• 한국통신학회논문지
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• 제21권9호
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• pp.2444-2455
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• 1996

In this paper, we investigate the performance of convolutional coded DS/CDMA system equipped with a noncoherent M-ary orthogonal modulation scheme, and operating in multi-user environments over slow and freuency nonselective Nakagami-m fading channels with an additive white Gaussian noise (AWGN). An expression for the pariwise error probability that can be used to compute the upper bound of coded system is first derived. performance of the DS/CDMA system with and without the convolutional codes are then compared. We have obsered that the convolutional coded can compensate the degradation quite well in multi-user situations over the Nakagami fading channels with the AWGN. For the case of an extreme fading, however, it has been seen that the convolutional code reaches its limit to improve the overall system performance as the number of users increse.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
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• pp.905-908
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• 2008

In this paper, an Adaptive Modulation (AM) system with an efficient turbo-coded Vertical-Bell-lab Layered Space-Time (V-BLAST) technique is proposed. The proposed decoding algorithm adopts iteratively the extrinsic information from a Maximum a Posteriori (MAP) decoder as a priori probability in the two decoding procedures of the V-BLAST scheme of ordering and slicing. In this analysis, each MIMO channel is assumed to be a part of the system of performance improvement.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.421-424
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• 2002

In this paper, we introduce an encoder design technique of multiple symbol trellis coded modulation for noncoherent continuous phase frequency shift keying (MTCM/NCPFSK) on the interleaved Rician fading channel. To find dominant factors which affects the error probability of MTCM/NCPFSK, we derive the pairwise error probability (PEP) of MTCM/NCPFSK and find that the error probability mainly depends on the effective length of error event and the corresponding squared product distance (SPD) for the small value of Rician parameter K. Using this performance criteria, we search for the optimal encoder of MTCM/NCPFSK for the interleaved Rician fading channel. We also compare that encoder with the encoder designed for additive white Gaussian noise channel.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1682-1691
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• 2015

In this paper, a real time implementation of selective harmonic elimination pulse width modulation (SHEPWM) using Real Coded Genetic Algorithm (RGA), Particle Swarm Optimization technique (PSO) and a new technique known as Linearization Method (LM) for Single Phase Matrix Converter (SPMC) is designed and discussed. In the proposed technique, the switching frequency is fixed and the optimum switching angles are obtained using simple mathematical calculations. A MATLAB simulation was carried out, and FFT analysis of the simulated output voltage waveform confirms the effectiveness of the proposed method. An experimental setup was also developed, and the switching angles and firing pulses are generated using Field Programmable Gate Array (FPGA) processor. The proposed method proves that it is much applicable in the industrial applications by virtue of its suitability in real time applications.

• 대한전자공학회논문지
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• 제27권12호
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• pp.1792-1799
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• 1990

Two cases of block coded phase/frequncy modulations are investigated. minimum Euclidean distances are calculated as the function of modulation index h and rotation angle \ulcorner in the cases of 2-FSK/4-PSK and 2-FSK/8-PSK. Method of signal set partitioning is described, especially for the case of 2-FSK/8-PSK. The results are compared with S.I. Sayegh's work and shown better performance. For example, with simple parity check and repetition codes, we can get coding gain of 3 dB in the case of 2-FSK/4-PSK with block length n=4. We get 5.33 dB in the case of 2-FSK/8-PSK with n=4. And it is believed that we can get higher coding gain with proper combinations of block code and n-FSK/m-PSK type channel signal constellations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1954-1971
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• 2017

In this work, first, a multiuser detection (MUD) algorithm based on component-level soft interference cancellation and linear minimum mean square error (CLSIC-LMMSE) is proposed, which can enhance the bit error ratio (BER) performance of the traditional SIC-LMMSE-based MUD by mitigating error propagation. Second, for non-binary low density parity check (NB-LDPC) coded high-order modulation systems, when the proposed algorithm is integrated with partial mapping, the receiver with iterative detection and decoding (IDD) achieves not only better BER performance but also significantly computational complexity reduction over the traditional SIC-LMMSE-based IDD scheme. Extrinsic information transfer chart (EXIT) analysis and numerical simulations are both used to support the conclusions.

• 한국항행학회논문지
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• 제15권4호
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• pp.591-595
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• 2011

본 논문에서는 차세대 유럽형 방송 시스템인 DVB-T2(Digital Video Broadcasting-Second Generation Terrestrial) 수신기의 핵심블록인 BICM(Bit Interleaved Coded Modulation) 모듈의 구조를 설계하고 DSP(Digital Signal Processor) TMS320C6474를 통해 구현하였다. 실험결과를 통해 8비트 이상을 사용하는 고정소수점 BICM 모듈이 부동소수점 BICM 모듈과 거의 동일한 BER(Bit Error Rate) 성능을 나타냄을 알 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2071-2074
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• 2002

This paper introduces an encoder design method of Turbo TCM (Trellis Coded Modulation) with symbol puncturing. TTCM consists of two simple trellis codes in parallel and modulator. To obtain an good encoder, we calculate the free distance by the assumption that the punctured symbol is transmitted from the subset that consist of signals with the same systematic bit at random. We develop a search program to find the component encoder which maximize the free distance. Especially, for 8-PSK with code rate 2/3, we search for the component codes. We find a new encoder which has better BER performance than that of Robertson′s encoder. We verify the results through the simulation."

• 한국통신학회논문지
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• 제17권9호
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• pp.1020-1028
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• 1992

본 논문에서는 TCM(Trellis Coded Modulation)에서 연집에러 검출 및 최대 확률론적 복호 방식으로 구성된 연집에러 정정을 위한 적응 복호방식을 제시하고 있다. 복호기는 보통 비터비 복호기로서 동작하고, 미터비 복호기에 의해 정정될 수 없는 에러가 검출될 경우 연집 에러 정정 모드로 절환된다. 이동통신에서의 채널특성인 연집에러가 빈번히 발생하는 다경로 페이딩 채널에서 적응 복호방식을 이용한 TCM은 기존의 방식에 비해 비트오율면에서 향상된 성능을 나타내고 있다.

• 한국통신학회논문지
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• 제26권11A호
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• pp.1803-1811
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• 2001

본 논문에서는 미국의 유선 케이블 모뎀 규격인 MCNS(Multimedia Cable Network System) DOCSIS(Data Over Cable Service Interface Specification)를 만즉하는 하향 채널의 64/256-QAM 수신부 FEC(Forward Error Correction)를 분석하였다. FEC는 기본적으로 RS(Reed-Solomon) 계층과 TCM(Trellis Coded Modulation) 계층으로 구분되며, 여기에 추가적으로 interleaving과 randomizer 계층들이 결합되어 있다. AWGN(Additive White Gaussian Noise) 환경에서의 BER(Bit Error Rate) 성능평가를 통해 수신부 연판정 비터비 복호기(soft Viterbi decoder)의 추적 깊이(trace-back depth)와 양자화 레벨(quantization level)의 크기에 따라 부호화 이득이 변함을 확인하였다.