Communication device and CFR processing method thereof

Abstract

To provide a PAPR (Peak to Average Power Ratio) reduction method in a communication device, and more specifically, a method for performing CFR (Crest Factor Reduction) processing on a signal for reducing a PAPR in a communication device like a repeater.SOLUTION: A communication device includes: a first CFR module that generates a first processing signal by performing CFR processing on an original signal; and a second CFR module that generates a second processing signal by performing CFR processing on the first processing signal. The first processing signal is generated using a first sampling rate, and the second processing signal is generated using a second sampling rate. According to the present invention, even a communication device with a low sampling rate can effectively remove a peak component of an input signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for reducing PAPR (Peak to Average Power Ratio) in a communication device, and more particularly to a method for CFR (Crest Factor Reduction) processing of a signal in order to reduce PAPR in a communication device such as a repeater. [Background technology]

[0002] A repeater is an electronic device that receives a signal and retransmits it at a higher level or power. The signals used in repeaters often have a high PAPR (Peak-to-Average Power Ratio). This causes problems that limit the efficiency of the power amplifier implemented in the repeater. Therefore, various PAPR reduction methods have been proposed to improve the efficiency of the power amplifier.

[0003] CFR (Crest Factor Reduction) is one such method. CFR samples the input signal, detects the peaks of the sampled signal, and then compares the peak value with a preset threshold. If the peak value exceeds the threshold, the peak value is reduced by the amount of the excess, so that the overall signal peak value is kept below the set threshold.

[0004] In the conventional CFR method, if the peak (magnitude peak) position of the input signal does not coincide with the sampling timing, the peak value cannot be accurately estimated. In this case, the peak part of the signal is not sufficiently removed, and peak components that exceed the threshold remain.

[0005] To solve this problem, a multistage CFR method is typically used, in which the signal that has undergone primary CFR processing is passed through a CFR block with the same configuration once or more times to reduce the amplitude of the remaining peak signal. However, this method is ineffective when the sampling position and the peak position do not coincide. Of course, the sampling position can be made to coincide with the peak position by increasing the sampling rate, but increasing the sampling rate can either make it impossible to implement due to limitations on the FPGA's processing speed, or it can result in an excessive increase in the FPGA's logic capacity, requiring the use of a high-spec FPGA. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2013 / 0114761 [Patent Document 2] U.S. Patent No. 10,826,739 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve the above-mentioned problems, the present invention provides a communication device and a CFR processing method thereof that can effectively remove peak components of a signal even at a low sampling rate.

[0008] The technical problems that the technical idea of ​​the present invention aims to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] According to one aspect of the present invention, a communication device is disclosed, comprising a first CFR module that performs CFR processing on an original signal to generate a first processed signal, and a second CFR module that performs CFR processing on the first processed signal to generate a second processed signal, wherein the first processed signal is generated using a first sampling rate and the second processed signal is generated using a second sampling rate.

[0010] According to an embodiment, the second CFR module performs CFR processing on the first processed signal based on a different time point from that of the first CFR module to generate the second processed signal, and the first sampling rate and the second sampling rate are set to be equal.

[0011] According to an embodiment, the communication device further includes a sample shifter that shifts the first processed signal by a predetermined time and outputs the first processed signal, and the second CRF module performs CFR processing on the signal input from the sample shifter to generate the second processed signal.

[0012] In some embodiments, the preset time period corresponds to less than the first sampling rate.

[0013] In some embodiments, the preset time period corresponds to half the first sampling rate.

[0014] According to another aspect of the present invention, a method for CFR processing an original signal in a communication device having a plurality of CFR modules is disclosed, the method including the steps of CFR processing the original signal to generate a first processed signal, and CFR processing the first processed signal to generate a second processed signal, wherein the first processed signal is generated using a first sampling rate and the second processed signal is generated using a second sampling rate.

[0015] In some embodiments, the step of generating the second processed signal includes a step of CFR processing the first processed signal based on a time point different from that of the first CFR module to generate the second processed signal, and the first sampling rate and the second sampling rate are set to be equal.

[0016] According to an embodiment, the CFR processing method further includes a step of shifting the first processed signal by a predetermined time and outputting the shifted first processed signal, and the step of generating the second processed signal includes CFR processing the shifted first processed signal to generate the second processed signal.

[0017] In some embodiments, the preset time period corresponds to less than the first sampling rate.

[0018] In some embodiments, the preset time period corresponds to half the first sampling rate. [Effects of the Invention]

[0019] The communication device and the CFR processing method thereof according to the present invention can effectively remove peak components exceeding a threshold from a signal even at a low sampling rate.

