KR20080103867A - Apparatus for papr reduction of ofdm signal and method thereof - Google Patents

Abstract

An apparatus and a method for reducing a PAPR(Peak-To-Average Power Ratio) of an OFDM(Orthogonal Frequency Division Multiplexing) signal minimize a delay time by reducing the number of sub block combinations. A serial and parallel converter(100) converts successively inputted data to the parallel data. A block divider(110) divides data converted to the parallel into the sub block. An inverse Fourier transformer(120) performs the IFFT(Inverse Fast Fourier Transform) of each sub block. A flipping unit(130) generates the OFDM transmission candidate symbols which is phase-rotated by multiplexing each transformed sub block by a phase rotation factor and sequentially flipping the sub block. A selecting unit(150) selects the signal with the minimum non-linear distortion among the OFDM transmission candidate symbols as the final transmission symbol.

Description

Apparatus for PAPR reduction of OFDM signal and method algorithm for reducing peak power to average power ratio of orthogonal frequency division multiplexing signal

1 is a block diagram showing the configuration of an apparatus for reducing the peak power to average power ratio of an orthogonal frequency division multiplexing signal according to the present invention.

Figure 2 illustrates the flow of a method for reducing the peak power to average power ratio of an orthogonal frequency division multiplexed signal according to the present invention.

FIG. 3 shows the signals transmitted and processed in the configuration of the apparatus of FIG. 1 and partially reconstructed by function.

4 shows the results of BER performance improvement when the transmission method according to the present invention is applied.

5 illustrates a PSD of an OFDM signal distorted by nonlinear TWTA.

TECHNICAL FIELD The present invention relates to communications, and the present invention relates to an apparatus and method for improving the peak-to-average power ratio (PAPR) characteristic caused by a plurality of carriers essential for use in an orthogonal frequency division multiplexed communication system (OFDM). It is about.

Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) systems are currently considered as the most likely candidates for use in transmission schemes in many systems, including next-generation mobile radio communication systems. The spectral efficiency is maximized by multiplexing into multiple orthogonal subchannels, and shows better performance than conventional single carrier modulation system in frequency selective channel environment.

Modulation and demodulation at the transceiver is also handled using an Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT). Is possible. Therefore, it is currently being adopted as the standard for several systems such as IEEE802.11a (WLAN), European HIPERLAN / 2, Japanese MMAC, and European digital broadcast DAB and DVB-T.

However, despite these advantages, orthogonal frequency division multiplexing (OFDM) systems have a disadvantage of having a high peak power to average power ratio (PAPR). This high PAPR leads the high output power amplifier (HPA) required for OFDM signal transmission to the nonlinear region, resulting in nonlinear distortion of the OFDM signal, leading to a decrease in bit error rate (BER) performance. In addition, out-of-band radiation and intermodulation between subcarriers can result in spectral growth of multicarrier signals so that the transmit power amplifier can operate in a linear region (e.g. This requires a large input backoff, which leads to inefficiency and cost increases in power changes. Moreover, this has a negative impact on the battery life of mobile devices and therefore the potential benefits of OFDM systems in low-cost applications may be less valuable due to the high PAPR. Therefore, OFDM communication system researches for reducing PAPR are very important and various methods and methods have been studied.

Recently, various methods for reducing PAPR have been proposed. Among them, there are amplitude clipping, block coding, and phase adjustment methods. Clipping method is a method of forcibly cutting the size to a certain value when the signal size becomes larger than a predetermined value. Although this method is the simplest, it causes in-band noise due to nonlinear operation, which degrades the BER performance of the OFDM signal and results in out-of-band adjacent channel interference. interference occurs.

The block coding method is a method of transmitting a signal having a high PAPR by applying a coding scheme using a coding table, which can lead to error correction and signal-free distortion transmission. However, as the spectral efficiency and the size of the coding table increase, the complexity thereof is increased. There is a disadvantage that the amount of calculation increases.

The phase rotation method includes a partial transmit sequence (hereinafter referred to as PTS) and selective mapping (hereinafter referred to as SLM). Both the PTS and SLM schemes are quite efficient for reducing PAPR without nonlinear distortion.

PTS divides the input symbol sequence having length N into several subblocks, performs IFFT for each block, multiplies each phase-block transformed component in time domain, and adds them all to add in-phase peaks. It is possible to reduce the signal values to lower the PAPR. However, this approach increases considerably as the number of phase rotation elements and subblocks increases.

