Description:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2003

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION

“METHOD AND SYSTEM FOR CREST FACTOR REDUCTION”

APPLICANT:

Name : Sterlite Technologies Limited

Nationality : Indian

Address : 3rd Floor, Plot No. 3, IFFCO Tower,
Sector – 29, Gurugram, Haryana
122002

The following specification particularly describes the invention and the manner in which it is to be performed:
TECHNICAL FIELD
The present disclosure relates to communication networks and signal processing and more specifically relates to a method for crest factor reduction to reduce the Peak-to-Average Power Ratio (PAPR) of input signals and a system implementing such a method.

BACKGROUND
To optimize the efficiency/linearity trade-off, crest factor reduction (CFR) techniques are classically implemented along with digital predistortion (DPD) to control the operating point of power amplifiers. In other words, the CFR techniques are used to reduce the Peak to Average Power Ratio (PAPR) of an input signal so that the power amplifiers can operate more efficiently. In practice, there are different CFR techniques to reduce the PAPR, such as clipping and filtering, peak windowing, and peak cancellation, for example. The ‘clipping and filtering’ is a conventional method that includes hard clipping and low-pass filtering and the ‘peak windowing’ aims to smooth the sharp corners from hard clipping. Similarly, the ‘peak cancellation’ is an algorithm to reduce the PAPR of a signal and aims to strike a balance between the out-of-band emission and in-band waveform quality when compressing the signal to a target PAPR. The target PAPR can’t be achieved by one iteration, therefore, multiple iterations are performed.
Some of the prior art references are given below regarding the CFR techniques and PAPR reduction:
“EP3309959B1” discloses an amplification system that can be used in a base station or an eNodeB. The amplification system comprises a crest factor reduction module configured to clip the input signal and a digital pre-distortion module configured to pre-distort the clipped signal and at least one power amplifier configured to amplify the pre-distorted signal. The crest factor reduction module is configured to dynamically adapt a clipping radius according to a load factor and/or a modulation of the input signal to decrease the peak average ratio (PAR).
“US9148096B2” discloses a method and device to control an input signal of a power amplifier. The device includes a CFR device and a digital predistortion (DPD) device. The CFR device includes a CFR unit, which applies the CFR process by clipping the magnitude of the input signal to a certain level to decrease the PAR prior to transmission. The CFR device also includes a threshold determiner for determining the CFR threshold.
“US20210176107A1” discloses a system and method implemented in a wireless node for performing ultra-wideband Crest Factor Reduction (CFR) to reduce the PAPR of a baseband signal. The baseband signal is processed sequentially by the CFR, the Digital Predistortion (DPD), the Power Amplifier (PA), and the band filters and goes to the antenna. The wireless node performs a first CFR step on a plurality of input signals at a first sampling rate with joint peak detection and band-specific noise shaping. Further, the wireless node performs a second CFR step on the resulting plurality of input signals at a second sampling rate with joint peak detection and joint noise shaping where the second sampling rate is higher than the first sampling rate. The wireless node performs multi steps clipping and filtering approach in order to achieve an optimal EVM versus PAPR performance without compromising in-band emission requirement.
“US9806929B2” discloses a crest factor reduction (CFR) architecture implementing a new CFR algorithm suitable for mobile system implementations that would include the possibility to control both the adjacent channel leakage ratio (ACLR) and the error vector magnitude (EVM) of the output digital signal. The CFR architecture includes an Out-of-band (OOB) distortions block those blocks, isolates and enhances the out-of-band distortions of the input signal.
A non-patent literature entitled “A Joint Crest Factor Reduction and Digital Predistortion for Power Amplifiers Linearization Based on Clipping-and-Bank-Filtering” discloses a clipping-and-bank-filtering (CABF) based joint CFR/DPD approach when the input signal can have multiple carriers. The proposed approach takes full advantage of the joint CFR/DPD paradigm in terms of complexity reduction while simultaneously providing better linearization performances than conventional joint CFR/DPD methods in both single-carrier and multi-carrier cases.
Another non-patent literature entitled “Augmented Iterative Learning Control for Neural-Network-Based Joint Crest Factor Reduction and Digital Predistortion of Power Amplifiers” discloses a new approach to realizing a joint CFR and DPD model using neural networks (NN). The proposed approach uses augmented iterative learning control (AILC) algorithm for training the neural network signals. The neural network model generates a target signal by using the AILC algorithm that results in a clipped linearized signal at the power amplifier output.
While the prior arts cover various approaches for crest factor reduction or PAPR reduction, none of them is simple and efficient at the same time and reduces the PAPR in one iteration. Therefore, there is room for improvement. In light of the above-stated discussion, there is a need to overcome the above stated disadvantages.

