KR100681925B1 - Multi-stage peak windowing method for papr reduction of ofdma downlink system and ofdma downlink system therefor - Google Patents

Abstract

A multi-step peak windowing method for reducing a peak to average power ratio of an OFDMA downlink system and an OFDMA downlink system therefor are provided to reduce a PAPR(Peak to Average Power Ratio) and improve a BER(Bit Error Rate) and an EVM(Error Vector Magnitude) by adapting a multi-step threshold value. A threshold value adjustment constant storage unit(41) stores threshold value adjustment constant set information. A threshold value control unit(42) stores threshold value information, and sequentially outputs a multiplication value of an amplitude threshold value and elements of a threshold value adjustment constant set stored in the threshold value adjustment constant storage unit(41) so that peak windowing is performed for a signal column. A peak detection unit(43) receives the signal column to perform the peak windowing, and a threshold value outputted from the threshold value control unit(42). The peak detection unit(43) receives the threshold value sequentially and detects a position of a peak having an amplitude above the threshold value from the signal column. The peak detection unit(43) outputs the signal column, the detected peak position, and the multiplication value. A peak windowing unit(43) performs peak windowing by adapting the threshold value to the signal column corresponding to the peak of the signal column according to the information outputted from the peak detection unit(43). A peak windowing unit(44) feedbacks the peak-windowed signal column to the peak detection unit(43) as a signal column to perform peak windowing in the next step.

Description

Multi-stage peak windowing method for PAPR reduction of OFDMA downlink system and OFDMA downlink system therefor}

1 is a configuration diagram of an OFDMA downlink system to which a PAPR reduction technique is applied;

2 is a view for explaining a conventional peak windowing technique,

3A and 3B are diagrams for explaining excessive signal suppression by a conventional peak windowing technique;

4 is a conceptual diagram illustrating a multi-stage peak windowing method in a PAPR reduction unit of the present invention;

5 is a block diagram of a PAPR reduction unit according to an embodiment of the present invention;

6 is a flowchart sequentially illustrating operations of an embodiment of the PAPR reduction unit according to an embodiment of the present invention;

7 to 9 is a graph showing the BER performance of the multi-stage peak windowing method of the present invention,

10 and 11 are graphs showing the EVM performance of the multi-step peak windowing method of the present invention;

12 is a graph showing the spectral performance of the multi-step peak windowing method of the present invention.

<Description of Symbols for Main Parts of Drawings>

10: symbol generation unit 20: upsampling unit

30: symbol filtering unit 40: PAPR reduction unit

41: threshold adjustment constant storage 42: threshold control unit

43: peak detector 44: peak windowing section

50: DA converter

The present invention relates to a multi-stage peak windowing method for PAPR reduction of an OFDMA downlink system and an OFDMA downlink system for the same. More particularly, the present invention relates to a peak in an orthogonal frequency division multiplexing access (OFDMA) downlink system. Multistage peak windowing method for PAPR reduction of OFDMA downlink system with excellent bit error rate performance while avoiding excessive signal distortion of existing peak windowing technique applied to reduce peak to average power ratio (PAPR) It is about.

In OFDMA systems, performance degradation is caused by signals with high peak-to-average power ratios that occur when multiple subcarrier signals overlap in phase, and the peak-to-average power ratio (PAPR) problem due to superposition of subcarriers is high. In an OFDMA system that transmits data, an RF power amplifier, that is, a transmission high power amplifier (HPA), reduces the efficiency and causes nonlinear distortion of a signal, thereby distorting spectral characteristics and causing a bit error rate (BER). It has the disadvantage of degrading performance.

Accordingly, various studies have been conducted to reduce the PAPR.

As shown in FIG. 1, a transmitting side of the OFDMA system, that is, a downlink system, scrambles and channel codes a user data binary signal, performs a QAM modulation and an inverse fast Fourier transform, and then inserts a guard interval (CP) to transmit to a receiving side. Symbol generation unit 10 for generating a symbol of the up, the up-sampling unit 20 for performing the up-sampling and zero-pad process to facilitate the implementation of the RF stage, intermediate to the added zero (Zero) The symbol filtering unit 30 and the DA converter 50 are configured to filter the symbols by obtaining values, and the PAPR reduction unit 40 to which a technique for reducing PAPR is applied is the symbol filter 30 and the DA converter ( 50).