Similar to the PTS method, the SLM method using a phase rotation element is a method of transmitting the sequence having the lowest PAPR by multiplying V statistically independent length N sequences by the frequency wholesaler to the same input data of length N. As with the PTS method, which is sensitive to the number of subblocks, the number of phase rotation elements and the number of V statistically independent sequences increases and the complexity of the IFFT process is required.

Therefore, the proposed method to reduce the complexity of the PTS is the iterative partial transmit sequence (hereinafter referred to as I-PTS). Although I-PTS has a slight performance degradation compared to the conventional PTS method, it can be used as a sub-optimal technique because it can greatly reduce the computational complexity.

In the conventional PTS method, all combinations of subblocks and phase rotation elements are considered in finding an optimal phase rotation element (for example, when subblock V = 4 and two phase rotation elements of 1, -1 are used, 2 ^ Four sub-block combinations are considered.) The I-PTS method uses a flipping algorithm to use PAPR using only one phase rotation element of 1 and -1 and the first phase rotation element of all subblocks. After measuring and flipping only the next one subblock to -1, the PAPR is measured. If the value becomes smaller compared to the previous value, the phase rotation element of -1 is maintained as the optimal phase rotation element. Maintain the phase rotation element.

By flipping all V subblocks in this manner, the complexity of subblock combining of the conventional PTS can be reduced to V sets having V additions. However, although the I-PTS scheme can significantly reduce the computational complexity than the conventional PTS scheme, there is a problem in that the performance of reducing the PAPR is degraded as much as that of the PTS scheme which leads the optimal subblock combination.

The technical problem to be solved by the present invention is to solve the above problems of performance degradation, by transmitting an OFDM signal having a minimum non-linear distortion, regardless of the type of modulation scheme and the number of subcarriers, An apparatus and method for reducing the peak power to average power ratio of an orthogonal frequency division multiplexing signal to effectively reduce PAPR) and to have a minimum nonlinear distortion.

An apparatus for reducing the peak power to average power ratio of an orthogonal frequency division multiplexing signal according to the present invention for solving the above technical problem, in the orthogonal frequency division multiplexed communication (OFDM) to convert the data sequentially input in parallel Serial-to-parallel conversion unit; A block dividing unit dividing the data converted in parallel into sub-blocks; An inverse Fourier transform unit for inverse fast Fourier transform of each subblock; A flipping unit to multiply each transformed sub-block by a phase rotation element and to flip sequentially to generate OFDM transmission candidate symbols rotated in phase; And a selector for selecting a signal having the smallest nonlinear distortion degree among the OFDM transmission candidate symbols as the final transmission symbol.

The apparatus further includes an estimator for estimating a nonlinear characteristic of the high output power amplifier that varies according to the transmission time, wherein the selection unit estimates through the estimator by passing the high output power amplifier for all OFDM transmission candidate symbols. Deviation between a nonlinear distortion OFDM transmission candidate symbol and a corresponding OFDM transmission candidate symbol before passing the high output power amplifier is measured, and the OFDM transmission candidate symbol having the smallest deviation value is selected as the final transmission symbol.

According to the present invention for solving the other technical problem, the method for reducing the peak power to average power ratio of the orthogonal frequency division multiplexing signal, in the orthogonal frequency division multiplexed communication (OFDM), converts sequentially input data in parallel Making; Dividing the data converted in parallel into sub-blocks; Inverse fast Fourier transforming each of the sub-blocks; Multiplying each transformed sub-block by a phase-rotation element and flipping them sequentially to generate phase-shifted OFDM transmission candidate symbols; And selecting a signal having the smallest nonlinear distortion degree among the OFDM transmission candidate symbols as the final transmission symbol.

And after generating the OFDM transmission candidate symbols, estimating a non-linear characteristic of the high output power amplifier that varies with transmission time. The method may further include selecting and transmitting the final transmission symbol as the final transmission symbol. The smallest deviation is obtained by measuring the deviation between the nonlinear distortion OFDM transmission candidate symbol estimated by the estimator through the high output power amplifier and the corresponding OFDM transmission candidate symbol before passing the high output power amplifier for all OFDM transmission candidate symbols. The OFDM transmission candidate symbol having the value is selected as the final transmission symbol.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram showing the configuration of an apparatus for reducing the peak power to average power ratio of an orthogonal frequency division multiplexing signal according to the present invention.

