• Title/Summary/Keyword: code combining

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Code Combining Cooperative Diversity in Long-haul Transmission of Cluster based Wireless Sensor Networks

  • Asaduzzaman, Asaduzzaman;Kong, Hyung-Yun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.5 no.7
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    • pp.1293-1310
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    • 2011
  • A simple modification of well known Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is proposed to exploit cooperative diversity. Instead of selecting a single cluster-head, we propose M cluster-heads in each cluster to obtain a diversity of order M. The cluster-heads gather data from all the sensor nodes within the cluster using same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative diversity protocol which is similar to coded cooperation that maximizes the performance of the proposed cooperative LEACH protocol. The implementation of the proposed cooperative strategy is analyzed. We develop the upper bounds on bit error rate (BER) and frame error rate (FER) for our proposal. Space time block codes (STBC) are also a suitable candidate for our proposal. In this paper, we argue that the STBC performs worse than the code combining cooperation.

The Softest handoff Design using iterative decoding (Turbo Coding)

  • Yi, Byung-K.;Kim, Sang-G.;Picknoltz, Raymond-L.
    • Journal of Communications and Networks
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    • v.2 no.1
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    • pp.76-84
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    • 2000
  • Communication systems, including cell-based mobile communication systems, multiple satellite communication systems of multi-beam satellite systems, require reliable handoff methods between cell-to-cell, satellite-to-satellite of beam-to-team, respectively. Recent measurement of a CDMA cellular system indicates that the system is in handoff at about 35% to 70% of an average call period. Therefore, system reliability during handoff is one of the major system performance parameters and eventually becomes a factor in the overall system capacity. This paper presents novel and improved techniques for handoff in cellular communications, multi-beam and multi-satellite systems that require handoff during a session. this new handoff system combines the soft handoff mechanism currently implemented in the IS-95 CDMA with code and packet diversity combining techniques and an iterative decoding algorithm (Turbo Coding). the Turbo code introduced by Berrou et all. has been demonstrated its remarkable performance achieving the near Shannon channel capacity [1]. Recently. Turbo codes have been adapted as the coding scheme for the data transmission of the third generation international cellular communication standards : UTRA and CDMA 2000. Our proposed encoder and decoder schemes modified from the original Turbo code is suitable for the code and packet diversity combining techniques. this proposed system provides not only an unprecedented coding gain from the Turbo code and it iterative decoding, but also gain induced by the code and packet diversity combining technique which is similar to the hybrid Type II ARQ. We demonstrate performance improvements in AWGN channel and Rayleigh fading channel with perfect channel state information (CSI) through simulations for at low signal to noise ratio and analysis using exact upper bounding techniques for medium to high signal to noise ratio.

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Sign Reversal Channel Switching Method for Space-Frequency Block Code in Orthogonal Frequency Division Multiplexing System (직교 주파수 분할 다중화 시스템의 공간 주파수 블록 코딩에서의 부호 반전 채널 스위칭 기법)

  • Jung, Hyeok-Koo
    • Journal of Korea Society of Industrial Information Systems
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    • v.25 no.5
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    • pp.13-21
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    • 2020
  • This paper proposes a sign reversal channel switching method in space-frequency block code for orthogonal frequency division multiplexing system. In case of sending source data on other antenna, it is necessary for the receiver to change combining method according to the channel variation. If one does not know the predefined channel switching sequence, it is not possible to decode the received data precisely. In transmit data symbols' exchanges for a channel switching, data symbols are exchanged according to a format of space-frequency block code. In this paper, we proposes a simple sign reversal method except exchanging data symbols between transmit antennas. It is shown that this method occurs another combining method for a simple encryption in the receiver.

Approximate Expression of Bit Error Rate in Uplink MC-CDMA Systems with Equal Gain Combining

  • Develi, Ibrahim;Akdagli, Ali
    • Journal of Communications and Networks
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    • v.15 no.1
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    • pp.25-30
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    • 2013
  • Uplink multicarrier code-division multiple-access (MC-CDMA) with equal gain combining (EGC) over Nakagami fading channels is considered. An improved expression which is a feasible alternative for the bit error rate (BER) performance evaluation of MC-CDMA signals is proposed. Simulated annealing algorithm is employed to obtain the optimum value of the coefficients belonging to the proposed expression. Numerical examples show that the performance curves computed by the improved expression are in good agreement with the results obtained by the exact expression. Thus, the proposed expression can improve the accuracy of BER performance evaluation that has been realized by the approximate expression.

A Combining Scheme to Reduce Power Consumption in Cooperation and Cyclic Code for Wireless Sensor Networks (협력-순환 부호를 이용한 무선 센서 네트워크에서의 전력 소모 감소를 위한 결합기법에 관한 연구)

  • Kong, Hyung Yun;Hwang, Yun Kyeong;Hong, Seong Wook
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.8 no.6
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    • pp.63-69
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    • 2008
  • In this paper, our goal is to find a power-effective protocol that improves the accuracy of transmission in sensor networks. Therefore we propose a cooperative communication protocol based on MRC(Maximal Ratio Combining) and cyclic code. In our proposal, one sensor node assists two others to communicate with a clusterhead that can get diversity effect and MRC can improve diversity effect also. The proposed protocol with cyclic code can correct error up to 3-bit and reduce decoding complexity compared with convolutional code. Simulation results reveal proposed protocol can save the network energy up to 6dB over single-hop protocol at BER(Bit Error Rate) of $10^{-2}$.

