• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.57-62
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• 2014

This paper proposes the improving the equalization performance using the adaptive modulus concept to the MCMA blind equalizer in order to the reduction of intersymbol interference which occurs in the band limited and time dispersive communication channel. In MCMA blind algorithm, it is possible to reducing the amplitude and phase rotation of intersymbol interference without training sequence, the fixed constant modulus of transmission signal is used. But in proposed algorithm, the modulus are adaptively varies according to the equalizer output signal, then the improved equalization performance were obtained by the computer simulation. For this, the recovered signal constellation that is the output of the equalizer, the convergence performance by MSE, MD (maximum distortion) and residual isi characteristic learning curve were used. The propose algorithm has fairly good performance compared to the traditional MCMA algorithm in the same adaptive equalization algorithm.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.4
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• pp.262-266
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• 2013

In OFDM system, cyclic prefix (CP) is used to eliminate the inersymbol interference that is caused by the channel dispersion. However, a long CP reduces the data transmission rate. An alternative to a logn CP is the a time domain channel shortening filter at the receiver that shortens the effective channel, thus a short CP is used in spite of a long channel impulse response. In the paper, we compare a various channel shortening techniques; minimum shortened signal to noise ratio (MSSNR), minimum interblock interference (min-IBI), and minimum ISI (min-ISI).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1154-1163
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• 2007

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response. In order to prevent a loss of bandwidth efficiency due to the use of a CP, residual intersymbol interference cancellation (RISIC) method has recently been developed. In this paper, we first apply the RISIC algorithm to the space-time block coded (STBC) OFDM and the space-frequency block coded (SFBC) OFDM with insufficient CP. It is shown that in the STBC OFDM, tail cancellation as well as cyclic restoration of the RISIC should be repeated. Second, we propose iterative channel estimation method for the RISIC in the STBC OFDM system with insufficient CP. Based on the expectation-maximization (EM) algorithm, the proposed estimation method exploits the extrinsic probabilities of the channel decoder iteratively. The performance of the proposed method is evaluated by computer simulation in a multipath fading environment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.99-104
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• 2015

This paper proposes the RMMA (Region based Multiple Modulus Algorithm) algorithm that is possible to improving the performance of MMA adaptive equalization algorithm in order to the reduction of intersymbol interference occurs at the communication channel. In RMMA algorithm, the output constellation of equalizer are divided by 4 different regions in order to get the error signal for adapting the channel characteristic, and the small error signal is obtained by mapping each region to 4-QAM signal. The conversion effect of constant modulus from nonconstant modulus signal was obtained. In this paper, the adaptive equalization performance of proposed RMMA were evaluated comared to the present MMA. As a result of computer simulation, the convergence speed and residual quantity were improved in residual isi and MD. Especially the superiorities of robustness was confirm in SER performance compared to present MMA.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.33-36
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• 2000

DS-CDMA (direct sequence-code division multiple access) 시스템에서 여러 사용자가 동일 주파수 대역을 공유함으로써 다중 접속 간섭 (multiple access interference; MAI)이 발생하고 시스템의 성능을 크게 제한한다. 이러한 다중 접속 간섭을 제거하여 전송 신호의 질을 높이고 용량을 증대시키는 중요한 신호 처리 기술 가운데 하나가 적응 간섭 억제 기술이다. 적응 간섭 억제 기술 가운데 CMA (constant modulus algorithm) 기반의 블라인드 적응 간섭 억제기는 훈련수열을 필요로 하지 않고 빠른 수렴을 통하여 간섭을 효과적으로 제거할 수 있으나, 다중 경로 환경에서 심벌간 간섭 (intersymbol interference; ISI)이 증대되어 기존의 적응 수신기보다 악화된 성능을 보인다. 본 논문에서는 CMA를 기반으로 훈련 수열 없이 빠른 수렴을 하며 MAI와 ISI를 효과적으로 제거하기 위한 다이버시티 결합기 구조의 적응 간섭 억제기를 제한한다. 다중 경로 페이딩 채널 환경에서 기존의 블라인드 적응간섭 억제기와의 성능 비교 결과, 제안된 방식이 다중경로에 의한 ISI의 영향을 효과적으로 제거하여 우수한 성능을 얻을 수 있음을 확인하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.409-411
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• 2013

