阅读说明：本技术 一种基于索引调制的降低ofdm信号峰均比值的方法 (Method for reducing peak-to-average ratio of OFDM (orthogonal frequency division multiplexing) signal based on index modulation ) 是由 谢映海 吴斌 李先怀 李宏文 于 2020-04-27 设计创作，主要内容包括：一种基于索引调制的降低OFDM信号峰均比值的方法,步骤如下：从编码后信息比特流中提取K个信息比特信号并循环左移；执行频域星座信号映射、插入导频及IFFT运算,生成OFDM信号；计算OFDM信号的峰均比值,发射符合要求的OFDM信号,否则从生成的OFDM信号中选出峰均比值最小的信号发射；信号接收端接收信号后进行去除循环前缀、FFT运算、信道估计及星座相位逆旋转,然后分组得到由行向量构成的矩阵；分别计算行向量对应的能量值,能量值最小值对应的位置为索引调制0信号的位置,与能量值最小值对应的行向量编号为V；从矩阵删除第V个行向量后从上到下逐列读取得到新信号,将新信号循环右移16-V位即得到待译码信号。(A method for reducing OFDM signal peak-to-average ratio based on index modulation comprises the following steps: extracting K information bit signals from the coded information bit stream and circularly moving left; performing frequency domain constellation signal mapping, pilot frequency insertion and IFFT operation to generate an OFDM signal; calculating the peak-to-average ratio of the OFDM signals, transmitting the OFDM signals meeting the requirements, and otherwise selecting the signal with the minimum peak-to-average ratio from the generated OFDM signals for transmission; after receiving the signals, the signal receiving end removes the cyclic prefix, performs FFT operation, performs channel estimation and constellation phase reverse rotation, and then groups the signals to obtain a matrix formed by row vectors; respectively calculating energy values corresponding to the row vectors, wherein the position corresponding to the minimum value of the energy values is the position of an index modulation 0 signal, and the row vector number corresponding to the minimum value of the energy values is V; and deleting the V-th row vector from the matrix, reading the V-th row vector from top to bottom column by column to obtain a new signal, and circularly right-shifting the new signal by 16-V bits to obtain a signal to be decoded.)

1. A method for reducing the peak-to-average ratio of OFDM signals based on index modulation is characterized by comprising the following steps:

s1, at the signal sending end, extracting K information bit signals from the coded information bit stream;

s2, circularly shifting the extracted signal bit signal by X bit to the left, wherein the initial value of X is 0;

s3, performing frequency domain constellation signal mapping on the K information bit signals after the circulation left shift, mapping each n bits into a constellation point on a carrier, adding a 0 signal on the last constellation point after mapping of 15 x n bits is completed, wherein n is a modulation order;

s4, constellation phase rotation is carried out on the constellation points of the non-zero part in the constellation signal generated after the mapping is finished;

s5, inserting pilot frequency into the constellation signal after phase rotation and carrying out IFFT operation to generate an OFDM signal;

s6, calculating the peak-to-average ratio of the generated OFDM signal, comparing the peak-to-average ratio with a set threshold, if the peak-to-average ratio is not more than the set threshold C, determining that the peak-to-average ratio of the OFDM signal meets the requirement, entering the subsequent signal processing flow and transmitting, and if the peak-to-average ratio is more than the set threshold C, entering the step S7;

s7, judging whether X is larger than W, if X is larger than W, selecting a signal with the minimum peak-to-average ratio from the generated OFDM signals, entering a subsequent signal processing flow and transmitting, otherwise, making X equal to X +1, and returning to the step S2, wherein W is an upper limit value of the information bit cycle shift frequency, and when the peak-to-average ratio of the generated OFDM signals is smaller than or equal to a set threshold value C, or the cycle frequency exceeds the upper limit value, the transmission process of the signal is finished;

s8, a signal receiving end receives signals, and the signals are sequentially subjected to cyclic prefix removal, FFT (fast Fourier transform) operation, channel estimation and constellation phase reverse rotation, so that a signal Y is obtained after constellation phase reverse rotation;

s9, grouping the signals Y with the length of 16 to obtain a matrix YY consisting of 16 row vectors;

s10, respectively calculating energy values corresponding to the 16 line vectors, selecting a minimum value from the obtained energy values, taking the position corresponding to the minimum value of the energy values as the position of an index-modulated 0 signal, and numbering the line vector corresponding to the minimum value of the energy values as V;

s11, deleting the V-th row vector from the matrix YY, reading from top to bottom column by column to obtain a signal Z with the length of 15 ÷ 16 XN 1, and circularly right-shifting the signal Z by 16-V bits to obtain a signal to be decoded; and decoding the signal to be decoded to finish the transmission process of the signal.