The PAPR reduction technique of the PAPR reduction unit 40 includes a clipping technique and a peak windowing technique, and the clipping technique seriously increases the out-of-band radiation, and solves these disadvantages. The proposed peak windowing technique has the effect of reducing the peak-to-average power ratio while reducing out-of-band radiation.

As shown in FIG. 2, the peak windowing technique reduces the peak-to-average power ratio by lowering x (n) -Γ, which is the portion of the signal sequence above the threshold Γ in the input peak signal x (n), using a given window function. In addition, since the peak signal is lowered using the window function, the increase in the out-of-band radiation can be minimized by reducing the abrupt change in the signal sequence.

When the amplitude threshold of the transmission signal is Γ, a set representing a position of a peak to which the peak windowing technique is applied among signal values exceeding the threshold may be defined as follows.

When the peak windowing technique is applied, an additional peak detection technique is needed to locate the peak.

The window function applied to the peak windowing technique can be expressed as follows.

Here, s (n) means a scale function that is multiplied by the time axis input signal sequence x (n), which can be expressed as follows.

는 피크 인덱스 값을 의미하고,

는 피크에 적용할 윈도우의 스케일 값,

은 피크 윈도잉에 적용되는 윈도우 함수를 의미한다.From here,

Means the peak index value,

Is the scale value of the window to apply to the peak,

Denotes a window function applied to peak windowing.

On the other hand, in the conventional peak windowing technique as described above, since the signal exceeding the amplitude threshold of the transmission signal is limited to only one peak windowing, as shown in FIG. If there is a peak that is relatively large compared to the amplitude of the adjacent signal among the peaks, there is a problem that performance degradation may occur by excessively limiting the adjacent signal around the peak.

이 중복 가산된 스케일 함수

의 적용으로 인하여 과도한 신호 억제가 발생하고, 이로 인한 신호 손실이 커지게 된다는 단점이 있다.That is, in the case of the input signal as shown in Figure 3a, as shown in Figure 3b, the window scale value to be applied to the two peaks

This duplicate added scale function

Due to the application of excessive signal suppression occurs, resulting in a large signal loss is disadvantageous.

Accordingly, the present invention is to solve the above-mentioned disadvantages and problems of the prior art, and is applied to continuous peaks when the conventional peak windowing technique is applied in an Orthogonal Frequency Division Multiplexing Access (OFDMA) downlink system. Multistage thresholds are applied to solve the problem of excessive signal suppression due to the overlapping of the windows. Thus, multi-stage peak window for PAPR reduction of OFDMA downlink system with excellent bit error rate performance while preventing excessive signal distortion of the conventional peak windowing technique It is an object of the present invention to provide a Ying method.

The object of the present invention is to reduce the peak to average power ratio (PAPR) of the transmission signal by performing a peak windowing to lower the portion of the signal sequence beyond the amplitude threshold (Γ) of the transmission signal using a given window function In an Orthogonal Frequency Division Multiplexing Access (OFDMA) downlink system, the PAPR reduction unit stores information on a set of threshold adjustment constants {αi} having M threshold adjustment constants α _i as elements. A threshold adjustment constant storage unit; Stores the amplitude threshold value (Γ) information, and is stored in the threshold adjustment constant storage unit in the amplitude threshold value (Γ) so that the peak windowing by applying the M α _i sequentially to the signal sequence to perform the peak windowing A threshold controller for sequentially outputting α ₁ Γ to α _M Γ which are values obtained by multiplying each element α _i of the threshold adjustment constant set; Receives a signal sequence to perform peak windowing and the threshold α _i Γ output from the threshold controller, detects a position of a peak having an amplitude greater than or equal to the threshold α _i Γ from the signal sequence, and detects the signal sequence and the detected peak. A peak detector for outputting a position and the α _i Γ information; According to the information output from the peak detector, the peak windowing is performed by applying the threshold α _i Γ to the signal sequence of the portion corresponding to the peak of the signal sequence, and the peak windowing signal sequence is subjected to the peak windowing of the next step. A peak windowing part feeding back to the peak detector as a signal sequence to be performed; Is achieved by an OFDMA downlink system.