[0020] Furthermore, the communication device and the CFR processing method thereof according to the present invention can effectively reduce PAPR even in FPGA logic that operates at a low clock rate.

[0021] The effects obtained by the embodiments according to the technical concept of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a functional configuration diagram of a general CFR module. [Figure 2]FIG. 2 is a block diagram illustrating a configuration of a CFR processing unit according to an embodiment of the present invention. [Figure 3] FIG. 2 is a block diagram illustrating a configuration of a CFR processing unit according to an embodiment of the present invention. [Figure 4] 1 is an exemplary diagram illustrating the configuration of a sample shifter according to an embodiment of the present invention. [Figure 5] 10 is a graph showing the results of removing signal peaks using multiple CFR modules without a sample shifter. [Figure 6] 10 is a graph showing a signal processing result processed by a CFR processing unit according to an embodiment of the present invention. [Figure 7] 1 is a graph comparing the amplitudes of an original signal, a first-order CFR processed signal, a second-order CFR processed signal, and a signal processed according to the present invention. [Figure 8] 1 is a flowchart of a CFR processing method according to an embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0023] The technical concept of the present invention can be variously modified and can have various embodiments, and therefore, specific embodiments are illustrated in the drawings and will be described in detail. However, this is not intended to limit the technical concept of the present invention to the specific embodiments, and it should be understood that the technical concept of the present invention includes all modifications, equivalents, and alternatives that fall within the scope of the technical concept of the present invention.

[0024] In explaining the technical concept of the present invention, if a detailed description of the related prior art is deemed to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Furthermore, numbers (e.g., 1, 2, etc.) used in the description of this specification are merely identification symbols for distinguishing one component from another.

[0025] Furthermore, in this specification, when a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled to or connected to the other component, but unless otherwise specified, it may also be coupled to or connected via another component in between.

[0026] In addition, the terms "module," "device," "subsystem," etc. used in this specification refer to a unit that processes at least one function or operation, and this is embodied in hardware or software, such as a processor, microprocessor, microcontroller, CPU (Central Processing Unit), GPU (Graphics Processing Unit), APU (Accelerate Processor Unit), DSP (Drive Signal Processor), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), or a combination of hardware and software.

[0027] It should be understood that the division of components in this specification merely represents a division according to the main function of each component. That is, two or more components described below may be combined into one component, or one component may be divided into two or more components according to further subdivided functions. It goes without saying that each component described below may perform some or all of the functions of other components in addition to its own main function, and that some of the main functions of each component may be exclusively performed by other components.

[0028] Hereinafter, various embodiments according to the technical concept of the present invention will be described in detail.

[0029] Figure 1 shows the functional configuration of a typical CFR module.

[0030] Referring to FIG. 1, the CFR module 100 is configured to reduce the magnitude of components (peaks) in an input signal (hereinafter referred to as the “original signal”) that are greater than a predetermined threshold, and includes a peak detector 110, a cancellation pulse generator 120, and a delay 130.

[0031] The peak detector 110 detects peaks in the magnitude of the original signal. For example, the peak detector calculates the change in signal magnitude between samples and determines the point where the sign of the change in magnitude changes from positive to negative as a peak. If the magnitude of the detected peak is greater than a predetermined threshold, the peak detector obtains the difference between the peak and the threshold.

[0032] The cancellation pulse generator 120 generates a cancellation pulse corresponding to the peak detected by the peak detector 110 and the original signal, and outputs the cancellation pulse to the subtractor 140 .

[0033] The delay 130 synchronizes the original signal with the cancellation pulse by delaying the original signal (the remainder excluding the portion input to the peak detector 110) corresponding to the delay time required for the peak detector 110 and the cancellation pulse generator 120 to perform the above operations.

[0034] The subtractor 140 combines the original signal input from the delay unit 130 and the cancellation pulse input from the cancellation pulse generator 120, and outputs a "signal from which the portion of the signal whose magnitude is greater than or equal to the threshold has been removed" (hereinafter referred to as the "processed signal").

[0035] The operation of the CFR module 100 described above is a publicly known technology, and therefore further detailed description thereof will be omitted. Furthermore, the operation of the CFR module 100 described above is merely an example, and it is clear that the scope of the present invention is not limited to this operation. Furthermore, hereinafter, the operation of the CFR module 100 to remove peaks from an original signal and output a processed signal will be abbreviated as a "CFR processing operation."

[0036] On the other hand, the present invention includes a configuration in which the CFR processing operation is performed multiple times, and in particular, a unique "sample shift operation" (specific operations of which will be described later) is performed between each CFR processing operation. Hereinafter, the CFR processing of an original signal according to one embodiment of the present invention will be described with reference to FIGS. 2 and 3.

[0037] 2 and 3 are block diagrams of a CFR processing unit according to an embodiment of the present invention.

