CN112968854A - Segmentation threshold peak clipping method suitable for medium-voltage carrier system - Google Patents

Segmentation threshold peak clipping method suitable for medium-voltage carrier system Download PDF

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CN112968854A
CN112968854A CN202110149724.2A CN202110149724A CN112968854A CN 112968854 A CN112968854 A CN 112968854A CN 202110149724 A CN202110149724 A CN 202110149724A CN 112968854 A CN112968854 A CN 112968854A
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peak clipping
peak
value
threshold
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CN112968854B (en
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徐剑英
盛云
李亮
王亚梁
李铭贺
于洋
王林涛
汤鑫
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Qingdao Topscomm Communication Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H04L27/2623—Reduction thereof by clipping

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Abstract

The invention provides a segmented threshold peak clipping method suitable for a medium-voltage carrier system, which comprises the steps of firstly calculating the peak value of a time domain signal under different phase combinations to replace the peak-to-average ratio; performing peak clipping processing of different thresholds on time domain signals of different phase combinations, and obtaining a frequency domain sequence through FFT (fast Fourier transform); calculating the power and phase of each subcarrier of the frequency domain sequence; the minimum value of the quality parameter of each subcarrier represents the distortion parameter of the current threshold value under the threshold value; and then calculating the threshold corresponding to the maximum value of the distortion parameter corresponding to all thresholds under the current phase combination as the optimal peak clipping threshold, finally counting the optimal peak clipping threshold under each segment in a segmented manner, selecting the corresponding minimum peak clipping threshold when the proportion is more than or equal to 80 percent as the optimal peak clipping threshold of the segment, and storing the optimal peak clipping threshold. The invention carries out segmentation processing aiming at different peak values, and calculates the optimal peak clipping threshold value under each segment, thereby improving the problem of error rate reduction caused by peak clipping.

