• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.195-215
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• 2021

Multipath Transport Control Protocol (MPTCP) is a transport layer protocol that enables multiple TCP connections across various paths. Due to path heterogeneity, it incurs more energy in a multipath wireless network. Recent work presents a set of approaches described in the literature to support systems for energy consumption in terms of their performance, objectives and address issues based on their design goals. The existing solutions mainly focused on the primary system model but did not discourse the overall system performance. Therefore, this paper capitalized a novel stochastically multipath scheduling scheme for data and path capacity variations. The scheduling problem formulated over MPTCP as a stochastic optimization, whose objective is to maximize the average throughput, avoid network congestion, and makes the system more stable with greater energy efficiency. To design an online algorithm that solves the formulated problem over the time slots by considering its mindrift-plus penalty form. The proposed solution was examined under extensive simulations to evaluate the anticipated stochastic optimized MPTCP (so-MPTCP) outcome and compared it with the base MPTCP and the energy-efficient MPTCP (eMPTCP) protocols. Simulation results justify the proposed algorithm's credibility by achieving remarkable improvements, higher throughput, reduced energy costs, and lower-end to end delay.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.108-116
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• 1989

The simulator described here-LOSIM(LOgic SIMulator)-was developed to verify the logic design for VLSI(Very Large Scale Integrated) circuits at mixed level. In this paper, we present a modeling approach to obtain more accurate results than conventional logic simulators [5-6,9] for general elements, functional elements, transmission gates and tri-state gates using eight signal values and two gignal strengths. LOSIM has the capability which can perform timing and hazard analysis by using assignable rise and fall delays. We also prosent an efficient algorithm to accurately detectdynamic and static hazards which may be caused by the circuit delays. Our approach is based on five logic values and the scheduled time. LOSIM has been implemented on a UN-3/160 workstation running Berkeley 4.2 UNIX, and the program is written in C language. Static RAM cell and asynchronous circuit are illustrated as an example.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.18-29
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• 2007

The main objective of this paper is to propose a new stability analysis method for a networked control system with multiple packet transmission. The new scheduling method that can guarantee the maximum time delay and discrete switch state equation model which represent a network data loss is proposed. The equivalent model of a MIMO(multi-input multi-output) networked control system is derived from a state space model of linear time invariant interconnected systems in the form of asynchronous dynamical system. Using this model, this paper presents new stability theorems that can determine stability of the networked control system with regard to time delay, data loss, and the number of transmission packets. Simulation results verify the effectiveness of proposed stability analysis method.

• Tribology and Lubricants
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• v.31 no.3
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• pp.79-85
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• 2015

RC delay is a critical issue for achieving high performance of ULSI devices. In order to minimize the RC delay time, we uses the CMP process to introduce high-conductivity Cu and low-k materials on the damascene. The low-k materials are generally soft and fragile, resulting in structure collapse during the conventional high-pressure CMP process. One troubleshooting method is electrochemical mechanical polishing (ECMP) which has the advantages of high removal rate, and low polishing pressure, resulting in a well-polished surface because of high removal rate, low polishing pressure, and well-polished surface, due to the electrochemical acceleration of the copper dissolution. This study analyzes an electrochemical state (active, passive, transpassive state) on a potentiodynamic curve using a three-electrode cell consisting of a working electrode (WE), counter electrode (CE), and reference electrode (RE) in a potentiostat to verify an electrochemical removal mechanism. This study also tries to find optimum conditions for ECMP through experimentation. Furthermore, during the low-pressure ECMP process, we investigate the effect of current density on surface roughness and removal rate through anodic oxidation, dissolution, and reaction with a chelating agent. In addition, according to the Faraday’s law, as the current density increases, the amount of oxidized and dissolved copper increases. Finally, we confirm that the surface roughness improves with polishing time, and the current decreases in this process.