In addition, the above object of the present invention is to provide a PAPR for reducing the peak-to-average power ratio (PAPR) of the transmission signal by performing a peak windowing that lowers the portion of the signal sequence beyond the amplitude threshold (Γ) of the transmission signal using a given window function A reduction control unit, wherein the PAPR reduction unit includes a threshold adjustment constant storage unit for storing information on a set of threshold adjustment constants {αi} having M threshold adjustment constants α _i as an element, amplitude threshold value Γ information, and the threshold adjustment; A threshold controller for providing a threshold to be applied in each peak windowing step using a constant, a peak detector for detecting a peak by applying a threshold provided by the threshold controller, and the threshold controller for the detected peak signal. Orthogonal frequency component consisting of a peak windowing section that applies a threshold to perform peak windowing In the orthogonal frequency division multiplexing access (OFDMA) downlink system, as a peak windowing method of the PAPR reduction unit, the threshold control unit adjusts a threshold value stored in the threshold control constant storage unit, an M value of the number of peak windowing steps. A first step of initializing the number of elements of the constant set and initializing i value, which is an index value of the threshold adjustment constant, to 0; A second process of requesting input of a threshold value to the threshold controller by the peak detector, when a signal string to perform peak windowing is input; The threshold value control unit extracts α _i, which is an index value of 1 plus a previous i value, from the threshold adjustment constant storage unit, and inputs α _i Γ multiplied by the extracted α _i to an amplitude threshold value Γ to the peak detector. A third process of doing; The peak detector detects a position of a peak having an amplitude equal to or greater than the input threshold α _i Γ from the signal sequence to perform the peak windowing, and extracts the signal sequence, the detected peak position, and the α _i Γ information from the peak window. A fourth process of inputting into a recording part; The peak windowing unit performs peak windowing by applying the threshold α _i Γ to a signal string corresponding to the peak among the signal strings to be subjected to the peak windowing, and performs the peak windowing signal string in a next step. A fifth step of inputting the signal to the peak detector as a signal sequence to be performed and feeding back to the second step; Multi-step peak windowing method for reducing the PAPR of the OFDMA downlink system, characterized in that by sequentially suppressing the peak from the relatively larger peak than the surrounding signal of the signal sequence portion over the M threshold through the peak windowing of the M stage Is achieved by.

Details of the above object and technical configuration of the present invention and the resulting effects thereof will be more clearly understood from the following detailed description based on the accompanying drawings.

First, FIG. 4 is a conceptual diagram for explaining a multi-step peak windowing method in a PAPR reduction unit of the present invention.

As shown, the PAPR reduction unit 40 for performing the peak windowing in the present invention performs a peak windowing of the total M steps for the signal to be transmitted and then inputs to the DA conversion unit 50. In the figure, W denotes the length of the window, and the window length W is equally applied in each step of different thresholds.

In performing peak windowing of the total M stages, the threshold in the i th stage is α _i Γ, and α _i is a threshold adjustment constant for adjusting the threshold, and satisfies the conditions of Equation 1 below.

That is, as can be seen in Equation 1, the multi-stage peak windowing method of the present invention sequentially applies the peak windowing from the larger threshold to the smaller threshold, so that a larger peak is preferentially compared to surrounding signals. Since the peak windowing is applied again, since there is a continuous peak within the window length, it is possible to prevent the problem of being excessively suppressed redundantly.

For example, when the α _i set for applying a threshold in multiple stages is {α _i } = {2.0, 1.5, 1.2, 1.0}, the PAPR reduction unit 40 first suppresses peak signals exceeding a threshold of 2Γ. Then, again, a threshold of 1.5 Γ is applied to suppress the peak signals. Similarly, subsequent application of 1.2 [gamma] and [gamma] sequentially results in suppressing all peak signals above the threshold [gamma], without peak signals exceeding the threshold [gamma] being excessively suppressed more than necessary.

Next, Figure 5 is a block diagram of a PAPR reduction unit according to an embodiment of the present invention.

As shown, in the present invention, a method for reducing peak-to-average power ratio (PAPR) of a transmission signal by performing peak windowing that lowers a portion of a signal string exceeding an amplitude threshold value (Γ) of the transmission signal using a given window function. The PAPR reduction unit 40 according to the embodiment includes a threshold adjustment constant storage unit 41, a threshold control unit 42, a peak detection unit 43, and a peak windowing unit 44.

The threshold adjustment constant storage unit 41 stores information on a set of threshold adjustment constants {αi} having M threshold adjustment constants α _i as elements as satisfying the condition of Equation (1).

