• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.175-178
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• 1998

In this paper, turbo codes with the DC-free trellis codes based on partition chain as constituent codes are presente. And efficient methods to design the DC-free turbo codes are introduced. An iterative decoding with the MAP algorithm is used for the decoding of the turbo codes designed by various methods. As results of simulations, the presented DC-free turbo codes show better error performances than the DC-free trellis codes.

• Journal of Communications and Networks
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• 제18권1호
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• pp.40-49
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• 2016

In this paper, we present a symbol-level iterative source-channel decoding (ISCD) algorithm for reliable transmission of variable-length codes (VLCs). Firstly, an improved source a posteriori probability (APP) decoding approach is proposed for packetized variable-length encoded Markov sources. Also proposed is a recursive implementation based on a three-dimensional joint trellis for symbol decoding of binary convolutional codes. APP channel decoding on this joint trellis is realized by modification of the Bahl-Cocke-Jelinek-Raviv algorithm and adaptation to the non-stationary VLC trellis. Simulation results indicate that the proposed ISCD scheme allows to exchange between its constituent decoders the symbol-level extrinsic information and achieves high robustness against channel noises.

• 한국산학기술학회논문지
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• 제5권5호
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• pp.409-412
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• 2004

본 논문에서는 감소된 복잡도를 가진 Turbo TCM(Turbo Trellis Coded Modulation) 구조를 제안하고 그 성능을 분석한다. Turbo Codes와 대역폭 효율을 증대시키기 위한 변조기술을 적용한 부호화기를 구성하고 수신기에서는 이진 Turbo Codes와 유사한 형태지만 다소 상이한 심벌 대 심벌 MAP 반복복호를 사용한다. 반복복호에 따른 성능 분석을 했으며 제안된 구조는 Gray mapping을 이용한 Turbo Codes와 비교한 결과 $BER=10^{-2}$인 경우 약 2.5dB 우수한 이득을 얻음을 알 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.273-276
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• 2001

In this thesis we propose symbol-based decoding for turbo codes which is used SOVA as a decoding algorithm. The proposed turbo codes that is interleaved on symbol-by-symbol basis and inputted as n-bit symbols to the decoder. This method makes that the stages of the original trellis are merged together and the trellis depth is reduced by 1/n. We research turbo codes with symbol size n=2 in this paper and its performance.

• 대한전자공학회논문지TC
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• 제43권8호
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• pp.59-68
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• 2006

채널 부호의 균일 오율에 대한 연구는 부가성백색가우시안 채널에 대해 국한되어 연구되어 왔으며, 기하학적 균일성으로 불려왔다. 본 논문에서는 전송 채널과 수신기를 완전히 묘사해주는 확률밀도함수를 직접 다루어 균일 오율 특성을 다중 송수신안테나가 사용되는 시공간 부호로 확장한다. 또한 빠른 페이딩 채널에서 곱거리 스펙트럼를 고려한 기하학적 균일 시공간 부호 설계 과정을 보여준다. 균일 오율 특성으로 부호 검색의 복잡도가 현격히 감소하고, 이런 복잡도 감소는 높은 상태 수를 갖는 시공간 격사상 부호에 대해서도 최적의 부호 검색을 가능하게 한다. 모의 실험을 통해 새로 설계된 부호가 다른 알려진 부호들에 비해 빠른 페이딩 채널에서 더 좋은 성능을 가지는 것을 확인한다.

• Journal of Communications and Networks
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• 제5권2호
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• pp.174-183
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• 2003

Space-Time (ST) codes are known to provide high transmission rates, diversity and coding gains. In this paper, a tight upper bound on the error probability of ST codes over rapid fading channels is presented. Moreover, ST codes suitable for rapid fading channels are presented. These codes are designed using the QPSK and 16-QAM signal constellations. The proposed codes are based on two different encoding schemes. The first scheme uses a single trellis encoder, whereas the second scheme uses the I-Q encoding technique. Code design is achieved via partitioning the signal space such that the design criteria are maximized. As a solution for the decoding problem of I-Q ST codes, the paper introduces a low-complexity decoding algorithm. Results show that the I-Q ST codes using the proposed decoding algorithm outperform singleencoder ST codes with equal complexity. The proposed codes are tested over fading channels with different interleaving conditions, where it is shown that the new codes are robust under such imperfect interleaving conditions.