The apparatus includes a serial-to-parallel converter 100 for converting sequentially input data in parallel, a block divider 110 for dividing the parallel-converted data into subblocks, and an inverse fast Fourier transform for each subblock. Fourier transform unit 120, a flipping unit 130 for multiplying each of the transformed sub-blocks by a phase rotation element and flipping them sequentially to generate the OFDM symbols candidate phase rotated, a high output power amplifier that varies according to the transmission time An estimator 140 estimating nonlinear characteristics and a selector 150 selecting a signal having the smallest nonlinear distortion degree among the OFDM transmission candidate symbols as the final transmission symbol.

Figure 2 illustrates the flow of a method for reducing the peak power to average power ratio of an orthogonal frequency division multiplexed signal according to the present invention.

Sequentially converting the input data in parallel (step 200), dividing the parallel converted data into sub blocks (step 210), and inverse fast Fourier transforming the respective sub blocks (step 220), respectively Non-linear characteristics of the high output power amplifier varying according to transmission time after generating the OFDM transmission candidate symbols rotated by multiplying the sub-blocks by the phase rotation element and sequentially flipping the phase transmission OFDM symbols (step 230), and generating the OFDM transmission candidate symbols. In operation 240, a signal having the smallest nonlinear distortion degree among the OFDM transmission candidate symbols is selected as the final transmission symbol and transmitted (operation 250).

FIG. 3 shows the signals transmitted and processed in the configuration of the apparatus of FIG. 1 and partially reconstructed by function.

The serial / parallel conversion and block division block 100 of FIG. 3 includes both the serial / parallel conversion unit and the block division of FIG. 1, and the IFFT 120 is the same as the inverse Fourier transform unit 120 of FIG. 1. The reference numeral 135 is a component that generates a signal x (n) by adding v subblocks, and the HPA 155 is a high-pwer amplifier. As shown in FIG. 1, the output of the estimator 140 may be returned to the selector 150, and only the data transmission path is omitted in FIG. 1.

의 서브캐리어를 가지는 OFDM 신호열

로 표시될 수 있다.The serial / parallel converter 100 converts data sequentially input in parallel. Such conversion can be easily carried out using a commercially available element. The result of this parallel conversion is

OFDM signal sequence with subcarriers of

It may be represented as.

This signal sequence can be represented by the following equation.

는 입력 데이터 심볼 시퀀스이고, t는 이산 시간 인덱스를 나타낸다. N은 일반적으로 매우 크기 때문에 중심 극한 이론에 따라 x(t)는 가우시안 분포로 대략화 되어진다. 이것이 OFDM 신호가 기타 단일 캐리어 시스템보다 더 높은 PAPR을 가지는 이유가 될 것이다. here

Is an input data symbol sequence, and t represents a discrete time index. Since N is usually very large, x (t) is approximated by a Gaussian distribution according to the central limit theory. This is the reason why the OFDM signal has higher PAPR than other single carrier systems.

PAPR of an OFDM signal is usually defined as the ratio of the average power of the signal to the maximum power of the signal, where the equation is:

Where E [·] is defined as the expected value.

4 설정하여 각 샘플들로부터 좀 더 정확한 PAPR을 측정할 수 있다. In addition, the theoretical maximum PAPR value of the OFDM signal having N subcarriers is 10 log (N) dB, and the oversampling factor is measured as follows to determine the actual PAPR value

4 can be set to measure more accurate PAPR from each sample.

를 V개의 디스조인트(disjoint) 서브블록

들로 나눈다.The block divider 110 of Figure 1 is the frequency domain OFDM input sequence as described above

V disjoint subblocks

Divide into fields

Data carried in each subblock is allocated to a certain number of consecutive subcarriers without intersecting with each other, and a portion where no data is carried in each subblock is provided as an input of an inverse Fourier transform unit by inserting a number 0.

The inverse Fourier transform unit 120 performs inverse fast Fourier transform on the subblocks, and the flipping unit 130 acts on the subblocks to generate transmission candidate symbols. An inverse fast Fourier transform can be performed in an inverse fast Fourier transform.

M transmission candidate symbols appear according to the following equation.