OBJECT OF THE DISCLOSURE
A principal object of the present disclosure is to provide a method for crest factor reduction to reduce the Peak-to-Average Power Ratio (PAPR) of input signals and a system implementing such a method.
Another object of the present disclosure is to provide a simplified clipping and filtering approach using novel thresholding and noise reduction methods to reduce the PAPR of the input signals in one iteration.
Yet another object of the present disclosure is to improve the performance in linearity and power efficiency in data waveforms by implementing crest factor reduction (CFR) in conjunction with digital predistortion (DPD) as a linearization technique.

SUMMARY
Accordingly, the present disclosure provides a method and a system implementing the method for improving data waveforms. The method comprises dynamically defining, by a crest factor reduction (CFR) unit, a predefined threshold as:

CF=(max|z(n)|/mean|z(n)| )(s)
where T is the predefined threshold, CF is a clipping factor and s is the standard deviation of the input signal. The method further comprises comparing, by the CFR unit, an input signal with the predefined threshold and determining, by the CFR unit, if an input signal level of the input signal (z(n)) is greater than the predefined threshold. Further, the method comprises clipping, by the CFR unit, the input signal to form a clipped signal when the input signal level is greater than the predefined threshold, wherein steps of determining and clipping are performed at detection of at least one peak in the input signal, wherein clipping is based on error vector magnitude (EVM). At least one peak is the input signal level, which is greater than the predefined threshold.
The method is performed in conjunction with digital predistortion (DPD). Alternatively, the method is performed without digital predistortion (DPD). The method reduces the peak-to-average power ratio (PAPR) of the input signal, wherein the PAPR of the input signal is a ratio of peak power to an average power of the input signal.
The method further comprises removing, by the CFR unit, noise added while clipping and removing, by the CFR unit, out-of-band distortions from the clipped signal to get a linear clipped signal.
These and other aspects herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention herein without departing from the spirit thereof.

BRIEF DESCRIPTION OF FIGURES
The invention is illustrated in the accompanying drawings, throughout which reference letters indicate corresponding parts in the drawings. The invention herein will be better understood from the following description with reference to the drawings, in which:
FIG. 1 illustrates a block diagram of a system implementing the crest factor reduction (CFR) technique to reduce the Peak-to-Average Power Ratio (PAPR) of an input signal.
FIG. 2 and FIG. 3 illustrate clipping of the input signal to reduce the PAPR in conjunction with FIG. 1.
FIG. 4 illustrates a reference architecture of a (CFR) unit to perform crest factor reduction in conjunction with FIG. 1.
FIG. 5 is a flow chart illustrating a method to improve data waveforms using the CFR technique.
FIG. 6 is a flow chart illustrating a method to improve the data waveforms using the CFR technique.
FIG. 7 and FIG. 8 illustrate the results of the CFR technique explained in the present disclosure.