2. The method for reducing the peak-to-average ratio of an OFDM signal based on index modulation of claim 1, wherein: k is the number of encoded information bits carried by the data subcarriers, K is N1 × N × 15 ÷ 16, and N1 is the number of data subcarriers in one OFDM signal.

3. The method of reducing the peak-to-average ratio of an OFDM signal of claim 2, wherein: when the value of N1 cannot be divided by 16, the remaining subcarriers are mapped by using a conventional constellation mapping mechanism.

4. The method for reducing the peak-to-average ratio of an OFDM signal based on index modulation of claim 1, wherein: the upper limit W of the number of information bit cyclic shifts is 15.

Technical Field

The invention belongs to the technical field of signal processing, and particularly relates to a method for reducing the peak-to-average ratio of an OFDM signal based on index modulation.

Background

The OFDM communication technology has the advantages of high spectral efficiency, resistance to multipath fading, easy implementation, and the like, and is one of mainstream technologies in a wireless broadband communication system. As shown in fig. 1, the signal transmission and reception flow of the OFDM communication system is: at a signal sending end, the coded information bit signal is subjected to carrier constellation mapping, then constellation phase rotation is carried out, then pilot frequency is inserted, IFFT operation (inverse fast Fourier transform) and cyclic prefix addition are carried out, and finally the signal is sent out by a radio frequency front end of the signal sending end. At a signal receiving end, after a radio frequency front end of the signal receiving end receives a signal, an opposite operation process is carried out, a cyclic prefix is removed, FFT (fast Fourier transform) operation is carried out, then channel estimation, constellation phase inverse rotation and de-mapping are carried out, and a signal to be decoded is obtained.

One significant disadvantage of OFDM communication systems is that the instantaneous value of the output signal fluctuates considerably, i.e. the peak-to-average ratio of the transmitted signal is high. With the increase of the number of subcarriers in a signal and the modulation order of the signal, the signal peak-to-average ratio (PAPR for short) of the OFDM communication system also increases, thereby causing various problems such as increase of hardware cost and reduction of system communication performance, and therefore, the corresponding PAPR suppression algorithm is always a key technology of the OFDM communication system. The existing OFDM communication system peak-to-average ratio suppression algorithm mainly balances the peak-to-average ratio suppression effect and system indexes such as transmission performance and complexity. The PAPR suppression algorithm can be mainly classified into two major categories, namely, a predistortion technique and a non-distortion technique, wherein the common predistortion technique includes an amplitude limiting method, a compression expansion method, a peak offset method and other algorithms; common distortion-free technical algorithms include an encoding method, a reserved subcarrier method, a multi-signal replacement method and the like. For the predistortion technology, since the PAPR suppression algorithm will have an effect on the received signal, it is necessary to make a compromise between PAPR performance and transmission performance by optimizing distortion noise; for distortion-free techniques, a balance between the effectiveness and the implementation complexity of the PAPR suppression algorithm needs to be considered. There is room for improvement in existing PAPR suppression algorithms.

Disclosure of Invention

The invention aims to provide a method for reducing the peak-to-average ratio of an OFDM signal based on index modulation.

In order to achieve the purpose, the invention adopts the following technical solutions:

a method for reducing the peak-to-average ratio of an OFDM signal based on index modulation comprises the following steps:

s1, at the signal sending end, extracting K information bit signals from the coded information bit stream;

s2, circularly shifting the extracted signal bit signal by X bit to the left, wherein the initial value of X is 0;

s3, performing frequency domain constellation signal mapping on the K information bit signals after the circulation left shift, mapping each n bits into a constellation point on a carrier, adding a 0 signal on the last constellation point after mapping of 15 x n bits is completed, wherein n is a modulation order;

s4, constellation phase rotation is carried out on the non-zero constellation points in the constellation signals generated after the mapping is finished;

s5, inserting pilot frequency into the constellation signal after phase rotation and carrying out IFFT operation to generate an OFDM signal;

s6, calculating the peak-to-average ratio of the generated OFDM signal, comparing the peak-to-average ratio with a set threshold, if the peak-to-average ratio is not more than the set threshold C, determining that the peak-to-average ratio of the OFDM signal meets the requirement, entering the subsequent signal processing flow and transmitting, and if the peak-to-average ratio is more than the set threshold C, entering the step S7;

