阅读说明：本技术 一种基于中压载波迭代削峰降低峰均比的方法 (Method for reducing peak-to-average ratio based on medium-voltage carrier iterative peak clipping ) 是由 徐剑英 李亮 于洋 郭桂雨 王亚梁 汤鑫 王林涛 于 2021-01-12 设计创作，主要内容包括：本发明涉及一种基于中压载波迭代削峰降低峰均比的方法,属于宽带电力线载波通信技术领域。削峰法是一种通过预失真手段降低峰均比的方法,本发明中的迭代削峰滤波通过对频域数据进行插值,然后IFFT后转化为时域波形,对时域数据削峰,然后再经过FFT取出频域数据,进行频域滤波,再转化为时域波形数据,经过多次IFFT/FFT迭代处理,最终时域数据当达到峰均比阈值后,将最后一次的时域波形发送出去。本发明的主要特点在于通过多次削峰滤波能够有效的降低峰均比,并且每次迭代有添加了频域滤波,发送的时域波形数据不会有带外泄露的问题。(The invention relates to a method for reducing peak-to-average power ratio based on medium-voltage carrier iterative peak clipping, belonging to the technical field of broadband power line carrier communication. The iterative peak clipping filtering in the invention is to interpolate frequency domain data, then transform the frequency domain data into time domain waveform after IFFT, clip the peak of the time domain data, then take out the frequency domain data through FFT, filter the frequency domain, transform into time domain waveform data, through IFFT/FFT iterative processing for many times, finally the time domain data sends out the last time domain waveform when reaching the peak-to-average ratio threshold. The method has the main characteristics that the peak-to-average ratio can be effectively reduced through multiple times of peak clipping filtering, frequency domain filtering is added in each iteration, and the problem of out-of-band leakage of the transmitted time domain waveform data is solved.)

1. A method for reducing peak-to-average power ratio based on iterative peak clipping of medium-voltage carriers is characterized by comprising the following steps:

step 1: vector a of modulation signals_i＝[a₀,a₁,a₂...a_N-1]Wherein N is the number of subcarriers, M is selected as an oversampling factor, M-1 0 s are added in front of each element in the vector A to generate a new vector C_k＝[c₀,c₁,c₂...c_N*M-1]The number of elements in C is N M, the elements in vector A are uniformly distributed in vector C, and the address L of A in C is recorded₀,l₁,l₂...l_N-1]；

Step 2: carrying out IFFT on the newly generated vector, and selecting time domain waveform data of which part generates the vector;

and step 3: by PAPR 10lg (max (| s)_n|²)/(∑|s_n|²/N)) formula, calculating the PAPR of the time domain waveform data, wherein S_nIs the value in the domain waveform data, N is the number of elements in the time domain waveform data, and the result is compared with a threshold St if the PAPR at that time is<Step 5, entering St; if PAPR is>If St is determined, the peak-to-average ratio needs to be reduced, and the step 4 is carried out;

and 4, step 4: performing peak clipping processing on the time domain waveform generated by the vector C, wherein the peak clipping parameter is V, namely when the element of the time domain waveform data is larger than V, the time domain waveform data is equal to V, and if the element of the time domain waveform data is smaller than-V, the time domain waveform data is equal to-V, and then FFT is applied to the time domain waveform data after peak clipping to obtain a group of vectors D_k＝[d₀,d₁,d₂...d_N*M-1]Extracting element B according to address L_i＝[b₀,b₁,b₂...b_N-1]And returning to the step 1 to repeat the operation, wherein the vector A in the step 1 is assigned by the vector B in the step 4 until the target PAPR is reached<＝St；

And 5: the vector a is subjected to IFFT, and the generated time domain waveform is transmitted onto the power line channel.

2. The method according to claim 1, wherein the peak-to-average ratio threshold St in step 3 is set according to requirements, and is generally set to a maximum value of a linear operating region of the power amplifier.

3. The method as claimed in claim 1, wherein the peak-clipping parameter V in step 3 is set to 90% of the maximum value of the symbol time domain waveform data.