DETAILED DESCRIPTION
In the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be obvious to a person skilled in the art that the invention may be practiced with or without these specific details. In other instances, well known methods, procedures and components have not been described in detail so as not to unnecessarily obscure aspects of the invention.
Furthermore, it will be clear that the invention is not limited to these alternatives only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art, without parting from the scope of the invention.
The accompanying drawings are used to help easily understand various technical features and it should be understood that the alternatives presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another.
Unlike conventional techniques, the present disclosure provides a simplified clipping and filtering approach using a novel thresholding and noise reduction method to reduce the Peak-to-Average Power Ratio (PAPR) of an input signal (or baseband input signal) in one iteration. To improve the performance in linearity and power efficiency in data waveforms, the present disclosure utilizes crest factor reduction (CFR) in conjunction with digital predistortion (DPD) as a linearization technique, wherein the high PAPR of the input signal (e.g., PAPR of the 4G/5G signals) is reduced before the DPD stage. In the approach provided by the present disclosure, the input signal is clipped to form a clipped signal after checking that the input signal level of the input signal is greater than a predefined threshold. The comparison of the input signal level with the predefined threshold and clipping of the input signal is performed after the detection of at least one peak in the input signal.
The technique disclosed herein is purely a baseband technique and can be implemented in FR-1 and FR-2 radios, wherein FR-1 defines bands in the sub-6 GHz spectrum (although 7125 MHz is the maximum) and FR-2 defines bands in the mmWave spectrum. Additionally, the technique disclosed herein supports SISO (Single Input Single Output) and MIMO (Multiple Input Multiple Output) systems. Generally, in a SISO system, a single antenna is used for transmission and reception. The antennas perform the activity of both transmitting and receiving the signal in order to establish the datalink. Similarly, in a MIMO system, multiple antennas are used for transmission and reception. The MIMO system achieves much higher data rates because of a technique (spatial multiplexing) used to transmit data simultaneously across multiple antennas.
Further, a neural model may be incorporated to reduce the bit error rate (BER) in the overall system.
Now, simultaneous reference is made to FIG. 1 through FIG. 4, in which FIG. 1 illustrates a block diagram of a system (100) implementing the crest factor reduction (CFR) technique to reduce the Peak-to-Average Power Ratio (PAPR) of an input signal; FIG. 2 and FIG. 3 illustrate clipping (200) and (300) of the input signal to reduce the PAPR in conjunction with FIG. 1 and FIG. 4 illustrates a reference architecture of a crest factor reduction (CFR) unit (102) to perform crest factor reduction in conjunction with FIG. 1.
The system (100) is an amplification system that comprises the crest factor reduction (CFR) unit (102), a digital pre-distortion (DPD) unit (104) and at least one power amplifier (PA) (106).
Broadly, the CFR unit (102) is configured to receive an input signal (z(n)) (also referred to as a baseband signal or baseband input signal) and perform clipping and filtering on the input signal by using crest factor reduction (CFR) technique. In general, the crest factor is a parameter of a waveform or signal, that evaluates the ratio of peak values to the effective value and the CFR technique is a digital technique used to reduce Peak to Average Power Ratio (PAPR) of a transmitted wireless signal for efficient operation of power amplifiers. Generally, the CFR technique employs peak detection and then peak cancellation by subtracting a cancellation pulse from the detected peaks, to reduce peak amplitude and thereby reducing the PAPR.
Particularly, a peak manager (402) (as shown in FIG. 4) of the CFR unit (102) receives the input signal (z(n)) and determines, by comparing the input signal with a predefined threshold, if an input signal level has at least one peak that is greater than the predefined threshold, where the input signal level is equal to the at least one peak. Upon determining that the input signal level is greater than the predefined threshold, the peak manager (402) of the CFR unit (102) clips the magnitude of the input signal in one or more stages (Clip stage 1, Clip stage 2…......Clip stage K) based on the requirement to form a clipped signal as shown in FIG. 4. The at least one peak is detected and clipped by an amount greater than the predefined threshold value before processing additional samples. If the clipped signal has a peak equal to the predefined threshold, then an intermediate clipping/additional clipping is not required. FIG. 2 and FIG. 3 show example peaks (202, 302) and corresponding clipping points (204, 304). The peak manager (402) of the CFR unit (102) continuously checks the input signals and performs clipping based on detection of the at least one peak. The clipping is based on an error vector magnitude (EVM) that is a measure to quantify the performance of a radio frequency transmitter or receiver.
Advantageously, this process reduces the PAPR, which is a ratio of peak power to an average power of the input signal. Typically, PAPR is a measurement of a waveform that is calculated from a peak amplitude of a waveform divided by an RMS value of the waveform and is expressed in decibels (dB). The PAPR is typically measured for a transmitted signal in an OFDM (Orthogonal frequency-division multiplexing) system. Reduction in the PAPR of the input signal is desired for the efficient performance of the system (100) as a high PAPR has been recognized as one of the major practical problems involving OFDM modulation and the power amplifier (106) becomes saturated if a large waveform peak is given to it. Thus, causing intermodulation distortion in the transmitted signal.
As mentioned above that the CFR unit (102) utilizes clipping and filtering techniques, any clipping technique like classical clipping (CC), deep clipping (DC), and smooth clipping (SC), for example may be implemented. During the clipping and filtering, first, amplitude peaks of the input signal above a certain threshold (predefined threshold) are extracted as a clipping noise (or noise) as shown from equation 1 to equation 4 below. The clipping noise is a noise introduced in the clipping step, which is preferably filtered out of the useful frequency band of the input signal.
That is, an intermediate clipping stage is determined by performing the clipping step on the input signal using a clipping factor as expressed using equation (1):