s7, judging whether X is larger than W, if X is larger than W, selecting a signal with the minimum peak-to-average ratio from the generated OFDM signals, entering a subsequent signal processing flow and transmitting, otherwise, making X equal to X +1, and returning to the step S2, wherein W is an upper limit value of the information bit cycle shift frequency, and when the peak-to-average ratio of the generated OFDM signals is smaller than or equal to a set threshold value C, or the cycle frequency exceeds the upper limit value, the transmission process of the signal is finished;

s8, a signal receiving end receives signals, and the signals are sequentially subjected to cyclic prefix removal, FFT (fast Fourier transform) operation, channel estimation and constellation phase reverse rotation, so that a signal Y is obtained after constellation phase reverse rotation;

s9, grouping the signals Y with the length of 16 to obtain a matrix YY consisting of 16 row vectors;

s10, respectively calculating energy values corresponding to the 16 line vectors, selecting a minimum value from the obtained energy values, taking the position corresponding to the minimum value of the energy values as the position of an index-modulated 0 signal, and numbering the line vector corresponding to the minimum value of the energy values as V;

s11, deleting the V-th row vector from the matrix YY, reading from top to bottom column by column to obtain a signal Z with the length of 15 ÷ 16 XN 1, and circularly right-shifting the signal Z by 16-V bits to obtain a signal to be decoded; and decoding the signal to be decoded to finish the transmission process of the signal.

Further, K is the number of encoded information bits carried by the data subcarriers, K is N1 × N × 15 ÷ 16, and N1 is the number of data subcarriers in one OFDM signal.

Further, when the value of N1 cannot be divided by 16, the remaining subcarriers are mapped by using a conventional constellation mapping mechanism.

Further, the upper limit W of the number of times of information bit cyclic shifts is 15.

According to the technical scheme, the method utilizes the idea of index modulation, the sending end introduces silent subcarrier index mapping in the traditional constellation mapping link, the sending sequence of the frequency domain signals of the activated subcarriers in each OFDM symbol is indicated by utilizing the position of the silent subcarrier, and meanwhile, the OFDM sending signals with low peak-to-average ratio values are obtained by utilizing the optimized selection of the frequency domain signal sending sequence. Because the index OFDM system adopts a block modulation mode, the correlation among subcarriers is enhanced, the subcarrier distribution has certain sparsity, the mode does not need to transmit sideband information, the algorithm complexity at the transmitting side and the receiving side is very low, compared with the traditional OFDM signal, the method only loses a very small amount of information transmission rate, the receiving performance is improved, and the complementary cumulative distribution function of the OFDM transmission signal is 10^-4The peak-to-average power ratio is also reduced, and a better effect of reducing the peak-to-average power ratio can be obtained.

Drawings

In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.

Fig. 1 is a flow chart of transmission and reception of an OFDM signal;

FIG. 2 is a flow chart of signal processing at the transmitting end of the method of the present invention;

FIG. 3 is a diagram of a first constellation mapping of an information bit signal according to an embodiment of the present invention;

FIG. 4 is a graph of 2 nd constellation mapping of an information bit signal according to an embodiment of the present invention;

fig. 5 is a graph of complementary cumulative distribution functions of the transmitted signals for different numbers of left shifts of the cycle.

Detailed Description

In order to make the aforementioned and other objects, features and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The Index Modulation (IM) technology has the advantages of good inter-subcarrier interference resistance, higher energy efficiency performance, lower error rate under the interleaving condition, more flexible system configuration and the like. The method of the invention is based on index modulation, frequency domain subcarriers are divided into active subcarriers and silent subcarriers, constellation point symbols are transmitted by the active subcarriers, the silent subcarriers send zeros, index bit information is implicit in the selection of the subcarriers for transmission, namely, a transmitting terminal transmits extra data by selecting different combinations, and the peak-to-average ratio value of a transmitted signal is reduced by optimizing and selecting the transmission sequence of the constellation signals on the frequency domain.

