• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.835-843
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• 2006

Multicast can send one copy of each packet to each member of the multicast group. Network resource is utilized effectively, consequently, it is suitable for one-to-many environments. reliability and flow control, however, are not supported basically, it is not suitable or transmission of multimedia data which have a time restriction. In this paper, we present a network model and a multicast retransmission scheme The proposed scheme remove ack-explosion from sender through local recovery and performs local retransmission when time restriction is satisfied on receiver by considering the state of receiver's buffer. Mathematical analysis and simulation are conducted to prove performance of the proposed scheme. The results are shown that the proposed scheme consumes a lower network bandwidth than the existing network model and guarantees QoS of receivers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.93-100
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• 2006

This paper presents a multi-sensor data simulator and a data fusion algorithm for tracking high dynamic flight target from Radar and Telemetry System. The designed simulator generates time-asynchronous multiple sensor data with different data rates and communication delays. Measurement noises are incorporated by using realistic sensor models. The proposed fusion algorithm is designed by a 21st order distributed Kalman Filter which is based on the PVA model with sensor bias states. A fault detection and correction logics are included in the algorithm for bad data and sensor faults. The designed algorithm is verified by using both simulation data and actual real data.

• Journal of Korea Multimedia Society
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• v.1 no.2
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• pp.154-161
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• 1998

This paper proposes a parallel processor system which processes cultural assets image recognition and retrieval algorithm in real time. A serial algorithm which is developed for the parallel processor system is parallellized. The parallel processor system consists of a control unit, 100 PE(Processing Elements), and 10 Park's multi-access memory systems which has 11 memory modules per each one. The parallel processor system is simulated by CADENCE Verilog-XL which is a package for the hardware simulation. With the same simulated results as that of the serial algorithm, the speed ratio of the parallel algorithm to the serial one is 81. The parallel processor system we proposed is quite effective for cultural assets image processing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.660-666
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• 2004

Transmitted data may be compensated by using estimated channel values that are obtained with pilot symbols in OFDM-CDMA systems. Generally, a USE (Minimum Mean-Squared Error) estimator using correlations between pilot symbols gives good results, but its structure is so complicated. Starting with a modification of PA (Pilot-Aided) algorithm using pilot symbols and PADD (Pilot-Aided Decision-Directed) algorithm using both pilot and data symbols, a new channel estimation algorithm with more simpler structure is proposed. The performance of this algorithm is evaluated with varying mobile speed in a Ralyleigh multipath fading environment through computer simulations. The simulation results show that the proposed channel estimation algorithm outperforms a conventional PA algorithm.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.3022-3024
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• 2005

연성 PCB(flexible printed circuit board)는 현재 노트북 PC와 디지털 카메라등에 적용되며, 굴곡성이 강하고 소형화 및 조립에 용이하여 주로 기판 사이나주기판과 외부 커넥터사이에 데이터의 전송매체로써 널리 사용되는 핵심부품이다. 근래에 개발되는 PCB 기반의 고성능 신호처리회로들은 데이터 전송율이 수백 MHz에서 수 GHz에 이르고 있으며, 신호선과 유전체, 접지판의 구조적 특성에 따라서, 반사 효과와 같은 신호무결성 문제들이 파생되어 신호의 최대성능을 제한하게된다. 이에 따라 적절한 임피던스 제어를 통하여 고성능신호들의 왜곡을 상쇄시키는 기술이 중요하게 되었다. 본 논문에서는 연성 PCB 전송라인을 위한 임피던스 모델을 대상으로 각 모델의 주요 특징 및 정확성을 분석하였다. 연성 PCB의 전송라인은 보통 전통적인 마이크로스트립 라인의 특성 임피던스 모델에 비해 신호선의 너비가 크며, 이를 반영한 개선된 수학적 임피던스 모델들이 제안되어 있다. 따라서 본 논문은 기존의 마이크로스트립 전송라인과 연성 PCB 전송라인에 적합한 수학적 모델들을 이용하여 신호 무결성 문제를 모의할 수 있는 CAE(computer-aided engineering) 도구의 임피던스 측정 결과를 비교 및 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.331-337
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• 2017