where z(n)ic is an intermediate step of clipping, T is a clipping threshold (predefined threshold) and z(n) is the input signal that needs to be clipped.
The predefined threshold may be defined dynamically and is obtained using equation (2) as:

where CF is a clipping factor, which is a product of the standard deviation of the input signal and a ratio between the maximum input signal and means of the input signal and is obtained using equation (3):

where (s) is the standard deviation of the input signal.

Due to clipping, the clipping noise is introduced, which is given below as f(n) in equation (4):
Second, the clipping noise is filtered/removed to limit its spectral contents within certain frequency ranges and third, the filtered clipping noise is subtracted from the original input signal, yielding an output with reduced PAPR as shown in equations 5 and equation 6. Since clipping is a non-linear process, it may cause severe uncorrelated noise such as in-band distortion and out-band distortion, where the in-band distortion leads to Error Vector Magnitude (EVM), Signal-to-Noise Ratio (SNR) and Block Error Rate (BLER) degradation, while the out-band distortion may cause Adjacent Channel Leakage Ratio (ACLR) failure. The uncorrelated noise is removed from the clipped signal to get a linear clipped signal by filtering the spectrum, i.e., by shaping the spectrum and removing out-of-band distortions from the clipped signal using equation (5), which will generate the clipped and filtered signal:

Hence, the clipped signal with low PAPR is given as equation (6):