Description

Segmentation threshold peak clipping method suitable for medium-voltage carrier system
Technical Field
The invention belongs to the technical field of power line communication, and particularly relates to a segmented threshold peak clipping method suitable for a medium-voltage carrier system.
Background
A medium voltage carrier communication system is a multi-carrier communication system that employs OFDM modulation and demodulation. OFDM (Orthogonal Frequency Division Multiplexing) signals are widely used in 10kV power line communication systems due to their advantages of high spectrum utilization efficiency, strong multipath resistance, and the like. However, the OFDM signal is affected by a high peak-to-average ratio, which results in low energy and ultimately instability of the entire communication system.
The method for restraining the peak-to-average power ratio in the amplitude limiting class mainly comprises the following methods, one method is a clipping method, also called a peak clipping method, and is the most direct and simplest amplitude limiting method, however, no better evaluation criterion exists for the proportion and the threshold value of peak clipping, and the income brought by the peak clipping method under certain scenes is far less than the reduction of the error rate; the other is a peak windowing method, which performs windowing functions on a signal with a high peak-to-average ratio in a time domain, such as a cosine window, a khrser window, a hamming window and a gaussian window, but the peak windowing method prevents carriers from being orthogonal, brings in-band waveform distortion and out-of-band spectrum leakage, and the windowing is related to peak information, so that the optimal windowing function and coefficient cannot be obtained in practice; the other method is a companding transform method, which increases the overall average power of the signal by increasing the amplification factor of a low amplitude value, thereby achieving the effect of inhibiting the peak-to-average ratio.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a segmented threshold peak clipping method suitable for a medium-voltage carrier system, based on the difference of optimal thresholds of the current peak clipping method under each peak-to-average ratio, the peak is segmented, and each segment of peak clipping threshold meets the minimum criterion of the bit error rate, so that the overall peak clipping effect is better, and the communication performance of the current system is improved.
In order to achieve the above object, the present invention provides a method for clipping peak by using segmented threshold suitable for medium voltage carrier system, which comprises the following steps:
step 1: carrier machine to OFDM time domain signal y with different phase combinationi(alpha) calculating to obtain a peak-to-average ratio, and in order to save calculation efficiency, replacing the peak-to-average ratio by a peak value of a time domain signal, wherein alpha represents a peak clipping threshold value, and i represents the ith phase combination;
step 2: OFDM time-domain signal y for all different phase combinationsi(alpha) carrying out peak clipping processing on different thresholds to obtain a clipped OFDM time domain signal
Figure BDA0002931700730000011
And step 3: for OFDM time domain signal after peak clipping
Figure BDA0002931700730000012
Performing peak-to-average ratio calculation, and then performing FFT (Fast Fourier Transform) processing to obtain corresponding frequency domain sequence
Figure BDA0002931700730000013
And 4, step 4: by means of frequency domain sequences
Figure BDA0002931700730000014
Calculating the power and the phase of each subcarrier of each phase combination under different peak clipping thresholds, and calculating the quality parameter rho of the subcarrier according to the power and the phase differencei(α), wherein the mass parameter is calculated as follows:
Figure BDA0002931700730000015
wherein the content of the first and second substances,
Figure BDA0002931700730000016
represents the power of the nth sub-carrier,
Figure BDA0002931700730000017
represents the phase of the nth sub-carrier,
Figure BDA0002931700730000018
representing the original phase of the nth subcarrier;
and 5: selecting the minimum value of each subcarrier quality parameter in the frequency domain sequence of each phase combination under different peak clipping thresholds to represent the distortion parameter under the current phase combination of the current peak clipping threshold;
step 6: selecting a peak clipping threshold corresponding to the maximum value of the distortion parameter corresponding to each peak clipping threshold under the current phase combination as the optimal peak clipping threshold under the current phase combination;
and 7: and setting a peak segmentation step value step, wherein the peak segmentation step value is generally segmented into 3-4 segments. Counting the optimal peak clipping threshold value under each section, calculating the proportion smaller than each peak clipping threshold value in each section, and selecting the corresponding minimum peak clipping threshold value as the optimal peak clipping threshold value of the section when the proportion is larger than or equal to 80%;
and 8: and (4) storing the optimal peak clipping threshold value under each peak value, returning to the step 1, repeatedly operating, and performing time domain peak clipping processing.
The invention has the beneficial effects that: 1. the optimal threshold value does not need to be calculated in real time, only the peak clipping is carried out according to the stored threshold value of each peak value, and the calculation complexity is far lower than that of other methods in specific implementation. 2. According to the optimal threshold adjustment under each section of peak value, the problem of error rate reduction caused by peak clipping in the prior art can be reduced. 3. An evaluation index-quality parameter related to the error rate is formulated at a sending end, and the evaluation is carried out after the complex demodulation processing of a receiving end is not needed.
Drawings
Fig. 1 is a flowchart of the operation of the segmentation threshold peak clipping method applicable to the medium-voltage carrier system according to the present invention.
Fig. 2 is a peak clipping threshold map of the segmented threshold peak clipping method applicable to the medium voltage carrier system according to the present invention.
Detailed Description
The technical solution in the embodiments of the present invention is clearly and completely described below with reference to the drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the method for determining the optimal threshold of the present invention comprises the following specific steps:
step 1: carrier machine to OFDM time domain signal y with different phase combinationi(alpha) calculating to obtain a peak-to-average ratio, and in order to save calculation efficiency, replacing the peak-to-average ratio by a peak value of a time domain signal, wherein alpha represents a peak clipping threshold value, and i represents the ith phase combination;
step 2: OFDM time-domain signal y for all different phase combinationsi(alpha) carrying out peak clipping processing on different thresholds to obtain a clipped OFDM time domain signal
Figure BDA0002931700730000021
And step 3: for OFDM time domain signal after peak clipping
Figure BDA0002931700730000022
Performing peak-to-average ratio calculation, and then performing FFT (Fast Fourier Transform) processing to obtain corresponding frequency domain sequence
Figure BDA0002931700730000023
And 4, step 4: by means of frequency domain sequences
Figure BDA0002931700730000024
Calculating the power and the phase of each subcarrier of each phase combination under different peak clipping thresholds, and calculating the quality parameter rho of the subcarrier according to the power and the phase differencei(α), wherein the mass parameter is calculated as follows:
Figure BDA0002931700730000025
wherein the content of the first and second substances,
Figure BDA0002931700730000026
represents the power of the nth sub-carrier,
Figure BDA0002931700730000027
represents the phase of the nth sub-carrier,
Figure BDA0002931700730000028
representing the original phase of the nth subcarrier;
and 5: selecting the minimum value of each subcarrier quality parameter in the frequency domain sequence of each phase combination under different peak clipping thresholds to represent the distortion parameter under the current phase combination of the current peak clipping threshold;
step 6: selecting a peak clipping threshold corresponding to the maximum value of the distortion parameter corresponding to each peak clipping threshold under the current phase combination as the optimal peak clipping threshold under the current phase combination;
and 7: and setting a peak segmentation step value step, wherein the peak segmentation step value is generally segmented into 3-4 segments. Counting the optimal peak clipping threshold value under each section, calculating the proportion smaller than each peak clipping threshold value in each section, and selecting the corresponding minimum peak clipping threshold value as the optimal peak clipping threshold value of the section when the proportion is larger than or equal to 80%;
and 8: and (4) storing the optimal peak clipping threshold value under each peak value, returning to the step 1, repeatedly operating, and performing time domain peak clipping processing.
As shown in fig. 2, the present invention determines different peak clipping thresholds according to different peak-to-average ratios.
TABLE 1
PAPR>10 ≤5 6 7 ≥8
Minimum specific gravity 12.63％ 52.65％ 24.84％ 6.01％
PAPR≤10 ≤5 6 7 ≥8
Minimum specific gravity 41.92％ 40.14％ 12.9％ 5.05％
As shown in Table 1, the peak reduction threshold is 7 if the PAPR is >10 and 6 if the PAPR is less than or equal to 10.
Finally, it should be noted that: the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and a person of ordinary skill in the art can make modifications or equivalents to the specific embodiments of the present invention with reference to the above embodiments, and such modifications or equivalents without departing from the spirit and scope of the present invention are within the scope of the claims of the present invention as set forth in the claims.

