• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.181-184
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• 2000

In this paper, performance of an optical CDMA system with PCCC and SCCC is simulated and compared. It is assumed that optical channel is an intensity modulated (IM) channel and direct-detection scheme is employed to detect the received optical signal. The modulation scheme used is pulse-position-modulation (PPM). The performance is evaluated in terms of bit error probability. From the simulation results, it is shown that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity.

• 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.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.107-107
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• 2004

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.895-901
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• 2016

The next generation wireless and satellite communications require high transmission efficiency and high reliability to provide various services with subscribers. To satisfied these requirements, incorporated MIMO (Multiple Input Multiple Output) system with FTN (Faster Than Nyquist) techniques based on layered space time coded method are considered in the paper. To improve performance, STTC (Space Time Trellis Code) was employed as an inner code. As the same as SISO (Single Input Single Output) system, the outer codes are turbo codes. In receiver side, BCJR algorithm is used for STTC decoding in order to eliminate interferences induced by FTN transmission. They can yield significantly increased the data rates and improved link reliability without additional bandwidth. Therefore, we proposed a new decoding model for MIMO FTN model and confirmed that performance was improved compared to conventional SISO model according to amount of interference for FTN.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.111-116
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• 2009

In this paper, we propose a phase offset estimation algorithm which is based on turbo coded digital broadcasting system. The phase estimator is an estimator outside turbo code decoder using LMS (Least Mean Square) algorithm to estimate the phase of next state. While the conventional LMS algorithm with a fixed step size is easy implemented, it has weak points that are difficult the channel estimation and tracking in the multipath environment. To resolve this problem, we propose new phase offset estimation method with a variable step size LMS (VS-LMS). Additionally, we propose a scheme which consists of a conventional LMS. The performance is verified by computer simulation according to a fixed phase offset and a increased phase offset, the proposed algorithm improve the bit error rate performance than the conventional algorithm.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.43 no.4 s.310
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• pp.73-79
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• 2006

Due to the powerful correcting performance, turbo codes have been adopted in many communication standards such as W-CDMA(Wideband Code Division Multiple Access), CDMA2000, etc., and implemented by hardware in many kind of fields. Although several hardware structures and improved algorithm have been proposed, these problems such as hardware area, operating speed and power consumption are still a major issue to be solved in practical implementations. In this paper, we designed the turbo-code decoder using MAX -SCALE operation derived from the posterior probability optimization. The proposed circuit has been measured their performance on Matlab and MaxPlusII and implemented on the FPGA As a result, when implementing the proposed algorithm on the FPGA, this circuit only occupies 616 logic elements. And comparing the performance with the MAP(Maxirnum a Posteriori) decoding algorithm, the operating speed was increased by about 40%(56.48MHz) and BER(Bit Error Rate) was increased by 6.12.

• Journal of the Korea Society for Simulation
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• v.17 no.1
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• pp.17-22
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• 2008

Double-binary turbo code has been adopted as an error control code of various future communication systems including wireless metropolitan area networks(WMAN) due to its powerful error correction capability. One of the components affecting the performance of turbo code is internal interleaver. In 802.16 d/e system, an almost regular permutation(ARP) interleaver has been included as a part of specification, however it seems that the interleaver is not optimized in terms of decoding performance. In this paper, we propose three optimization methods for the interleaver based on spatial distance, spread and minimum distance between original and interleaved sequence. We find optimized interleaving parameters for each optimization method and evaluate the performances of the proposed methods by computer simulation under additive white Gaussian noise(AWGN) channel. Optimized parameters can provide up to 1.0 dB power gain over the conventional method and furthermore the obtainable gain does not require any additional hardware complexity.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.124-130
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• 2013

The performance of underwater acoustic communication system is sensitive to the ISI(Inter-Symbol Interference) due to delay spread develop of multipath signal propagation. The equalizer is used to combat the ISI. In this paper, the performances of underwater acoustic communication with turbo equalizer were evaluated by real data collected in Korean littoral sea. As a result, when one iterative decoding using turbo equalizer is applied, the performance was improved 1.5 dB than the case of the non-iterative equalizer at BER $10^{-4}$. In the case of two or three iterations the performance was enhanced about 3.5 dB, but the performance wasn't improved any more in the case of more than three times.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.410-418
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• 2022

Channel reliability estimation for iterative codes such as turbo codes is very important factor in time varying underwater acoustic channel, an incorrect estimation of channel reliability induced performance degradation. Therefore, this paper presents an optimal channel reliability estimation method for turbo coded FSK signal with rate of 1/3. The estimated BER algorithm is a method that can estimate the reliability of received data by comparing received data and decoded data, and we determine optimal channel reliability by using the method. In order to analyze the performance, the experiment was conducted on a lake in Munkyeong city by moving in the range of 300 m to 500 m. At the result of applying presented method to failed decoding packets, we confirm all packets are decoded successfully.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.1051-1059
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• 2013

This paper proposes a complexity reduced list sphere decoding (LSD) scheme for joint iterative soft detection scheme for coded MIMO system. The conventional LSD scheme is based on searching the candidates with a fixed radius. However, once the candidate list is full, it is highly probable that the radius can be reduced. By reducing the radius, the complexity can be also reduced. We propose a simple and efficient radius update method for complexity reduction of list version sphere decoding and its application to iterative soft MIMO detection. We evaluate the performance of the proposed scheme with a joint soft-input-soft-ouput iterative MIMO detection in combination with turbo codes. Simulation results show that the proposed methods provide substantial complexity reduction while achieving similar bit error rate (BER) performance as the conventional LSD scheme.