• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.625-629
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• 2011

In this study, we analyzed the signal environment of 17 DGNSS stations operated by DGPS Central Office through TEQC quality checking, visibility analysis and site visits. With TEQC, we produced times series of four indices of TEQC quality checking: observation ratio, L1 pseudorange multipath, L2 pseudorange multipath, and the frequency of cycle slip events. From visibility analysis, the directions where missing observations are happening were identified and the result was verified through onsite investigation. Without considering TEQC indices at the six sites(Palmido, Eochungdo, Geomundo, Pyeongchang, Seongju, and Chungju), the average TEQC indices were: 98% observation ratio, 0.19m of L1 pseudorange multipath, 0.71m of L2 pseudorange multipath, and 1.3 cycle slips per 1000 observations. The observation ratios at Palmido and Eochungdo were low. It was found that receiver settings were incorrect so that they could track the P2 signal of GPS satellites with L2C capability. No signal-blocking obstacles were found around the Geomundo station except the lighthouse. Thus, we guess that the poor TEQC indices at the site are believed to be caused by problems in the GPS hardware or cables. The low observation ratio at Pyeongchang is being caused by the surrounding hills blocking the satellite view from the south to the northwest directions. Even though all of four TEQC indices were bad at Seongju and Chungju stations, we found that the signal reception environment at the two sites is in good condition. We think that the quality indices got poor probably because of malfunctioning equipment. So, further investigation is needed for the Seongju and Chungju sites.

• Proceedings of the IEEK Conference
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• 2001.06d
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• pp.53-56
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• 2001

This paper presents a computationally efficient post-processing algorithm for HDTV. The proposed algorithm can reduce both blocking artifacts and mosquito noise while preserving the sharpness and naturalness of the reconstructed video signal. Performance improvements compared with other techniques are obtained according to simulation results.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1247-1252
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• 2004

ATC(Automatic Train Control) system employed in Bundang urban transit is operated in accordance with automatic blocking equipment. Using AF(Audio Frequency) track circuits installed at a block section, the block signal is automatically controlled and the safety of train operation is supported. In this paper, we investigate the operation mode of bundang urban transit and analyze the operation algorithm of ATC on-board system.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.687-690
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• 2004

본 논문에서는 음란유해콘텐츠를 기술적으로 차단하기 위해 신호처리 기법에 기반한 방법을 제안하고자 한다. 지금까지의 기술적인 방법 등이 목록기반과 단어기반에 기초한 방법이기 때문에 음란콘텐츠가 제대로 차단이 되지 않은 경우가 많았다. 이를 위해 본 논문에서는 신호처리에 기반하여 음란 유해 콘텐츠를 차단하는 방법을 제안하고자 한다. 끝으로 실험에 의해 제안한 방법의 유용성을 입증하고자 한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.315-318
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• 2013

A novel foveation filter method is proposed in DCT domain. For countering the blocking and ringing artifacts, we devise the tools measuring the signal gradient, the block signal variations in the DCT domain. Each measurement is properly applied to each enhancement region and smoothing region. The proposed method optimally adapts the enhancement factors to the characteristics of the underlying signals and so maximizes the enhancement performances with significantly suppressing the artifacts. The subjective and objective evaluations verify that the proposed method sustains producing the improved video qualities for various sequences without tuning any parameters to individual sequences.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2664-2673
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• 1997

The signal fading distortion has effect on the capacity of cellular mobile communication systems. The short term fading is solved by signal processing techniques depending on the radio communication methods, but another distortion compensation techniques are necessary to combat long term fading. in this paper, we have simulated the call processing in DS-CDMA system using distributed antennas to overcome the long term fading. From the simulation results, we have conformed that the blocking probability of a new call andthe forced probability of handoff-request-call have decreased by increasing the number of distributed antennas.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.6
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• pp.600-606
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• 1992

The series connection of power switching semiconductor elements is essential when a high voltage converter is made, so researches are being conducted to further develop this technology. In the series connection of power switching semiconductor elements, the main problem is that simultaneous conduction at turn-on and simultaneous blocking at turn-off together with voltage balancing are unattainable because of the difference of their switching characteristics. In this paper a novel series connection algorithm is proposed, which can implement not only the synchronization of the points of turn-on and turn-off time but the dynamic voltage balancing in spite of the difference of each switching characteristics. The proposed method is that the compensated control signal is attained from the voltage feedback signal and applied to the series-connected power transistors independently. Computer simulation and experimental results verify its validity.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.1
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• pp.15-20
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• 2002

The frame coding inside the screen for a video coder has a big influence on the quality of the whole frame. The standardized video coder uses DCT, however it can give rise to a low image quality due to the blocking effect at low bit rate. This paper proposes a video coding method for an image quality improvement in human visual aspects. With the proposed method, the perceptual weight is coded with SPIHT and VLC by applying it into the frame and the visual noises are eliminated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.957-966
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• 1998

In this paper an imrpoved Signal-to-Interference ratio(SIR)-based call admission control(CAC) algorithm for DS-CDMA cellular system is proposed and its performance is analyzed. This algorithm uses Residual-Capacity defined asthe additional number of initial calls that a base station can accept such that system-wide outage probability will guaranteed to remain below a certain level. the residual capcity at each cell is calculated according to the reverse-link SIR measured not only at the home cell but also the adjacent cells. Then the adjacent cell interference-coupling coefficient .betha. is used. In this work we propose an improved algorithm that .betha. varies according to the traffic load of the home cell. The influence of traffic condition on system performance, namely blocking probability and outage probability, is then examined via simulation. The performance of the improved algorithm is evaluated both under homogeneous and hot spot traffic loads. The results show that the improved algorithm outperforms conventional algorithms under all load values. Under over-load situation, especially, the improved algorithm gives almost constant outage performance the QoS(quality of service) can be guranted.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.73-78
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• 2004

There are random, continuous, and periodic allocation methods in the time slot sequence integrity for the multi-slot call. In the T-S-T switch, there are 2 time switch and the 2*2 space switch. Three time-slot allocation methods are suggested for the simulation. In the simulation, the searching times for time-slots on a multi-slot call is chosen to 32, and the simulation time is chosen to 100,000 seconds. Three kinds of calls are supposed for a multi-slot call : one time-slot call, two time-slot call, and 6 time-slot call. In the simulation, the carried traffic and the blocking probability are calculated on the 3 different traffic cases of 8:1:1, 6:2:2, 4:3:3(one time-slot : two time-slot : 6 time-slot) multi slot calls. It is shown that the blocking probability for the periodic time slot allocation method is best. As a result, the periodic time-slot allocation method is the proper one for the multi-slot ATM switch.