Technical Field

The invention relates to the technical field of broadband power line carrier communication, in particular to a method for reducing peak-to-average power ratio based on medium-voltage carrier iterative peak clipping.

Background

An important drawback of OFDM transmission is the high peak-to-average power ratio of the transmitted signal. Since OFDM modulation superimposes several subcarrier signals in the time domain, if the symbol phases on the subcarriers are the same, a very high time domain power peak-to-average ratio is caused, and therefore a certain peak-to-average ratio reduction technique needs to be adopted.

The existing technology for reducing the peak-to-average power ratio comprises a predistortion technology, a coding technology and the like, the coding technology has high capability of reducing the peak-to-average power ratio, but the calculation amount required by the coding technology is large, redundant information needs to be added, the traditional peak clipping technology carries out peak clipping on transmission time domain waveform data, then the time domain waveform data after the peak clipping is filtered, a part of out-of-band signal transmission still exists, not only can interference be caused on communication equipment of a nearby frequency band, but also a part of sending capability can be wasted.

Disclosure of Invention

In order to solve the above problems, the present invention provides a method for reducing peak-to-average ratio based on iterative peak clipping of medium voltage carrier, which achieves the purpose of reducing the equal-to-average ratio by repeatedly performing peak clipping on a time domain signal, and meanwhile, does not interfere with communication equipment, and has small calculation amount and no need of adding redundant information.

The invention discloses a method for reducing peak-to-average power ratio based on iterative peak clipping of medium-voltage carrier, which comprises the following steps:

step 1: sampling the vector to modulate a signal vector A_i＝[a₀,a₁,a₂...a_N-1]Wherein N is the number of subcarriers, M is selected as an oversampling factor, M-1 0 s are added in front of each element in the vector A to generate a new vector C_k＝[c₀,c₁,c₂...c_N*M-1]The number of elements in C is N M, the elements in vector A are uniformly distributed in vector C, and the address L of A in C is recorded₀,l₁,l₂...l_N-1]；

Step 2: carrying out IFFT operation on the newly generated vector, and selecting a real part of the vector to generate time domain waveform data of the vector;

and step 3: by PAPR 10lg (max (| s)_n|²)/(∑|s_n|²/N)) formula, calculating PAPR (peak-to-average ratio) of the time-domain waveform data, where S_nIs the value in the time domain waveform data, N is the number of elements in the time domain waveform data, and the result is compared with a threshold St if the PAPR at that time is the<Step 5, entering St; if PAPR is>St, indicating that the peak-to-average ratio needs to be reduced, and entering step 4;

and 4, step 4: performing peak clipping processing on the time domain waveform generated by the vector C, wherein the peak clipping parameter is V, namely when the element of the time domain waveform data is larger than V, the time domain waveform data is equal to V, and if the element of the time domain waveform data is smaller than-V, the time domain waveform data is equal to-V, and then FFT is applied to the time domain waveform data after peak clipping to obtain a group of vectors D_k＝[d₀,d₁,d₂...d_N*M-1]Extracting element B according to address L_i＝[b₀,b₁,b₂...b_N-1](when the PAPR is calculated for the first time, the vector B is consistent with the vector A, and the vector C is consistent with the vector B), then the operation is repeated by returning to the step 1, and the vector A in the step 1 is assigned by the vector B in the step 4 until the target PAPR is reached<＝St；

And 5: and performing IFFT on the vector A, and transmitting the generated time domain waveform to a power line channel.

Further, the peak-to-average ratio threshold St in step 3 is set according to the requirement, and is generally set to the maximum value of the linear operating region of the power amplifier.

Further, the peak clipping parameter V in step 3 is set according to actual conditions, and is usually set to 90% of the maximum value of the symbol time domain waveform data.

The invention has the beneficial effects that:

1. the method for reducing the peak-to-average power ratio by the peak clipping method is simple to implement, and has obvious effect of reducing the peak-to-average power ratio by the method of continuous time domain peak clipping, FFT extraction of useful signals and interpolation, and can effectively inhibit the peak value of the signals.

2. Compared with the conventional peak clipping method, the iterative peak clipping method only transmits IFFT of the position of the modulation signal vector, can effectively prevent out-of-band and does not lose extra power.