The threshold controller 42 stores the amplitude threshold value Γ information of the transmission signal applied in the peak windowing in the final stage, and sequentially stores the M α _i with respect to the signal sequence x (n) to be subjected to the peak windowing. In order to achieve the applied peak windowing, each peak windowing is performed by the amplitude threshold value Γ, which is a value obtained by multiplying each element α _{i of the} set of threshold adjustment constants stored in the threshold adjustment constant storage 41 by α ₁ Γ to α _M Γ. In this step it is responsible for the output to the peak detector 43 in sequence.

At this time, the threshold controller 42 outputs M value which is the number of peak windowing steps before performing peak windowing on a specific input signal sequence x (n) in order to sequentially output α ₁ Γ to α _M Γ. Initializes the number of elements of the threshold adjustment constant set stored in the threshold adjustment constant storage unit 41, initializes the value of i, which is the index value of the threshold adjustment constant, to 0, and then sets 1 to the previous i value at the start of the peak windowing step. an extract obtained by adding α to the value of the index value _i from the threshold control constant storage section 41, and provides the product of Γ α _i α _i on the extracted amplitude threshold value (Γ) by the peak detector 43.

Next, the peak detector 43 receives the signal sequence x _i-1 (n) to perform the i-th peak windowing and the i th threshold α _i Γ output from the threshold controller 42, and the signal sequence x _{i. -} detecting the position of the peaks having an amplitude above the threshold value or more α _i Γ from ₁ (n) and the signal sequence x _i-1 (n) and the detected peak position and the α _i Γ information the peak window ingbu (44 It is responsible for outputting to).

The peak detector 43 receives an input signal signal x (n) (x (n) = x ₀ (n)) from the symbol filtering unit 30 to perform the peak windowing in the first step and starts an operation. by entering the x ₀ (n) to ingbu 44 thereto for receiving feed back the peak windowing the signal x ₁ (n), feeding back the re x ₁ by entering the (n) peak windowing the signal x ₂ (n) for this When the peak windowing of the M stage is performed in a receiving manner, and the signal x _M (n) in which the last stage peak windowing has been performed is fed back from the peak windowing section 44, it is obtained by the signal x _s ( n) (x _s (n) = x _M (n)).

On the other hand, the peak detector 43 is a peak position of a signal sample that is greater than the amplitude of the adjacent signal samples while the amplitude of the plurality of signal samples constituting the signal sequence x _i-1 (n) is greater than or equal to the threshold α _i Γ When the amplitude threshold of the transmission signal is Γ, a set representing a position of a peak to which the peak windowing technique is applied among signal values exceeding the threshold may be defined as follows.

In addition, when the peak window 43 receives the peak windowed signal x _i (n) with respect to x _i-1 (n) from the peak windowing section 44, the peak detector 43 returns to the threshold controller 42 again. The threshold value is requested, and the threshold detection process receives the threshold value of the next step from the threshold controller 42 and repeats the peak detection process. When the peak detection unit 43 finally detects the peak of the M-th step and performs peak windowing, the peak-detected signal x _s (n) (x _s (n) = x _M (n). ) Is output to the DA converter 50.

On the other hand, when the peak detection unit 43 does not detect a peak signal above a certain threshold, the peak detection unit 43 should request the threshold value of the next step again to the threshold control section 42.

Next, the peak windowing unit 44 performs the peak windowing by applying the threshold α _i Γ to the signal sequence corresponding to the peak according to the information output from the peak detector 43, and extracts the peak windowed signal sequence. The signal is fed back to the peak detector 43 as a signal string to perform the peak windowing of the next step.

Γ를 입력 신호 x(n)의 진폭으로 나눈 값을 1에서 감산한 값이다.The peak windowing may be performed by applying a window function w (n) for peak windowing to each time axis input peak signal string x (n) at a position where the peak windowing section 44 is detected as a peak. It means an operation of outputting the peak windowed signal x (n) * s (n) by multiplying the sum multiplied by the scale value c (n) of the window by subtracting the scale function s (n) from 1. Where the scale value c (n) of the window is the application threshold

Γ divided by the amplitude of the input signal x (n) minus one.

The window function applied to the peak windowing technique can be expressed as follows.

Here, s (n) means a scale function that is multiplied by the time axis input signal sequence x (n), which can be expressed as Equation 3 below.

,

,

는 피크 인덱스 값을 의미하고,

는 피크에 적용할 윈도우의 스케일 값,

은 피크 윈도잉에 적용되는 윈도우 함수를 의미한다.In Equation 3,

Means the peak index value,

Is the scale value of the window to apply to the peak,

Denotes a window function applied to peak windowing.

