• ETRI Journal
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• v.43 no.2
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• pp.184-196
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• 2021

The research domain of underwater communication has garnered much interest among researchers exploring underwater activities. The underwater environment differs from the terrestrial setting. Some of the main challenges in underwater communication are limited bandwidth, low data rate, propagation delay, and high bit error rate (BER). As such, this study assessed the underwater acoustic (UWA) aspect and explored the expression of error performance based on t-distribution noise. Filter orthogonal frequency-division multiplexing refers to a new waveform candidate that has been adopted in UWA, along with turbo and polar codes. The empirical outcomes demonstrated that the noise did not adhere to Gaussian distribution, whereas the simulation results revealed that the filter applied in orthogonal frequency-division multiplexing could significantly suppress out-of-band emission. Additionally, the performance of the turbo code was superior to that of the polar code by 2 dB at BER 10-3.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1966-1973
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• 1999

In this paper, we introduce the concept of a HAPS(High Altitude Platform Station) system which is expected to be a next generation communication system and suggest several error correcting codes to provide high quality services. Since a HAPS system encounters serious signal attenuation due to rain and scattering in the air, concatenated codes which have a high coding gain is considered to be a proper error correcting method. In this paper, we provide performance analyses result of two candidate coding schemes for a HAPS. The first one is a conventional concatenated coding scheme, and the second one is a iterative decoding method known as Turbo Codes.

• ETRI Journal
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• v.26 no.6
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• pp.615-621
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• 2004

Next generation mobile communication system, such as IMT-2000, adopts Turbo codes due to their powerful error correction capability. This paper presents a block-wise maximum a posteriori (MAP) Turbo decoding structure with a low memory requirement. During this research, it has been observed that the training size and block size determine the amount of required memory and bit-error rate (BER) performance of the block-wise MAP decoder, and that comparable BER performance can be obtained with much shorter blocks when the training size is sufficient. Based on this observation, a new decoding structure is proposed and presented in this paper. The proposed block-wise decoder employs a decoding scheme for reducing the memory requirement by setting the training size to be N times the block size. The memory requirement for storing the branch and state metrics can be reduced 30% to 45%, and synthesis results show that the overall memory area can be reduced by 5.27% to 7.29%, when compared to previous MAP decoders. The decoder throughput can be maintained in the proposed scheme without degrading the BER performance.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.49-50
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• 2006

Digital satellite systems are usually integrated with terrestrial systems to provide various services, and in these cases they should satisfy the performance objectives defined by the terrestrial systems. Recommendation ITU-R S.1062 specifies the performance of digital satellite systems. The performance objectives were given in terms of bit error probability divided by the average number of errors per burst versus percentage of time. This paper presents theoretical method to estimate performance measure of digital satellite systems defined in Recommendation ITU-R S.1062. We show performance estimation results of duo-binary Turbo codes, and verify them by comparing to the simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.533-536
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• 2005

MAP algorithm is known for optimal decoding algorithm of Turbo codes, but it has very large computational complexity and delay. Generally log-MAP algorithm is used in order to overcome the defect. In this paper we propose modified scheme of the state metric calculation block which can improve the computation speed in log-MAP decoder and simple linear offset unit without using LUT. The simulation results show that the operation speed of the proposed scheme is improved as compared with that of the past scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.282-284
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• 2010

1962년 Gallager에 의해서 처음 제안된 LDPC 부호는 터보부호(turbo codes)와 마찬가지로 Shannon의 채널용량 한계(channel capacity limit)에 가까운 성능을 보였지만 당시 기술력으로 구현이 불가능한 복잡도로 인해 오랫동안 잊혀져왔다. 1995년 Mackay 와 Neal은 이를 재발견하였고 간단한 확률적 복호법을 이용하여 LDPC 부호의 성능이 매우 우수함을 보였다. 또한 1997년 Mackay는 q>2일 때 LDPC 부호를 GF(q)상에서 구성할 경우에 성능이 더 좋아짐을 보였다. 본 논문에서는 이진 bit로 구성된 같은 길이의 정보 비트(information bit)를 통해 16-QAM 변조를 사용했을시 Binary LDPC 부호와 Non Binary LDPC 부호의 성능을 비교 분석하고, 최적의 성능을 가지는 LDPC 부호의 설계에 대해 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.121-123
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• 2004

시공간 블록부호는 송신단에서 여러 개의 안테나를 사용하여 무선 통신의 신뢰도를 높인다. 그런데 4개의 송신안테나를 사용하는 시공간 블록부호는 다이버시티 차수 4와 전송률 1을 동시에 얻을 수 없다. 직교 시공간 블록부호는 다이버시티 차수 4를 유지하지만 전송률에서 손해를 보는 반면, 준직교 시공간 블록부호는 다이버시티 이득에서 손해를 보면서 전송률 1을 유지한다. 본 논문에서는 준직교 시공간 블록부호의 복호기에서 최대 우도 복호 방법으로 비트별 연성결정값을 출력하고, 터보부호와 연접하여 다양한 전송률에서 직교 및 준직교 시공간 블록부호의 성능을 비교하였다.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.161-162
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• 2008

In this paper we design an irregular low-density parity-check (LDPC) code for a multi-input multi-output (MIMO) system. The considered MIMO system is minimum mean square error soft-interference cancellation (MMSE-SIC) detector. The MMSE-SIC detector and the LDPC decoder exchange soft information and consist a turbo iterative detection and decoding receiver. Extrinsic information transfer (EXIT) charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the input-output transfer chart of the MMSE-SIC detector. It is shown that the performance of the designed LDPC code is much better than that of conventional LDPC code optimized for the AWGN channel.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.663-666
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• 2004

In this paper, a modified-SOYA (soft output viterbi algorithm) of turbo codes is proposed for quantized channel receiver filter outputs. We derive optimum branch values for the Viterbi algorithm. Here we assume that received filter outputs are quantized and the channel is additive white Gaussian noise. The optimum non-uniform quantizer is used to quantize channel receiver filter outputs. To compare the BER (bit error rate) performance we perform simulations for the modified SOYA algorithm and the general SOYA

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7B
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• pp.1301-1312
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• 2000

본 논문에서는 트렐리스 복호 방식을 이용한 블록 터보 부호의 이로적인 성능 바운드와 함께 내부 구성 부호의 변형 및 내부 구성 부호의 연결 방법에 따른 성능의 변화를 살펴본다. 또한 효율적인 복잡도 감소 기법을 적용한 반복 복호 기법을 소개하고 시뮬레이션을 통하여 성능을 분석한 결과를 제시한다. 가우시안 채널에서의 시뮬레이션 결과에 따르면 본 논문에서 제시한 기법은 약 1/10정도의 복잡도를 가지고서도 전체 트렐리스를 탐색한 기법에 거의 근접하는 성능을 얻을 수 있음이 보여졌다.