• Journal of Internet Computing and Services
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• v.12 no.5
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• pp.11-19
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• 2011

In this paper, Service Boundary Line approximation method is proposed to improve the accuracy of aggregated link state information for source routing in transport networks that conduct hierarchical QoS routing. The proposed method is especially useful for aggregating links that have both delay and bandwidth as their QoS parameters. This method selects the main path weight in the network and transports the data to the external networks together with the aggregation information, reducing information distortion caused from the loss of some path weight during aggregation process. In this paper, the main path weight is defined as outlier. Service Boundary Line has 2k+5parameters. k is the number of outliers. The number of storage spaces of Service Boundary Line changes according to the number of outliers. Simulation results show that our approximation method requires a storage space that 1.5-2 times larger than those in other known techniques depending on outlier selection method, but its information accuracy of proposed method in the ratio between storage space and information accuracy is higher.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.264-274
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• 2014

Time synchronization becomes a critical issue in underwater acoustic networks (UANets) because nodes cooperate together or individually work by communicating each other in diverse underwater applications. Compared with the time synchronization approaches in terrestrial networks, several intrinsic limitations of UANets (e.g., the unavailability of GPS, long propagation delay, mobility due to currents, limited energy consumption, or low data rate) need to be considered in synchronizing the timing among underwater nodes. For the purpose of developing more efficient time synchronization protocols for UANets, we review the existing approaches, which estimate both the clock offset and the clock skew of underwater nodes. Finally, we outline the state-of-the art time synchronization protocols for UANets by comparing and summarizing them according to their synchronization characteristics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1188-1195
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• 2006

This paper presents an efficient design method of 2-D state-space digital filter based on an improved branch-and -bound algorithm. The resultant 2-D state-space digital filters whose coefficients are represented as the sum of two power-of-two terms, are attractive for high-speed operation and simple implementation. The feasibility of the proposed method is demonstrated by several experiments. The results show that the approximation error and group delay characteristic of the resultant filters are similar to those of the digital filters which designed in the continuous coefficient space.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.603-610
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• 1998

This paper develops a 7 DOF vehicle model to study the effects of the active suspension on ride. The model is used to derive a control law for the active suspension using a full state linear optimal control technique. A wheelbase preview type active suspension is also considered in the control law derivation. The time delay between wheelbases is approximated using Pade approximation technique. The ride model is extended to a 14 DOF handling model. The 14 DOF handling model includes lateral, longitudinal, yaw and four wheel spin motions in addition to the 7 DOF ride model. A control law which is derived considering only ride related parameters is used to study the effects of the active suspension on a vehicle handling. J-turn maneuver simulation results show that the active suspension has a slower response in lateral acceleration and yaw rate, a bigger steady state lateral acceleration and an oversteer tendency. Lane changing maneuver simulation results show that the active suspension has a little bigger lateral acceleration but a much smaller roll angle and roll motion. Braking maneuver simulation results show that the active suspension has a much smaller pitch angle and pitch motion.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.549-555
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• 2000

We propose an approximate algorithm to analyze the queuing system with n bursty and heterogeneous arrival processes. Each input process is modeled by Interrupted Bernoulli Process(IBP). We approximate N arrival processes by a single state variable and subsequently simplify the transition probability matrix of the Markov chain associated with these N arrival processes. Using this single state variable of arrival processes, we describe the state of the queuing system and analyze the system numerically with the reduced transition probability matrix. We compute the queue length distribution, the delay distribution, and the loss probability. Comparisons with simulation data show that the approximation algorithm has a good accuracy.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.141-146
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• 1996

Hand posture and force, which define aspects of the way an object is grasped, are features of robotics manipulation. A means for specifying these grasping "flavors" has been developed that uses an instrumented glove equipped with joint and force sensors. The new grasp specification system is being used at the Pennsylvania State University (Penn State) in a Virtual Reality based Point-and-Direct(VR-PAD) robotics implementation. In the Computer Integrated Manufacturing (CIM) Laboratory at Penn State, hand posture and force data were collected for manipulating bricks and other items that require varying amounts of force at multiple pressure points. The feasibility of measuring desired grasp characteristics was demonstrated for a modified Cyberglove impregnated with FSR (Force Sensitive Resistor) pressure sensors in the fingertips. A joint/force model relating the parameters of finger articulation and pressure to various lifting tasks was validated for the instrumented "wired" glove. Operators using such a modified glove may ultimately be able to configure robot grasping tasks in environments involving hazardous waste remediation, flexible manufacturing, space operations and other flexible robotics applications. In each case, the VR-PAD approach improved the computational and delay problems of real-time multiple-degree-of-freedom force feedback telemanipulation.ck telemanipulation.