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A Study on Joint Coding System using VF Arithmetic Code and BCH code

  • Sukhee Cho;Park, Jihwan;Ryuji Kohno
    • Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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    • 1998.12a
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    • pp.537-545
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    • 1998
  • This paper is the research about a joint coding system of source and channel coding using VF(Variable-to-fixed length) arithmetic code and BCH code. We propose a VF arithmetic coding method with EDC( Error Detecting Capability) and a joint coding method in that the VF arithmetic coding method with EDC is combined with BCH code. By combining both the VF arithmetic code with EDC and BCH code. the proposed joint coding method corrects a source codeword with t-errors in decoding of BCH code and carries out a improvement of the EDC of a codeword with more than (t+1)-errors in decoding of the VF arithmetic coding with EDC. We examine the performance of the proposed method in terms of compression ratio and EDC.

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Differential Code-Filtering Correlation Method for Adaptive Beamforming

  • Hefnawi Mostafa;Denidni Tayeb A.
    • Journal of Communications and Networks
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    • v.7 no.3
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    • pp.258-262
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    • 2005
  • An adaptive beamforming system based on code filtering and differential correlation approaches is proposed. The differential correlation method was originally proposed for time delay estimation of direct sequence code division multiple access (DS-CDMA) systems under near-far ratio conditions and the code filtering correlation algorithm, on the other hand, was proposed for array response estimation in DS-CDMA systems under perfect power control. In this paper, by combining differential correlation concept with the code filtering beamforming technology, an accurate estimate of the beam forming weights and an enhanced performance of DS-CDMA systems under sever near-far ratio conditions is achieved. The system performance in terms of beam pattern and bit-error-rate (HER) shows that the proposed adaptive beamformer outperforms the conventional code filtering correlation technique.

Optimum and Sub-optimum Decoding Methods of Space-Time Trellis Coded Code Division Multiple Access Systems (시공간 트렐리스 부호화 CDMA 시스템의 최적, 준최적 복호 방식과 성능 연구)

  • Ki, Young Min;Kim, Dong Ku
    • Journal of Advanced Navigation Technology
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    • v.6 no.2
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    • pp.130-137
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    • 2002
  • We present Space-Time Trellis Coded Code Division Multiple Access systems, which maintain the full diversity and coding gain of Space-Time Trellis Codes(STTC) and have the immunity to performance degradation caused by multipath fading. These STTC CDMA systems are constructed by adding the spreading and despreading processes of PN codes to STTC systems. In multipath fading channels, delay spreaded signals are detected and combined, then decoded. According to the combining and decoding methods, there are four decoding methods. There are optimum ML decoding without combining, adding multipath signals in each receive antenna before decoding, combining multi path signals in each antenna before decoding, and combining all received signals before decoding. Performance of these methods is proportional to complexity. Besides, all methods are shown to compensate the irreducible error rate which appears in multipath fading channels.

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Wind Turbine Simulation Program Development using an Aerodynamics Code and a Multi-Body Dynamics Code (풍력발전시스템의 유연체 다물체 동역학 시뮬레이션 프로그램 개발)

  • Song, Jin-Seop;Rim, Chae-Whan;Nam, Yong-Yun;Bae, Dae-Sung
    • New & Renewable Energy
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    • v.7 no.4
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    • pp.50-57
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    • 2011
  • A wind turbine simulation program for the coupled dynamics of aerodynamics, elasticity, multi-body dynamics and controls of turbine is newly developed by combining an aero-elastic code and a multi-body dynamics code. The aero-elastic code, based on the blade momentum theory and generalized dynamic wake theory, is developed by NREL(National Renewable Energy Laboratory, USA). The multi-body dynamics code is commercial one which is capable of accounting for geometric nonlinearity and twist deflection. A turbulent wind load case is simulated for the NREL 5-MW baseline wind turbine model by the developed program and FAST. As a result, the two results agree well enough to verify the reliability of the developed program.

Design of sub-code Multi-Code Hybrid DS/FH-SS System for the Efficient Data Transmission (효율적인 데이터 전송을 위한 sub-code 멀티코드 하이브리드 DS/FH-SS 시스템 설계)

  • Kong Hyung-Yun
    • The KIPS Transactions:PartC
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    • v.12C no.2 s.98
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    • pp.223-228
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    • 2005
  • The existing mobile communication system called DS/CDMA system, which is serviced widely nowadays, has some problems such as the severe ISI and multiple access interferences under the multi-path fading channel when applied to high-speed data transmission like multimedia transmission. To compensate these problems, we propose a sub-code multi-code hybrid DS/FH (Frequency Hopping) SS (Spread Spectrum) System by combining the multi-code system that restrains the multiple access interference with the hybrid DS/FH SS technique that reduces ISI(Intersymbol Interference) effect for high-speed transmission. Moreover, we implement and propose the sub-code technique to remedy the problems of the generic multi-code system. To verify the performance of the proposed system, the computer simulations are executed under the various channel environments.