• Title, Summary, Keyword: SLM

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A Low Complexity SLM-PRSC Hybrid Scheme for OFDM PAPR Reduction (OFDM 신호의 PAPR 감소를 위한 저복잡도의 SLM-PRSC 결합 기법)

  • Han, Seung-Woo;Yang, Suck-Chel;Shin, Yo-An
    • Proceedings of the IEEK Conference
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    • pp.21-22
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    • 2006
  • In this paper, to improve OFDM PAPR reduction performance of the conventional SLM method, we propose an effective SLM-PRSC hybrid scheme based on the repeated utilization of identical PRSC sequences in time domain. In the proposed scheme, after performing the SLM for the frequency domain OFDM symbol excluding the pre-determined PRSC positions, the final SLM-PRSC hybrid sequence with the lowest PAPR, which is generated by adding the time domain PRSC sequence to the results of the SLM is selected as the transmitted OFDM symbol. In particular, since the identical PRSC sequences generated a priori are repeatedly used for every OFDM symbol, excessive IFFT calculations are avoided. Moreover, the selected PRSC symbols in the frequency domain may be utilized as an overhead information for the SLM. Simulation results reveal that the proposed SLM-PRSC hybrid scheme can remarkably improve the PAPR reduction performance of the conventional SLM, while avoiding excessive increase of IFFT and PAPR calculations and the overhead for the SLM.

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An SLM-PRSC Hybrid Scheme for PAPR Reduction of OFDM Signals (OFDM 신호의 PAPR 감소를 위한 SLM-PRSC 결합 기법)

  • Yang, Suck-Chel;Han, Seung-Woo;Shin, Yo-An
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.6C
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    • pp.565-571
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    • 2007
  • In order to improve PAPR (Peak-to-Average Power Ratio) reduction performance of the conventional SLM (Selective Mapping) for OFDM (Orthogonal Frequency Division Multiplexing) signals, we propose an effective SLM-PRSC (PAPR Reduction Sub-Carrier) hybrid scheme. In the proposed scheme, after performing the SLM for the frequency domain OFDM symbol excluding pre-determined PRSC positions, the SLM-PRSC hybrid sequence with the lowest PAPR generated by adding the time domain PRSC sequence to the results of the SLM, is selected as the transmitted OFDM signal. Since the identical PRSC sequences generated a priori are repeatedly used for every OFDM symbol, excessive IFFT (inverse Fast Fourier Transform) calculation is avoided. Simulation results show that the proposed scheme significantly improves the PAPR reduction performance of the conventional SLM, while avoiding excessive increase of IFFT calculation and the overhead for the SLM.

Performance Analysis of the Symbol Grouping SLM Scheme for PAPR Reduction of OFDM System (OFDM시스템의 PAPR 저감을 위한 심벌 그룹핑 SLM 기법의 성능분석)

  • Choi Ik-Young;Son Sung-Chan;Oh Chang-Heon
    • Journal of Digital Contents Society
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    • v.5 no.2
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    • pp.143-150
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    • 2004
  • In this paper, we propose and analyze a new scheme which uses the same scramble codes to each group after symbol grouping to reduce the PAPR (peak-to-avenge power ratio) problem in OFDM system. The conventional SLM scheme randomizes OFDM symbols entered into IFFT block by several scramble codes and then transmits the lowest one among PAPRs. Therefore, the SLM scheme can reduce the additional information as many as the number of grouped OFDM symbols by using same scramble codes after M grouping of sub-carriers. It can also improve PAPR performance more than conventional SLM scheme when we use scramble codes as same as those numbers of SLM scheme.