The CFR unit (102) may further utilize an up-sampler (404) and a down sampler (406), where the up-sampler (404) may be placed sequentially before the peak manager (402) to increase the sampling rate of the input signal and the down sampler (406) may be placed sequentially after the peak manager (402) to reduce the sampling rate of the clipped signal provided by the peak manager (402).
The clipped signal from the CFR unit (102) is fed to the DPD unit (104). The DPD unit (104) is configured to apply digital pre-distortion on the clipped signal received from the CFR unit (102). The CFR unit (102) implementing CFR in conjunction with the DPD unit (104) implementing DPD act as a linearization technique and improve the performance in linearity and power efficiency in data waveforms (input signal). In general, DPD is a linearization technique that provides an effective method to linearize the power amplifiers and correct impairments in the PAs. The DPD enables cost-efficient nonlinear PAs to run in their nonlinear regions with minimized distortions that result in higher output power and greater power efficiency.
The pre-distorted clipped signal from the DPD unit (104) is transmitted to the at least one PA (106) that amplifies the pre-distorted clipped signal. In general, a power amplifier is commonly used in a variety of applications for a number of purposes including applying gain to a signal to generate an amplified output signal. The input signal is processed sequentially by the CFR unit (102), the DPD unit (104), at least one PA (106), and band filters (not shown) and further transmitted to a corresponding antenna.
Alternatively, the system (100) may not include the DPD unit (104).
FIG. 5 is a flow chart (500) illustrating a method to improve data waveforms using the CFR technique. The steps mentioned in the flow chart (500) are performed by the system (100).
At step 502, the CFR unit (102) determines if the input signal level is greater than the predefined threshold. At step 504, the CFR unit (102) clips the input signal to form the clipped signal when the input signal level is greater than the predefined threshold, wherein the steps of determining and clipping are performed at detection of the at least one peak in the input signal, whereby reducing the peak-to-average power ratio of the input signal.
FIG. 6 is a flow chart (600) illustrating a method to improve the data waveforms using the CFR technique. The steps mentioned in the flow chart (600) are performed by the system (100).
At step 602, the CFR unit (102) dynamically defines the predefined threshold. At step 604, the CFR unit (102) compares the input signal with the predefined threshold to determine if the input signal level is greater than the predefined threshold. At step 606, the CFR unit (102) clips the input signal to form the clipped signal when the input signal level is greater than the predefined threshold. At step 608, the CFR unit (102) removes noise added while clipping (i.e., clipping noise) and the out-of-band distortions from the clipped signal to get the linear clipped signal. The method, hence, reduces the peak-to-average power ratio of the input signal.
Advantageously, the methods described herein are a simplified clipping and filtering approach using novel thresholding and noise reduction techniques to reduce the PAPR (i.e., to improve the data waveforms) of the input signal in one iteration.
It may be noted that the methods described in the flow chart (500) and the flow chart (600) utilize the equations mentioned above. For the sake of brevity, the operations and functions of the CFR unit (102) are not repeated again while describing FIG. 5 and FIG. 6. The various actions, acts, blocks, steps, or the like in the flow chart (500 and 600) may be performed in the order presented, in a different order or simultaneously. Further, in some implementations, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention.
FIG. 7 and FIG. 8 illustrate the results of the CFR technique explained in conjunction with FIG. 1 to FIG. 6, where FIG. 7 is a graph (700) plotted between the PAPR and relative frequency and FIG. 8 is a graph (800) plotted between the PAPR and EVM.
The embodiments disclosed herein can be implemented using at least one software program running on at least one hardware device and performing network management functions to control the elements.
It will be apparent to those skilled in the art that other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention. While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above-described embodiment, method, and examples, but by all embodiments and methods within the scope of the invention. It is intended that the specification and examples be considered as exemplary, with the true scope of the invention being indicated by the claims.
The methods and processes described herein may have fewer or additional steps or states and the steps or states may be performed in a different order. Not all steps or states need to be reached. The methods and processes described herein may be embodied in, and fully or partially automated via, software code modules executed by one or more general purpose computers. The code modules may be stored in any type of computer-readable medium or other computer storage device. Some or all of the methods may alternatively be embodied in whole or in part in specialized computer hardware.
The results of the disclosed methods may be stored in any type of computer data repository, such as relational databases and flat file systems that use volatile and/or non-volatile memory (e.g., magnetic disk storage, optical storage, EEPROM and/or solid-state RAM).
The various illustrative logical blocks, modules, routines, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure.
Moreover, the various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a general purpose processor device, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. A general-purpose processor device can be a microprocessor, but in the alternative, the processor device can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor device can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor device includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor device can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor device may also include primarily analog components. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.
The elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of a non-transitory computer-readable storage medium. An exemplary storage medium can be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor device. The processor device and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor device and the storage medium can reside as discrete components in a user terminal.
Conditional language used herein, such as, among others, "can," "may," "might," "may," “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain alternatives include, while other alternatives do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more alternatives or that one or more alternatives necessarily include logic for deciding, with or without other input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular alternative. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.
Disjunctive language such as the phrase “at least one of X, Y, Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain alternatives require at least one of X, at least one of Y, or at least one of Z to each be present.
While the detailed description has shown, described, and pointed out novel features as applied to various alternatives, it can be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the scope of the disclosure. As can be recognized, certain alternatives described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others
, Claims:CLAIMS