Meanwhile, in the present invention, the number M of peak windowing steps is equal to the number of elements of a set of threshold adjustment constants stored in the threshold adjustment constant storage 41, and the signal on which the M th peak windowing is performed is a DA converter ( 50).

To this end, the threshold controller 42 may compare the i value and the M value before providing the threshold value α _i Γ and transmit the information together to the peak detector 43 if the two values are the same, in which case the peak detector After 43 the peak windowing of the corresponding step is performed, when the peak windowed signal sequence is input from the peak windowing section 44, the signal sequence outputs the corresponding signal sequence without executing a threshold request to the threshold controller 42 any more. can do.

In another embodiment, the threshold controller 42 compares the i value with the M value before providing the threshold value α _i Γ, and if the i value is greater than the M value, the threshold detector 42 provides the threshold value α _i Γ to the peak detector 43. Instead, the signal output may be instructed. In this case, the peak detector 43 may output a signal string that is a result of the previous peak windowing step without proceeding with the further peak detection process.

Meanwhile, the configuration of the PAPR reduction unit 40 of FIG. 5 is only an example, and the PAPR reduction unit 40 may perform multi-step peak windowing even with a configuration different from that of FIG. 5.

Next, FIG. 6 is a flowchart sequentially illustrating operations of a PAPR reduction unit according to an embodiment of the present invention.

As shown, in order to perform the multi-step peak windowing, the PAPR reduction unit 40 of the present invention initializes the number of peak windowing steps M and i by using previously stored threshold adjustment constant set information. In the drawing, as an example, M is 4, and accordingly, the PAPR reduction unit 40 initializes i to 0 and initializes M to 4 (S101).

Next, when a signal sequence to perform peak windowing is input to the PAPR reduction unit 40, the PAPR reduction unit 40 is configured to 1 before the i value in order to sequentially apply the threshold values for each step for performing peak windowing. Is added (S102), and it is determined whether the value is greater than four (S103). If the value i is greater than 4, since all four steps of peak windowing have been performed, the peak windowing signal, that is, the previous signal sequence, is output to the DA converter 50 (S106). In step S104, a peak signal having an amplitude of α _i Γ or more is detected by applying α _i Γ obtained by multiplying the amplitude threshold value Γ by _i, which is an index value of _i plus one.

When a peak signal having an amplitude of α _i Γ or more is detected, the PAPR reduction unit 40 performs peak windowing by applying α _i Γ as a threshold value to each peak signal (S105), and again, the peak window of the next step. In order to perform the Ying, the process returns to step S102 by adding 1 to the value i.

By the above process, the PAPR reduction unit 40 of the present invention performs a total of four steps of peak windowing when the number of elements of the threshold adjustment constant set is four, that is, the fourth threshold adjustment constant is Since 1 is finally applied to the threshold value, the peak windowing is performed and the peak windowed signal is output, so that the signal having limited the amplitude of the transmission signal sequence below the amplitude threshold can be transmitted to the receiving side.

Next, FIGS. 7 to 11 compare the performance of the conventional peak windowing technique and the clipping technique with the performance of the multi-step peak windowing method of the present invention based on the simulation environment.

The simulation environment was set up based on the OFDMA standard WiBro system standardization document. For the WiBro system with 10MHz bandwidth, 768 data subcarriers and 96 pilot subcarriers among 1024 subcarriers were set, and the data subcarrier modulation method was QPSK. The pilot subcarrier applied 2.5dB amplified BPSK. The guard interval is set to 1/8 of the effective symbol length, and the multi-step windowing is made up of four stages, and the threshold set {α _i } used is {2.0, 1.5, 1.2, 1.0}.

First, Figures 7 to 9 are graphs comparing the BER performance, Figure 7 shows a case where the PAPR threshold is 2dB, Figure 8 shows a case of 4dB, Figure 9 is SNR is 10dB, PAPR threshold is 2dB, 4dB In this case, BER performance is shown according to the window length.

Because the clipping technique minimizes signal distortion, BER performance is best, while out-of-band radiation is very large. As can be seen in the graphs of FIGS. 7 and 8, the multi-stage peak windowing technique proposed in the present invention mitigates excessive suppression of the signal by a relatively large peak, and thus the conventional peak. We can see that the BER performance is better than the Conventional Peak Windowing technique.

In addition, as can be seen in Figure 9, as the window length is longer, the conventional peak windowing technique causes severe performance degradation. However, the multi-stage peak windowing technique of the present invention has a small probability of overlapping peaks when the window length is short, but there is no significant difference from the performance of the conventional technique. However, the longer the window length, the BER performance is improved.