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A low-complexity PAPR reduction SLM scheme for STBC MIMO-OFDM systems based on constellation extension

  • Li, Guang;Li, Tianyun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.6
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    • pp.2908-2924
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    • 2019
  • Multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is widely applied in wireless communication by virtue of its excellent properties in data transmission rate and transmission accuracy. However, as a major drawback of MIMO-OFDM systems, the high peak-to-average power ratio (PAPR) complicates the design of the power amplifier at the receiver end. Some available PAPR reduction methods such as selective mapping (SLM) suffer from high computational complexity. In this paper, a low-complexity SLM method based on active constellation extension (ACE) and joint space-time selective mapping (AST-SLM) for reducing PAPR in Alamouti STBC MIMO-OFDM systems is proposed. In SLM scheme, two IFFT operations are required for obtaining each transmission sequence pair, and the selected phase vector is transmitted as side information(SI). However, in the proposed AST-SLM method, only a few IFFT operations are required for generating all the transmission sequence pairs. The complexity of AST-SLM is at least 86% less than SLM. In addition, the SI needed in AST-SLM is at least 92.1% less than SLM by using the presented blind detection scheme to estimate SI. We show, analytically and with simulations, that AST-SLM can achieve significant performance of PAPR reduction and close performance of bit error rate (BER) compared to SLM scheme.

디지털 홀로그래피를 위한 SLM 기술

  • Kim, Yong-Hae;Hwang, Chi-Seon;Chu, Hye-Yong
    • Information and Communications Magazine
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    • v.31 no.2
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    • pp.21-28
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    • 2014
  • 본고에서 디지털 홀로그래피를 위한 SLM중 대표적인 몇 가지 기술에 대한 동향을 살펴보았다. 먼저 SLM픽셀 피치에 따른 홀로그램 영상의 특성에 대해 논의하고, 픽셀화된 SLM으로써 현재 상용화 되고 있는 DMD SLM 과 LCoS SLM의 특성에 대해 살펴 보았다. 픽셀화 되지 않은 SLM 인 음향 광학 변조기와 OASLM 에 대해서도 살펴 보았다. 양질의 디지털 홀로그래피를 구현하기 위하여 궁극적으로 필요한 픽셀 피치 1 ${\mu}m$ 이하 SLM 의 개발 현황과 복소 변조 SLM 에 대해서도 알아보았다.

A Computational Complexity Reduction Scheme for SLM Based OFDM Communication Systems (SLM 기반의 OFDM 통신 시스템을 위한 계산 복잡도 저감 기법)

  • Cho, Soo-Bum;Hyun, Kwang-Min;Park, Sang-Kyu
    • Journal of Internet Computing and Services
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    • v.13 no.2
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    • pp.13-20
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    • 2012
  • SLM (Selected Mapping) is an efficient PAPR (Peak-to-Average Power Ratio) reduction scheme without transmitted signal distortion in OFDM (Orthogonal Frequency Division Multiplexing) systems. However, enormous IFFTs (Inverse Fast Fourier Transforms) are needed to generate sufficient candidate OFDM signals, which cause the SLM to become quite complex. In this paper, we propose a new SLM scheme that replaces the IFFT operations with a conversion of the first candidate OFDM signal. The proposed scheme significantly reduces computational complexity, while it shows almost the same PAPR performance as the conventional SLM scheme.

홀로그램 단말을 위한 LC기반 대면적 SLM 기술

  • Hwang, Chi-Seon;Kim, Yong-Hae;Kim, Gi-Hyeon;Byeon, Chun-Won;O, Him-Chan;Pi, Jae-Eun;Choe, Ji-Hun;Kim, Jin-Ung
    • Information and Communications Magazine
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    • v.32 no.3
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    • pp.44-51
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    • 2015
  • 디지털 홀로그램 디스플레이는 SLM을 이용하여 홀로그램 영상을 구현하므로, 홀로그램 영상의 품질은 SLM에 의하여 제한되게 된다. 따라서, 대면적 광시야각의 홀로그램 단말을 개발하기 위해서는 대면적 초고해상도의 SLM이 필수적이다. 그런데, 지금까지의 홀로그램은 주로 상용 SLM인 LCoS나 DMD를 기반으로 구현되었다. 이러한 상용 SLM의 경우에는 패널의 크기가 작고 픽셀 피치가 커서, 대면적으로 홀로그램 영상을 구현하는 것과 광시야각을 구현하는 데 있어서는 아직까지 한계를 보이고 있으며, 이에 따라 대면적 초고해상도의 SLM 개발이 요구되고 있다. 본고에서는 지금까지 홀로그램 디스플레이를 구현하는데 이용되어온 주요한 SLM인 LCoS, DMD, LCD등에 대하여 살펴보고, 이러한 SLM이 가진 한계를 극복할수 있는 기술로 대면적 디스플레이 기술을 기반으로 LCoS 기술을 구현하고자하는 SLMoG 기술에 대하여 소개고자 한다.

