Communication device and its CFR processing method

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 performing CFR (Crest Factor Reduction) processing on a signal to reduce PAPR in a communication device such as a repeater. Background Art

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

[0003] CFR (Crest Factor Reduction) is one of such methods. In CFR, an input signal is sampled, a peak of the sampled signal is detected, and then the peak value is compared with a preset threshold value. If the peak value exceeds the threshold value, the peak value is reduced by the excess amount, so that the overall peak value of the signal can be kept below the set threshold value.

[0004] In the conventional CFR method, if the magnitude peak position of the input signal does not match the sampling timing, an accurate peak value cannot be estimated. In this case, there is a problem that the peak portion of the signal is not sufficiently removed, and peak components exceeding the threshold value remain.

[0005] Typically, to solve these problems, a multistage CFR (Condensed Frame Rate) method is used, in which the signal processed with primary CFR is passed through a CFR block of the same configuration one or more times to reduce the magnitude of the remaining peak signal. However, this method is also ineffective when the sampling position and the peak position do not coincide. Of course, the sampling rate can be increased to make the sampling position and the peak position coincide, but increasing the sampling rate either becomes impossible due to the limitations of the FPGA's processing speed, or it leads to the problem of having to use a high-spec FPGA due to an excessive increase in the FPGA's logic capacity. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2013 / 0114761 [Patent Document 2] U.S. Patent No. 10826739 [Overview of the project] [Problems that the invention aims to solve]

[0007] To solve the aforementioned problems, the present invention aims to provide 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 concept of this invention aims to solve are not limited to those 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 processes an original signal using CFR to generate a first processed signal, and a second CFR module that processes the first processed signal using CFR 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] In one embodiment, the second CRF module performs CFR processing on the first processed signal with reference to a different time point than the first CFR module to generate the second processed signal, but the first sampling rate and the second sampling rate are set to be equal.

[0011] Depending on the embodiment, the communication device further includes a sample shifter that shifts and outputs the first processed signal for a preset time, while the second CRF module generates the second processed signal by performing CFR processing on the signal input from the sample shifter.

[0012] Depending on the embodiment, the preset time corresponds to less than the first sampling rate.

[0013] Depending on the embodiment, the preset time corresponds to half of the first sampling rate.

[0014] In another aspect of the present invention, a method for CFR processing an original signal in a communication device comprising a plurality of CFR modules is disclosed, comprising 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] According to an embodiment, the step of generating the second processed signal includes the step of performing CFR processing on the first processed signal with reference to 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 to each other.

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

[0017] According to an embodiment, the preset time corresponds to less than the first sampling rate.

[0018] According to an embodiment, the preset time corresponds to half of 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 in a signal even at a low sampling rate.

[0020] In addition, the communication device and the CFR processing method thereof according to the present invention can effectively reduce PAPR even in FPGA LOGIC operating with a low clock.

[0021] Effects obtained by the embodiments according to the technical idea of the present invention are not limited to the effects mentioned above, and other effects not mentioned herein will be clearly understood by those skilled in the art from the following description. Brief Description of the Drawings

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

[0023] While the technical idea of the present invention can be modified in various ways and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail herein. However, this is not intended to limit the technical idea of the present invention to the specific embodiments, and it should be understood that the technical idea of the present invention includes all modifications, equivalents or alternatives falling within the scope of the technical idea of the present invention.

[0024] In describing the technical idea of the present invention, when it is determined that a detailed description of related known art unnecessarily obscures the gist of the present invention, the detailed description thereof will be omitted. In addition, numerals (e.g., first, second, etc.) used in the description process of the present specification are merely identification symbols for distinguishing one component from another component.

[0025] Furthermore, in this specification, when one component is referred to as being "connected" or "linked" with another component, it should be understood that the component may be directly connected to or linked with the other component, but unless otherwise stated, it may also be connected or linked through other components in between.