• 한국통신학회논문지
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• 제21권8호
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• pp.2063-2076
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• 1996

In this thesis, in order to apply a punctured convolutional codes to the trellis coded modulation(TCM), an efficient punctured trellis coded modulation(PTCM) based on the decomposition of the metric into orthogonal components is presented. Also, a simulation is performed in an additive white Gaussian noise(AWGN) and a rician fading channel modeling the mobile satellite channel. The PTCM combines punctured convolutional coding with MPSK modulation to provide a large coding gain in a power-limited or bandwidth-limited channel. However, in general the use of the punctured convolutional code structure in the decoder results in a performance loss in comparison to trellis codes, due to difficulties in assigning metrics. But, the study shows no loss in performance for punctured trellis coded MPSK in comparison to TCM, and what is more, the punctured convolutional codes results in some savings in the complexity of Viterbi decoders, compared to TCM of the same rate. Also, the results shows that the punctured trellis coded .pi./8 shift 8PSK is an attractive scheme for power-limited and band-limited systems and especially, the Viterbi decoder with first and Lth phase difference metrics improves BER performance by the mobile satellite channel.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
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• pp.335-338
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• 2002

For high data rate transmission over wireless fading channels, space-time trellis ceding techniques can be employed to increase the Information capacity of the communication system dramatically. In this paper, we consider the concatenated space time LDPC (Low Density Parity Check) codes. Extra ceding gains In addition to the diversity advantage is shown to be achieved for certain space-time trellis codes transmitted over quasi-static lading channels.

• 전자공학회논문지S
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• 제35S권3호
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• pp.47-53
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• 1998

Multi-dimensional DC-free trellis codes based on two-dimensional constellation which can be omplemented more easily than conventional codes are proposed and their performances are analyzed in this paper. 2N-dimensional constellation of the proposed codes is constructed by concatenating N 2-dimensional constellation. Thus, for the proposed codes, information bits can be assigned easily to each signal point of the 2-dimensional consteellation and DC-free characteristic can be simply obtained by the symmetric structure of the constellation. In addition, since Viterbi decoder can calculate multi-dimensional Euchlidean distance between signals by simple sum of each 2-dimensional Euclidean distanc, decoding complexity can be reduced. The performance analysis shows that the proposed codes have almost same spectral characteristic and error performance as compared with conventional codes. However, the complexity is shown to be reduced further due to the construction method of contellation and the simple decoding algorithm of the proposed codes.

• 한국ITS학회 논문지
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• 제8권6호
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• pp.141-148
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• 2009

STBC는 부호이득을 얻을 수 없지만, 비교적 적은 부호기와 복호기의 복잡도를 가지고 완전한 다이버시티 이득을 얻을 수 있다. 따라서 STBC는 부호이득이 없기 때문에 부호이득을 얻을 수 있는 외부 부호와 결합되어 사용하여야 한다. 본 논문에서는 완전한 다이버시티 이득과 함께 상당한 부호이득을 얻기 위하여, MTCM부호와 STBC를 결합한 시스템을 고려하였다. 공정한 성능 비교를 위하여 동일한 전송 전력, 동일한 대역폭 효율 그리고 동일한 상태 수를 전제하고, 고려한 시스템과 기존에 알려진 STTC부호와 FER 성능 비교를 실시하였다. 모의실험 결과, MTCM부호와 STBC를 결합한 시스템의 성능은 빠른 레일리 페이딩 채널에서 2개의 송신기 안테나와 1개의 수신기 안테나를 사용하는 STTC부호 보다 우수한 성능을 보여주었다.