An OFDM signal contains N subcarriers, which are numbered from 1 to N, and these subcarriers include a plurality of guard subcarriers, 1 dc subcarrier, a plurality of pilot subcarriers carrying pilot signals, and data subcarriers carrying coded bits, which are located on both sides. The set of carrier numbers corresponding to the data subcarriers is: index ═ a₁,a₂,…,a_N1]，1≤a₁＜a₂＜…＜a_N1≤N1N1 indicates the number of data subcarriers in an OFDM signal, the number K of coded information bits carried by N1 data subcarriers is N1 × N × 15 ÷ 16, N is a modulation order, which is the number of information bits carried by one constellation point, for example, N is 1 in BPSK modulation, and N is 2 in QPSK modulation, for example, the value of N1 cannot be divided by 16, and the remaining subcarriers are mapped by using a conventional constellation mapping mechanism, but the flow of the method of the present invention is not affected, and for convenience of description, N1 may be divided by 16.

The method of the present invention is described below with reference to fig. 2, and the steps of the method of the present invention are as follows:

s1, at the signal transmitting end, extracting K information bit signals from the encoded information bit stream, and recording as B _0 ═ B₁,b₂,…,b_K]，b_K＝0 or 1，k＝1,…,K；

S2, circularly shifting the extracted signal bit signal by X bit to the left, wherein the initial value of X is 0;

s3, performing frequency domain constellation signal mapping on the K information bit signals: using a conventional constellation mapping relationship to map every n bits into a constellation point on a carrier, adding a 0 signal to the last constellation point after mapping of every 15 × n bits is completed, the first constellation mapping relationship is shown in fig. 3, and the constellation signal generated after mapping is:

n-1, 15,17, 31, N1-15, N1-1, S denotes a set of modulation constellation points of the frequency domain signal;

when the value of N1 cannot be divided by 16, the remaining subcarriers are mapped by using a traditional constellation mapping mechanism, the remaining subcarriers (for example, the remaining 8) are all constellation point signals and do not contain zero signals, the subcarriers of the whole division part and the subcarriers of the remaining part are combined together to generate an OFDM signal, and each 16 subcarriers of the whole division part contain 1 signal 0;

s4, constellation phase rotation is carried out on the non-zero constellation points in the constellation signals generated after mapping is completed, the constellation rotation mechanism of the invention is the same as the traditional constellation phase rotation mechanism, and the phase of the zero constellation points is still 0 after rotation, so rotation is not needed;

s5, inserting pilot frequency into the constellation signal after phase rotation and carrying out IFFT operation to generate an OFDM signal;

s6, calculating the peak-to-average ratio of the generated OFDM signal, comparing the peak-to-average ratio with a set threshold, if the peak-to-average ratio is not more than the set threshold C, determining that the peak-to-average ratio of the OFDM signal meets the requirement, entering the subsequent signal processing flow and transmitting, and if the peak-to-average ratio is more than the set threshold C, entering the step S7; the signal processing flow and the transmitting flow are consistent with those of the existing method, which is not an innovative point of the present invention and is not described herein again;

s7, determining whether X is greater than W, if X is greater than W, selecting a signal with the smallest peak-to-average ratio from the generated OFDM signals, entering a subsequent signal processing flow and transmitting the signal, where W is an upper limit value of the number of cyclic shifts of the information bit, W in this embodiment is 15, and when X is greater than 15, the generated OFDM signals include 15 OFDM signals sequentially generated based on an initial binary signal B _0 and 15 binary signals of signals B _1 to B _15 after cyclic left shift based on the initial binary signal B _0, and peak-to-average ratios of the 16 OFDM signals are all greater than a set threshold C;

otherwise, let X be X +1, and return to step S2, except for the first time of frequency domain constellation signal mapping, the information bit signal has been circularly left-shifted every time of frequency domain constellation signal mapping, for example, when step S2 is executed in the 2 nd cycle, the information bit signal is circularly left-shifted by 1 bit, and the obtained new signal B _1 is ═ B₂,…,b_K,b₁]By analogy, when step S2 is executed in the 3 rd loop, the information bit signal is left-shifted by 2 bits, and the obtained new signal B _1 is [ B ═ B₃,…,b_K,b₁,b₂](ii) a In the loop executing step S2, the frequency domain constellation signal mapping is performed based on the new signal obtained after the loop left shift, for example, based on the signal B _1 ═ B₂,…,b_K,b₁]Run 2 ndObtaining constellation signal record when mapping frequency domain constellation signal

