• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.217-225
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• 2009

Tone injection scheme has been known as one of peak to average power ratio (PAPR) reduction methods deployable to multi-carrier system like orthogonal frequency division multiplexing (OFDM). The basic idea in tone injection scheme is to enforce the constellation size larger so that each of original constellation points is mapped into the preassigned distinct locations. According to the tone injection scheme, it increases symbol power highly induced inherently by expanding constellation to get optimal PAPR reduction. In the other hand, to get optimal power increase, the PAPR would be reduced insufficiently with limited tone injection signal. To withstand these problems, this paper consider the reduction of the PAPR and power increase problem simultaneously, Toward this, the tone injection scheme accomplished by employing the weighted sum genetic algorithm which has been utilized to solve multi-objective optimization problem (MOOP). The simulation results verifies that the proposed scheme can control the effective PAPR performance and alleviation of power increase flexibly by the weight value at the expense of relatively low complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.163-169
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• 2011

Partial transmit sequence (PTS) algorithm is known as one of the most efficient ways to reduce the peak-to-average power ratio (PAPR) in the orthogonal frequency division multiplexing (OFDM) system. The PTS algorithm, however, requires large numbers of computation to implement. Thus there has been a trade-off between performance of PAPR reduction and computational complexity. In this paper, the performance of PAPR reduction and computation complexity of PTS algorithms are analyzed and compared through computer simulations. Subsequently, a new PTS algorithm is proposed which can be a reasonable method to reduce the PAPR of OFDM when both the performance of PAPR reduction and computational complexity are considered simultaneously.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.583-591
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• 2008

OFDM (orthogonal frequency division multiplexing) has serious problem of high PAPR (peak-to-average power ratio). Recently, CI/OFDM (carrier interferometry OFDM) system has been proposed for the low PAPR. However, CI/OFDM system shows another problem of ICI because of phase offset mismatch due to the phase noise. In this paper, to simultaneously reduce the PAPR and ICI effects, we propose an A-CI/OFDM (advanced-CT/OFDM). This method improves the BER performance by use of the margin of phase offset at CI codes. Propose system to reduce the effect the phase noise, even though it shows a little bit higher PAPR than conventional CI/OFDM, so we apply the PTS among the PAPR reduction techniques to proposed system to mitigate this problem. Therefore, it improves the total BER performance because the proposed method can decrease the effect of phase noise and get the gain in PAPR reduction performance. From the simulation results, we can show the performance comparison between the conventional OFDM, CI/OFDM and A-CI/OFDM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.690-696
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• 2005

It is very important to reduce the PAPR(Peak to Average Power Ratio) in the OFDM(Orthogonal Frequency Division Multiplexing) communication system. The proposed method in this paper is an effective PAPR reduction method using the Golay complementary codes without my side information. There are some PAPR reduction methods with the complementary code pairs or sequences. They are usually a type of the forward ewer correction codes so that they produce more redundancies and lower down the code rate. Because of this, the information rate may be cut down or more bandwidth must be required. In this paper, we propose a PAPR reduction method that uses the multi-phase complementary code f3r converting the 4-QAM into 16-QAM constellation. It does not change the code rate and does not require the side information.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1239-1247
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• 2003

OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmission in the frequency selective lading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose the DSI(dummy sequence insertion) method for OFDM communication system. Some sub-carriers are inserted for PAPR reduction. They carry the specified dummy data sequence which are used for only PAPR reduction and do not work as side information like the conventional PTS(partial transmit sequence) or SLM(selected mapping) method. We use the complementary sequence and the combination of the correlation sequence as the dummy sequence. Flipping technique is used for the DSI method to get the effective PAPR reduction. It is important that BER of the proposed method is independent of the damage of the dummy data sequence. And DSI method has better spectral efficiency than the conventional block coding. On the other hand, threshold PAPR method is applied to cut down the processing time. However, this DSI method is not better than the conventional PTS method in the respect of the PAPR reduction performance. The DSI method includes the threshold PAPR lower than the PAPR of the OFDM signal, reduces the processing time and improves the BER performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1172-1180
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• 2007

OFDM system has very good high spectral efficiency and the robustness to the frequency-selective fading. Because of the high PAPR, OFDM signals can be distorted in nonlinear HPA(High Power Amplifier). So, to overcome the nonlinear distortion, it is very important to reduce the IMD value. With respect to the BER performance, IMD reduction method is better than the PAPR reduction method. However, IMD reduction method has much more system complexity because of the additional FFT processor in transmitter. In this paper, we study the OFDM communication system based on the IMD reduction method using SPW method. A new IMD reduction method is proposed to reduce the computational complexity. SPW method is to divide the input OFDM data into several sub-blocks and to multiply phase weighting values with each sub-blocks for the reduction of PAPR or IMD. Unlike the conventional method, the system size and computational complexity can be reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1548-1553
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• 2000

In this paper, an effective peak power reduction scheme for a downlink OFDM-CDMA system is proposed. Using the partial parallel transform(PPT) structure, peak-to-average power ratio(PAPR) can be reduced. The patterns of inputs of Inverse Fast Fourier Transform(IFFT) are more randomized in this structure by allotting the subcarriers to each users. At the cost of complexity we can obtain reduced PAPR and multiple access interference(MA) Computer simulations are carried out from the viewpoint of PAPR and demonstrated the improved PAPR performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.976-984
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• 2006

OFDM system is very useful for the high speed communication system. However, OFDM system has a serious problem of high PAPR that results from the so many subcarriers in the same phase. This OFDM signal is distorted through the nonlinear HPA(High Power Amplifier). Tone reservation method is to insert tone signal in several types to reduce the PAPR after iterating this process by changing the tone signal. Also discrete cosine transform(DCT) can reduces the PAPR as multiplying the cosine value to change the angle and mix up with the data. In the paper, the combination of the TR method and DCT method is newly proposed for more effective reduction of the PAPR. Simulation results show that the proposed method outperforms the conventional simple TR method and DCT method with respect to the PAPR reduction and BER performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.586-593
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• 2005

It is very important to reduce the PAPR(Peak to Average Power Ratio) in the OFDM(Orthogonal Frequency Division Multiplexing) communication system. We propose an ACE(Active Constellation Extension) method that does not require the side information unlike the conventional PTS and SLM method. This ACE method is to clip the OFDM signal for the PAPR reduction. Then, the basic constellation actively moves into the higher level of M-QAM for the constellation extension due to the clipping. The already existing M-QAM system can be available so that it can be easily realized. So, we can get the target PAPR by the extension of the constellation level. In this paper, we can find the PAPR reduction of 4 dB by the 16-QAM extension, and can achieve the target PAPR by the 64-QAM ACE(Active Constellation Extension).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.200-220
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• 2016

Orthogonal frequency division multiplexing (OFDM) signals suffer from the problem of large peak-to-average power ratio (PAPR) which complicates the design of the analog front-end of the system. Companding is a well-known PAPR reduction technique that reduces the PAPR by transforming the signal amplitude using a deterministic function. In this paper, a novel piecewise linear companding transform is proposed. The design criteria for the proposed transform is developed by investigating the relationships between the compander and decompander's profile and parameters with the system's performance metrics. Using analysis and simulations, we relate the companding parameters with the bit error rate (BER), out-of-band interference (OBI), amount of companding noise, computational complexity and average power. Based on a set of criteria developed thereof, we formulate the design of the proposed transform. The main aim is to preserve the signal's attributes as much as possible for a predetermined amount of PAPR reduction. Simulations are carried out to evaluate and compare the proposed scheme with the existing companding transforms to demonstrate the enhancement in PAPR, BER and OBI performances.