• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.34-40
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• 2012

In wireless communication system, fading is an unavoidable problem. Hence, errors in form of BER are introduced with the transmitted signal. It is necessary to recognize the behavior of these errors in different fading channels. To obtain the mathematical solution for the average bit error rate(BER) of coherent MPSK, some techniques are presented. In this paper, the impact of diversity is also analyzed over slow and flat Rician fading channel. In here, the value of modulation index, M is varied and the effects of its variation are also depicted. So, these performance curves with different diversity values and fading parameter are useful to design and evaluate the radio channel for faithful communication system.

• Journal of the Korea Society of Computer and Information
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• v.19 no.5
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• pp.1-10
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• 2014

The proposed scheme schedules given real-time tasks so that energy consumption of multicore processors would be minimized while meeting tasks' deadline and tolerating a permanent fault based on the primary-backup task model. Whereas the previous methods minimize the overlapped time of a primary task and its backup task, the proposed scheme maximizes the overlapped time so as to decrease the core speed as much as possible. It is analytically verified that the proposed scheme minimizes the energy consumption. Also, the proposed scheme saves up to 77% energy consumption of the previous method through experimental performance evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.725-733
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• 2006

In this paper, we propose an algorithm which makes the frequency of output signal synchronize with frequency of input signal in Equalization Digital On-channel Repeater (EDOCR) system which was proposed to overcome the disadvantage of conventional Digital On-Channel Repeater (DOCR). Also, we verify the algorithm by using the mathematical equivalent model and analysis the performance by implying the algorithm to EDOCR. The main idea is to use the frequency offset information, which comes from carrier recovery in the receiving part of EDOCR, when the demodulated symbol is re-modulated in transmitting part. Based on the proposed algorithm, EDOCR not only makes the output signal synchronized with input signal in frequency but also emit the output signal which satisfies the ATSC transmission standard without additional equipments such as Global Positioning System (GSP).

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.927-934
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• 2002

In order to provide various multimedia services in a wireless network, the call admission control for wireless channels should be resolved at the time of call setup and handoff by moving mobile terminal. In this paper. we propose a reliable DCAC( Distributed Call Admission Control)scheme using virtual cluster concept. The proposed DCAC scheme considers the state of $1^{st}$ and $2^{nd}$ adjacent cells to provide a reliable call handling. The proposed scheme is analyzed by simulations and mathematical methods.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.233-234
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• 2017

본 논문에서는 수학적 모델링과 성능 분석을 통해 LVDC 용 3상 Dual Active Bridge (DAB) 컨버터의 효율을 증가시킬 수 있는 다양한 방법에 대해서 제안하고자 한다. 3상 DAB 컨버터의 경우 양방향 전력 변환을 필요로 하는 고전력 응용에서 많이 사용되고 있다. 이는 3상 DAB 컨버터가 영전압 스위칭이 가능할 뿐만 아니라, 단상 DAB 컨버터 대비 낮은 도통 손실을 가질 수 있기 때문이다. 고전압/고전류 응용의 경우 대부분 능동 소자로 IGBT가 사용되는데, 따라서 대전력 응용에서 3상 DAB 컨버터의 영전압 스위칭이 가능한 장점을 퇴색시키고, 높은 스위칭 손실을 야기한다. 뿐만 아니라 3상 DAB 컨버터의 경우 고부하 상태에서 높은 순환 전류로 인해 도통 손실이 증가한다. 따라서 본 논문에서는 상기의 단점을 극복하기 위하여 IGBT의 턴-오프 전류를 최소화 시키고, RMS 전류를 낮출 수 있는 설계 방법을 제안하고자 한다. 모의시험과 5 kW급 시작품을 이용한 실험결과를 통해 제안하고자 하는 설계 방법의 타당성을 검증하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.22-24
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• 2005

