• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.435-441
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• 2001

In this paper, we proposed adaptive MMSE receiver, which use channel equalizer to eliminate the interference due to multi-path fading and adaptive filter to eliminate the multiple access interference. The unique features of proposed receiver schemes are as following. We use pilot channel to estimate the channel coefficients exactly and guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signals. The length of channel equalizer also can be reduced with the help of guard symbols. Especially utilizing adaptive code-matched filter(AMMSE) when the user population is high and SNR is not low we accepts excellent performance improvement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1108-1115
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• 2005

In this paper, we propose a practical iterative channel estimation and decoding method for an LDPC-coded frequency hopping OFDMA system in the uplink of a packet-based cellular system. In the method, the channel gain and noise variance are iteratively estimated with both pilot symbols and LDPC decoder outputs to provide more reliable decoding metrics in intercell interference (ICI) environments. In addition, the channel correlation coefficient is also estimated to select proper filter coefficients according to the channel variation rate. Through simulations under the various channel conditions and different receiver configurations, it is shown that the proposed iterative receiver improves the performance without boosting the pilot power and mitigates the adverse effects of the non-uniform ICI.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.8
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• pp.26-33
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• 2017

Vehicle communication can facilitate efficient coordination among vehicles on the road and enable future vehicular applications such as vehicle safety enhancement, infotainment, or even autonomous driving. In the $3^{rd}$ Generation Partnership Project (3GPP), many studies focus on long term evolution (LTE)-based vehicle communication. Because vehicle speed is high enough to cause severe channel distortion in vehicle-to-vehicle (V2V) environments. We can utilize channel estimation methods to approach a reliable vehicle communication systems. Conventional channel estimation schemes can be categorized as least-squares (LS), decision-directed channel estimation (DDCE), spectral temporal averaging (STA), and smoothing methods. In this study, we propose a smart channel estimation scheme in LTE-based V2V environments. The channel estimation scheme, based on an LTE uplink system, uses a demodulation reference signal (DMRS) as the pilot symbol. Unlike conventional channel estimation schemes, we propose an adaptive smoothing channel estimation scheme (ASCE) using quadratic smoothing (QS) of the pilot symbols, which estimates a channel with greater accuracy and adaptively estimates channels in data symbols. In simulation results, the proposed ASCE scheme shows improved overall performance in terms of the normalized mean square error (NMSE) and bit error rate (BER) relative to conventional schemes.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.144-149
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• 2016

In this paper, we analyze a QPSK MODEM over underwater acoustic channel model. Ambient noises and parameters of underwater environments debase the BER performance of an underwater modem. In the paper, the BER performance of uncoded QPSK and rate-2/3 convolutional coded QPSK is analyzed. And To improve BER Performance, we apply a channel equalization technique to the underwater modem.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.182-184
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• 2010

최근 3D HDTV에 대한 연구가 활발히 이루어지고 있다. 우리나라에서도 3D HDTV 표준을 제정하기 위한 준비가 이루어지고 있으며, 이와 같은 흐름에 맞추어 기존의 ATSC 전송 방식을 확장한 전송 방식이 연구되고 있다. 확장된 ATSC 전송 방식은 지상파 3D HDTV 방송을 목표로 하고, 프레임 구조를 중국의 지상파 방송 표준인 DMB-T와 유사하게 PN 시컨스와 데이터가 연속되는 구조로 모델링하여 이용하고자 한다. 연구되고 있는 확장한 전송방식은 기존의 ATSC 시스템의 VSB 변조방식을 기반으로 한다. 그러므로 원활한 수신을 위해서는 반송파 주파수 오차(심볼속도 대비 최대 1%)를 정확하게 추정하고 복구하여야 한다. 기존 ATSC 시스템은 주파수 대역(DC 1.25V)의 파일럿 신호를 이용하여 반송파 주파수 복구를 하였지만, 확장된 ATSC 시스템은 프레임 헤드 부분인 PN 시컨스를 이용한다. 본 논문에서는 확장된 ATSC 전송 시스템 방식에 적용 가능한 반송파 주파수 복구 방식을 제안하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.390-396
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• 2009

MC-DS-CDMA is technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of PSAM MC-DS-CDMA system with the application of STBC antenna diversity is analyzed. The BER performance of this system over multipath fading environment is evaluated, considering the channel estimation ernr, carrier frequency offset, and the nonlinear high power amplifier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.815-820
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• 1998

A new coding algorithm which has spectrum notches at the DC and Nyquist Frequency for maximizing the effect of the in-band pilot insertion in order to make the symbol timing or carrier recovery easy is proposed. It is shown that this algorithm uses one encoder and gives the similar spectrum characteristics to that of the existing OF00 code which uses two encoder. In this paper, the proposed new coding algorithm is explained andits spectrum characteristics is compared with the of OF00 code using computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.817-823
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• 2010

MC-DS-CDMA is technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of PSAM MC-DS-CDMA system with the application of MRRC antenna diversity is analyzed. The BER performance of this system over multipath fading environment is evaluated, considering the channel estimation error, carrier frequency offset, and the nonlinear high power amplifier.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.23-25
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• 2015

최근 디지털 방송의 새로운 서비스에 대한 소비자의 기대와 무선 통신 및 영상 압축 기술의 발전으로 인해 차세대 방송 기술에 대한 관심이 고조되고 있다. 미국 방송 표준화 기구인 ATSC에서는 차세대 국제 방송 표준을 위해 ATSC 3.0을 시작하였고, 고정 방송 및 이동 방송의 동시 서비스 제공을 목표로 하고 있다. TDM을 사용하여 두 방송 서비스를 제공하는 경우 ATSC 3.0 융합형 3DTV 서비스를 제공할 수 있으며, 모바일 방송의 파일럿 심볼을 이용한 채널 추정이 가능하므로 고정 방송만을 제공하는 경우보다 채널 등화 성능 측면에서 더 유리하다. 이에 본 논문에서는 ATSC 3.0 융합형 3DTV를 위한 채널 등화 시뮬레이터를 설계 및 구현하여 고정 방송 환경과 성능을 비교한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1283-1288
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• 2007

An equalization technique for OFDM systems in tine variant fading environment is described. Time variant channels lead to interchannel interference which increases the bit mr rate. A frequency domain equalizer using pilot symbols is proposed. The equalizer decreases the interchannel interference affecting the error performance. The effectiveness of the proposed technique is analyzed via computer simulation.