• ETRI Journal
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• v.19 no.4
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• pp.344-362
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• 1997

The delay which is one of the quality of service parameters is considered to be a crucial factor for the effective usage of real-time audio and video streams in interactive multimedia collaborations. Among the various causes of the delay, we focus in this paper on the local delay concerned with the schemes which handle continuous inflow of encoded data from constant or variable bit-rate audio and video encoders. We introduce two kinds of implementation approaches, pull model and push model. While the pull model periodically pumps out the incoming data from the system buffer, the push model receives events from the device drivers. From our experiments based on Windows NT 3.51, it is shown that the push model outperforms the other for both constant and variable bit-rate streams in terms of the local delay, when the system suffers reasonable loads. We interpret this experimental data with M/G/1 multiple vacation queuing theories, and show that it is consistent with the queuing theoretic interpretations.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.285-293
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• 2005

Whenever mobile node moves a new domain in multicast environments. Both handoff and join multicast group always occur. These procedures take a much of delay time and lost the packets in flight. Handoff delay is a significant factor fot the QoS of mobile node in mobile environments. In this paper. we propose a new handoff scheme which supports multicast and guarantees a low handoff delay in IPv6. The scheme makes adjacent subnets the member of multicast tree. After that, this eliminates packet loss and reduces the handoff delay time. Simulation shows that the proposed scheme takes a low delay and lower packet loss rate than the remote-subscription scheme.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.3
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• pp.205-214
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• 2024

The aircraft delay rate has increased nearly three times in 2023 due to change in Korea policy of delay criteria. One of the primary causes of delays in domestic flights is related to reactionary delays, with Turnaround Time being a key factor. To mitigate reactionary delays and reduce aircraft delays, it is essential to establish an appropriate Turnaround Time and integrate it into flight schedules. This study aims to analyze the appropriate Turnaround Time for aircraft operating at Gimpo, Gimhae, and Jeju International Airports, which handle a high frequency of domestic flights. The research applies air traffic simulation, using variables such as current flight schedules, actual flight times, Turnaround Time, and flight routes to simulate actual conditions. Based on this analysis, the study seeks to identify the fitting Turnaround Time across various scenarios. The findings are expected to address reactionary delays and help reduce overall delay rates in domestic flights.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.5
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• pp.32-38
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• 2009

FTT(Fast Fourier Transform) processor is widely used in OFDM(Orthogonal Frequency Division Multiplesing) system. Because of the increased requirement of mobility and bandwidth in the OFDM system, they need large point FTT processor. Since the size of memory which stores the twiddle factor coefficients are proportional to the N of FFT size, we propose a new method by which we can reduce the size of the coefficient memory. In the proposed method, we exploit a counter and unsigned multiplier to generate the twiddle factor indices. To verify the proposed algorithm, we design TFCGs(Twiddle Factor Coefficient Generator) for 1024pint FFTs with R2SDF(Radix-2 Single-Path Delay Feedback), $R2^3SDF,\;R2^3SDF,\;R2^4SDF$ architectures. The size of ROM is reduced to 1/8N. In the case of $R2^4SDF$ architecture, the area and the power are reduced by 57.9%, 57.5% respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.181-188
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• 2012

In this paper, the measurement data is analyzed and channel parameters are derived through MIMO Channel measurements at 781MHz considering outdoor multi-path environment. 781MHz frequency band currently operates the DTV system. However, it will be allocated new mobile communication frequency band. The channel characteristics at 781MHz seem to be similar existing mobile communication system at 900MHz but a study on channel characteristics of signal transfer process is necessary because there is incomplete study in mobile networks at 781MHz. To avoid interference with Korean DTV broadcasting, we measured channel characteristics in city/suburban areas of Jeju island by channel sounder and $4{\times}4$ antenna of the ETRI(Korea Electronics and Telecommunications Research Institute). Path Loss, Delay Spread, Angular Spread and K-factor were derived based on measured data.

• Journal of Korea Multimedia Society
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• v.8 no.3
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• pp.372-378
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• 2005

When a mobile node changes a sub network using Mobile IP, it must register its current location to the home agent. If a mobile node is far from its home network, the Binding Update (BU) time delay is longer and affects its connection state. To solve such a BU delay problem, a new component in HMIPv6, called MAP, supports the mobility of mobile node to reduce the signaling delay in handover However, in hierarchical MAP architecture, the register concentration to a specific MAP may be occurred, which affects the network management wholly. In this paper, we propose a MAP selection scheme based on ioad balancing by the mobility factor and the traffic property. By the mobility factor and the traffic property, a mobile node can select a adequate MAP on its mobility factor and traffic characteristic.

• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.619-624
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• 2011

A significant factor limiting the ranging accuracy of Loran (Long Range Navigation) signal is the additional secondary factor (ASF) in the time of arrival (TOA) measurements. Precise ASF values are essential if Loran deliver the high absolute accuracies demanded for aircraft approach, maritime harbour entrance. We measured the absolute propagation delay between Pohang Loran signal and Loran receiver output signal by comparing with Cesium atomic clock. In this study we measured ASFs between Pohang 9930M station and the 12 measurement points in the Yeongil Bay by using the measurement technique of absolute time delay. The measurement points were spaced at interval of 3 km by 3 km. An E-field antenna and an H-field antenna were used to improve the accuracy of ASF measurements and a DGPS (Differential GPS) receiver was used for accurate positions. We have gotten the result that the measured ASFs were compared with the predicted ASFs through this measurement technique.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.48-58
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• 2020

Naval weapons systems of the Republic of Korea are acquired through the Defense Planning Management System. Recently, acquisition of some naval ships have been delayed, and the causes of the delays have been recognized as inappropriate project management at the Execution Phase. However, we argue that the delay problem in naval ships acquisition should be approached, with due regard for the entire Defense Planning Management System. That is, We should try to investigate from Planning Phase to those of Programming, Budgeting and Execution Phases. Therefore, in this study, we investigated the actual cases of the delay in naval acquisition at all phases of the Defense Planning Management System. Based on the investigation, we tried to identify the naval ship Acquisition Delay Factors and find out the Weights of those factors. As the next step, we calculated the Influence Measures on the naval missions, including the Cost of Naval Capability Gap derived from the delays in acquisition of naval ships. As a final step, we calculated the Acquisition Delay Measures based on the interrelationship between the Acquisition Delay Factors and the Influence Measures. Then we evaluated and analyzed what the results stand for. Finally, we made suggestions for future improvement. The improvement suggestions we made for preventing delay in acquisition of naval ships in this study are as follows. First, we need a shift in perception. It is necessary to measure the Acquisition Delay Factors in acquiring naval ships and manage them from the Planning Phase. Second, resolution must be concerted efforts. All relevant agencies, not just a few, should work together to resolve the problems of acquisition delay. Third, analysis must be based on the accumulation of data. This allows the elaborating of naval ship Acquisition Delay Factors and Delay Measures. If this research method is applied to other military weapons systems in the future, we may be able to not just identify the Acquisition Delay Factors in acquisition of other military weapons systems, but also pursue improvement in those cases.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.1
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• pp.93-100
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• 1993

This study was carried out to investigate the relationship between the traffic signal systmes and the air pollutants emitted by the motor vehicles at Kangnam Intersection. One of the most important measures of effectiveness (MOE) in traffic studies is the delay to vehicles in the system. Delay represents indirect costs to the motorist in terms of time loss and a direct cost in terms of fuel consumption during idling. The results of TRANSYT-7F modeling was correlated among delay, fuel consumption and total travel tiem. Air pollutants emission rate can be calculated by the results of modeling and the Korean type emission factor. As expected the highest emissions, for air pollutants, are observed during the morning rush hours (07 : 00-10 : 00). For better results of modeling, the TRANSYT-7F model needs to modify for the Korean type of traffic model. The results of this study indicate that the variation of air pollutants emission rates were closely related to the traffic signal system.

• Journal of applied mathematics & informatics
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• v.26 no.3_4
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• pp.811-818
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• 2008

Biological systems with both protein-protein and protein-gene interactions can be modeled by differential equations for concentrations of the proteins with time-delay terms because of the time needed for DNA transcription to mRNA and translation of mRNA to protein. Values of some parameters in the mathematical model can not be measured owing to the difficulty of experiments. Also values of some parameters obtained in a normal stress condition can be changed under pathological stress stimuli. Thus it is important to find the effective way of determining parameters values. One approach is to use optimization algorithms. Here we construct an optimal system used to find optimal parameters in the equations with nonnegative time delays and apply this optimization result to the Nuclear factor-${\kappa}B$ pathway.