We Claim:

A method for improving data waveforms, the method comprising:
determining, by a crest factor reduction (CFR) unit (102), if an input signal level of an input signal (z(n)) is greater than a predefined threshold; and
clipping, by the CFR unit (102), the input signal to form a clipped signal when the input signal level is greater than the predefined threshold, wherein steps of determining and clipping are performed at the detection of at least one peak in the input signal,
whereby reducing the peak-to-average power ratio (PAPR) of the input signal.

The method as claimed in claim 1, wherein the PAPR of the input signal is a ratio of peak power to an average power of the input signal.

The method as claimed in claim 1, wherein the method is performed in conjunction with digital predistortion (DPD).

The method as claimed in claim 1, wherein the method is performed without digital predistortion (DPD).

The method as claimed in claim 1 further comprising comparing, by the CFR unit (102), the input signal with the predefined threshold.

The method as claimed in claim 1 further comprising removing, by the CFR unit (102), noise added while clipping.

The method as claimed in claim 1 further comprising removing, by the CFR unit (102), out-of-band distortions from the clipped signal to get a linear clipped signal.

The method as claimed in claim 1 further comprising dynamically defining, by the CFR unit (102), the predefined threshold.

The method as claimed in claim 1, wherein the predefined threshold is defined by:

CF=(max|z(n)|/mean|z(n)| )(s)
where T is the predefined threshold, CF is a clipping factor and s is the standard deviation of the input signal.

The method as claimed in claim 1, wherein clipping the input signal further comprises clipping the input signal based on error vector magnitude (EVM).

The method as claimed in claim 1, wherein at least one peak is detected and clipped by an amount greater than the predefined threshold before processing additional samples.

The method as claimed in claim 1, wherein the at least one peak is the input signal level that is greater than the predefined threshold.

The method as claimed in claim 1, wherein if the clipped signal has a peak equal to the predefined threshold, then an intermediate clipping is not required.

A system (100) for improving data waveforms, the system (100) comprising a crest factor reduction (CFR) unit (102) configured to:
determine if an input signal level of an input signal (z(n)) is greater than a predefined threshold; and
clip the input signal to form a clipped signal when the input signal level is greater than the predefined threshold, wherein steps of determining and clipping are performed at the detection of at least one peak in the input signal,
whereby reducing the peak-to-average power ratio (PAPR) of the input signal.

The system as claimed in claim 14, wherein the PAPR of the input signal is a ratio of peak power to an average power of the input signal.

The system as claimed in claim 14, wherein the system (100) implements digital predistortion (DPD).

The system as claimed in claim 14, wherein the system (100) does not use digital predistortion (DPD).

The system as claimed in claim 14, wherein the CFR unit (102) is configured to compare the input signal with the predefined threshold.

The system as claimed in claim 14, wherein the CFR unit (102) is configured to remove noise added while clipping.

The system as claimed in claim 14, wherein the CFR unit (102) is configured to remove out-of-band distortions from the clipped signal to get a linear clipped signal.

The system as claimed in claim 14, wherein the CFR unit (102) dynamically defines the predefined threshold.

The system as claimed in claim 14, wherein the predefined threshold is defined by:

CF=(max|z(n)|/mean|z(n)| )(s)
where T is the predefined threshold, CF is a clipping factor and s is the standard deviation of the input signal.

The system as claimed in claim 14, wherein the input signal is clipped based on error vector magnitude (EVM).

The system as claimed in claim 14, wherein the at least one peak is detected and clipped by an amount greater than the predefined threshold before processing additional samples.

The system as claimed in claim 14, wherein the at least one peak is the input signal level that is greater than the predefined threshold.

The system as claimed in claim 14, wherein if the clipped signal has a peak equal to the predefined threshold, then an intermediate clipping is not required.