• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.738-745
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• 2009

Underwater acoustic communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes receive signal to make error floor. In this paper, we propose the underwater communication system using various channel coding schemes such as RS coding, convolutional code, turbo code and concatenated code for overcoming the multipath effect in underwater channel. As shown in simulation results, characteristic of multipath error is similar to that of random error. So interleaver has not effect on error correcting. For correcting of error floor by multipath, it is necessary to use strong channel codes like turbo code. Turbo code is one of the iterative codes. And the performance of concatenated codes including RS code has better performance than using singular channel codes.

• Journal of Communications and Networks
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• 제2권1호
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• pp.76-84
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• 2000

Communication systems, including cell-based mobile communication systems, multiple satellite communication systems of multi-beam satellite systems, require reliable handoff methods between cell-to-cell, satellite-to-satellite of beam-to-team, respectively. Recent measurement of a CDMA cellular system indicates that the system is in handoff at about 35% to 70% of an average call period. Therefore, system reliability during handoff is one of the major system performance parameters and eventually becomes a factor in the overall system capacity. This paper presents novel and improved techniques for handoff in cellular communications, multi-beam and multi-satellite systems that require handoff during a session. this new handoff system combines the soft handoff mechanism currently implemented in the IS-95 CDMA with code and packet diversity combining techniques and an iterative decoding algorithm (Turbo Coding). the Turbo code introduced by Berrou et all. has been demonstrated its remarkable performance achieving the near Shannon channel capacity [1]. Recently. Turbo codes have been adapted as the coding scheme for the data transmission of the third generation international cellular communication standards : UTRA and CDMA 2000. Our proposed encoder and decoder schemes modified from the original Turbo code is suitable for the code and packet diversity combining techniques. this proposed system provides not only an unprecedented coding gain from the Turbo code and it iterative decoding, but also gain induced by the code and packet diversity combining technique which is similar to the hybrid Type II ARQ. We demonstrate performance improvements in AWGN channel and Rayleigh fading channel with perfect channel state information (CSI) through simulations for at low signal to noise ratio and analysis using exact upper bounding techniques for medium to high signal to noise ratio.

• 방송공학회논문지
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• 제14권5호
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• pp.650-653
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• 2009

Turbo-coded CDMA system is analyzed and simulated in an indoor wireless infrared channel. The indoor infrared channel is modeled as a non-directed diffuse link. From the simulation results, it is confirmed that the turbo coding is very effective in improving BER (bit error rate) performance, and outperforms BCH code.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.165-168
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• 2000

The bit error rate(BER)of the data passed through Wideband-Code Division Multiple Access (W-CDMA) system with turbo-codes structure is presented. The performance of turbo-codes under W-CDMA system is estimated for various users and iteration numbers of decoding. The channel model is Additive White Gaussian Noise(AWGN) and Rayleigh fading channel. When iteration number increases, bit error probability of turbo-codes decreases. and when the number of users increase, bit error probability of turbo-codes increases.

• 한국통신학회논문지
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• 제22권7호
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• pp.1427-1436
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• 1997

Turbo codes, decoded through an iterative decoding algorithm, habe recently been shown to yidel remarkable coding gains close to theoretical limits in the Gaussian channel environment. This thesis presents the performance of Turbo code through the computer simulation. The performance of modified Turbo code is compared to that of the conventional Turbo codes. The modified Turbo code reduces the time delay in decoding with minimal effect to the performance for voice transmission sytems. To achieve the same performance, random interleaver the size of which is no less than the square root of the original one should be used. Also, the modified Turbo code is applied to MC-CDMA system, and its performance is analyzed under the Rayleigh Fading channel environment. In Rayleigh fading channel environment, due to the amplitude distortion caused by fading, the interleaver of the size twice no less than that in the Gaussian channel enironment was required. In overall, the modified Turbo code maintained the performance of the conventional Turbo code while the time delay in transmission and decoding was reduced at the rate of multiples of two times the squared root of the interleaver size.

• 한국통신학회논문지
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• 제25권6B호
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• pp.1068-1073
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• 2000

본 논문에서는 고밀도 광 기록 시스템에서 런길이 제한 조건이 없는 채널 비트로 인해 발생하는 심각한 ISI와 비선형 왜곡을 극복하기 위한 방법으로 트랠리스를 바탕으로한 등화기(Trellis-Based Equalizer, TBE)와 터보 코드를 연접한 TE(Turbo Equalization)/TC(Turbo Code) 검출 방법을 제안한다. 모의 실험은 채널 밀도 S=4.6과 S=7에서 지터의 양이 15% 존재할 때 코드율을 4/5, 8/9, 16/17로 변화시켜가며 행하였다. TE/TC 구조는 비트 에러율 $10^{-5}$를 24dB이상에서 만족함을 확인할 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.273-276
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• 2000

Recently, Turbo code has been considered for channel coding in IMT-2000(International Mobile Telecommunication-2000) system, because it offers better error correcting capability than the traditional convolution/viterbi coding . In this paper, a turbo code decoder for speech transmission in IMT-2000 system with frame size 192 bits, constrait length K=3, generator polynomials G(5,7) and code rate R=1/3 is designed using SOVA(Soft Output Viterbi Algorithm) and block interleaver

• 한국산업정보학회논문지
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• 제9권2호
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• pp.17-22
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• 2004

In this paper, a concatenated RS and Turbo code is proposed for OFDM system over burst error channel. The concatenated code used in this study is a RS(255,202) code and a rate 1/2 turbo code. The turbo code uses 2 recursive systematic convolutional (RSC) code as the constituent codes and the parity bit are punctured to get the desired code rate. It is shown by simulation that the conventional OFDM system fails when there exists burst noise. The concatenated RS and turbo code obtains at least 5dB gain over the turbo code at the bit error probability of 10/sup -3/.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.213-216
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• 2001

In this paper, the performance of an OFDM/CDMA system with turbo coding is analyzed and simulated in a multipath fading channel. Bit error probability is derived fDr a Rayleigh fading channel. In an OFDM/CDMA system, an OFDM and a CDMA techniques are combined to exploit the advantages of both techniques. For decoding of turbo code, MAP decoding algorithm is employed. From the simulation results. it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity. Also, it is shown that the BER performance is substantially improved by increasing the interleaver length for a fixed code rate and the increasing number of iterations used in the decoding process. The results in the paper can be applied to the design of OFDM-based CDMA system.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 추계종합학술대회논문집
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• pp.13-16
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• 2000

최근의 이동통신 시스템에서 오류 정정 부호화 방식으로 사용되는 Turbo Code의 성능은 부호기에 내재되어 부호의 자유 거리 결정에 큰 영향을 미치는 인터리버와 복호기에서 수행되는 반복 복호에 의한 것이다. 하지만 우수한 성능을 얻기 위해 수신과정에서 많은 지연시간이 요구되는데 이는 주로 인터리버의 크기에 의존하게 된다 또한 Turbo Code는 페이딩 채널 상에서도 신뢰성 있는 강력한 코딩 기법으로 알려져, 최근 ITU 둥에서 IMT-2000과 같은 차세대 이동 통신에서 채널 코드의 표준으로 채택되었다. 따라서 본 논문에서는 복잡도는 2배로 증가하나 성능을 개선시킨 터보 복호기를 제안하고, 차세대 무선 멀티미디어 통신에서 실시간 음성 덴 비디오 서비스를 제공시 복호 지연시간을 단축시키기 위해 가변 복호 방법을 이용하여 AWCN과 페이딩 채널 환경에서의 컴퓨터 모의 실험을 통해 성능 분석을 하였다.