[0038] Referring to FIG. 2, a communication device 200 according to an embodiment of the present invention includes a first CFR module 210, a sample shifter 220, and a second CFR module 230.

[0039] When an original signal is input, the first CFR module 210 detects peaks of the original signal using a preset first sampling rate, generates pulses corresponding to the detected peaks, and primarily removes the peaks of the original signal.

[0040] The sample shifter 220 shifts or delays the phase of the input signal by a preset time. The signal output from the first CFR module 210 is shifted or phase-delayed by the sample shifter 220 and then input to the second CFR module 230.

[0041] When the second CFR module 230 receives a shifted or phase-delayed signal from the sample shifter 220, it detects peaks using a preset second sampling rate, generates pulses corresponding to the detected peaks, and secondarily removes the peaks of the original signal.

[0042] The operation of the second CFR module 230 is similar to that of the first CFR module 210, but the sampling timing is different. This is because the signal input to the second CFR module 230 is the signal input from the sample shifter 220. Therefore, even if the first sampling rate and the second sampling rate are the same, the positions of the original signal sampled by the first CFR module 210 and the second CFR module 230 may be different.

[0043] FIG. 3 illustrates a specific configuration of the first CFR module 210, the sample shifter 220, and the second CFR module 230 of the communication device 200 according to one embodiment of the present invention.

[0044] That is, the first CFR module 210 includes a first peak detector 310 , a first cancellation pulse generator 320 , and a first delay 330 .

[0045] The first CFR module 210 samples the input original signal at a first sampling rate, detects peaks, generates cancellation pulses to control the peaks, and then outputs a first processed signal.

[0046] The first processed signal is input to the sample shifter 220. The sample shifter 220 shifts or phase-delays the first processed signal by a preset time and outputs the result. The preset time is shorter than the period of the first sampling rate, e.g., half the period of the first sampling rate. The sample shifter 220 is implemented using an FIR filter with multiple taps, and the number of FIR filter taps varies depending on the ratio of the bandwidth of the original signal to the sampling rate. In addition, the FIR filter coefficients are set to flatten the filter's frequency characteristics across the entire signal band so that the original signal has symmetrical values ​​without being distorted in the spectrum. Therefore, the wider the bandwidth of the original signal, the wider the frequency characteristic must be maintained across a wider frequency band, requiring an FIR filter with more taps.

[0047] An example of a configuration for implementing the function of sample shifter 220 is shown in Figure 4. Since there are various configurations of sample shifter 220 other than the example shown in Figure 4, it is clear that any one configuration of sample shifter 220 cannot limit the scope of the present invention.

[0048] The second CFR module 230 includes a second peak detector 340 , a second cancellation pulse generator 350 , and a second delay 360 .

[0049] The second CFR module 230 receives the signal processed by the sample shifter 220. The second CFR module 230 samples the input signal at a second sampling rate, detects peaks, generates cancellation pulses to control the peaks, and then outputs a second processed signal.

[0050] Here, the signal input to the second CFR module 230 is a signal that has been shifted or phase delayed by the sample shifter 220. Therefore, even if the first sampling rate and the second sampling rate are equal, the position of the original signal sampled by the second peak detector 340 may differ from the position of the original signal sampled by the first peak detector 310.

[0051] With this configuration, the communication device 200 according to the present invention can effectively remove peak components from the original signal even at a low sampling rate. The results of removing peak components according to the present invention will now be described with reference to Figures 4 to 6.

[0052] FIG. 5 is a graph showing the results of removing signal peaks using multiple CFR modules without a sample shifter, and FIG. 6 is a graph showing the results of signal processing performed by a CFR processing unit according to one embodiment of the present invention.

[0053] 5 illustrates an example in which peak components of an original signal are removed only by the first CFR module 210 and the second CFR module 230 without the sample shifter 220. As shown in FIG. 5, without the sample shifter 220, the peak portions detected by the first CFR module 210 and the second CFR module 230 are very similar, and residual peaks that are not removed by the first CFR module 210 may not be completely removed by the second CFR module 230. Therefore, even after peak removal processing by the first CFR module 210 and the second CFR module 230, components that exceed a preset threshold may remain.

[0054] 6, a case where the peak component of the original signal is removed using the first CFR module 210, the sample shifter 220, and the second CFR module 230 is illustrated. The sample shifter 220 shifts the first processed signal by a predetermined time (t shift ) for a predetermined time (t shift ) is a value corresponding to half the first sample rate. Therefore, the peak portion detected by the first CFR module 210 is completely different from the peak portion detected by the second CFR module 230. st It can be seen that the remaining peak portions that are not removed in the second processed signal (2 processed signal) are completely removed through the second CFR module 230. Unlike FIG. 5, the second processed signal (2 processed signal) in FIG. nd It can be seen that the processed signal has no components that exceed the threshold.