이동 컴퓨팅 환경에서 통신 네트워크가 갖는 무선 채널 대역폭의 협소함과 이동 단말기의 에너지 제약으로 인해, 다수의 이동 클라이언트들에게 데이터를 전달할 때에는 다수의 클라이언트들의 동시 데이터 접근을 지원하는 브로드캐스트 방법을 사용함으로써 제약점들을 보완할 수 있다. 본 논문에서는 클라이언트의 에너지와 데이터에 대한 접근시간(access time)의 효율을 높이기 위해 데이터의 접근빈도(access frequency)를 고려한 브로드캐스트 방법과 브로드캐스트 인덱스를 추가하는 방법을 함께 반영한 OAF(Data Access Frequencies)브로드캐스팅 기법을 제안한다. DAF브로드캐스팅 기법은 데이터의 접근빈도를 고려한 인덱스를 교차하여 추가함으로써 접근빈도가 높은 데이터를 원하는 다수의 사용자에 대한 접근시간을 줄임으로써 모든 사용자의 평균 접근시간을 줄이는데 목적이 있다. 수학적 분석을 통해 DAF브로드캐스팅 기법을 평가하고 기존의 브로드캐스트 방법과 DAF브로드캐스팅 기법의 성능을 비교 분석한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1201-1206
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• 2007

In this paper, we propose an algorithm that improve network lifetime by adjusting cluster size according to location information of sensor node in wireless sensor network (WSN) using clustering algorithm. The collected sensing information by sensor nodes in each cluster are transferred to sink node using inter-cluster communications method. Cluster head (CH) that located nearby sink node spend much more energy than those of far from sink node, because nearer CH forwards more data, so network lifetime has a tendency to decrease. Proposed algorithm minimizes energy consumption in adjacent cluster to sink node by decreasing cluster size, and improve CH lifetime by distributing transmission paths. As a result of mathematical analysis, the proposed algorithm shows longer network lifetime in WSN.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.82-98
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• 1994

A mathematical model for the hydrodynamic forces acting on the ship manoeuvring in waves is formulated and a numerical method for the problem is developed. The motion of a ship, which manoeuvres in waves, may be thought to have two components; one is a high frequency component due to encounter waves, and the other is a low frequency component due to manoeuvring motion. So the method of two time scale expansion is used to divide linear boundary value problem. For the effects of waves on the manoeuvring motion of a ship, only the second order drift forces are considered. The integral equation for the velocity potential is solved by 3 dimensional panel method and hydrodynamic forces are calculated by direct integral method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.109-114
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• 2024

The effect of inter-channel coupling in multi-channel monopulse receiver is expected to increase by miniaturization trend of receiver. Therefore, in this paper, calibration method is proposed to compensation for inter-channel coupling in receiver of monopulse radar. And it can prevent distortion of angle information of target. Hardware configuration that consists of switch, directional coupler, matched load, ADC(Analog to Digital Converter), signal source of calibration is proposed to calibration. Total nine scattering parameters are obtained by controlling the switch and signal source of calibration. After that, method for restoring the undistorted signal is proposed using the mathematical relationship between the monopulse signal output from the antenna and the monopulse signal passing through the multi-channel receiver in the presence of inter-channel coupling.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.9-18
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• 2024

The importance of active sonar systems is emerging due to the quietness of underwater targets and the increase in ambient noise due to the increase in maritime traffic. However, the low signal-to-noise ratio of the echo signal due to multipath propagation of the signal, various clutter, ambient noise and reverberation makes it difficult to identify underwater targets using active sonar. Attempts have been made to apply data-based methods such as machine learning or deep learning to improve the performance of underwater target recognition systems, but it is difficult to collect enough data for training due to the nature of sonar datasets. Methods based on mathematical modeling have been mainly used to compensate for insufficient active sonar data. However, methodologies based on mathematical modeling have limitations in accurately simulating complex underwater phenomena. Therefore, in this paper, we propose a sonar signal synthesis method based on a deep neural network. In order to apply the neural network model to the field of sonar signal synthesis, the proposed method appropriately corrects the attention-based encoder and decoder to the sonar signal, which is the main module of the Tacotron model mainly used in the field of speech synthesis. It is possible to synthesize a signal more similar to the actual signal by training the proposed model using the dataset collected by arranging a simulated target in an actual marine environment. In order to verify the performance of the proposed method, Perceptual evaluation of audio quality test was conducted and within score difference -2.3 was shown compared to actual signal in a total of four different environments. These results prove that the active sonar signal generated by the proposed method approximates the actual signal.