• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1042-1050
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• 2014

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Turbo Equalization method based on layered Space Time Codes has improved performance compared to conventional UWA communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10C
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• pp.923-929
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• 2003

Turbo processing have been known as methods close to Shannon limit in the aspect of wireless multi-input multi-output (MIMO) communications similarly to wireless single antenna communication. The iterative processing can maximize the mutual effect of coding and interference cancellation, but LDPC coding has not been used for turbo processing because of the inherent decoding process delay. This paper suggests a LDPC coded MIMO system with turbo parallel space-time (Turbo-PAST) processing for high-speed wireless communications and proposes a average soft-output syndrome (ASS) check scheme at low signal to noise ratio (SNR) for the Turbo-PAST system to decide the reliability of decoded frame. Simulation results show that the suggested system outperforms conventional system and the proposed ASS scheme effectively reduces the amount of turbo processing iterations without performance degradation from the point of average number of iterations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.11B
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• pp.1872-1878
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• 2000

Turbo Code는 반복 부호 알고리듬을 사용함으로써 백색 가우시안 잡음(AWGN)채널 환경하에서 Shannon의 한계에 가까운 성능을 보이는 오류정정 방식으로 제안되었다. 그러나 Turbo code는 반복복호로 인해 매 복호시마다 큰 인터리버와 복호기를 거쳐야 하기 때문에 수신과정에서 커다란 지연을 요구하게 된다. 따라서 차세대 무선 멀티미디어 통신에서 실시간 음성서비스나 화상서비스를 제공하는데 어려움이 많다. 본 논문에서는 기존의 터보 복호기를 변형하여 매 복호시 각각의 복호기에서 LLR 출력시퀀스를 발생시킴으로써 반복 복호 횟수를 줄이는 방법을 제안하였다. 이렇게함으로서 기존의 Toubo code가 갖는 성능은 크게 변화시키지 않으면서 각각의 정보프레임을 가변적으로 복호함으로서 반복 복호로 인한 시간 지연을 줄였다.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.9-11
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• 2009

It is well-known that the performance of turbo codes can be improved by allocating different energies per code symbol. In this paper, based on this observation, we propose a joint encoding and modulation scheme for quadrature amplitude modulated turbo code systems. In the proposed scheme, the amount of energy difference between the turbo coded symbols is optimized by optimizing the constellation of quadrature amplitude modulation(QAM). The proposed scheme offers better coding gain compared to the conventional combination of binary turbo code and QAM at the bit error rate of $10^{-5}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2C
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• pp.161-166
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• 2008

In the parallel-architecture turbo codes, the constituent interleaver must avoid memory collision. This paper proposes a collision-free interleaver structure composed of a Latin square matrix and pre-designed interleavers. Our proposed interleavers can be easily optimized for various information block sizes and for various degrees of parallelism. Their performances were evaluated by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.841-847
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• 2009

In this paper we propose a high-performance Hybrid ARQ scheme employing Chase combining based on LDPC (Low-Density Parity-Check) codes. The proposed scheme uses symbol mapping diversity and turbo demodulation to improve decoding performance. We analyze the performance of the proposed scheme by EXIT (EXtrinsic Information Transfer) chart and compare its performance with several symbol mappings.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3A
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• pp.173-179
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• 2002

In this paper, we suggest more precise performance analysis method of turbo interleavers based on two criteria; performance bounds like Union Bound and weight frequency of codewords. In order to present our new method, we employ block pseudo random, and so-called prime interleavers in compliance of 3GPP standard, respectively, We also applied this method to S-random interleavers that have different window size, S. 3GPP complied turbo encoder, decoder, and AWGN channel are implemented by using MATLAB for our performance analysis. According to our analysis, both criteria should be taken into account coincidently to predict the performance of newly designed interleavers.

• Journal of Advanced Navigation Technology
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• v.7 no.1
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• pp.30-37
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• 2003

In this paper, we have analyzed the BER (Bit Error Rate) performance of MC-CDMA systems under indoor wireless environment with class A impulsive noise suggested by Middleton. For the performance evaluation, we considered from strong to weak impulsive noise characteristics. And we have evaluated the degree of performance improvement by using turbo code as a compensation technique to impulsive noise. From the result of analysis, it is found powerful performance improvement scheme must be adopted in the system under impulsive noise environment, and when turbo code scheme is adopted, system BER performance is improved by the $10^{-2}$. As the impulsive noise characteristics approaches AWGN characteristics, the degree of performance improvement by adopting turbo code become larger.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1633-1641
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• 2004

In satellite digital broadcasting and satellite internet, severe burst errors occur in the high-speed return channel from the satellite to mobiles. In this paper, we analyze the performance of the forward error correction (FEC) coding method in the Rayleigh fading return channel. We first investigate the channel model of Loo, LutB, Vucetic and Corazza. We then compare the performance of the convolutional, Reed-Solomon (RS), convolution-RS concatenation, and Turbo codes in rayleigh fading channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.646-651
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• 2003

In this paper, we investigate the performance comparisons of various turbo interleavers which are adopted as a standard such as IMT-2000 and satellite DVB(digital video broadcasting). The bit error rate performance is calculated by the fixed point computer simulations over Rayleigh fading channels. For a fair comparison, the simulation is performed on the basis of equal the interleaver size as we can. From the results, it is shown that the turbo interleaver in W-CDMA outperforms the turbo interleavers in CDMA2000 and satellite DVB. The performance gains are even larger as the interleaver size is increased.