• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.1009-1018
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• 2003

A new fading channel estimation technique is proposed for an OFDM based modem In the ITS system. The algorithm is based on the transfer function extraction of the channel using the pilot signals and compensated the channel preceding the equalization. The newly derived algorithm is division-free arithmetic operations allows the faster circuit operation and the smaller circuit size. Proposed techniques compensate firstly the distortion which is generated at fading channels and secondly eliminate inter-symbol interference. All algorithms are suitability estimated and improved for a system implementation using digital circuits. As the results, the circuit size is reduced by 20% of the conventional design and achieved about 10% performance improvement at low SNR under 10dB in case of ITS system adapted 16-QAM mode.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.143-146
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• 2002

전화음성의 경우 전화 회선의 채널 대역폭 제한과 통화로 형성시 달라지는 채널의 특성으로 인하여 마이크 음성에 비하여 인식 성능이 많이 저하된다. 본 연구에서는 연속 숫자음 전화음성의 인식율 향상을 위해 채널 왜곡 보상 기법들을 적용하고, HTK 기반의 인식 실험을 통해 보상 기법에 따른 인식 성능을 비교하였다. 채널 왜곡 보상 기법으로 CMN, RASTA, RTCN 등을 적용하고, 각 보상 기법에 따라 HMM의 state 수, mixture 수를 바꾸어 가며 인식 실험한 결과를 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.12B
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• pp.2060-2068
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• 2000

이 논문은 선형 송·수신 필터의 메모리와 증폭기의 비선형성에 기인하는, 메모리 있는 비선형 시스템의 인식(identification)과 보상에 대해 다룬다. 이와 같은 비선형 시스템은 메모리가 있는 두 개의 선형 시스템 사이에 메모리 없는 비선형 시스템이 있는 것으로 모델링할 수 있으며, 통계적 경사 근사법(stochastic gradient method)으로 선형 시스템의 필터 계수와, 다항식으로 표현되는 비선형 시스템의 계수를 구한다. 이렇게 모델링 되는 통신 채널은 통계적 경사 근사법과 간접 학습 구조를 사용하여 전치 보상기를 설계함으로써 보상한다. 여기서 제시한 비선형 보상 방법은 특정한 통신 채널 모델이 필요 없으며, 적응적으로도 적용이 가능하다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.49-52
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• 2004

본 논문에서는 켑스트럼 기반의 후두질환 음성의 자동감별시, 훈련 및 테스트 마이크 불일치로 인한 채널 왜곡을 보상하기 위한 방법에 대해 연구를 하였다. 특징벡터 영역에서의 채널보상 방법으로 기존의 Cepstral Mean Subtraction (CMS) 방법과 Pole Filtering CMS (FPCMS) 방법을 이용하였다 실험결과 FPCMS를 적용한 경우 기존의 CMS에 비해 우수한 성능을 보이고, $40\%$의 인식 오류 감소를 얻었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.1
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• pp.84-91
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• 2008

In this paper, we propose a Sequency domain based BPM-UWB receiver compensating for distortion in the multi-path channel. We give a mathematical derivation for the proposed receiver which exploits a matched filter theory for optimum reception. We also analyze the system performance and present the simulation results that show the performance enhancement of the proposed system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.517-529
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• 2011

In this paper, the parameters of the RTT (Radio Transmission Techniques) for SANET (Ship Ad-hoc NETwork), which is considered for the next generation maritime communication systems, are set up. A channel model has been analyzed based on the practical measured maritime wireless channel in VHF (Very-High Frequency) for SANET system. Also, by considering the frame structure including preamble, guard time and pilots for both single and multi-carrier systems, the BER (Bit Error Rate) performances are evaluated and analyzed in the aspects of channel compensation and channel coding techniques. Based on the simulation results, optimal modulation & coding schemes are suggested for SANET. That is, in single-carrier system by using differential modulation schemes, channel compensation is not necessary. However, channel coding is helpful to achieve additional gain. On the other hand, when 16-QAM modulation is employed in multi-carrier system, the implementation of both channel compensation and channel coding techniques show huge performance gain for various of K values, which are related to different maritime environments, and the rolling effects of wave.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.882-890
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• 2008

To overcome the limit of the time-domain based channel estimation caused by the ADC speed, this paper present a new BPM-UWB receiver where the channel estimations and the compensations are digitally performed in the frequency domain. We theoretically show that the channel estimation can be accomplished by exploiting the periodicity of a training sequence consisting of finite number of pulses. We also present the digital receiver structure to implement the proposed system and derive its BER performances. Through computer simulations, we show the proposed receiver can dramatically improve the BER performances due to the incorporation of the estimated channel frequency response.

• Journal of the Korea Computer Industry Society
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• v.7 no.1
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• pp.39-46
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• 2006

Multipath diversity reception is applied to the compensation of the distortion of channel, which occurs in transmission of data at rapid speed. DS/BPSK systems are composed of the equipment with reception structure combined with a compensation algorithm to diversity branch. The efficiency of the system is evaluated from the point of view of average bit error rate according to SNR. In order to remove intersymbol interference, this algorithm is applied to time-invariant channel at every diversity branch with the number of L. As a result, the average bit error rate is saturated by $10^{-2}$ at the conventional compensation algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.55-64
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• 2010

In this paper, we propose a new compensation scheme for combined channel distortions and RF impairments based on the analysis of the impacts of IQ(In-phase/Quadrature) imbalance and phase noise on the OFDM(Orthogonal Frequency Division Multiplexing) system in the direct conversion transceiver and frequency selective fading channel distortion. The proposed scheme estimates the combined distortion by the use of training symbols and the residual distortion by pilot symbols and compensates the combined distortion, including IQ imbalance, phase noise and multipath fading at the same time. The simulation results show that the proposed scheme compensates the combined distortion of IQ imbalance, phase noise and multipath fading simultaneously.

• Journal of IKEEE
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• v.23 no.3
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• pp.1046-1053
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• 2019

In a multi-channel single-ended system, the far-end crosstalk (FEXT) due to mutual inductance and mutual capacitance between two adjacent channels critically limit the bandwidth. FEXT causes crosstalk-induced jitter (CIJ) and crosstalk-induced glitch (CIG) which leads to timing margin and voltage margin degradations, respectively. Therefore, FEXT must be compensated in order to increase eye opening and achieve high data-rate. It can be compensated in transmitter by controlling the timing of the data or reshaping the waveform of the signal. Also, FEXT can be compensated in receiver by generating mimicked FEXT using high-pass filter. In this paper, recent techniques to compensate FEXT are investigated, with discussions of their pros and cons.