10 and 11 are graphs comparing the EVM performance, and FIG. 12 is a graph showing the spectral performance.

Error Vector Magnitude (EVM) is defined as the Euclidean distance of transmitted and received signals on constellations when signals are transmitted assuming an ideal channel environment. Therefore, EVM is used as a measure of basic performance evaluation of a transmit / receive system. If the transmission signal is called x (n) and the reception signal is y (n), the EVM can be expressed as Equation 4 below.

10 shows EVM reduction with increasing threshold of each PAPR reduction techniques. As can be seen in FIG. 10, the peak windowing technique results in degradation of EVM performance when compared to the clipping technique. However, as can be seen in FIG. 12, the peak windowing technique has excellent spectral performance compared to the clipping technique.

In addition, since the probability that the input signal of the time base generates a peak of 8 dB or more is very small, if the PAPR threshold has a large value of 8 dB or more, the EVM of the two techniques does not show a big difference.

In addition, it can be seen that the multi-stage peak windowing technique of the present invention shows excellent EVM performance compared to the conventional peak windowing technique. When the PAPR threshold is 2 dB, the conventional peak windowing technique and the multi-stage peak windowing technique of the present invention are shown. If the window length W is 65, the difference is more than 0.15 EVM.

11 shows EVM performance with increasing window length. As can be seen in FIG. 11, as the window length increases, the conventional peak windowing technique causes severe performance degradation. On the other hand, the multi-stage peak windowing technique of the present invention is not significantly different from the performance of the conventional technique when the window length is short, but the performance is improved as the window length is longer.

12 shows the spectral performance of the PAPR threshold fixed at 2dB and the clipping technique, the conventional peak windowing technique, and the multistage peak windowing technique proposed by the present invention. As we saw in the comparison of BER performance and EVM performance, the clipping technique has better performance in terms of BER and EVM than the peak windowing technique, but as shown in FIG. 12, the peak windowing technique has superior spectral performance than the clipping technique. It can be confirmed that has.

In addition, the multi-step peak windowing technique of the present invention always exhibits the same spectral performance as the conventional peak windowing technique, regardless of the window length.

As those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features, the embodiments described above should be understood as illustrative and not restrictive in all aspects. Should be. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

Therefore, according to the multi-stage peak windowing method for reducing the PAPR of the OFDMA downlink system of the present invention, in a communication system inducing high PAPR, the peak of a signal exceeding a certain threshold is generated very close to or the amplitude of the adjacent signal among the peaks exceeding the threshold. Compared with the existing peak windowing technique, the PAPR can be effectively reduced when there is a relatively large peak, compared with the conventional peak windowing technique.

Claims (19)

Orthogonal Frequency Division Multiplexing with a PAPR Reduction Unit to reduce the peak-to-average power ratio (PAPR) of the transmission signal by performing peak windowing that lowers the portion of the signal sequence beyond the amplitude threshold of the transmission signal using a given window function In an Orthogonal Frequency Division Multiplexing Access (OFDMA) downlink system, The PAPR reduction unit,