[0026] Furthermore, terms such as "~part," "~device," and "~child" as used herein refer to a unit that processes at least one function or operation, which is embodied in hardware and software such as processors, microprocessors, microcontrollers, CPUs (Central Processing Units), GPUs (Graphics Processing Units), APUs (Accelerate Processor Units), DSPs (Drive Signal Processors), ASICs (Application Specific Integrated Circuits), and FPGAs (Field Programmable Gate Arrays), or a combination of hardware and software.

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

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

[0029] Figure 1 is a functional configuration diagram of a typical CFR module.

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

[0031] The peak detector 110 detects peaks by receiving the magnitude of the original signal. For example, the peak detector calculates the change in signal magnitude between samples and defines the point where the sign of that value changes from positive to negative as the 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 cancel pulse generator 120 generates cancel pulses corresponding to the peak and original signals detected by the peak detector 110 and outputs them to the subtractor 140.

[0033] The delay unit 130 synchronizes the original signal and the cancel pulse by delaying the original signal (the remainder excluding the portion input to the peak detector 110) in accordance with the delay time required while the peak detector 110 and the cancel pulse generator 120 perform the aforementioned 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 to output a signal from which the portion of the signal whose magnitude exceeds a threshold has been removed (hereinafter referred to as the "processed signal").

[0035] Since the operation of the CFR module 100 described above is already publicly available technology, a further detailed explanation will be omitted. Furthermore, the operation of the CFR module 100 described above is merely illustrative, and it is clear that the scope of the present invention is not limited to this operation. In the following, the operation in which the CFR module 100 removes peaks from the original signal and outputs a processed signal will be abbreviated as "CFR processing operation".

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

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

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

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

[0040] The sample shifter 220 shifts or phase-delays the input signal for a preset time. The signal output from the first CFR module 210 is shifted or phase-delayed through the sample shifter 220 before being 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 and generates pulses corresponding to the detected peaks to secondarily remove the peaks from 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 equal, the positions of the original signals sampled by the first CFR module 210 and the second CFR module 230 may be different.

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

[0044] In other words, the first CFR module 210 comprises a first peak detector 310, a first cancel pulse generator 320, and a first delay unit 330.

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

[0046] The sample shifter 220 receives a first processing signal as input. The sample shifter 220 shifts or phase-delays the first processing signal for a preset time and outputs it. Here, the preset time is shorter than the period of the first sampling rate, for example, corresponding to half the period of the first sampling rate. The sample shifter 220 is implemented using an FIR filter composed of multiple taps, the number of FIR filter taps varies depending on the ratio of the original signal bandwidth to the sampling rate. The FIR filter coefficients are set to flatten the frequency characteristics of the filter across the entire signal bandwidth so that the original signal has mutually symmetrical values ​​without distortion in the spectrum. Therefore, the larger the bandwidth of the original signal, the wider the frequency characteristics must be maintained over an even wider frequency band, requiring an FIR filter with more taps.

[0047] An example of a configuration for realizing the function of the sample shifter 220 is illustrated in Figure 4. Since there are various configurations of the sample shifter 220 other than those illustrated in Figure 4, it is clear that no single configuration of the sample shifter 220 can limit the scope of the present invention.

[0048] The second CFR module 230 includes a second peak detector 340, a second cancel pulse generator 350, and a second delay unit 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 the peak, generates a cancellation pulse to control the peak, 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 of the original signal even at a low sampling rate. The results of peak component removal by the present invention will be described below with reference to Figures 4 to 6.

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

[0053] Referring to Figure 5, an example is shown in which the peak components of the original signal are removed using only the first CFR module 210 and the second CFR module 230 without the sample shifter 220. As illustrated in Figure 5, without the sample shifter 220, the peak portions detected by the first CFR module 210 and the peak portions detected by the second CFR module 230 are very similar, and residual peaks 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 exceeding a preset threshold may remain.

