• Title/Summary/Keyword: Code Rate

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A Novel M-ary Code-Selected Direct Sequence BPAM UWB Communication System

  • Bai, Zhiquan;Kwak, Kyung-Sup
    • ETRI Journal
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    • v.28 no.1
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    • pp.95-98
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    • 2006
  • In this letter, a novel M-ary code-selected direct sequence (DS) ultra-wideband (UWB) communication system is presented. Our purpose is to achieve a high data rate by an M-ary code-selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence is selected by the $log_2M$/2 bits from the DS gold code set. This scheme can accomplish both a high data rate without increasing the system bandwidth or changing the pulse shape and improve the BER with an increase of modulation level M even at a lower signal-to-noise ratio (SNR). The receiver signal processing algorithm is given for an MCSDS-BPAM UWB system over an ideal AWGN channel and correlation receivers.

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On a Reduced-Complexity Inner Decoder for the Davey-MacKay Construction

  • Jiao, Xiaopeng;Armand, M.A.
    • ETRI Journal
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    • v.34 no.4
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    • pp.637-640
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    • 2012
  • The Davey-MacKay construction is a promising concatenated coding scheme involving an outer $2^k$-ary code and an inner code of rate k/n, for insertion-deletion-substitution channels. Recently, a lookup table (LUT)-based inner decoder for this coding scheme was proposed to reduce the computational complexity of the inner decoder, albeit at the expense of a slight degradation in word error rate (WER) performance. In this letter, we show that negligible deterioration in WER performance can be achieved with an LUT as small as $7{\cdot}2^{k+n-1}$, but no smaller, when the probability of receiving less than n-1 or greater than n+1 bits corresponding to one outer code symbol is at least an order of magnitude smaller than the WER when no LUT is used.

Design and Implementation of Rain Fade Countermeasure Scheme for Ka-band Satellite System with DVB-RCS (DVB-RCS Ka 대역 위성 지구국 시스템에서의 강우감쇠 보상기법 구현)

  • Shin, Min-Su;Jin, Kwang-Ja;Lee, Ho-Jin
    • Proceedings of the KIEE Conference
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    • 2002.11c
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    • pp.210-213
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    • 2002
  • This paper addresses the design and implementation of compensation of rain attenuation for Ka-band satellite communication system complied with DVB-RCS[2]. A structure of rain fade compensation scheme in the Ka-band satellite communication system is presented. Rain fade compensation scheme in this paper is mainly applied into return-link, which is the path through which user terminal transmit the data tn hub system providing a service. Symbol rate and code rate of channel code are used as variable transmission parameter for rain fade compensation. For estimation of channel environment, SNR of the user terminal which is measured by demodulator of hub system is used. Rain fade compensation scheme in the paper changes the symbol rate and/or code rate according to the measured SNR so that it can compensate the attenuation of the signal.

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Performance Analysis of Holographic Data Storage Depending on the Number of Levels Per Pixel of the Code Rate 1/2 Modulation Codes (부호율 1/2인 변조부호의 픽셀당 레벨 수에 따른 홀로그래픽 데이터 저장장치 성능 분석)

  • Jeong, Seongkwon;Lee, Jaejin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.10
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    • pp.16-20
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    • 2015
  • We propose three multi-level modulation codes of the code rate 1/2 for holographic data storage considered as a promising candidate for next generation storage systems. Since a pixel with multi-levels can represent more than 1 bit, it is possible to increase the storage capacity and have many codewords. Thus, we can choose a code that the minimum distance is as far as possible. When we compare the codes with the code rate 1/2, the performance of the code with small number of levels is better than that of large number of levels.

Code Acquisition with Receive Diversity and Constant False Alarm Rate Schemes: 1. Homogeneous Fading Circumstance (수신기 다양성과 일정 오경보 확률 방법을 쓴 부호획득: 1. 균질 감쇄 환경)

  • Kwon Hyoung-Moon;Oh Jong-Ho;Song Iick-Ho;Lee Ju-Mi
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.4C
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    • pp.371-380
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    • 2006
  • The performance characteristics of the cell averaging(CA), greatest of(GO), and smallest of(SO) constant false alarm rate(CFAR) processors in homogeneous environment are obtained and compared when receiving antenna diversity is employed in the pseudonoise code acquisition of direct-sequence code division multiple access (DS/CDMA) systems. From the simulation results, it is observed that the CA CFAR scheme has the best performance and the GO CFAR scheme has almost the same performance as the CA CFAR scheme in homogeneous environment. In Part 2 of this paper, the CA, GO, and SO CFAR processors for code acquisition in nonhomogeneous environment are addressed.

