• 대한전자공학회논문지TC
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• 제41권10호
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• pp.69-77
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• 2004

본 논문에서는 ATM 망에서의 효율적인 트래픽 제어를 위하여 언어적인 규칙과 퍼지 추론부로 구성되는 퍼지 로직에서 퍼지 규칙을 생성하였다. 퍼지 규칙 내부에 포함된 제어 파라메터들은 주어진 성능 함수를 최소화하도록 학습된다. 즉, 전체 트래픽 도착율과 버퍼의 점유율에 따라 퍼지집합 이론을 통하여 추론한 후 그 비퍼지화값으로 접속된 트래픽에 대해 서버에서의 서비스율을 제어하도록 하였다. 또한, 생성된 퍼지 규칙의 타당성을 검증하기 위하여 MATLAB6.5에서와 온라인 빌드업으로 규칙에 대한 실험결과를 보인다. 그 결과, 전체 트래픽 도착율과 버퍼의 점유율에 따라 효율적으로 서버에서의 서비스율이 제어 됨을 확인하였다.

• 대한산업공학회지
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• 제23권1호
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• pp.23-37
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• 1997

In this paper, performance analysis of video traffic shaper for Motion Picture Experts Group (MPEG) video traffic in on ATM network are investigated. Traffic shaping for MPEG video traffic is proposed as a traffic control function in ATM networks. The proposed shaper smoothes video traffics by controling the output rate of the buffer, which is placed in an MPEG source, according to I,B,P frame sequences of MPEG. In performance analysis of an video traffic shaper, a periodic botch arrival model is suggested to describe cell streams in a frame of MPEG video traffic. The queueing model which has periodic independent botch arrival and periodic deterministic service time is used to obtain the cell loss ratio, the mean cell delay, and the measure of smoothing effect. Simulation results are used to validate this queueing model. The cell loss performance of ATM multiplexer is measured by simulation study with real MPEG-1 data. From the viewpoint of traffic load, the cell loss ratio is observed to be considerably high, which is considered to result from the burstiness of MPEG video traffic. As a result, it is shown that the shaping decreases cell loss ratio of multiplexer. The results of this paper can be employed to establish a basic guideline in the implementation of a traffic control scheme and the design of ATM multiplexer for MPEG video traffic.

• 한국IT서비스학회지
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• 제7권2호
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• pp.137-148
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• 2008

This paper measures and compares the traffic of a series of Massively Multi-player On-line Role Playing Game (MMORPG). The purpose of this analysis is to characterize the MMORPG traffic and compare the traffic characteristics of those games caused by the game structure difference between 2D and 3D environment. The target game is 'Lineage I' and 'Lineage II' which represent world's largest MMORPGs in terms of the number of concurrent users. We collect about 280 giga bytes and 1 tera bytes of packet headers, respectively. We compare packet size, packet inter-arrival time and bandwidth usage of these two games. The MMORPG traffic consists of two kinds of packets: client-generated upstream packets and server-generated downstream packets. We observe that the upstream packet size of payload has grown from 9 bytes to 19 bytes, while the average payload size of downstream packets has grown from 37 bytes to 318 bytes. This asymmetry of growing rate is caused by 3D game structure. Packet inter-arrival time becomes shorter from average 2 milliseconds to 58 microseconds. Bandwidth consumption per client has grown from 4 kbps to 20 kbps. We find that there is a linear relationship between the number of users and the bandwidth usage in both case.

• 인터넷정보학회논문지
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• 제18권6호
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• pp.65-73
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• 2017

Congestion occurring at wireless sensor networks(WSNs) causes packet delay and packet drop, which directly affects overall QoS(Quality of Service) parameters of network. Network congestion is critical when important data is to be transmitted through network. Thus, it is significantly important to effectively control the congestion. In this paper, new mechanism to guarantee reliable transmission for the important data is proposed by considering the importance of packet, configuring packet priority and utilizing the settings in routing process. Using this mechanism, network condition can be maintained without congestion in a way of making packet routed through various routes. Additionally, congestion control using packet service time, packet inter-arrival time and buffer utilization enables to reduce packet delay and prevent packet drop. Performance for the proposed mechanism was evaluated by simulation. The simulation results indicate that the proposed mechanism results to reduction of packet delay and produces positive influence in terms of packet loss rate and network lifetime. It implies that the proposed mechanism contributes to maintaining the network condition to be efficient.

• Journal of Communications and Networks
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• 제4권2호
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• pp.128-135
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• 2002

We propose a new space priority mechanism, and analyze its performance in a single Constant Bit Rate (CBR) server. The arrival process is derived from the superposition of two types of traffics, each in turn results from the superposition of homogeneous ON-OFF sources that can be approximated by means of a two-state Markov Modulated Poisson Process (MMPP). The buffer mechanism enables the Asynchronous Transfer Mode (ATM) layer to adapt the quality of the cell transfer to the Quality of Service (QoS) requirements and to improve the utilization of network resources. This is achieved by "Selective-Delaying and Pushing-ln"(SDPI) cells according to the class they belong to. The scheme is applicable to schedule delay-tolerant non-real time traffic and delay-sensitive real time traffic. Analytical expressions for various performance parameters and numerical results are obtained. Simulation results in term of cell loss probability conform with our numerical analysis.

