• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.3-5
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• 2007

This paper presents decision feedback equalizers using a recurrent neural network trained algorithm using extended Kalman filter(EKF) and sigma-point Kalman filter(SPKF). EKF is propagated, analytically through the first-order linearization of the nonlinear system. This can introduce large errors in the true posterior mean and covariance of the Gaussian random variable. The SPKF addresses this problem by using a deterministic sampling approach. The features of the proposed recurrent neural equalizer And we investigate the bit error rate(BER) between EKF and SPKF.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1995년도 제12회 음성통신 및 신호처리 워크샵 논문집 (SCAS 12권 1호)
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• pp.76-80
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• 1995

Differential pulse code modulation 구조의 Line spectrum pairs 양자화기에 높은 차수 LSP 파라미터 값은 낮은 차수 LSP 파라미터 값보다 커야한다는 LSP 파라미터의 순서화 특징을 이용하여 양자화하는 방법을 제시한다. 31 비트/프레임에서 1 dB 이하의 스펙트럴 왜곡을 갖는 명료한 음질을 보였다. 또한 LSP 주파수의 순서화 특성은 벡터-스칼라 결합 양자화기에 적용하였다. 벡터-스칼라 결합 양자화기에서는 26비트/프레임에서 명료한 음질을 보였다. 새로운 LSP 양자화 방법들은 전송에러 발생시 성능을 시험하고, 전송 에러에 강인하도록 프레임간 예측을 위해 Moving Average 예측기를 사용한다.

• 대한전자공학회논문지
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• 제27권9호
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• pp.1378-1385
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• 1990

In this paper we propose a model which can predict well the logical errors come from the charge redistribution in domino gates. In this model the effect of the intrinsic capacitance between gate and channel of MOSFET's is considered. This effect is more important than the parasitic capacitance effect. The error by the proposed model is only 8% of that by the currently used model. This model can be used as a guide-line in the design of domino circuits.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1984년도 추계학술발표회논문집
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• pp.11-14
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• 1984

When the received sequence is not identical to the transmitted code word due to the channel nose effect, it is necessary to detect and correct errors. In this paper, it is shown how to construct the encoder and the decoder using cyclic product codes. this system combines random and burst error correction and is easily decodable. Performance has been obtained as expected.

• 정보보호학회논문지
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• 제1권1호
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• pp.66-78
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• 1991

본 논문에서는 스트림 암호시스템의 종류와 오류전파 특성에 대해 분석한다. 또한, 암호문 전송중 전송로상에서 발생하는 오류르 제어할 목적으로 DSEC(31, 27) RS 부호를 암호문 귀환암호시스템에 내부오류제어 및 외부오류제어로 분류하여 적용하고 오류정정과정을 분석한다.

• Journal of Communications and Networks
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• 제11권2호
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• pp.134-147
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• 2009

Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.

• 제어로봇시스템학회논문지
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• 제15권3호
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• pp.346-352
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• 2009

UTC (Coordinated Universal Time) has been made by the comparison results and the statistical analysis of primary clocks maintained by national standard institutes. Some kinds of technique have been used for international time transfer; since 1980s the study on methods and development of time transfer has conducted with activation of GPS application. And the more accurate and easier method made it use the official time transfer method for the generation of UTC. But recently TWSTFT (Two-Way Satellite Time and Frequency Transfers) as well as GPS time transfer are increasing in number because the TWSTFT is able to improve the accuracy and precision of time comparison owing to the elimination of the ionospheric and tropospheric delay errors thanks to the reciprocal propagation path. In this paper, we introduce the TWSTFT results by a multi-channel modem comparing with GPS P3-code.

• Journal of Communications and Networks
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• 제16권1호
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• pp.45-55
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• 2014

The paper investigates the problem of designing the multiple-antenna relay in a two-way relay network by taking into account the imperfect channel state information (CSI). The objective is to design the multiple-antenna relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. In particular, the worst-case transmit power at the multiple-antenna relay is minimized while guaranteeing the worst-case quality of service requirements that the received signal-to-noise ratio (SNR) at both sources are above a prescribed threshold value. Since the worst-case received SNR expression is too complex for subsequent derivation and processing, its lower bound is explored instead by minimizing the numerator and maximizing the denominator of the worst-case SNR. The aforementioned problem is mathematically formulated and shown to be nonconvex. This motivates the pursuit of semidefinite relaxation coupled with a randomization technique to obtain computationally efficient high-quality approximate solutions. This paper has shown that the original optimization problem can be reformulated and then relaxed to a convex problem that can be solved by utilizing suitable randomization loop. Numerical results compare the proposed multiple-antenna relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. Finally, the feasibility of the proposed design and the associated influencing factors are discussed by means of extensive Monte Carlo simulations.

• International Journal of Contents
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• 제11권1호
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• pp.7-14
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• 2015

In this paper, we derive the outage probability for M-ary phase shifting keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) burst transmission (BT) of adaptive decode-and-forward (ADF) cooperative relay systems over quasi-static Rayleigh fading channels. Within a burst, there are pilot symbols and data symbols. Pilot symbols are used for channel estimation schemes and each relay node's transmission mode selection schemes. At first, we focus on ADF relay systems in which the probability density function (PDF) is derived on the basis of error events at relay nodes corresponding to channel estimation errors. Next, the average outage probability is derived as an approximate expression for an arbitrary link signal-to-noise ratio (SNR) for different modulation orders. Its accuracy is demonstrated by comparison with simulation results. Further, it is confirmed that BT-ADF relay systems with pilot symbol based channel estimation schemes enables to select correctly decoded relay nodes without additional signaling between relay nodes and the destination node, and it is verified that the ideal performance is achieved with small SNR loss.

• 전자공학회논문지
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• 제49권11호
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• pp.211-216
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• 2012

최근 심해 해난 구조 통신, 해저 탐사와 환경오염에 대한 모니터링과 같은 서비스에서 수중 음향 채널을 통한 데이터의 전송은 고속이 요구되고 있다. 그러나 수중 음향 채널은 매우 복잡하고 지속적인 시변 특성을 가지므로 양질의 통신 서비스를 제공하기란 쉽지 않다. 이러한 수중 음향 채널의 열악한 환경상에서 고속의 데이터 전송율과 신뢰성 그리고 강건성을 제공하기 위해서 다중경로 지연확산과 동기오류를 가지는 OFDM 시스템에 대한 성능개선 방안을 제안한다.