,

,

A threshold adjustment constant storage unit for storing information on a set of threshold adjustment constants {αi} having M threshold adjustment constants α _i as elements; The threshold control constant storage unit is stored in the amplitude threshold value Γ to store amplitude threshold value Γ information, and to perform peak windowing by sequentially applying the M α _i Γ to a signal sequence to perform peak windowing. A threshold controller for sequentially outputting α ₁ Γ to α _M Γ which is a value multiplied by each element α _i of the stored set of threshold adjustment constants; Receiving a signal sequence to perform peak windowing and the threshold α _i Γ output from the threshold controller step by step, detecting a position of a peak having an amplitude greater than or equal to the threshold α _i Γ from the signal sequence, and detecting the signal sequence and the detection. A peak detector for outputting the peak position and the α _i Γ information; According to the information output from the peak detector, the peak windowing is performed by applying the threshold α _i Γ to the signal sequence corresponding to the peak in the signal sequence, and the peak windowing signal sequence is performed in the next step. A peak windowing unit feeding back the peak detection unit as a signal string to be divided; OFDMA downlink system, characterized in that consisting of. The method of claim 1, The peak detector, And a peak position of a signal sample having an amplitude greater than or equal to the threshold α _i Γ and greater than an amplitude of adjacent signal samples among the plurality of signal samples constituting the signal sequence x (n). The method according to claim 1 or 2, The peak detector, And when a signal string for performing peak windowing is input, requesting input of a threshold value to the threshold controller. The method of claim 3, The threshold control unit, Initialize M, the number of peak windowing steps, to the number of elements of the threshold adjustment constant set stored in the threshold adjustment constant storage unit, initialize i value, the index value of the threshold adjustment constant, to 0, and input a threshold value from the peak detection unit. If the request prior to extract a value obtained by adding 1 to the value of i α _i as an index value from the threshold control constant storage section, enter the α _i Γ multiplying the extracted α _i to the amplitude threshold value (Γ) by the peak detector OFDMA downlink system, characterized in that. The method of claim 4, wherein The threshold control unit, Comparing the value obtained by adding 1 to the previous i value with the M value, and when the value obtained by adding 1 to the previous i value is greater than the M value, instructs the peak detector to output a signal, The peak detector, And outputting a previous peak windowed signal according to a signal output instruction from the threshold controller. The method of claim 4, wherein The threshold control unit, When the value of the previous i value plus 1 is compared with the M value, and the value of the previous i value plus 1 is equal to the M value, the peak detection unit indicates that the current i value is equal to the M value. Input the indicating information together with the α _i Γ value, The peak detector, If from the threshold value control information that indicates the current value of i is the same as the value of M when the input together with the α _i Γ value, the α apply _i Γ by peak windowing the signal is the peak fed back from the window ingbu, OFDMA downlink system, characterized in that for outputting a feedback signal. The method of claim 6, The peak detector, When only the α _i Γ value is input from the threshold controller, when the peak windowed signal is fed back from the peak windowing unit by applying the α _i Γ, the threshold controller requests the next α _i Γ for the next step. OFDMA downlink system. The method of claim 1, The OFDMA downlink system, A symbol generator for generating a symbol of a signal to be transmitted to a receiver by scrambling and channel coding a user data binary signal, performing QAM modulation and inverse fast Fourier transform, and inserting a guard interval (CP). An up-sampling unit that performs a sampling and zero-pad process, a symbol filtering unit which obtains intermediate values of added zeros, filters symbols, and inputs them to the PAPR reduction unit, and the PAPR reduction unit A DA converter for converting a digital signal output from the analog signal further, And the PAPR reduction unit performs peak windowing on the signal sequence output from the symbol filtering unit in step M, and outputs the peak windowed signal to the DA converter. The method of claim 1, The peak windowing unit, The scale function s (n) obtained by subtracting the sum of the window function w (n) for peak windowing and the scale value c (n) of the window to be applied to the peak from each time-axis input peak signal sequence at the detected position OFDMA downlink system, characterized in that for performing peak windowing by multiplying &lt; RTI ID = 0.0 &gt; The method of claim 9, The scale value c (n) of the window to be applied to the peak is a value obtained by subtracting the threshold α _i Γ by the amplitude of the input signal from 1. A PAPR reduction unit for reducing peak-to-average power ratio (PAPR) of a transmission signal by performing peak windowing that lowers a portion of a signal string exceeding an amplitude threshold value (Γ) of a transmission signal using a given window function, and reduces the PAPR. Blowing