Claims (2)

1. A segmentation threshold peak clipping method suitable for a medium-voltage carrier system is characterized by comprising the following steps:
step 1: carrier machine to OFDM time domain signal y with different phase combinationi(alpha) calculating to obtain peak-to-average ratio, in order to save calculationEfficiency, peak-to-average ratio is replaced by the peak value of the time domain signal, wherein alpha represents a peak clipping threshold value, and i represents the ith phase combination;
step 2: OFDM time-domain signal y for all different phase combinationsi(alpha) carrying out peak clipping processing on different thresholds to obtain a clipped OFDM time domain signal
Figure FDA0002931700720000011
And step 3: for OFDM time domain signal after peak clipping
Figure FDA0002931700720000012
Performing peak-to-average ratio calculation, and then performing FFT (Fast Fourier Transform) processing to obtain corresponding frequency domain sequence
Figure FDA0002931700720000013
And 4, step 4: by means of frequency domain sequences
Figure FDA0002931700720000014
Calculating the power and the phase of each subcarrier of each phase combination under different peak clipping thresholds, and calculating the quality parameter rho of the subcarrier according to the power and the phase differencei(α), wherein the mass parameter is calculated as follows:
Figure FDA0002931700720000015
wherein the content of the first and second substances,
Figure FDA0002931700720000016
represents the power of the nth sub-carrier,
Figure FDA0002931700720000017
represents the phase of the nth sub-carrier,
Figure FDA0002931700720000018
representing the original phase of the nth subcarrier;
and 5: selecting the minimum value of each subcarrier quality parameter in the frequency domain sequence of each phase combination under different peak clipping thresholds to represent the distortion parameter under the current phase combination of the current peak clipping threshold;
step 6: selecting a peak clipping threshold corresponding to the maximum value of the distortion parameter corresponding to each peak clipping threshold under the current phase combination as the optimal peak clipping threshold under the current phase combination;
and 7: and setting a peak segmentation step value step, wherein the peak segmentation step value is generally segmented into 3-4 segments. Counting the optimal peak clipping threshold value under each section, calculating the proportion smaller than each peak clipping threshold value in each section, and selecting the corresponding minimum peak clipping threshold value as the optimal peak clipping threshold value of the section when the proportion is larger than or equal to 80%;
and 8: and (4) storing the optimal peak clipping threshold value under each peak value, returning to the step 1, repeatedly operating, and performing time domain peak clipping processing.
2. The method as claimed in claim 1, wherein the step value is 5-6 segments when the peak coverage is too large.
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