• 한국통신학회논문지
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• 제31권12C호
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• pp.1150-1156
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• 2006

본 논문에서는 $M\geq3$이고 $p\equiv{\pm}1$ mod M인 경우에 대해서 주기가 $p^m-1$인 M진 Sidel'nikov 수열의 $F_p$ 상에서의 선형복잡도의 하계와 1-오류 선형복잡도의 상계를 유도한다. 특히 $m\geq4$이고 $p\equiv-1$ mod 3인 경우에는 3진 Sidel'nikov 수열의 정확한 1-오류 선형복잡도를 계산한다. 이 결과들을 바탕으로 선형복잡도와 1-오류 선형복잡도의 주기에 대한 비율의 근사적 특성을 제시한다.

• 한국통신학회논문지
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• 제31권9C호
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• pp.846-852
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• 2006

${\kappa}$-오류 선형복잡도는 통신 시스템 및 스트림 암호 시스템 등에 사용되는 수열의 안정성 여부를 판단하는 중요한 척도이다. 본 논문은 p가 소수이고 2가 모듈로 $p^2$의 원시근일 때 $p^m$-주기 이진 수열의 k-오류 선형복잡도와 해당 오류벡터를 효과적으로 구할 수 있는 알고리듬을 소개한다. 또한 암호학적인 관점에서 정의된 ${\kappa}$-오류 선형 복잡도의 의미를 부호 이론의 관점에서 살펴봄으로써 부호어의 길이가 $p^m$인 이진 순환 부호를 효과적으로 복호할 수 있는 알고리듬을 소개하며 이러한 부호의 최소 거리에 관한 중요한 성질들을 유도한다.

• 한국통신학회논문지
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• 제33권1C호
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• pp.6-11
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• 2008

주기 수열에서 각 주기의 임의의 위치에 r개의 심볼을 추가하는 경우, 더 긴 주기를 가지는 수열을 얻을 수 있다. 본 논문에서는 주기 수열에 r개의 심볼을 추가한 수열의 선형복잡도에 대한 기존 결과들을 정리하고 GF(p)상에서 정의된 최대주기 수열에 1개의 심볼을 추가함으로써 얻어지는 수열들의 선형복잡도의 분포를 분석한다. 그리고 이진 최대주기 수열들의 1-심볼 추가 k-오류 선형복잡도에 대한 새로운 사실들을 유도함으로써 수열의 안정성을 평가한다.

• ETRI Journal
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• 제32권4호
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• pp.588-595
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• 2010

This paper proposes encoding and decoding for nonlinear product codes and investigates the performance of nonlinear product codes. The proposed nonlinear product codes are constructed as N-dimensional product codes where the constituent codes are nonlinear binary codes derived from the linear codes over higher order alphabets, for example, Preparata or Kerdock codes. The performance and the complexity of the proposed construction are evaluated using the well-known nonlinear Nordstrom-Robinson code, which is presented in the generalized array code format with a low complexity trellis. The proposed construction shows the additional coding gain, reduced error floor, and lower implementation complexity. The (64, 24, 12) nonlinear binary product code has an effective gain of about 2.5 dB and 1 dB gain at a BER of $10^{-6}$ when compared to the (64, 15, 16) linear product code and the (64, 24, 10) linear product code, respectively. The (256, 64, 36) nonlinear binary product code composed of two Nordstrom-Robinson codes has an effective gain of about 0.7 dB at a BER of $10^{-5}$ when compared to the (256, 64, 25) linear product code composed of two (16, 8, 5) quasi-cyclic codes.

• ETRI Journal
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• 제40권2호
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• pp.218-226
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• 2018

Multiuser detection (MUD) and channel estimation techniques in space-division multiple-access aided orthogonal frequency-division multiplexing systems recently has received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean-squared error (MMSE) MUD exhibits poor performance, although it achieves lower computational complexity. With almost the same complexity, an MMSE with successive interference cancellation (SIC) scheme achieves a better bit error rate performance than a linear MMSE multiuser detector. In this paper, hybrid ML-MMSE with SIC adaptive multiuser detection based on the joint channel estimation method is suggested for signal detection. The simulation results show that the proposed method achieves good performance close to the optimal ML performance at low SNR values and a low computational complexity at high SNR values.

• 한국통신학회논문지
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• 제35권7A호
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• pp.623-631
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• 2010

In this paper, various of pilot-assisted channel estimation techniques for 3GPP LTE downlink are tested under multipath Rayleigh fading channel. At first, the conventional channel estimation techniques are applied with linear zero-forcing (ZF) equalizer, such as one dimensional least square (1-D LS) linear interpolation, two dimensional (2-D) wiener filter, the time and frequency dimension separate wiener filter and maximum likelihood estimator (MLE). Considering the practical implementation, we proposed two channel estimation techniques by combining time-dimension wiener filter and MLE in two manners, which showed a good tradeoff between system performance and complexity when comparing with conventional techniques. The nonlinear decision feedback equalizer (DFE) which can show a better performance than linear ZF equalizer is also implemented for mitigating inter-carrier interference (ICI) in our system. The complexity of these algorithms are calculated in terms of the number of complex multiplications (CMs) and the performances are evaluated by showing the bit error rate (BER).

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.658-665
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• 2013

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

• 전자공학회논문지D
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• 제34D권11호
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• pp.1-8
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• 1997

In this paper, we propose a new method for the improvement of linearizing and adaptive convergence charateristics of the feedforward linear power amplifier. In this circuit, errors at the signal cancellation stage can be compensated at the error cancellation stage and the overall linearizaton and adaptation characteristics of the linear amplifier are improved. The broadband characteristics and linearizing capability are improved without increasing the complexity of circuits and the signal processing structure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1954-1971
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• 2017

In this work, first, a multiuser detection (MUD) algorithm based on component-level soft interference cancellation and linear minimum mean square error (CLSIC-LMMSE) is proposed, which can enhance the bit error ratio (BER) performance of the traditional SIC-LMMSE-based MUD by mitigating error propagation. Second, for non-binary low density parity check (NB-LDPC) coded high-order modulation systems, when the proposed algorithm is integrated with partial mapping, the receiver with iterative detection and decoding (IDD) achieves not only better BER performance but also significantly computational complexity reduction over the traditional SIC-LMMSE-based IDD scheme. Extrinsic information transfer chart (EXIT) analysis and numerical simulations are both used to support the conclusions.

• 한국전자파학회논문지
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• 제20권12호
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• pp.1287-1296
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• 2009

채널의 상태가 시간에 따라 수시로 변하는 전송 환경에서 수신된 신호에 대한 잡음 비를 추정하는 것이 중요하다. 대부분의 SNR 추정기는 MF(Matched Filter) 후 수신된 샘플로 추정이 이루어진다. 하지만 이런 기법들은 무선 통신에서 채널의 상태에 민감한 특성을 갖는다. 하지만 수신기의 front-end에서 모아진 데이터들을 이용하는 선형 예측(LP: Linear Prediction) 기법을 기반으로 하는 신호 대 잡음 비 추정 알고리즘은 이에 비해 안정된 성능을 보인다. 본 논문에서는 LP 기반의 SNR 추정기를 소개하고, 기존의 LP 기법 기반으로 하는 SNR 추정 알고리즘의 계산 복잡도를 줄이기 위한 새로운 기법을 제안한다. 본 논문에서 제안하는 알고리즘은 Linear Prediction 오차를 구하는 과정에서 순방향 오차와 그 conjugate 값을 이용하여 SNR 추정 과정을 보다 간단하게 한다.