,

,

A threshold adjustment constant storage unit which stores information on a set of threshold adjustment constants {αi} having M threshold adjustment constants α _i as elements, and each peak using an amplitude threshold value and the threshold adjustment constant. A threshold window that provides a threshold to be applied in the windowing step, a peak detector that detects a peak by applying the threshold provided by the threshold controller, and a peak window by applying the threshold provided by the threshold controller to the detected peak signal. In the Orthogonal Frequency Division Multiplexing Access (OFDMA) downlink system comprising a peak windowing unit for performing a peak, the PAPR reduction unit's peak windowing method, A first step of the threshold controller initializing M, the number of peak windowing steps, to an element number of a set of threshold adjustment constants stored in the threshold adjustment constant storage unit, and initializing i, a index value of the threshold adjustment constant, to 0; and; A second process of requesting input of a threshold value to the threshold controller by the peak detector, when a signal string to perform peak windowing is input; The threshold value control unit extracts α _i, which is an index value of 1 plus a previous i value, from the threshold adjustment constant storage unit, and inputs α _i Γ multiplied by the extracted α _i to an amplitude threshold value Γ to the peak detector. A third process of doing; The peak detector detects a position of a peak having an amplitude equal to or greater than the input threshold α _i Γ from the signal sequence to perform the peak windowing, and extracts the signal sequence, the detected peak position, and the α _i Γ information from the peak window. A fourth process of inputting into a recording part; The peak windowing unit performs peak windowing by applying the threshold α _i Γ to a signal string corresponding to the peak among the signal strings to be subjected to the peak windowing, and performs the peak windowing signal string in a next step. A fifth step of inputting the signal to the peak detector as a signal sequence to be performed and feeding back to the second step; Multi-stage peak windowing for PAPR reduction of an OFDMA downlink system, characterized in that by sequentially suppressing the peak of the signal sequence portion over the amplitude threshold relative to the surrounding signal through the peak windowing over the M stage Way. The method of claim 11, In the fourth process, The peak detector, Multi-step for reducing the PAPR of the OFDMA downlink system, characterized in that for detecting the peak position of the signal sample of the plurality of signal samples constituting the signal sequence is greater than the threshold value α _i Γ and more than the amplitude of the adjacent signal samples as a peak position Peak windowing method. The method according to claim 11 or 12, wherein In the third process, The threshold value control unit compares a value obtained by adding 1 to a previous i value and the M value. When the value obtained by adding 1 to the previous i value is equal to the M value, the current i value is equal to the M value. Multi-step peak windowing method for reducing the PAPR of the OFDMA downlink system, characterized in that to input the information indicating that the same with the α _i Γ to the peak detector. The method of claim 13, In the second process, The peak detector, When information indicating that α _i Γ and a current i value is equal to M is input from the threshold controller in the previous peak windowing step, the peak windowed signal is received from the peak windowing unit in the previous peak windowing step. Multi-step peak windowing method for reducing the PAPR of the OFDMA downlink system, characterized in that when the signal sequence to perform the peak windowing is input, the peak windowing process is terminated and the signal sequence to perform the peak windowing is output as it is. . The method of claim 14, The OFDMA downlink system, A symbol generator for generating a symbol of a signal to be transmitted to a receiver by scrambling and channel encoding a user data binary signal, inserting a guard interval (CP) after QAM modulation and inverse fast Fourier transform, and for easy implementation of an RF stage. An up-sampling unit that performs a sampling and zero-pad process, a symbol filtering unit which obtains intermediate values of added zeros, filters symbols, and inputs them to the PAPR reduction unit, and the PAPR reduction unit A DA converter for converting a digital signal output from the analog signal further, In the second process, The peak detector outputs a signal sequence, which has been subjected to total M phase peak windowing, to the DA converter for the signal sequence output from the symbol filtering unit. . The method according to claim 11 or 12, wherein In the third process, The threshold controller compares a value obtained by adding 1 to a previous i value and the M value, and outputs a signal to the peak detector when the value obtained by adding 1 to the previous i value is greater than the M value. To indicate, In the fourth process, The peak detector, when instructed to output a signal from the threshold controller, terminates the peak windowing process and outputs the signal window peaked at the previous peak windowing step input from the peak windowing unit as it is. Multistage Peak Windowing Method for PAPR Reduction in Downlink Systems. The method of claim 16, The OFDMA downlink system, A symbol generator for generating a symbol of a signal to be transmitted to a receiver by scrambling and channel encoding a user data binary signal, inserting a guard interval (CP) after QAM modulation and inverse fast Fourier transform, and for easy implementation of an RF stage. An up-sampling unit that performs a sampling and zero-pad process, a symbol filtering unit which obtains intermediate values of added zeros, filters symbols, and inputs them to the PAPR reduction unit, and the PAPR reduction unit A DA converter for converting a digital signal output from the analog signal further, In the fourth process, The peak detector outputs a signal sequence, which has been subjected to total M phase peak windowing, to the DA converter for the signal sequence output from the symbol filtering unit. . The method of claim 11, In the fifth process, The peak windowing unit, The scale function s (n) obtained by subtracting the sum of the window function w (n) for peak windowing and the scale value c (n) of the window to be applied to the peak from each time-axis input peak signal sequence at the detected position Multi-step peak windowing method for reducing PAPR of an OFDMA downlink system, wherein The method of claim 18, In the fifth process, The scale value c (n) of the window to be applied to the peak is a value obtained by subtracting the threshold α _i Γ by the amplitude of the input signal from 1 to multi-step peak windowing for reducing the PAPR of the OFDMA downlink system. Way.

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