• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.1
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• pp.12-20
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• 1997

Physical interconnect such as Printed Circuit Board(PCB) traces introduces new challenges for parameter extraction and delay calculation for high-speed system design. PCB traces are dominated by frequency dependent LC propagation which makes precharacterization difficult for all possible configurations. Moreover, simulating the transient behavior of the trace for noise and delay analysis requries the combined used of a variety of models and techniques for efficiently handling lossy, low-loss, frequency dependent, and coupled transmission lines together with lumped elements. In this paper we explain how the frequency dependence caused by ground plane proximity and skin effects can be modeled using the adstracted models. These abstracted (lumped) models are SPICE-compatible and can be simulated in time-domain, along with precharacterized lumped parasitic elements and nonlinear driver and load models.

• ETRI Journal
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• v.38 no.1
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• pp.81-89
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• 2016

In this paper, a beam ID preamble (BIDP) technique, where a beam ID is transmitted in the physical layer, is proposed for efficient beam training in millimeter-wave cellular communication systems. To facilitate beam ID detection in a multicell environment with multiple beams, a BIDP is designed such that a beam ID is mapped onto a Zadoff-Chu sequence in association with its cell ID. By analyzing the correlation property of the BIDP, it is shown that multiple beams can be transmitted simultaneously with the proposed technique with minimal interbeam interference in a multicell environment, where beams have different time delays due to propagation delay or multipath channel delay. Through simulation with a spatial channel model, it is shown that the best beam pairs can be found with a significantly reduced processing time of beam training in the proposed technique.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.195-198
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• 2006

One of the major sources of error in precise GPS positioning since the turn-off the Selective Availability(SA) is the ionospheric propagation delay. For the last decades, a lot of the ionospheric researches based on a GPS network have been implemented throughout the world. Especially researches of the ionospheric modeling for Wide Area Argumentation System(WAAS) have been undertaken and published. In mid-latitude regions, typical spatial and temporal variations in ionospheric models delay tend to minimal. The developed ionospheric model calls for a 1.25 degree grid at latitudes and a 2.5 degree grid at longitudes. The precise grid TEC estimated by the inversion technique is also compared with global ionosphere maps(GIMs) which have been provided by several analysis centers(ACs). The results of initial investigations into the suitability of the proposed ionospheric modeling scheme in north-east Asia are presented.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.199-202
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• 2006

One of the major sources of error in precise GPS positioning since the turn-off the Selective Availability(SA) is the ionospheric propagation delay. For the last decades, a lot of the ionospheric researches based on a GPS network have been implemented throughout the world. Especially researches of the ionospheric modeling for Wide Area Argumentation System(WAAS) have been undertaken and published. In mid-latitude regions, typical spatial and temporal variations in ionospheric models delay tend to minimal. The developed ionospheric model calls for a 1.25 degree grid at latitudes and a 2.5 degree grid at longitudes. The precise grid TEC estimated by the inversion technique is also compared with global ionosphere maps(GIMs) which have been provided by several analysis centers(ACs). The results of initial investigations into the suitability of the proposed ionospheric modeling scheme in north-east Asia are presented.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.835-837
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• 1996

In this paper, a method for the daily maximum load forecasting which uses a chaotic time series in power system and artificial neural network(Back-propagation) is proposed. We find the characteristics of chaos in power load curve and then determine a optimal embedding dimension and delay time. For the load forecast of one day ahead daily maximum power, we use the time series load data obtained in previous year. By using of embedding dimension and delay time, we construct a strange attractor in pseudo phase plane and the artificial neural network model trained with the attractor mentioned above. The one day ahead forecast errors are about 1.4% for absolute percentage average error.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.22-27
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• 2012

In oceanic flight routes, HF radio and satellite data links have been used for air-to-ground communication, but these systems have long propagation delay and low data throughput. In this paper, we propose a reliable system to overcome the weakness of current HF radio and satellite communication systems for oceanic aeronautical flight routes. The proposed scheme uses only one aeronautical VHF channel in multi-hop oceanic communication environments and supports a hybrid type of multiple access, which consists of random access and TDMA (Time Division Multiple Access) scheme. The proposed system improves performance on delay and throughput as an effective solution to communicate end-to-end on the oceanic flight routes and strengthens the reliability of oceanic aeronautical communication.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.692-694
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• 1993

Acoustic noise from the various facilities makes man unpleasant and let researchers find the way for reducing it on environmental point of view. Special way to reduce the acoustic noise had suggested by the concept of Active Silencer. But, it has propagation delay time accumulated during the signal passage and howling effect. This paper suggestes a way to anhilate howling effects, and reduces the total delay time drasticaly by attaching microphone to the speaker. This paper will show how it works by some materials.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.9-14
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• 2008

In this paper, we propose the channel sounding scheme which is made for ideal communication between some application as well as the short distance of high speed data transmission in MIMO-OFDM system for Wireless PAN. This method is able to perceive the duration of the impulse response through the delaying of power delay profile, modeled a power delay profile which has an attenuate characteristic, and obtained the coefficient of channel response by ML (maximum likelihood). Through the amplitudes, phases and delays associated with each multipath component which were acquired from this channel sounding scheme, we can describe the wave propagation characteristics of channels between the transmitter and receiver so that the receiver could enhance not only the reliability but also the ability of communication link.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.77-84
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• 2015

This paper presents the design of a low-power, low area 256-radix 16-bit crossbar switch employing a 2D Hyper-X network topology. The Hyper-X crossbar switch realizes the high radix of 256 by hierarchically combining a set of 4-radix sub-switches and applies three modifications to the basic Hyper-X topology in order to mitigate the adverse scaling of power consumption and propagation delay with the increasing radix. For instance, by restricting the directions in which signals can be routed, by restricting the ports to which signals can be connected, and by replacing the column-wise routes with diagonal routes, the fanout of each circuit node can be substantially reduced from 256 to 4~8. The proposed 256-radix, 16-bit crossbar switch is designed in a 65 nm CMOS and occupies the total area of $0.93{\times}1.25mm^2$. The simulated worst-case delay and power dissipation are 641 ps and 13.01 W when operating at a 1.2 V supply and 1 GHz frequency. In comparison with the state-of-the-art designs, the proposed crossbar switch design achieves the best energy-delay efficiency of $2.203cycle/ns{\cdot}fJ{\cdot}{\lambda}2$.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.309-314
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• 2002

The ablation dynamics and cluster formation of $C_n^+$ ions ejected from 355 nm laser ablation of a graphite target in vacuum are investigated using a reflectron time-of-flight (RTOF) mass spectrometer. At low laser fluence, odd-numbered cluster ions with $3{\leq}n{\leq}15$ are predominantly produced. Increasing the laser fluence shifts the maximum size distribution towards small cluster ions, implying the fragmentation of larger clusters within the hot plume. The temporal evolution of $C_n^+$ ions was measured by varying the delay time of the ion extraction pulse with respect to the laser irradiation, providing significant information on the characteristics of the ablated plume. Above a laser fluence of $0.2J/cm^2$ , large cluster ions ($n{\geq}30$) are produced at relatively long delay times, indicating that atoms or small carbon clusters aggregate during plume propagation. The dependence of the intensity of ablated $C_n^+$ ions on delay time after laser irradiation shows that the most probable velocity of each cluster ion decreases with cluster size.