• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2207-2214
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• 2010

Underwater acoustic(UWA) communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of UWA channel causes signal distortion and error floor. In this paper, we proposed split input bits of channel decoder using method of maximum value, average value, LLR value for optimal estimation. Channel coding method is LDPC(N size=16000) standard in DVB-S2. As shown in simulation results, the performance of LLR value method is better than other methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2791-2797
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• 2010

In recent years, the goal of providing high speed wireless data services has generated a great amount of interest among the research community. Several researchers have shown that the capacity of the system, in the presence of flat Rayleigh fading, improves significantly with the use of combined MIMO and LDPC. To feed the soft values to LDPC decoder, the soft values must be calculated from multiple transmitter and receiver antennas in Rayleigh fading channel. It requires high computational complexity to get the soft symbols by increasing number of transmitter and receiver antennas. Therefore, this thesis proposed on effective algorithm for calculation of soft values from multiple antennas based on LLR. As result, This thesis shows that maximum 61% of computational complexity is reduced with a little loss of performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1281-1284
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• 2009

무선통신에서는 다양한 서비스, 높은 신뢰도와 함께 빠른 전송속도를 요구한다. 이러한 요구를 만족시키기 위해서 LDPC 부호와 MIMO 기술이 활발히 연구 중에 있다. 본 논문에서는 LDPC와 결합된 STC 모델을 설명하고, 여러개의 송신안테나로부터 송신되어 결합된 신호를 분리하기 위해 사용되는 Log-Likelihood Computation을 기존의 방식과 제안하는 저 계산량 알고리즘을 통한 방식을 비교, 분석하여 기존의 방식과 근접한 BER 성능을 유지 하면서 계산량 감소를 확인한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.10-21
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• 2015

Cellular Network assisted device-to-device (D2D) communication has been growing to reduce the overload of eNodeB and mitigate the frequency shortage. However, by sharing the uplink frequency resource with the cellular network, the interference between cellular and D2D is increased. In this paper, we propose the advanced receiver based on soft decision to reduce the interference between cellular and D2D. The proposed receiver can suppress and cancel the interference by calculating the unbiased estimation value of interference signal using minimum mean square error (MMSE) or interference rejection combing (IRC) receiver. The interference signal is updated using soft information expressed by log-likelihood ratio (LLR). We perform a system level simulation based on the 20-MHz bandwidth of the 3GPP LTE-A system. Simulation results show that the proposed receiver can improve SINR, throughput and spectral efficiency compared to conventional receivers.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.3-11
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• 2015

An advanced receiver which can manage inter-cell interference is required to cope with the explosively increasing mobile data traffic. 3rd Generation Partnership Project (3GPP) has discussed network assisted interference cancellation and suppression (NAICS) to improve signal-to-noise-plus-interference ratio (SINR) and receiver performance by suppression or cancellation of interference signal from inter-cells. In this paper, we propose the advanced receiver based on soft decision to reduce the interference from neighbor cell in LTE-Advanced downlink system. The proposed receiver can suppress and cancel the interference by calculating the unbiased estimation value of interference signal using minimum mean square error (MMSE) or interference rejection combing (IRC) receiver. The interference signal is updated using soft information expressed by log-likelihood ratio (LLR). We perform the system level simulation based on 20MHz bandwidth of 3GPP LTE-Advanced downlink system. Simulation results show that the proposed receiver can improve SINR, throughput, and spectral efficiency of conventional system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2004.11a
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• pp.169-174
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• 2004

이 논문에 서 는 DVB-S2 BC(Backward Compatibility) 모드에서 복조방식 에 따른 수신성 능을 분석하였다. 송신기는 DVB-S(HP)와 DVB-S2(LP) 스트림을 계층적 비대칭 8-PSK로 변조시킨 신호를 전송하며, 수신기는 계층적 변조 신호를 복조하기 위하여 LSB 에서 MSB순으로 복조하는 방식과 사분면 추정지수와 LLR 계산기를 이용한 계층적 복조방식을 적용할 수 있다. 이 논문은 두 복조방식에 대한 성능분석을 AWGN 및 비선형 채널에서 통계적 분석과 모의실험을 통하여 수행하였다.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.2-10
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• 2007

We analyzed the receiving performance of the DVB-S2 transmission system in the BC(Backward Compatibility) mode. The transmitter employs the hierarchical modulation, and the receiver can be implemented by the direct demodulation or the hierarchical demodulation. The performance of each demodulation scheme is analyzed by a statistical method and a computer simulation for the AWGN and nonlinear channels. The ratio of the LP/HP streams which is proper in the domestic satellite broadcasting environments, is also suggested.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.24-30
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• 2014

A digital RDA(Retrodirective Antenna) system is a retransmit system that received signal without prior information turn back by estimated phase of the signal to received direction. The RDA can decrease consumption of power by increase of directivity because signal concentrates on received direction compare to omni-direction antenna which transmit power all direction. Generally, the RDA is known to show better performance than the single-antenna system in multi-path environment. However, the RDA occurs performance degradation in serious ISI channel. In this paper, to solve this problem, we propose retrodirective antenna combined with turbo equalizer combined which can compensate serious ISI channel, we increase the BER performance through proposed retrodirective antenna combined with turbo equalizer in serious ISI channel.