S_1_n∈ S, N is 1, 14,16,17, 30,32, N1-15, N1-2, N1, as shown in the mapping relation diagram 4, each time constellation mapping is carried out, the position of 0 signal is moved one bit to the left from the position of the remainder 0 of division 16, namely the position of the remainder 15 of division 16, when X is 15, the position of 0 signal is moved fifteen bits to the left from the position of the remainder 0 of division 16, namely the position of the remainder 1 of division 16 is obtained, when the peak-to-average ratio of the generated OFDM signals is less than or equal to the set threshold C, or the cycle number exceeds 15 times, the transmission process of the signals is finished;

s8, the signal receiving end receives the signal, sequentially performs the conventional steps of removing the cyclic prefix, FFT operation, channel estimation, and constellation phase derotation, and obtains a signal Y ═ Y after constellation phase derotation₁,…,y_N1]；

S9, and Y ═ Y₁,…,y_N1]Grouping with the length of 16 to obtain a matrix consisting of 16 row vectors

S10, respectively calculating energy values corresponding to the 16 line vectors, namely summing the squared energy values of all elements in the line vectors, selecting a minimum value from the obtained energy values, taking the position corresponding to the minimum value of the energy values as the position of an index-modulated 0 signal, and numbering the line vector corresponding to the minimum value of the energy values as V;

s11, deleting the V-th row vector from the matrix YY, and reading column by column from top to bottom, resulting in a signal Z ═ 16 × N1 of length 15 ÷ 16N 1₁,…,z_N1×15/16]Then, the signal Z is circularly shifted to the right by 16-V bits to obtain a signal to be decodedSignal to be decodedAnd decoding by adopting the existing method to obtain a final signal. On the premise of judging the position of the index modulation 0 signal correctly, the signal Z is the encoded information bit signal B _0 ═ B₁,b₂,…,b_K]The corresponding received signal.

The set threshold C is a dynamic parameter, and is flexibly adjusted according to the number of subcarriers, the modulation mode and the performance of a power amplifier, when the set threshold C is larger, a transmitting end tries cyclic shift of a few times on an information bit signal to generate an OFDM signal meeting the requirement, the calculated amount is smaller, but the peak-to-average ratio of the OFDM signal is higher; when the set threshold C is smaller, the peak-to-average ratio of the transmitted signal is lower, but more attempts are needed to generate the OFDM signal satisfying the requirement, which results in a larger calculation amount. Therefore, the value of the set threshold value C is not specifically limited, and can be set by each equipment manufacturer according to the self condition in the actual application process.

For an OFDM signal comprising N subcarriers, the frequency domain input signal of the communication system is X ═ X₁,X₂,…,X_N]The time domain signal sequence of the communication system is x ═ x₁,x₂,…,x_N]，N is 1, 2. Peak-to-average ratio of signalMax (| x) in the formula_n|²) Representing the maximum value of the signal power, E (| x)_n|²) Representing the average power of the signal.

In general, a time domain Complementary Cumulative Distribution Function (CCDF) is used to describe the distribution of a signal peak-to-average ratio (PAPR), and the mathematical calculation formula is: pr (PAPR > z) is 1-Pr (PAPR < z).

According to the central limit theorem, the essence of the OFDM signal that the peak-to-average ratio occurs is that after the IFFT transformation is performed on the N frequency domain input signals, the obtained time domain signal tends to gaussian distribution, which becomes closer with the increase of the N value and the increase of the modulation order, and the gaussian distribution function has tail regions on the left and right sides, so that the time domain signal has a large value with a small probability.

The performance of the method of reducing the peak-to-average ratio of a signal is generally measured in the following 5 aspects: 1) the amount of sideband information; 2) the effect on transmission rate; 3) signal reception performance; 4) complexity of the algorithm; 5) the peak-to-average ratio of the transmitted signals decreases.

From the view of the amount of the sideband information, it can be seen from the signal processing flow of the method of the present invention that the receiving end can still perform the related processing flow on the received signal without any auxiliary information, so the amount of the sideband information is 0.

From the influence on the transmission rate, it can be seen from the signal processing flow of the method of the present invention that, in the new signal generation mechanism, the sending end uses 1/16 data subcarriers in each OFDM signal for index modulation, and is used to carry the number of times of right cyclic shift of the coded information bits corresponding to the OFDM signal, so the transmission rate is slightly decreased, which is about 6%.

From the viewpoint of signal reception performance, for the OFDM signal generation method of the present invention, the receiving side must determine the position corresponding to the index modulation signal from 16 possible positions with a very low error rate. Based on the processing principle of the OFDM signal, the received signal y on one subcarrier can be expressed as:

wherein h represents the fading coefficient corresponding to the subcarrier, S represents the transmitted signal on the subcarrier, and w represents the random noise term of the received measurement. Since the value of 1 subcarrier in every 16 subcarriers in the new signal is 0, the signal power of the rest nonzero subcarriers is 16/15 under the same power condition.