• Animal cells and systems
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• 제15권1호
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• pp.85-90
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• 2011

In 2001, we conducted a study to assess the effects of differential arrival times and nest-site selection on reproductive performance in a mixed-species heronry consisting of six species in Taeseong-ri, Chungbuk, Korea. We recorded the arrival dates, nest heights, clutch sizes, and brood sizes after 15-20 days of the age of the birds' chicks. The grey herons and cattle egrets arrived first and last, respectively, on the colony site. In the homogenous vegetation structure of the breeding site, the pitch pine trees (Pinus rigida) were mainly used for building nests on 48 of the 50 pine trees (96%). The breeding species vertically stratifies the nest sites according to their body size, except for the cattle egrets and black-crowned night herons that nested at sites higher than those predicted from their body size. The mean nest success rates of the six species under study were positively correlated with the mean nest heights. Our findings suggest that aggressive interspecific interactions among neighbors influence nest-site selection to enhance breeding success.

• 한국정보통신학회논문지
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• 제17권1호
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• pp.32-40
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• 2013

본 논문에서는 빔포밍과 입사각분석 기반 마스킹을 이용한 다채널 음성개선 알고리즘이 제안된다. 제안된 알고리즘에서는 LCMV 빔포밍을 수행한 후에 입사각 분석을 이용한 멜-주파수 위너필터가 적용되어 잔존하는 잡음을 제거한다. 성능 향상을 위해서 빔포밍의 적응 필터 학습률과 목표 음성 스펙트럼 검출을 위한 입사각 임계치가 최적화된다. 성능 지수로서 PESQ와 출력 SNR이 측정되었으며 실험 결과 제안한 알고리즘이 종전의 최소분산 빔포밍 기법보다 PESQ 관점에서 0.09, 출력 SNR 관점에서 5.75 dB의 성능 향상시킴을 알 수 있었다.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.853-859
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• 2022

In this study, we analyzed the instantaneous trajectory generation capability and target arrival rate of a mobile robot by changing the parameter of the TEB (Timed Elastic Band) Local Planner among local planners that affect the instantaneous obstacle avoidance ability of the mobile robot using ROS (Robot Operating System) simulation and real experience. As a result, we can expect a decrease in the target arrival time of the mobile robot through a decrease in the parameter values of the TEB Local Planner's min_obstacle_dist, inflation_dist, and penalty_epsilon. However, if this parameter is reduced too much, the risk of obstacle collision of the moving robot is increases, so it is important to combine the appropriate values to construct the parameter.

• 한국경영과학회지
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• 제38권3호
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• pp.37-50
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• 2013

The purpose of this study is to determine the indicators and the criteria to classify types of train delays of high-speed rail in South Korea. Types of train delays have divided into the chronic delays and the knock-on delays. The Indicators based on relevance, reliability, and comparability were selected with arrival delay rate of over five minutes, median of arrival delays of preceding train and following train, knock-on delay rate of over five minutes, correlation of delay between preceding train and following train on intermediate and last stations, average train headway, average number of passengers per train, and average seat usages. Types of train delays were separated using the Ward's hierarchical cluster analysis. The criteria for classification of train delay were presented by the Fisher's linear discriminant. The analysis on the situational characteristics of train delays is as follows. If the train headway in last station is short, the probability of chronic delay is high. If the planned running times of train is short, the seriousness of chronic delay is high. The important causes of train delays are short headway of train, shortly planned running times, delays of preceding train, and the excessive number of passengers per train.

• 한국항해학회지
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• 제21권1호
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• pp.1-11
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• 1997

Because of the sharp increase of its export and import container cargo volumes contrast to the lack of related Container Terminal facility, equipment and inefficient procedure, there is now heavy container cargo congestions in Pusan Container Terminal. As a result of such a situation, many container ships avoid their calls into Pusan port. This is a major cause that in tum kads to weakening intemational competitiveness of the Korean industry. This study, therefore, aims are to make a quantitative analysis of Container Terminal System through the computer simulation, especially focusing on its 4 sub-system of a handling system, 'it is checked whether the current operation is being performed effectively through the computer simulation. The overall findings are as folIows; Firstly, average tonnage of the ships visiting the BCTOC was 32,360 G/T in from January '96, to may '96. The average arrival interval and service time of container ships at BCTOC are 5.63 hours and 18.67 hours respectively. Ship's arrival and service pattern at BCTOC was exponential distribution with 95% confidence and Erlang-4 distribution with 99% confidence. Secondly, average waiting time and number of ships was 9.9 hours, 235 ships(38%) among 620 ships. Number of stevedoring container per ship was average 747.7 TED, standard deviation 379.1 TEU and normal distribution with 99% confidence. Thirdly, from the fact that the average storage days of containers at BCTOC are 2.75 days (3.0 days when import, 2.5 days when export). it is founds that most containers were transfered to the off-dock storage areas with the free periods(5 days when import, 4 days when export), the reason for which is considered to be the insufficient storage area at BCTOC. Fourthly, in the case of gate in-out at BCTOC, occupied containers and emptied containers are 89% and 11% respectively in the gate-in, 75% and 25% seperately in the gate-out. Finally, from the quantitative analysis results for container terminal at BCTOC, ship's average wating time of ships was found to be 20.77 hours and berth occupancy rate(${\rho}$) was 0.83. 5~6 berths were required in order that the berth occupancy rate(${\rho}$) may be maintained up to 60% degree.