를 부분 전송 시퀀스(Partial Transmit sequence)라고 부르며,

는 위상회전 요소로써 보통

값은 모든 서 브블록과 곱하게 되고, 곱해진 서브블록들은 도 3의 참조번호 135의 구성부에서 모두 더해짐으로써 하나의 위상 회전되어진 OFDM 심볼을 구성하게 된다. 또한 M은 전송 후보 신호

들의 수를 나타낸다. here

Is called the Partial Transmit sequence,

Is a phase rotation element

The value is multiplied by all the subblocks, and the multiplied subblocks are added in the component of reference numeral 135 of FIG. 3 to form one phase rotated OFDM symbol. M is also a transmission candidate signal

Indicates the number of these.

값을 사용하는 대신 {1, -1}을 사용한다. 또한 1과 -1을 곱한 서브블록들의 모든 컴비네이션 조합(

)을 만들어 OFDM 전송 후보 심볼로 생성하지 않고, 플립핑 알고리즘을 통해 전송 후보 심볼의 수를 V개로 줄인다.However, as mentioned above, the method used in the present invention is a kind of iterative partial transmission sequence method, and unlike the conventional partial transmission sequence method, the phase rotation element is used for the low complexity.

Instead of using a value, use {1, -1}. In addition, all combinations of subblocks multiplied by 1 and -1 (

The number of transmission candidate symbols is reduced to V through a flipping algorithm without generating the OFDM transmission candidate symbols.

The flipping process is as follows.

에

의 위상회전 요소를 곱한 후에 수학식 3을 따르는 결합된 OFDM 신호, 즉 하나의 OFDM 전송 후보 심볼을 선정하고, 다음 위상 회전 요소를 플립핑한 후 그 결합된 신호와 전 신호의 PAPR을 비교한 후 새로운 신호의 PAPR값이 더 낮으면 기존의 위상회전 요소는 플립핑된 새로운 위상회전 요소로 저장되고, 이것 또한 OFDM 전송 후보 심볼로 선정된다. 그 반대의 경우에는 기존의 위상회전 요소로 유지되며 그 결과도 마찬가지로 OFDM 전송 후보 심볼로 선정된다. all

on

After multiplying the phase rotation elements of, select a combined OFDM signal, i.e., one OFDM transmission candidate symbol, flip the next phase rotation element, and compare the combined signal with the PAPR of the previous signal. If the PAPR value of the new signal is lower, the existing phase rotation element is stored as a flipped new phase rotation element, which is also selected as an OFDM transmission candidate symbol. In the opposite case, it is maintained as an existing phase rotation element and the result is similarly selected as an OFDM transmission candidate symbol.

Each of the selected OFDM transmission candidate symbols passes through the nonlinear HPA 155. Among them, the signal having the smallest nonlinear distortion degree, that is, the signal having the smallest deviation value before and after passing through the HPA, is selected as the final transmission symbol. 150).

In this case, a mean square error (hereinafter referred to as MSE) may be used as a deviation, and as a result, a signal having the smallest MSE value is selected as the final transmission symbol.

The equation for MSE is

Where L is an oversampling index to find a more accurate peak value and r (n) represents a signal that has passed through HPA 155 as a sampled signal of r (t). Therefore, in order to calculate the MSE value, it is necessary to estimate the exact value of the r (n) signal, but it is not easy to actually measure it.

The nonlinear HPA 155 needs to be accurately characterized, and the nonlinear HPA, which is usually used as a radio-frequency (RF) transmission amplifier, has magnitude-to-magnitude (AM-AM) and magnitude-to-phase (AM-PM) conversion characteristics. Its characteristic is that it changes with time due to equipment aging, temperature change, and power supply change. Therefore, although more accurate HPA characteristics are required, it is difficult to know exactly the characteristics of AM-AM and AM-PM of the actual HPA. Therefore, it is necessary to find a method within a more feasible range. Use government 140. This provides the advantage that AM-AM and AM-PM can be estimated independently of each other and therefore independently.

Where x (n) and r (n) represent OFDM transmission signals before and after passing through HPA 155, respectively, and ρ (n) and θ (n) represent the magnitude and phase component of the input signal, respectively. D (n) and Each time n Is the change amount of AM-AM and AM-PM at the HPA 155 output.

으로 표현하고

각각 추정부(155)를 통해 추정된 크기와 위상의 오프셋(offset)이다. 따라서 위의 식을 이용하여 비선형 HPA(155)를 통과하기 전후의 OFDM신호의 크기와 위상 오프셋 값을 최소 평균 자승 (Least Mean Square) 업데이트 방식을 이용하여 추정할 수 있다. 아래 식이 그에 관한 수학식이다.Here, the output signal of the estimator 155, which is an adaptive nonlinear estimator,

Expressed as

Each is an offset of the magnitude and phase estimated by the estimator 155. Therefore, the magnitude and phase offset of the OFDM signal before and after passing through the nonlinear HPA 155 can be estimated using the least mean square update method using the above equation. The following equation is the equation for it.