In this work, we propose an improved form of Zhang's reversible data hiding technique in encrypted image. In the original work, average value of neighboring pixels is used for fluctuation calculation which fails to give good performance. In proposed scheme, to reduce the bit error rate a new function is calculated by summing difference from four neighboring pixels for measuring fluctuation. Moreover, modified calculation of fluctuation function is also proposed where border pixels are considered. The simulation results show that the performance of proposed method outperforms Zhang's and Hong's work. From the results, more information can be sent by using proposed system

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.175-180
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• 2012

In order to overcome the complexity and performance limit problems of superscalar processors, the multicore architecture has been prevalent recently. The configuration and the size of instruction and data caches greatly gives effect on the performance of multicore processors. Using SPEC 2000 benchmarks as input, the trace-driven simulation has been performed for the 2-core to 16-core architectures with different sizes of caches extensively. As a result, the 2-way set associative instruction and data cache with the size of 64KB brought the best cost-effective performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1182-1188
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• 2005

In this paper, various power delay profiles (PDP) are simulated to study the influence of the PDP shape on the bit error rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) communication systems. Assuming Rayleigh fading with 16-QAM modulation scheme, the simulation focuses on the investigation of the various shapes of the PDP which are often characterized by peaks, slope, attenuation and distance of an echo profile of waves. This yields information about the properties of the channel, and can be applied to decide the performance of the systems according to the channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.18-24
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• 2005

In this paper, a new trellis-coded differential unitary space-time modulation (TC-DUSTM) scheme based on amplitude/phase-shift-keying (APSK) signals is proposed. In particular, the design criterion of the trellis coding is proposed to combine the trellis coding and DUSTM scheme based on APSK constellation. From the computer simulations, we verify the superiority of the proposed TC-DUSTM based on APSK signals at the higher transmission rate. In addition, the proposed scheme can suppress the irreducible error of the differential scheme.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.286-286
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• 2023

물의 전체 순환 구조에서 토양수분이 차지하는 정량적 비중은 상대적으로 작지만, 강우-유출 과정의 비선형에 영향을 미치는 지배적 요인 중 하나이고, 토양 침식과 산사태, 농업생산량, 기후 변화 대응 등 광범위한 주제와 연관되어 있어, 토양수분의 물리과정에 대한 이해 증진과 예측 기술의 지속적인 개선이 필요하다. 본 연구에서는 금오공과대학교 유역 내에서 토양수분과 기상 요소를 실시간 관측하고, 기계학습 기법을 이용하여 토양수분을 단기 예측하는 기술을 개발하고 평가한다. 구체적으로는, 토양 관측 장비인 TEROS를 사용하여 표층 지점의 10cm, 심층 지점의 40cm에서의 토양수분, 토양장력과 토양온도를, 기상 관측 장비인 ATMOS를 사용하여 태양복사, 강수량, 기온, 풍속, 대기압 등 다양한 기상 요소를, 실시간 클라우드 방식으로 1여 년간 수집한 데이터를 활용한다. 또한, 과거 및 실시간 데이터를 기반으로 LSTM(Long-Short Term Memory) 기법을 사용하여 토양수분 예측 모형을 구축하고, 선행 예측 시간에 따른 모의 정확도를 평가한다. 기상 요소의 누적 등 자료 분석 방법이 표층 및 심층 토양수분 예측에 미치는 영향, 그리고 예측 모형 개선 방향에 대해 토의한다. 실시간 현장 관측 자료 및 인공지능 기반 단기 토양수분 예측 모의 기술은 소규모 유역의 수문순환 분석 및 물리기반 모형의 개선 등 다양한 분야에서 활용할 수 있을 것으로 기대된다.