As can be seen from the judgment algorithm of the corresponding position of the index modulation signal, in the 16 decision row vectors of the received signal, if the row vector corresponds to a non-zero subcarrier signal, the power of the row vector is:

and if the corresponding zero subcarrier signal is, the power is as follows:

theoretical research and simulation structure show that under the condition of larger N1 value, such as more than or equal to 96, under the condition of the same signal-to-noise ratio, the probability value Pr (P)_S≤P₀) Compared with the traditional OFDM signal, the signal power of the non-zero subcarrier in the new signal is 16/15, so that the receiving side can obtain the receiving decoding performance improvement of 10 × log10(16/15) ≈ 0.3dB under the same channel condition.

From the aspect of algorithm complexity, it can be seen from the signal processing flow of the method of the present invention that the algorithm complexity is closely related to the setting size of the setting threshold C. If the value of the set threshold value C is set to 0, the algorithm complexity reaches the highest, namely each OFDM signal needs to execute 16 IFFT operations and other auxiliary operations, so the algorithm complexity is about 16 times of that when a peak-to-average ratio reduction mechanism is not adopted; if the value of the set threshold value C is set to be infinite, the algorithm complexity is the lowest, the sending end only needs to perform 1 signal processing flow on the data load data, but the peak-to-average ratio performance of the signal is not optimized.

The theoretical analysis of the algorithm complexity is given below by the time-domain Complementary Cumulative Distribution Function (CCDF), setting the threshold value to C, and for a randomly generated OFDM signal, the probability value that the square PA of the maximum amplitude is greater than C is: pr { the square of the maximum amplitude of 1 OFDM symbol is greater than C } -, 1-Pr (PA ≦ C);

the applicant researches and discovers that operations such as cyclic left shift and the like which can obviously change the sending sequence of information bits are performed on 1 coded random information sequence, and then a series of OFDM signals generated based on the signal and the signal after cyclic left shift are all mutually independent through mixed mapping of traditional constellation mapping and index modulation, constellation phase rotation and IFFT operation, so that when the threshold of a sending end is set to be C, the probability value distribution of the cyclic left shift value X of the sending signal is as follows:

probability values corresponding to different cycle left shift values X

In general, the time-domain Complementary Cumulative Distribution Function (CCDF) of the transmitted signal of interest will be compared at 10 when evaluating the signal peak-to-average ratio (PAPR) case^-4The corresponding numerical value. The sending end can set the value of the set threshold value C to be the time domain Complementary Cumulative Distribution Function (CCDF) corresponding to the signal sending at 10^-4The corresponding value, i.e. Pr (PAPR > C) ═ 1-Pr (PAPR. ltoreq.C) ═ 10^-4(this value can be obtained by simulation using a computer).

In this case, when Pr (PAPR > C) ═ 10^-4When the probability value of the event occurrence is about 1, that is, the transmitting end keeps the same signal processing flow as the original algorithm in about 99.99% of the cases, and the probability value of the event occurrence is about 0 in X>In the case of 0, the OFDM signal generation process needs to be performed X times more. Therefore, compared with the traditional algorithm, the method for reducing the peak-to-average power ratio only increases a very small amount of computational complexity and can be almost ignored.

From the level of reducing the peak-to-average ratio of the transmitted signal, in the case of a large N value, the influence of the dc carrier, the two-side guard carriers, and the pilot signal on the peak-to-average ratio of the signal is negligible, so for convenience of simulation, it is assumed that all N-1024 carriers are data subcarriers, and the system adopts the QPSK modulation scheme, and the situations of the conventional OFDM signal and the Complementary Cumulative Distribution Function (CCDF) of the OFDM signal after using the optimization mechanism are as shown in fig. 5 (in fig. 5, the conventional signal is the one obtained by using the conventional signalThe OFDM signal without any processing is referred to, the new signal is the OFDM signal processed by the method of the invention), and the complementary cumulative distribution function of the peak-to-average ratio value of the transmitted signal is 10 after the optimization mechanism is adopted as can be seen from the simulation result^-4About 3.5dB of peak-to-average ratio is reduced, and a very good effect of reducing the peak-to-average ratio is obtained.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.