• Title/Summary/Keyword: Log-MAP

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Butterfly Log-MAP Decoding Algorithm

  • Hou, Jia;Lee, Moon Ho;Kim, Chang Joo
    • Journal of Communications and Networks
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    • v.6 no.3
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    • pp.209-215
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    • 2004
  • In this paper, a butterfly Log-MAP decoding algorithm for turbo code is proposed. Different from the conventional turbo decoder, we derived a generalized formula to calculate the log-likelihood ratio (LLR) and drew a modified butterfly states diagram in 8-states systematic turbo coded system. By comparing the complexity of conventional implementations, the proposed algorithm can efficiently reduce both the computations and work units without bit error ratio (BER) performance degradation.

Performance Analysis and Efficient Decoding Algorithm for Space-Time Turbo codes (시공간 turbo 부호의 성능 분석과 효율적인 복호 알고리즘)

  • Shin Na na;Lee Chang woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.4C
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    • pp.191-199
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    • 2005
  • Space-time turbo codes have been studied extensively as a powerful and bandwidth efficient error correction code over the wireless communication environment. In this paper, the efficient algorithm for decoding space-time turbo codes is proposed. The proposed method reduces the computational complexity by approximating a prior information for a iterative decoder. The performance of space-time turbo codes is also analyzed by using the fixed point implementation and the efficient method for approximating the Log-MAP algorithm is proposed. It is shown that the BER performance of the proposed method is close to that of the Log-MAP algorithm.

Performance Analysis of OFDM Systems with Turbo Code in a Satellite Broadcasting Channel (위성 방송 채널에서 터보 부호화된 OFDM 시스템의 성능 분석)

  • Kim, Jin-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.9 no.6
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    • pp.175-185
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    • 2009
  • In this paper, performance of OFDM systems with turbo code is analyzed and simulated in a satellite broadcasting channel. The performance is evaluated in terms of bit error probability. The satellite channel is modeled as a combination of Rayleigh fading with shadowing and Rician fading channels. As turbo decoding algorithms, MAP (maximum a posteriori), Max-Log-MAP, and SOVA (soft decision Viterbi output) algorithms are chosen and their performances are compared. From simulation results, it is demonstrated that Max-Log-MAP algorithm is promising in terms of performance and complexity. It is shown that performance is substantially improved by increasing the number of iterations and interleaver length of a turbo encoder. The results in this paper can be applied to OFDM-based satellite broadcasting systems.

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An Analysis of Search Log from a Story Database Service and a New Story Search Method based on Story Map (스토리 검색 서비스의 사용자 기록 분석 및 스토리맵에 의한 새로운 스토리 검색 방법)

  • Kim, Myoung-Jun
    • Journal of Digital Contents Society
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    • v.16 no.5
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    • pp.795-803
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    • 2015
  • is a service providing story synopsis that matches user's query. This paper analyzes the user log of and shows the tendency distribution of user creation in comparison to stories in database. We also investigate the log to see possible improvements on search method. This paper proposes a concept of Story Map, in which the query-answer information is projected into spatial coordinates, and a new story search UI based on it. Using the Story Map, users are able to see entire spatial distribution of story database so that they can quickly and intuitively find a story on the map.

The Method of Analyzing Firewall Log Data using MapReduce based on NoSQL (NoSQL기반의 MapReduce를 이용한 방화벽 로그 분석 기법)

  • Choi, Bomin;Kong, Jong-Hwan;Hong, Sung-Sam;Han, Myung-Mook
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.23 no.4
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    • pp.667-677
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    • 2013
  • As the firewall is a typical network security equipment, it is usually installed at most of internal/external networks and makes many packet data in/out. So analyzing the its logs stored in it can provide important and fundamental data on the network security research. However, along with development of communications technology, the speed of internet network is improved and then the amount of log data is becoming 'Massive Data' or 'BigData'. In this trend, there are limits to analyze log data using the traditional database model RDBMS. In this paper, through our Method of Analyzing Firewall log data using MapReduce based on NoSQL, we have discovered that the introducing NoSQL data base model can more effectively analyze the massive log data than the traditional one. We have demonstrated execellent performance of the NoSQL by comparing the performance of data processing with existing RDBMS. Also the proposed method is evaluated by experiments that detect the three attack patterns and shown that it is highly effective.