Extraction of Short Peptide Using Supported Liquid Membranes (Supported Liquid Membrane을 이용한 Short Peptide의 추출)

  • Lee, Jae-Heung;Park, Ki-Moon
    • Food Science of Animal Resources
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    • v.25 no.3
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    • pp.340-343
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    • 2005
  • The objective of this work was to study separation of short peptide (glycine-tyrosine) by using supported liquid membranes (SLMs) containing Aliquat as a cationic carrier, In the present investigation, the influence of pH of donor phase, concentrations of carrier and salt concentrations of acceptor phase on separation flux rate were investigated. Below pH 7.0 the flux rate was not affected by NaCl concentration or carrier concentration. However, the rate was increased significantly above pH 7.0. The rate with Hossain's SLM(H-SLM) containing $20\%$ Aliquat was about 3-fold higher with pH 9.0 at 0.25 M NaCl and 10-fold higher with pH 8.0 at 1.0 M NaCl than that with Duggan's SLM(D-SLM) containing $8\%$ Aliquat respectively. Furthermore, the rate with H-SLM was 10-fold higher at 1.0 M NaCl than the rate with 0.25 M NaCl, In conclusion, it would appear that the rate of separation was facilitated by using high salt concentrations together with high carrier concentrations above pH 7.0.

Implementation of Spatial Light Modulator(SLM) using a Commercial LCD Beam Projector

  • Ko, Jung-Hwan;Lee, Jae-Soo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.9
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    • pp.1-10
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    • 2006
  • In this paper, a new high resolution XGA-SLM is implemented through modification of a commercial TFT-LCD beam projector and its optical modulation characteristics as a spatial light modulator(SLM) is also analyzed. First, the optics module, projection lamp and fans are removed from a commercial beam projector and instead some electric circuits to compensate their removal are manufactured and then, by inserting them into the beam projector, a new XGA-SLM is finally implemented. Second, from some optical experimental results, this TFT-SLM is found to have a good optical linearity in amplitude and phase modulation characteristics as a function of the input gray levels. Especially, through implementation of a binary phase-type correlator such as BPEJTC by using the suggested TFT-LCD panel, the implemented SLM is proposed as a new relatively low-cost and high resolution SLM for optical information processing.

Adaptive SLM and Side Information Insertion Method (적응 SLM 방식과 부가정보 삽입기법)

  • 정락규;유흥균
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.3
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    • pp.276-282
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    • 2003
  • OFDM is effective for the high speed data transmission. However, the nonlinear distortion is a serious problem because of the high PAPR due to many subcarriers. The conventional SLM selects the OFDM signal with the lowest PAPR. In this method, OFDM data can be correctly recovered only if the side information about the phase sequence is transmitted to receiver. This paper proposes a new method of side information insertion into the conventional SLM and reduces the computational complexity by adaptive method. Performances are compared in case that three kinds of phase sequences are used for phase rotation factor. The adaptive SLM method has the same PAPR reduction as the conventional SLM method. The required BER can be guaranteed by the proposed method. When subcarrier number N=32, computational complexity is reduced to 48 %, 72 % and 51 % for the branch number U=4, 8 and 16, respectively.