power level information are sent to the radio frequency system 20. In this way, since the service data is sent by the baseband system to the radio frequency system, the baseband system knows the power level information of the service data, so that the power level information can be sent to the radio frequency system while transmitting the service data, thereby saving The time and resources occupied by the radio frequency system to calculate and judge the power level information of the service data. In this embodiment, the physical layer module is an actual interface module, and the module configures service data according to the configuration information sent by the MAC layer module, and sends data and power level information. The physical layer module 104 may further include: an analyzing unit, configured to include the foregoing in the power level information, in order to be able to adapt to a higher requirement for calculating and determining the power level of the signal that fluctuates more rapidly with the change of the user in the time domain. In the case of the power level information of the service data in different time domain segments (which may be in the case of a sub-frame in actual implementation), the time domain segments are analyzed from the service scheduling information delivered by the MAC layer module 102 (in practice) The power level information may be configured for each subframe; and the sending unit is configured to configure the power of the service data sent in each time domain segment as the power indicated by the power level information of the time domain segment. In this way, it can be more suitable for real-time acquisition of power level information of service data that changes rapidly in the time domain as the user changes. As shown in FIG. 1, the radio frequency system 20 can include: a lookup module 202 configured to find a pre-distortion coefficient corresponding to the received power level information from the radio frequency system 20; and the processing module 204 is configured to receive the The above service data is multiplied by the found predistortion coefficient to complete digital predistortion processing of the service data. In order to find the predistortion system corresponding to the received power level information, in actual application, the predistortion coefficients may be saved in a form of a table (which may be referred to as a predistortion coefficient table), and each predistortion coefficient table corresponds to a different one. The power level, each pre-distortion coefficient table is stored with a corresponding pre-distortion coefficient. Specifically, the searching module 202 can include: a searching unit configured to find and receive from a plurality of pre-distortion coefficient tables saved by the radio frequency system 20 a predistortion coefficient table corresponding to the above power level information; and an obtaining unit configured to obtain the predistortion coefficient from the found predistortion coefficient table. In order to continuously update the pre-distortion coefficients corresponding to different power levels according to actual conditions, the radio frequency system 20 may further include an update module 206 configured to update the pre-distortion coefficients in the plurality of pre-distortion coefficient tables held by the radio frequency system 20. As shown in FIG. 2, in the actual implementation, the above-mentioned search module 202 and processing module 204 can be implemented by a Field Programmable Gate Array (DSP) module, which is a digital signal processing (DSP). Processing the chip to implement the above-mentioned update module 206. In addition, in order to receive the service data (ie, baseband data) sent by the baseband system 10 and its corresponding power level information, the RF system 20 can also be configured with an interface FPGA module as an actual interface. The interface FPGA module and the IF FPGA module can also be combined according to actual needs. In this way, after analyzing the power level information (ie, power binning information) of different time domain segments according to the service scheduling information sent by the MAC layer module 102, the PHY layer module 104 compares the service data and the pair thereof. The power level information should be sent to the interface FPGA module of the RRU 20. After receiving the service data sent by the BBU 10 and the corresponding power level information, the interface FPGA module forwards the data to the IF FPGA module; the IF FPGA module performs the DPD parameter and parses the power level information transmitted by the interface FPGA module, according to The power level information causes the service data of different power levels to pass the corresponding pre-distortion coefficient table (ie, the pre-distortion coefficient table corresponding to the power level information is found, and the pre-distortion coefficient in the service data and the found pre-distortion coefficient table is obtained. Multiply). The DSP module is configured to extract the predistortion coefficient table for the data of different power levels collected by the intermediate frequency FPGA module, and periodically update the predistortion coefficient in the predistortion coefficient table. Obviously, the RF system may further include an RF link and a power amplifier module, configured to transmit the digital pre-distortion processed service data, and feed back the data to the IF FPGA module. 3 is a flowchart of a digital pre-distortion processing method according to an embodiment of the present invention, including the following steps: Step S302: A baseband system sends service data and corresponding power level information to a radio frequency system; Step S304, the radio frequency system acquires the foregoing power The pre-distortion coefficient corresponding to the level information, and the pre-distortion coefficient is used to perform digital pre-distortion processing on the service data. The baseband system transmits the service data and transmits the power level information corresponding to the service data to the radio frequency system, so that the radio frequency system can directly use the power level information to perform digital pre-distortion processing on the service data, thereby eliminating the need for the radio system to the service. The power level of the data is calculated and judged, which solves the problem that the computing power bin of the radio system has large occupied resources and pre-distortion errors in the related art, so that the current service data can be digitally pre-processed using the corresponding power level information in real time. The distortion processing saves resources and improves the efficiency and accuracy of the digital pre-distortion processing. Step S302 may include: the medium access control (MAC) layer module of the baseband system delivers the service to the physical (PHY) layer module of the baseband system. Scheduling information, where the service scheduling information includes power level information corresponding to service data of different users; the physical layer module configures power of the service data to be the power indicated by the power level information; Business And the data transmission power level information corresponding to the RF system. Thereby, the power level information corresponding to the service data is directly notified to the radio frequency system by the baseband system. In the foregoing method, the power level information sent by the baseband system may include power level information of the service data in different time zones; and the physical layer module configures the power of the service data as the power level letter. The power indicated by the information includes: the physical layer module analyzes the power level information of each time domain segment from the service scheduling information sent by the MAC layer; the physical layer module configures the power of the service data sent in each time domain segment as the time The power indicated by the power level information of the domain segment. In this way, it can be more adapted to generate rapidly fluctuating data as the user changes in the time domain. Step S304 includes: the radio frequency system locally searches for a pre-distortion coefficient corresponding to the received power level information; the radio frequency system multiplies the service data by the found pre-distortion coefficient to complete digital pre-distortion processing on the service data. . In practical applications, the specific manner in which the radio frequency system locally searches for the pre-distortion coefficient corresponding to the received power level information may include: finding and receiving power from the plurality of pre-distortion coefficient tables saved by the radio system. a predistortion coefficient table corresponding to the level information; obtaining the predistortion coefficient from the found predistortion coefficient table. Referring to the digital predistortion system shown in FIG. 2, the implementation process of the digital predistortion processing method of the digital predistortion system in the LTE TDD (Time Division Duplex) system according to the preferred embodiment of the present invention is as shown in FIG. The method includes the following steps: Step S402: The MAC layer module sends service scheduling information. Step S404, the PHY layer module obtains power binning information of different time domain segments by analyzing the service scheduling information. Specifically, the service scheduling information is obtained. The analysis is performed to find different power gear information (ie, power level information) of the control segment and the service segment in each subframe. Step S406, the PHY layer module sends the service data and the binning information to the interface FPGA of the RRU. Specifically, the power binning information and the number of symbols occupied by the control symbols are synchronously sent to the RRU through the control word. The interface FPGA module described above in step S402 to step S406 corresponds to step S302 in FIG. Step S408, the interface FPGA module of the RRU receives the baseband data and the power split information and sends the information to the intermediate frequency FPGA module. In step S410, the intermediate frequency FPGA module collects different gears from the radio frequency according to the power split information transmitted from the interface. The forward and feedback data of the link and the power amplifier module are sent to the DSP for extracting the predistortion coefficient; in step S412, the DSP extracts the predistortion coefficient, and downloads the coefficient to the intermediate frequency FPGA module; Step S414, the power binning information transmitted by the IF FPGA module is performed on the interface, and the data pre-distortion processing is performed by causing the service data of the corresponding power class and the control data to pass the corresponding pre-distortion coefficient in the time domain. The above steps S408 to S414 correspond to step S304 in FIG. Repeating the above step 4 to gather S410-step 4 gather S414 repeat iteration to achieve convergence of pre-distortion. From the above description, it can be seen that the present invention achieves the following technical effects: The resources occupied by the calculation power split of the radio frequency system are saved, the delay of the system and the lag of data and gear are avoided, and the system is improved. Performance and DPD adaptability, which can improve the indicators of power leakage. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device and, in some cases, may be different from the order herein. The steps shown or described are performed, or they are separately fabricated into individual integrated circuit modules, or a plurality of modules or steps are fabricated as a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A digital predistortion system comprising:

a baseband system, configured to send service data and corresponding power level information to the radio frequency system;

The radio frequency system is configured to acquire a pre-distortion coefficient corresponding to the power level information, and perform digital pre-distortion processing on the service data by using the pre-distortion coefficient.

2. The system of claim 1, wherein the baseband system comprises:

The media access control layer module is configured to send service scheduling information to the physical layer module, where the service scheduling information includes power level information corresponding to the service data;

The physical layer module is configured to configure the power of the service data to be the power indicated by the power level information, and send the configured service data and the power level information to the radio frequency system.

3. The system according to claim 2, wherein the physical layer module comprises:

The analyzing unit is configured to analyze the power level information of each time domain segment from the service scheduling information, where the power level information includes the power level information of the service data in different time segments;

The sending unit is configured to configure the power of the service data sent in each time domain segment as the power indicated by the power level information of the time domain segment.

The system according to any one of claims 1 to 3, wherein the radio frequency system comprises: a lookup module configured to find, from the radio frequency system, corresponding to the received power level information Predistortion coefficient

And a processing module, configured to multiply the service data by the found pre-distortion coefficient to complete digital pre-distortion processing on the service data.

The system of claim 4, wherein the searching module comprises:

a searching unit, configured to find a pre-distortion coefficient table corresponding to the power level information from a plurality of pre-distortion coefficient tables saved by the radio frequency system; And an obtaining unit, configured to obtain the pre-distortion coefficient from the found pre-distortion coefficient table.

The system of claim 5, wherein the radio frequency system further comprises:

And an update module, configured to update a pre-distortion coefficient in the plurality of pre-distortion coefficient tables saved by the radio frequency system.

7. A digital predistortion processing method, comprising:

The baseband system sends the service data and its corresponding power level information to the radio frequency system; the radio frequency system acquires a pre-distortion coefficient corresponding to the power level information, and performs digital pre-distortion on the service data by using the pre-distortion coefficient deal with.

8. The method according to claim 7, wherein the baseband system transmitting the service data and its corresponding power level information to the radio frequency system comprises:

The medium access control layer module of the baseband system sends service scheduling information to the physical layer module of the baseband system, where the service scheduling information includes power level information corresponding to the service data;

The physical layer module configures power of the service data as power indicated by the power level information;

The physical layer module sends the configured service data and the power level information to the radio frequency system.

The method according to claim 8, wherein the power level information includes power level information of the service data in different time domain segments; the physical layer module configures power of the service data as the The power indicated by the power level information includes:

The physical layer module analyzes the power level information of each time domain segment from the service scheduling information;

The physical layer module configures the power of the service data sent in each time domain segment as the power indicated by the power level information of the time domain segment.

The method according to any one of claims 7 to 9, wherein the radio frequency system extracts a pre-distortion coefficient corresponding to the power level information, and uses the pre-distortion coefficient to perform digital data on the service data. Predistortion processing includes: The radio frequency system locally finds a pre-distortion coefficient corresponding to the received power level information;

The radio frequency system multiplies the service data by the found pre-distortion coefficient to perform digital pre-distortion processing on the service data.