[0054] On the other hand, as shown in Figure 6, an example is given in which 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. The sample shifter 220 shifts the first processed signal for a preset time (t shift ) is shifted or phase delayed for a predetermined time (t). For example, if the first sampling rate and the second sampling rate are equal, a preset time (t) is used. shift ) is a value corresponding to half of the first sample rate. Therefore, the peak portion detected from the first CFR module 210 and the peak portion detected from the second CFR module 230 are completely different. As a result, the first processed signal (1 st It can be seen that the residual peak portion not removed by the processed signal (2) is completely removed through the second CFR module 230. Unlike Figure 5, the second processed signal (2) in Figure 6 nd The processed signal shows that there are no components that exceed the threshold.

[0055] Figure 7 is a graph comparing the amplitudes of the original signal, the primary CFR processed signal, the secondary CFR processed signal, and the signal processed by the present invention.

[0056] Referring to Figure 7, it can be seen that the components exceeding the threshold of the original signal were largely removed by the first processed signal, but that components still exceed the threshold.

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

[0058] On the other hand, when the primary processed signal is shifted or phase-delayed using the sample shifter 220 unique to the present invention, and then the secondary CFR processing is performed, it can be seen that components exceeding the threshold value are almost completely removed from the second processed signal.

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

[0060] A CFR processing method according to one embodiment of the present invention will be described below with reference to Figure 8. Each of the steps described below may be operations performed in the respective configurations of the communication device 200 described with reference to Figures 2 and 3, the first CFR module 210, the sample shifter 220, and the second CFR module 230, but for the sake of understanding and explanation, they will be referred to as operations performed in the communication device 200.

[0061] In step S710, the communication device 200 samples the original signal at a preset first sampling rate, then compares the magnitude of the sampled signal with a threshold value to detect peak portions, and performs a CFR (Conditional Frame Rate) processing operation to remove the detected peak portions. The signal that has undergone primary CFR processing through this step is referred to as the first processed signal.

[0062] In step S720, the communication device 200 sends the first processing signal for a predetermined time (t shift ) is shifted or phase delayed for a predetermined time (t). shiftThis value corresponds to half of the first sampling rate. Furthermore, since there are various specific configurations for shifting or phase-delaying the first processed signal, a detailed explanation of these will be omitted.

[0063] In step S730, the communication device 200 samples the first processed signal, which has been shifted or phase-delayed, at a preset second sampling rate. After comparing the magnitude of the sampled signal with a threshold, it detects the peak portion and performs a secondary CFR processing operation to remove the detected peak portion. The signal that has undergone secondary CFR processing through this step is referred to as the second processed signal.

[0064] Here, the second sampling rate is equal to the first sampling rate. Because a shifted or phase-delayed first processing signal is input, even if sampling is performed at a value equal to the first sampling rate, the sampled positions will differ. Therefore, according to the present invention, even if the first sampling rate and / or the second sampling rate are low, the peak components of the signal can be effectively removed, and FPGA LOGIC can be implemented at a low clock.

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

Claims

1. A first CFR module that generates a first processed signal by performing CFR processing on the original signal, A sample shifter that shifts the first processing signal by half the first sampling rate and outputs it, The system includes a second CFR module that performs CFR processing on a signal input from the aforementioned sample shifter to generate a second processed signal, The first processing signal is generated using a first sampling rate, The second processed signal is generated using the second sampling rate, A communication device in which the first sampling rate and the second sampling rate are set to be equal.

2. The second CFR module is, The communication device according to claim 1, wherein the first processed signal is subjected to CFR processing with reference to a time point different from that of the first CFR module to generate the second processed signal.

3. In a method for CFR processing of an original signal using a communication device equipped with multiple CFR modules, The steps include: generating a first processed signal by performing CFR processing on the original signal; A step of shifting the first processed signal by half the first sampling rate and outputting it, The process includes the step of performing CFR processing on a shifted first processed signal to generate a second processed signal, The first processing signal is generated using a first sampling rate, The second processed signal is generated using the second sampling rate, A CFR processing method in which the first sampling rate and the second sampling rate are set to be equal.

4. The step of generating the second processing signal is: The CFR processing method according to claim 3, further comprising the step of performing CFR processing on the first processed signal with reference to a time point different from the step of generating the first processed signal to generate the second processed signal.

Images