와

는 위의 적응 알고리즘(adaptive algorithm)을 위한 최적의 오프셋 계수를 찾기 위한 스텝 사이즈(step size)를 나타내며 위와 같은 수학식을 통해 HPA(155)의 변환 계수들의 값들을 하나 하나씩 추정해 낼 수 있다. The above equation is estimated using the gradient algorithm of the optimization theory, and the next signal is estimated by minimizing the difference between the signal passing through the current HPA and the estimated signal. here

Wow

Denotes a step size for finding an optimal offset coefficient for the above adaptive algorithm, and the values of transform coefficients of the HPA 155 can be estimated one by one through the above equation.

는 그레디언트 벡터(gradient vector)를 나타내며 이것을 이용하여 적응 알고리즘의 관한 식은 아래와 같다.here

Denotes a gradient vector, and the equation for the adaptive algorithm using this is

Therefore, the following equation was obtained using Equation 7,8, and the estimated amount of change in magnitude and phase due to the estimated HPA can be obtained through the following equation.

Where | · | And 을 represent magnitude and phase, respectively, and can estimate the OFDM signal passing through HPA 155 using the AM-AM and AM-PM transform coefficients of HPA estimated in Equation 7 above. Therefore, the method of obtaining the MSE value shown in Equation 4 can be approximated by the following equation through the value obtained in Equation 8.

This result can be applied to I-PTS, which has a low subblock combining complexity but has a disadvantage in that performance is lower than that of a conventional PTS.

In this case, the index of the OFDM symbol having the minimum MSE value can be represented by the following equation.

번째의 OFDM 전송후보 심볼의 MSE 값을 나타낸다.Where MSEi is

MSE value of the first OFDM transmission candidate symbol.

V of I-PTS as described earlier doggy A method that focuses on reducing only conventional PAPR by selecting and transmitting OFDM signals having a minimum MSE value, that is, a minimum nonlinear distortion, by applying the method according to the present invention as described above. We also consider the nonlinear distortion components of HPA. As a result, the result of adopting the method according to the present invention shows better BER performance than the method of reducing only the conventional PAPR value.

4 shows the results of BER performance improvement when the transmission method according to the present invention is applied. In FIG. 4, a comparison of the original OFDM symbol, the conventional PTS method (Conventional PTS), and the case where only I-PTS is applied (Conventional I-PTS) and the method according to the present invention (Proposed EI-PTS) are performed. The model uses a traveling wave tube amplifier (TWTA) model to set the input back-off (IBO) to 5.5 dB and is a result of experiments using 16-QAM modulation on the AWGN channel. In addition, the number of subcarriers N is set to 128, and the number of subblocks V = 4 or 16 is determined to compare the respective schemes.

As can be seen from the results of FIG. 4, it can be seen that the performance of the proposed method (Proposed EI-PTS) according to the present invention is significantly improved compared to the conventional method, and the conventional simply applied I-PTS method is less than the conventional PTS method. The performance of the scheme according to the present invention for transmitting a signal having a minimum nonlinear distortion through an adaptive nonlinear estimator to the I-PTS scheme to compensate for it is known because it has a transmission candidate symbol. Go beyond the PTS method. For example, when V = 4, 0.01% BER of each scheme is original OFDM 29 dB, conventional I-PTS and PTS, and the EI-PTS scheme to which the method according to the present invention is applied is about 27, 26.5, and 26, respectively. By indicating dB, the method according to the present invention can be seen that the performance is improved by approximately 1 dB over the conventional I-PTS method.

5 illustrates a PSD of an OFDM signal distorted by nonlinear TWTA. Nonlinear distortion caused by this high PAPR causes out-of-band emission and frequency spread in the frequency band. As can be seen in FIG. 5, the unmodified OFDM signal is compared with the OFDM signals to which the method according to the present invention (EI-PTS) is applied. As a result, the OFDM signal to which the method according to the present invention is applied has a much smaller band. It can be seen that the amount of out-of-band radiation varies according to the amount of external radiation and the output back off (OBO) value of the TWTA. In addition, when the OBO value of the nonlinear TWTA is 8 dB and V = 4, the OFDM signal according to the present invention shows an amount of out-of-band emission below -50 dB.