Drawings

In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

fig. 1 is a flowchart of a method for reducing peak-to-average ratio based on iterative peak clipping of medium-voltage carriers according to the present invention.

Fig. 2 is a schematic diagram illustrating comparison of the effect of the method for reducing the peak-to-average ratio based on the iterative peak clipping of the medium-voltage carrier in the present invention with that of the conventional peak clipping method.

Fig. 3 is a schematic diagram illustrating comparison between the iterative peak clipping and peak-to-average ratio reduction method based on medium-voltage carrier and a conventional peak clipping method CCDF in the present invention.

Fig. 4 is a schematic diagram of a comparison of the frequency spectrums of the iterative peak clipping and peak-to-average ratio reduction method based on the medium-voltage carrier according to the present invention and the conventional peak clipping method.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

As shown in fig. 1, the present invention provides a method for reducing peak-to-average ratio based on iterative peak clipping of medium voltage carrier, which specifically includes the following steps:

step 1: sampling the vector to modulate a signal vector A_i＝[a₀,a₁,a₂...a_N-1]Wherein N is the number of subcarriers, M is selected as an oversampling factor, M-1 0 s are added in front of each element in the vector A to generate a new vector C_k＝[c₀,c₁,c₂...c_N*M-1]The number of elements in C is N M, the elements in vector A are uniformly distributed in vector C, and the address L of A in C is recorded₀,l₁,l₂...l_N-1]；

Step 2: performing IFFT operation on the newly generated vector, and selecting a real part to generate time domain waveform data of the vector;

and step 3: calculating the PAPR (peak-to-average power ratio) of the time domain waveform data, comparing the result with a threshold St, if the PAPR at the moment is less than St, performing IFFT on the vector A, sending the generated time domain waveform to a power line channel, and if the PAPR is equal to St, entering the next step;

and 4, step 4: performing peak clipping processing on the time domain waveform generated by the vector C, wherein the peak clipping parameter is V, namely when the element of the time domain waveform data is larger than V, the time domain waveform data is equal to V, and if the element of the time domain waveform data is smaller than-V, the time domain waveform data is equal to-V, and then FFT is applied to the time domain waveform data after peak clipping to obtain a group of vectors D_k＝[d₀,d₁,d₂...d_N*M-1]Extracting element B according to address L_i＝[b₀,b₁,b₂...b_N-1](when the first PAPR calculation satisfies the threshold, vector B is consistent with vector A, and vector C is consistent with vector B), at this time, repeating steps 1-3, and assigning the vector A in step 1 by the vector B in step 4 until the target PAPR is reached<＝St；

And 5: the vector a is subjected to IFFT, and the generated time domain waveform is transmitted onto the power line channel.

Taking an example of a specific implementation and performing a simulation experiment on the example, a sampling rate of 40.96MHz and an FFT point number of 8192 are selected, when a frequency band is selected from 0.11MHz to 0.51MHz, 51 subcarriers are totally included in the frequency band, a PAPR threshold is 9.5dB, a peak clipping parameter is 0.7, and the number of iterations is 3. As shown in fig. 2, a comparison graph of the peak-to-average ratio of the original data, the peak-to-average ratio of the conventional peak clipping data, and the peak-to-average ratio of the original data after iterative peak clipping is shown in the graph, and the peak-to-average ratio of the data after 3 iterations is reduced by 0.8-1.2dB compared with the peak-to-average ratio of the conventional peak clipping data and is reduced by 1.8-2.2dB compared with the peak-to-average ratio of the original data under the condition of 20 times of simulation. Fig. 3 is a schematic diagram showing CCDF comparison of original data, conventional peak clipping data, and original data by iterative peak clipping, and it can be seen from the diagram that iterative peak clipping has a better effect of reducing peak-to-average ratio. Fig. 4 shows a comparison diagram of frequency spectrums of conventional peak clipping data and original data after iterative peak clipping, and it can be seen from the diagram that the frequency spectrum of the original data after iterative peak clipping has no out-of-band leakage, while the frequency spectrum of the conventional data after peak clipping has out-of-band leakage.