[0055] FIG. 7 is a graph comparing the amplitudes of the original signal, the first order CFR processed signal, the second order CFR processed signal, and the signal processed according to the present invention.

[0056] Referring to FIG. 7, it can be seen that the components exceeding the threshold of the original signal have been largely removed in the first processed signal, but components exceeding the threshold still exist.

[0057] Furthermore, if the second CFR processing is performed immediately after the first CFR processing without the sample shifter 220 specific to the present invention, it can be seen that the second processed signal still contains components that exceed the threshold.

[0058] On the other hand, when the first processed signal is shifted or phase delayed by the sample shifter 220 specific to the present invention and then subjected to second CFR processing, it can be seen that components exceeding the threshold are almost completely removed from the second processed signal.

[0059] FIG. 8 is a flowchart of a CFR processing method according to one embodiment of the present invention.

[0060] A CFR processing method according to an embodiment of the present invention will now be described with reference to Figure 8. Although each step described below may be an operation performed in each component of communication device 200 described with reference to Figures 2 and 3, namely, first CFR module 210, sample shifter 220, and second CFR module 230, they will be generally described as being performed in communication device 200 for ease of understanding and explanation.

[0061] In step S710, the communication device 200 samples the original signal at a preset first sampling rate, compares the magnitude of the sampled signal with a threshold, detects peaks, and performs CFR processing to remove the detected peaks. The signal that has undergone the first CFR processing is referred to as a first processed signal.

[0062] In step S720, the communication device 200 transmits the first processed signal for a predetermined time (t shift ) is shifted or phase delayed by a preset time (t shift) is a value corresponding to half the first sampling rate. In addition, since there are various specific configurations for shifting or phase-delaying the first processed signal, a detailed description thereof will be omitted.

[0063] In step S730, communication device 200 samples the shifted or phase-delayed first processed signal at a preset second sampling rate, compares the magnitude of the sampled signal with a threshold value to detect peaks, and performs a second CFR processing operation to remove the detected peaks. The signal that has undergone the second CFR processing is referred to as the second processed signal.

[0064] Here, the second sampling rate is equal to the first sampling rate. Since the first processed signal is input with a shift or phase delay, the sampling positions are different even if the first sampling rate is equal to the first sampling rate. Therefore, according to the present invention, even if the first sampling rate and / or the second sampling rate is low, the peak components of the signal can be effectively removed, and the FPGA logic can be implemented with a low clock.

[0065] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that the present invention can be modified and changed in various ways without departing from the spirit and scope of the present invention as defined in the following claims.

Claims

1. a first CFR module for CFR processing the original signal to generate a first processed signal; a second CFR module that performs CFR processing on the first processed signal to generate a second processed signal, the first processed signal is generated using a first sampling rate; The communication device, wherein the second processed signal is generated using a second sampling rate.

2. The second CRF module comprises: The first processed signal is CFR-processed based on a time point different from that of the first CFR module to generate the second processed signal; 2. The communication device according to claim 1, wherein the first sampling rate and the second sampling rate are set to be equal to each other.

3. The first processed signal may further include a sample shifter for shifting the first processed signal by a predetermined time and outputting the shifted signal.

3. The communication device according to claim 2, wherein the second CRF module performs CRF processing on the signal input from the sample shifter to generate the second processed signal.

4. 4. The communication device of claim 3, wherein the predetermined time corresponds to less than the first sampling rate.

5. 5. The communication device of claim 4, wherein the preset time corresponds to half the first sampling rate.

6. A method for CFR processing an original signal in a communication device having a plurality of CFR modules, comprising: CFR processing the original signal to generate a first processed signal; and CFR processing the first processed signal to generate a second processed signal, the first processed signal is generated using a first sampling rate; The CFR processing method, wherein the second processed signal is generated using a second sampling rate.

7. The step of generating the second processed signal comprises: a step of CFR processing the first processed signal based on a time point different from that of the first CFR module to generate the second processed signal; 7. The CFR processing method of claim 6, wherein the first sampling rate and the second sampling rate are set equal to each other.

8. The method further includes the step of shifting the first processed signal by a predetermined time and outputting the shifted signal. The step of generating the second processed signal comprises:

8. The CFR processing method according to claim 7, further comprising CFR processing the shifted first processed signal to generate the second processed signal.

9. 9. The CFR processing method of claim 8, wherein the preset time corresponds to less than the first sampling rate.

10. 10. The CFR processing method of claim 9, wherein the preset time corresponds to half of the first sampling rate.

Images