As described above, it can be seen that better performance can be obtained when using the method to which the present invention is applied.

Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. Examples included in the above description are introduced for the understanding of the present invention, and these examples do not limit the spirit and scope of the present invention. It will be apparent to those skilled in the art that various embodiments in accordance with the present invention in addition to the above examples are possible. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope will be construed as being included in the present invention.

In addition, it can be easily understood by those skilled in the art that each of the above steps according to the present invention can be variously implemented in software or hardware using a general programming technique.

And some steps of the invention may also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, CD-RW, magnetic tape, floppy disks, HDDs, optical disks, magneto-optical storage devices, and carrier wave (eg, Internet It also includes the implementation in the form of). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

According to the present invention, by applying the present invention to the conventional I-PTS scheme, the weakness of the performance is compensated for, and it is possible to reduce the high PAPR, which is the biggest problem due to the use of multiple carriers in the orthogonal frequency division multiplexing (OFDM) communication system. Due to this, the nonlinear distortion generated can be minimized and the power efficiency of the high output amplifier can be increased, thereby enabling high quality communication and reducing the number of subblock combinations, which is a problem of the conventional PTS. Minimizes the cost and provides the better transmission speed. As a result, it greatly improves the user's network environment.

Claims (8)

In Orthogonal Frequency Division Multiplexed Communication (OFDM), A serial-to-parallel converter for converting sequentially input data into parallel; A block dividing unit dividing the data converted in parallel into sub-blocks; An inverse Fourier transform unit for inverse fast Fourier transform of each subblock; A flipping unit to multiply each transformed sub-block by a phase-rotation element and to flip sequentially to generate candidate-phased OFDM transmission candidate symbols; And And a selector for selecting a signal having the smallest nonlinear distortion degree from among the OFDM transmission candidate symbols as a final transmission symbol. The apparatus of claim 1, wherein the peak power to average power ratio of the quadrature multiplexed signal is reduced. The method of claim 1, And an estimator for estimating nonlinear characteristics of the high output power amplifier which varies according to the transmission time. The selector measures the deviation between the nonlinear distortion OFDM transmission candidate symbol estimated by the estimator through all the OFDM transmission candidate symbols and the corresponding OFDM transmission candidate symbol before passing the high output power amplifier. And selecting the OFDM transmission candidate symbol having the smallest deviation value as the final transmission symbol to reduce the peak power to average power ratio of the orthogonal frequency division multiplexed signal. The method according to claim 1 or 2, The peak-to-average power ratio of the orthogonal frequency division multiplexing signal, characterized in that the deviation measured by the selector is a mean square error (MSE) between the estimated nonlinear distortion OFDM transmission candidate symbol and the corresponding OFDM transmission candidate symbol. Device to reduce. The method according to claim 1 or 2, The block dividing unit allocates a sub-block by inserting the number 0 in a portion in which data contained in each sub block does not cross each other and is allocated to a certain number of consecutive subcarriers. Generating a peak power to average power ratio of an orthogonal frequency division multiplexing signal. The method according to claim 1 or 2, And the inverse Fourier transform unit performs an inverse fast discrete Fourier transform. The method according to claim 1 or 2, And the phase rotation element of the flipping portion is a value of 1, -1. In Orthogonal Frequency Division Multiplexed Communication (OFDM), Converting sequentially input data in parallel; Dividing the data converted in parallel into sub-blocks; Inverse fast Fourier transforming each of the sub-blocks; Multiplying each transformed sub-block by a phase-rotation element and flipping them sequentially to generate phase-shifted OFDM transmission candidate symbols; And Selecting a signal having the least nonlinear distortion among the OFDM transmission candidate symbols as the final transmission symbol; and reducing the peak power to average power ratio of the orthogonal frequency division multiplexing signal. The method of claim 7, wherein After generating the OFDM transmission candidate symbols, estimating a nonlinear characteristic of the high output power amplifier that varies with transmission time; In the step of selecting and transmitting the last transmission symbol, all of the OFDM transmission candidate symbols pass through the high output power amplifier and corresponding nonlinear distortion OFDM transmission candidate symbols estimated by the estimator before passing the high output power amplifier. A method of reducing peak power to average power ratio of an orthogonal frequency division multiplexing signal, characterized by measuring the deviation between OFDM transmission candidate symbols and selecting the OFDM transmission candidate symbol having the smallest deviation as the final transmission symbol.

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