Analysis of the performance of Turbo codes on 3GPP2 (3GPP2에 적용된 터보부호의 성능 분석)

  • Hyeon, Seong-Hwan;Lee, Gyeong-Su;Park, Sin-Cheong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.2
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    • pp.1-6
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    • 2000
  • In this paper, simulations are performed using standards proposed by 3GPP and 3GPP2. From the view point of performance analysis based on Turbo code specification, performance of Turbo code in AWGN, proposed by 3GPP, is compared. To make comparison, experimental result of Turbo code that is performed on one of the many block sizes proposed by 3GPP2 in Rayleigh fading channel, is provided. Performance of Turbo decoders using Max_Log MAP and Log MAP are compared.

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Performance Analysis on Various Design Issues of Turbo Decoder (다양한 Design Issue에 대한 터보 디코더의 성능분석)

  • Park Taegeun;Kim Kiwhan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.12A
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    • pp.1387-1395
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    • 2004
  • Turbo decoder inherently requires large memory and intensive hardware complexity due to iterative decoding, despite of excellent decoding efficiency. To decrease the memory space and reduce hardware complexity, various design issues have to be discussed. In this paper, various design issues on Turbo decoder are investigated and the tradeoffs between the hardware complexity and the performance are analyzed. Through the various simulations on the fixed-length analysis, we decided 5-bits for the received data, 6-bits for a priori information, and 7-bits for the quantization state metric, so the performance gets close to that of infinite precision. The MAX operation which is the main function of Log-MAP decoding algorithm is analyzed and the error correction term for MAX* operation can be efficiently implemented with very small hardware overhead. The size of the sliding window was decided as 32 to reduce the state metric memory space and to achieve an acceptable BER.

Turbo Coded OFDM Scheme for a High-Speed Power Line Communication (고속 전력선 통신을 위한 터보 부호화된 OFDM)

  • Kim, Jin-Young;Koo, Sung-Wan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.1
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    • pp.141-150
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    • 2010
  • In this paper, performance of a turbo-coded OFDM system is analyzed and simulated in a power line communication channel. Since the power line communication system typically operates in a hostile environment, turbo code has been employed to enhance reliability of transmitted data. The performance is evaluated in terms of bit error probability. As turbo decoding algorithms, MAP (maximum a posteriori), Max-Log-MAP, and SOVA (soft decision viterbi output) algorithms are chosen and their performances are compared. From simulation results, it is demonstrated that Max-Log-MAP algorithm is promising in terms of performance and complexity. It is shown that performance is improved 3dB by increasing the number of iterations, 2 to 8, and interleaver length of a turbo encoder, 100 to 5000. The results in this paper can be applied to OFDM-based high-speed power line communication systems.

Methods to improve Log-MAP Decoding in Frequency Selective Fading Channels

  • Kim, Jeong-Su
    • Journal of the Korea Society of Computer and Information
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    • v.21 no.9
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    • pp.51-55
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    • 2016
  • High-capacity, high quality services should be guaranteed in mobile communication environment. Excellent channel coding and compensation techniques are required so as to improve data reliability on fading channels. In this paper, we propose a method using double pilots, estimates and compensates for the fading of information symbols. The proposed method using Log-MAP Turbo decoder through the iterative decoder, improves BER performance under the environment of the frequency selective fading channel. Compared to the existing methods, the suggested methods show functional improvement of approximately 3dB in case that the number of iteration decoding is 5 and BER is $10^{-4}$.

An Efficient Method that Incorporate a Channel Reliability to the Log-MAP-based Turbo Decoding (Log-MAP 방식의 Turbo 복호를 위한 효과적인 채널 신뢰도 부과방식)

  • 고성찬;정지원
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.3B
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    • pp.464-471
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    • 2000
  • The number of quantization bits of the input signals $X_k$,$Y_k$ need to be optimally determined through the trade-off between the H/W complexity and the BER performance in Turbo codes applications. Also, an effective means to incorporate a channel reliability $L_c$ in the Log-MAP-based Turbo decoding is highly required. because it has a major effect on both the complexity and the performance. In this paper, a novel bit-shifting approach that substitutes for the multiplying is proposed so as to effectively incorporate. $L_c$ in Turbo decoding. The optimal number of quantization bits of $X_k$,$Y_k$ is investigated through Monte-Carlo simulations assuming that bit-shifting approach is adopted. In addition. The effects of an incorrect estimation of noise variance on the performance of Turbo codes is investigated. There is a confined range in which the effects of an incorrect estimation can be ignored.

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