In this paper, we used FTN(Faster than Nyquist) method that is transmission method faster than Nyquist theory. FTN signaling introduces intersymbol interference(ISI), but increases the bit rate while preserving the signaling bandwidth. Therefore, we need compensating ISI caused by FTN. In this paper, we propose decoding method for FTN signal that using BCJR Equalizer and Turbo Equalization. first ISI of inputted signal is restored by BCJR Equalizer, and then restored signal inputted in LDPC decoder, and repeat the process using the Turbo Equalization improves performance. finally, we shows performance comparison according to reduce percentage of FTN signal.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.138-141
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• 2003

본 논문에서는 STTD(space Time Transmit diversify)를 적용한 적응변조 시스템의 성능을 분석하였다. 무선채널 환경에서는 지연파에 의한 ISI(Intersymbol interference)간섭으로 인해 전송 오율을 증가시키게 된다. 따라서, ISI간섭의 영향을 줄이기 위해 STTD를 적용함으로써 적응변조시스템의 성능개선 정도를 분석하였다. 결과에 의하면, STTD를 적용함에 따라 더 낮은 SNR에서도 변조 다치수가 높은 변조 모드를 선택함으로써 고속ㆍ고품질의 데이터 전송이 가능함을 알 수 있었다.

• ETRI Journal
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• v.45 no.6
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• pp.974-981
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• 2023

This paper presents a transition-limited pulse-amplitude modulation (TLPAM) signaling method to enable a high data rate and robust wireline communications. TLPAM signaling addresses the impact of high intersymbol interference (ISI) ratios in conventional M-ary PAM signaling methods by limiting the maximum voltage transition level between adjacent symbols. The implementation of a TLPAM signaling encoder is realized by setting back the most significant bits (MSBs) in the queue. The correlation between TLPAM's maximum transition level, effective data rate, and eye width/height is analyzed with various channel loss parameters, followed by characterization and measurement results with a realistic channel setup. The analysis and experimental results reveal the effectiveness of the proposed TLPAM signaling scheme for achieving a high data rate with minimal interference.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.417-422
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• 2005

When an optical pulse propagates through the atmospheric channel, it is attenuated and spreaded by the atmospheric turbulence. This pulse broadening produces the intersymbol interference(ISI) between adjacent pulses. Therefore, adjacent pulses are overlapped, and the bit rates and the repeaterless transmission length are limited by the ISI. In this paper, the ISI as a function of the refractive index structure constant that presents the strength of atmospheric turbulence is found using the temporal momentum function, and is numerically analyzed fer the basic SONET transmission rates. The numerical results show that ISI is gradually increasing at the lower transmission rate than the OC-192(9.953 Gb/s) system and is slowly converging after rapid increasing at the higher transmission rate than the OC-768(39.813 Gb/s) system as the turbulence is stronger. Also, we know that accurate information transmission is possible to 10[km] at the OC-48(2.488 Gb/s) system under any atmospheric turbulence, but is impossible under the stronger turbulence than $10^{-14}[m^{-2/3}]$ at the 100 Gb/s system, $10^{-13}[m^{-2/3}]$ at the OC-768 system, and $10^{-12}[m^{-2/3}]$ at the OC-192 system, because the ISI is seriously induced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.459-464
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• 2013

In this paper, we introduce a modulation code design problem where best selection of two-dimensional codewords are determined to reduce two-dimensional (2D) intersymbol interference (ISI) and interpage interference (IPI). Codeword selection problem is formulated as a quadratic integer programming model that minimizes intra- and inter-symbol differences subject to uniform symbol usage and minimal Hamming distance violations. Second integer programming model detects the occurrence of isolated pixel pattern in the selected codewords. The proposed models are applied to 4-level and 2-level 6/8 codes.