• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8C
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• pp.522-528
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• 2011

The iterative detection and decoding (IDD) has been shown to dramatically improve the bit error rate (BER) performance of the multiple-input multiple-output (MIMO) communication systems. However, these techniques require a high computational complexity since it is required to compute the soft decisions for each bit. In this paper, we show IDD comprised of sphere decoder with low-density parity check (LDPC) codes and present the tree search strategy, called a layer symbol search (LSS), to obtain soft decisions with a low computational complexity. In addition, an adaptive early termination is proposed to reduce the computational complexity during an iteration between an inner sphere decoder and an outer LDPC decoder. It is shown that the proposed approach can achieve the performance similar to an existing algorithm with 70% lower computational complexity compared to the conventional algorithms.

• The KIPS Transactions:PartC
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• v.11C no.1
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• pp.75-80
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• 2004

An iterative soft-decision decoding algorithm of block codes is proposed. With careful examinations of the first hard-decision decoding result, the candidate codewords are efficiently searched for. An approach to reducing decoding complexity and lowering error probability is to select a small number of candidate codewords. With high probability, we include the codewords which are at the short distance from the received signal. The decoder then computes the distance to each of the candidate codewords and selects the codeword which is the closest. We can search for the candidate codewords which make the error patterns contain the bits with small reliability values. Also, we can reduce the cases that we select the same candidate codeword already searched for. Computer simulation results are presented for (23,12) Golay code. They show that decoding complexity is considerably reduced and the block error probability is lowered.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.3
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• pp.149-154
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• 2017

The MCT-Adaboost algorithm chooses an optimal set of features in each rounds. On each round, it chooses the best feature by calculate minimizing error rate using feature index and MCT kernel distribution. The involved process of weak classification executed by a hard decision. This decision occurs some problems when it chooses ambiguous kernel feature. In this paper, we propose the modified MCT-Adaboost classification using soft decision. The typical MCT-Adaboost assigns a same initial weights to each datum. This is because, they assume that all information of database is blind. We assign different initial weights with our propose new algorithm using some statistical properties of involved features. In experimental results, we confirm that our method shows better performance than the traditional one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.9
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• pp.566-568
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• 2014

In this letter, an MMSE based iterative soft decision interference cancellation scheme for massive MIMO systems is proposed. To reduce the complexity, the proposed scheme uses the Sherman-Morrison-Woodbury formula to compute the entire MMSE filtering vectors in one iteration by one matrix inverse operation. Simulation results show that the proposed scheme also has a comparable BER to the conventional scheme for massive MIMO systems.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.255-257
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• 2011

본 논문에서는 지상파 3D HDTV 방송 서비스를 제공하기 위하여 기존의 유럽형 HDTV 방송 서비스인 DVB-T2 전송 시스템의 채널 부호군 중 외부부호로 쓰이는 BCH 부호를 연판정 복호가 가능한 Block Turbo Code로 대체함으로써 생기는 성능 이득과 높은 부호율을 달성하기 위한 방법을 제안하였다. 기존의 DVB-T2 시스템에서 외부부호로 쓰이는 BCH 부호의 부호율의 경우 0.994정도의 높은 부호율을 가진다. 따라서 이에 준하는 높은 부호율을 가지면서 연판정 복호가 가능한 BTC 부호를 제안하고, 기존의 BTC 보다 더 높은 부호율을 가지는 BTC 부호를 설계한다. 모의 실험을 통하여 새롭게 제안된 BTC 에서도 반복복호의 이득이 생기는 것을 확인하고 기존 DVB-T2 시스템의 BCH 부호보다 성능이 우수함을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.448-453
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• 2004

Conventional pragmatic TCMs need sector phase quantizer to apply Viterbi decoder which uses 3-bit soft decision. A symbol transformation applied to the incoming I-channel and Q-channel symbols allows to use Viterbi decoder without sector phase quantizer. We analyzed structure and performance of proposed decoder, and applied it to the turbo decoder. We know that the performance of proposed decoder is better than that of conventional decoder by 1 ［㏈］because of increasing of Euclidean distance.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.805-807
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• 2018

본 논문은 인공 대역 확장에서 스펙트럼 포락선 확장 시 발생하는 스펙트럼 왜곡을 줄이는 개선된 조합 매핑(Improved combined mapping) 알고리즘을 제안한다. 벡터양자화를 기반으로 하는 코드북 매핑(Codebook mapping)과 스펙트럼 포락선(Spectrum Envelope)의 선형 의존도를 이용한 선형 매핑(Linear mapping)을 사용하여 각각 확장된 광대역 LSP(Line Spectrum Pair)를 추론하고, 연판정(Soft-decision)을 통해 최적화된 LSP를 추론한다. 제안된 알고리즘으로 합성된 음성신호의 스펙트럼 왜곡(Spectrum Distortion)이 기존 조합매핑으로 얻은 음성 신호의 스펙트럼 왜곡보다 더 적은 왜곡을 갖는 결과를 나타내었다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1998.06a
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• pp.1021-1024
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• 1998

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.2
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• pp.153-160
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• 2017

Recently, the demand has continued to increase for higher data rates and improved multimedia services through wireless internet access. In order to increase the data rate and link reliability, 3GPP LTE/A and IEEE 802.16e/m WiMAX systems incorporate MIMO transmission schemes. Since the hardware complexity increases with the number of transmit data streams and mobile devices have limited physical dimensions, an multiple input multiple output (MIMO) ystem with two antennas at both the transmitter and the receiver ($2{\times}2$) is considered to be a possible solution for mobile devices. In this paper, a low-complexity soft output MIMO symbol detector based on Modified-SQRD is proposed for mobile devices with two transmit and two receive antennas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.841-849
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• 2012

This paper proposes an low-complexity soft-output multiple-input multiple-output (soft-MIMO) detection algorithm for achieving soft-output maximum-likelihood (soft-ML) performance under max-log approximation. The proposed algorithm is based on a parallel tree-search (PTS) applying a channel ordering by a sorted-QR decomposition (SQRD) with altered sort order. The empty-set problem that can occur in calculation of log-likelihood ratio (LLR) for each bit is solved by inserting additional nodes at each search level. Since only the closest node is inserted among nodes with opposite bit value to a selected node, the proposed node insertion scheme is very efficient in the perspective of computational complexity. The computational complexity of the proposed algorithm is approximately 37-74% of that of existing algorithms, and from simulation results for a $4{\times}4$ system, the proposed algorithm shows a performance degradation of less than 0.1dB.