Evaluation of the radiation damage effect on mechanical properties in Tehran research reactor (TRR) clad

  • Amirkhani, Mohamad Amin;Khoshahval, Farrokh
    • Nuclear Engineering and Technology
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    • v.52 no.12
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    • pp.2975-2981
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    • 2020
  • Radiation damage is one of the aging important causes in nuclear reactors. Radiation damage causes changes in material properties. In this study, this effect has been evaluated and analyzed on the clad of the Tehran research reactor (TRR). A grade 6061 aluminum is used as a clad in the TRR. The MCNPX code is used to designate the most sensitive location of the reactor and calculate neutron flux distribution. Then, a software using FORTRAN language programming is developed to process the particle track (PTRAC) output file of the MCNPX code. The SRIM code is used here to calculate the rate of displacement per atom. Moreover, the SPECOMP and SPECTER codes are also applied to estimate the displacement rate and compared with the results attained using the SRIM code. The rate of displacement per atom by the SPECTER and SRIM codes have been obtained 2.54 × 10-7 dpa/s and 2.44 × 10-7 dpa/s (QD method), respectively. Also, the mechanical properties have been evaluated using the RCC-MRx code and have been compared with experimental results. Finally, the change in the matter specification has been analyzed as a function of time.

Effective identification of dominant fully absorbing sets for Raptor-like LDPC codes

  • Woncheol Cho;Chanho Yoon;Kapseok Chang;Young-Jo Ko
    • ETRI Journal
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    • v.45 no.1
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    • pp.7-17
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    • 2023
  • The error-rate floor of low-density parity-check (LDPC) codes is attributed to the trapping sets of their Tanner graphs. Among them, fully absorbing sets dominantly affect the error-rate performance, especially for short blocklengths. Efficient methods to identify the dominant trapping sets of LDPC codes were thoroughly researched as exhaustively searching them is NP-hard. However, the existing methods are ineffective for Raptor-like LDPC codes, which have many types of trapping sets. An effective method to identify dominant fully absorbing sets of Raptor-like LDPC codes is proposed. The search space of the proposed algorithm is optimized into the Tanner subgraphs of the codes to afford time-efficiency and search-effectiveness. For 5G New Radio (NR) base graph (BG) 2 LDPC codes for short blocklengths, the proposed algorithm finds more dominant fully absorbing sets within one seventh of the computation time of the existing search algorithm, and its search-effectiveness is verified using importance sampling. The proposed method is also applied to 5G NR BG1 LDPC code and Advanced Television Systems Committee 3.0 type A LDPC code for large blocklengths.

Performance Comparison of Turbo Codes at Various Puncturing Rates (다양한 부호율로 펑처링된 터보 부호의 성능 비교)

  • 권이경;송홍엽
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.7A
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    • pp.1074-1079
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    • 1999
  • In this paper, the concept of puncturing is introduced to turbo code in order to implement various code as code rate varies.rates. First, several different puncturing matrices are applied into rate 1/3 encoder in order to produce various rate 1/2 turbo codes. By analyzing and comparing these results, we can show which puncturing pattern should be selected in order to maintain good performance. Second, we select some appropriate puncturing patterns which provide the best performance of turbo codes of various rates from 1/3 to 2/3 among all the possible candidates. Finally, we provide the change of required Eb/No at $P_b=10^{-4}$ as code rate varies.

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Performance Enhancement of SBC for Voice Signal Using Adaptive Postfiltering at the Medium Bit Rate (중간 전송율에서 적응 포스트 필터링을 이용한 음성용 SBC의 성능 향상)

  • 김원구;이남걸;윤대희;차일환
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.17 no.2
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    • pp.121-131
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    • 1992
  • In this paper, three methods are studied to enhance the performance of SBC ( Sub-Band Coding )schemes for voice signal at the medium bit rate between 12 kbps and If; kbps, and adaptive postfilteritng using human auditory characteristics Is (Bone at the decoder out put. First, GQMF(Generalized Quadrature Mirror Filter ) Is used instead of QME'((Quadrature MirrorFiltcr ) to have better performance. Second, by adaptive bit allocation to each sub-band, speech quality is enhanced and valuable rate ceding If possible. Third, corriparlson study oS thr: coder performance using APCM(Adaptive Pulse Code ModulatioTi) and ADPCM( Adaptive Differentiai Pulse Code Modulatiori) , Indicates that SB AfCM performance better than the other. Adaptive postfiltering at the decoder output enhances the quality of the coded speech. The two proposed postfiltering methods decrease the noise sufficiently at the expense of the low computational load.

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Recognition Performance Improvement of QR and Color Codes Posted on Curved Surfaces (곡면상에 부착된 QR 코드와 칼라 코드의 인식률 개선)

  • Kim, Jin-soo
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.3
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    • pp.267-275
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    • 2019
  • Currently, due to the widespread use of a smartphone, QR codes allow users to access a variety of added services. However, the QR codes posted on curved surfaces tend to be non-uniformly illuminated and bring about the decline of recognition rate. So, in this paper, the block-adaptive binarization policy is adopted to find an optimal threshold appropriate for bimodal image like QR codes. For a large block, its histogram distribution is found to get an initial threshold and then the block is partitioned to reflect the local characteristics of small blocks. Also, morphological operation is applied to their neighboring boundary at the discontinuous at the QR code junction. This paper proposes an authentication method based on the color code, uniquely painted within QR code. Through a variety of practical experiments, it is shown that the proposed algorithm outperforms the conventional method in detecting QR code and also maintains good recognition rate up to 40 degrees on curved surfaces.