• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1091-1099
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• 2015

UFMC(Universal-Filtered Multi-carrier) and FBMC(Filter Bank Multi-carrier) system are receiving attention as candidate waveforms for 5G mobile communication system. But, these systems have high PAPR(Peak to Average Power Ratio) problem because these systems use a number of subcarrier. In this paper, we propose DFT(Discrete Fourier Transform) spreading based DFT-s(spreading)-UFMC system and DFT-s-FBMC system in order to overcome the PAPR drawback. In order to evaluate PAPR performance of the proposed systems, we design and simulate OFDM(Orthogonal Frequency Division Multiplexing), UFMC, FBMC, DFT-s-OFDM, DFT-s-UFMC, DFT-s-FBMC system. As simulation results, each PAPR performance of DFT-s-OFDM system, DFT-s-UFMC system, and DFT-s-FBMC system rise by 2.7 dB, 2.8 dB, and 1.1 dB respectively by DFT spreading technique.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.139-145
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• 2008

There has been lots of studies on communication systems using millimeter wave recently in many countries, specially in newly assigned 57GHz ~ 64GHz ISM band. Among those studies, IEEE 802.15.3c standard proposes OFDM (Orthogonal Frequency Division Multiplexing) systems for high data rate transmission support. But OFDM method has the PAPR (peak-to-Average Power Radio) problem The PAPR problem is to decline the performance of the transmission system due to signals distorted severely when passing through nonlinear components such as ADC/DAC and power amplifiers. In order to solve the problem of P APR, this paper suggests SSC (Sine Soft Clipping) and analyzes the PAPR, CCDF, PSD, BER by applying SAW(Surface Acoustic Wave) filter and power amplifiers to IEEE 802.15.3.c OFDM WPAN systems.

• ETRI Journal
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• v.29 no.2
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• pp.231-233
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• 2007

One of the drawbacks in an OFDM system is the high peak-to-average power ratio (PAPR). Among a number of techniques to reduce the high PAPR, simple amplitude predistortion (SAP), a form of active constellation extension, has been proposed to effectively achieve the desired PAPR. In this letter, a novel scheme, simple amplitude and phase predistortion (SAPP), is proposed. In SAP the carriers' amplitude is utilized to combat the peak signal. Each amplitude is amplified according to its degree of contribution as a metric. In addition to amplitude, SAPP also utilizes the phase. Simulation results indicate that the proposed scheme provides better PAPR reduction than SAP.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.15-20
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• 2016

In this paper, we consider selective mapping (SLM) based OFDM systems without side information, where SLM is one of the promising peak-to-average power ratio (PAPR) reduction techniques due to its simplicity and no distortion in the transmitted signal. First, we construct a new phase sequence where a part of phase sequence is replaced by an orthogonal sequence. Based on the proposed phase sequence, we propose a new scheme for detecting coherently the index of the phase sequence used in transmitter without side information. Computer simulation shows that the proposed detection scheme performs well in SLM-based OFDM systems, and specifically outperforms the existing ones when channel variation is relatively small between sub-carriers used in phase sequence detection.

• 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.16 no.10 s.101
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• pp.1028-1035
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• 2005

OFDM system has high PAPR(Peak-to-Average-Power Ratio) problem. In this paper, we present a low complexity phase weighting method to reduce the computational quantity so that we can cut down the processing time of SPW method. Proposed method is derived from the DFT property of periodical sequences by which PAPR can be reduced efficiently. The simulation results show the same PAPR reduction efficiency of proposed method in comparison with conventional methods. It can reduce 2.15 dB of PAPR with two phase factors and 3.95 dB of PAPR with four phase factors. The computation analysis shows significant improvement in the low complexity phase weighting method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1147-1154
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• 2005

In this paper, we propose some PAPR(Peak to Average Power Ratio) reduction methods using WHT(Walsh Hadamard Transform) to reduce high PAPR generated in OFDM system because of multi carrier modulation. These proposed methods are the methods which has additional PAPR reduction performance without a loss of bandwidth efficiency and a large increment of calculation complexity than common PAPR reduction methods by combining the WHT with some common methods. In this paper, we propose two PAPR reduction methods made by combining a SLM(Selective Mapping) and DSI(Dummy Sequence Insertion) with a WHT. From simulation result, we can find that the PAPR reduction methods using a WHT can get about 1 dB additional PAPR reduction performance than common PAPR reduction methods; they are SLM and DSI. And, because our proposed methods have not only PAPR reduction effect, but also frequency diversity effect, more stabile data transmission is possible in nonlinear HPA and multipath fading channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.965-970
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• 2010

Because of a large number of subcarriers, the high PAPR(Peak-to-Average Power Ratio) is the major drawback of NC-OFDM system used for wireless communication system. Comb type pilot assignment is more efficient and lower computational complexity for the channel estimation than the block type pilot. However, even if the CAZAC(Constant Amplitude Zero Autocorrelation) matrix transform is used for the PAPR reduction of the data symbols, PAPR increases when the pilot is inserted in comb type with the data symbols. Therefore, in this paper, we additionally use a new SLM technique in order to lower the PAPR again even in the comb type pilot. Also, a new SLM technique suggested in this paper does not need any additional bandwidth for sending selection information for SLM. This combined method has good PAPR reduction performance and efficient data transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1219-1225
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• 2007

In this paper, we propose a new quasi-orthogonal space-time block code(QO-STBC) achieving full rate and full diversity for general QAM and quasi-static Rayleigh fading channels with four transmit antennas. This code possesses the quasi orthogonal property like the conventional minimum decoding complexity QO-STBC(MDC-QO-STBC), which allows independently a maximum likelihood(ML) decoding to only require joint detection of two real symbols. By computer simulation results, we show that the proposed code exhibits the identical BER performance with the existing MDC-QO-STBC. However, the proposed code has an advantage in the transceiver implementation since the original coding scheme may be modified so that increases of peak-to-average power ratio occur at only two transmit antennas, but the MDC-QO-STBC does at all of transmit antennas.

• The Journal of the Acoustical Society of Korea
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• v.28 no.5
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• pp.432-440
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• 2009

Recently, the necessity of underwater acoustic communication and demand for transmitting and receiving various data such as voice or high resolution image data are increasing as well. The performance of underwater acoustic communication system is influenced by underwater channel characteristic. Especially, a delay spread caused by reverberation and multi-path induces the ISI (Inter-Symbol-Interference) and reduces the communication performance. In this paper, we study the OFDM (Orthogonal Frequency Division Multiplexing) technique for robust the delay spread in underwater channel. We also use the clipping method to overcome the performance degradation in high PAPR (Peak-to-Average Power Ratio). We confirm the performances of underwater communication system by the underwater channel model simulation model and experiment in small water tank. As a result, the multi-carrier modulation with clipping method presented low BER and the previous single carrier modulation had high BER.