• Journal of Information Processing Systems
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• v.12 no.2
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• pp.275-294
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• 2016

A primary task in wireless sensor networks (WSNs) is data collection. The main objective of this task is to collect sensor readings from sensor fields at predetermined sinks using routing protocols without conducting network processing at intermediate nodes, which have been proved as being inefficient in many research studies using a static sink. The major drawback is that sensor nodes near a data sink are prone to dissipate more energy power than those far away due to their role as relay nodes. Recently, novel WSN architectures based on mobile sinks and mobile relay nodes, which are able to move inside the region of a deployed WSN, which has been developed in most research works related to mobile WSN mainly exploit mobility to reduce and balance energy consumption to enhance communication reliability among sensor nodes. Our main purpose in this paper is to propose a solution to the problem of deploying mobile data collectors for alleviating the high traffic load and resulting bottleneck in a sink's vicinity, which are caused by static approaches. For this reason, several WSNs based on mobile elements have been proposed. We studied two key issues in WSN mobility: the impact of the mobile element (sink or relay nodes) and the impact of the mobility model on WSN based on its performance expressed in terms of energy efficiency and reliability. We conducted an extensive set of simulation experiments. The results obtained reveal that the collection approach based on relay nodes and the mobility model based on stochastic perform better.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.850-857
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• 2012

A moving network is the usage model that provides the mobile stations to the communication service via the mobile relay deployed in the high-speed vehicle. The mobile relay periodically performs the signal strength measurement of the neighbor base stations to select the target base station during the handover procedure. The mobile stations experience the service disruption during the measurement of the mobile relay. In this paper, we propose the estimation based scanning method to overcome the service disruption of the mobile stations connected via the mobile relay. In the proposed method, mobile stations subordinated in the mobile relay periodically measure the signal strength of neighbor base stations in order to perform handover. The measured signal strength is used to estimate the signal strength between the mobile relay and the neighbor base station. We performed simulations in order to evaluate the performance of the proposed method in terms of the estimation accuracy and the overhead due to the exchange of channel information. By the simulation result, The estimation error is less than 4dBm when more than 6 mobile stations are used for the estimation. The overhead caused by the proposed method is less than that caused by the direct measurement of the mobile relay when the data rate is more than 8Mbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1261-1267
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• 1999

Frame relay (FR) service via an FR interface over a common asynchronous transfer mode (ATM) backbone network requires an FR-to-ATM interworking unit (IWU), the functionality of which directly impacts the engineering of the overall network in terms of capacity required, quality of service (QoS), and the interference among different types of services. This paper presents performance analysis of frame relay traffic in IWU. Additionally frame relay traffic policing using leaky bucket algorithm in this traffic model is carried out through computer simulation. Three measurements, the percentage of frames accepted as committed, the percentage of frames that accepted but marked eligible for diacard, and the percentage of frames that accepted that are discarded because of insufficient number of credits, are simulated variously in this paper.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.266-275
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• 2013

The exact closed-form expressions for outage probability and bit error rate of spectrum sharing-based multi-hop decode-and-forward (DF) relay networks in non-identical Rayleigh fading channels are derived. We also provide the approximate closed-form expression for the system ergodic capacity. Utilizing these tractable analytical formulas, we can study the impact of key network parameters on the performance of cognitive multi-hop relay networks under interference constraints. Using a linear network model, we derive an optimum relay position scheme by numerically solving an optimization problem of balancing average signal-to-noise ratio (SNR) of each hop. The numerical results show that the optimal scheme leads to SNR performance gains of more than 1 dB. All the analytical expressions are verified by Monte-Carlo simulations confirming the advantage of multihop DF relaying networks in cognitive environments.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.62-62
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• 2000

An auto-tuning PID controller which is adequate for temperature control is developed based on relay-control and pole-placement Using the critical frequency which is obtained from relay-control parameters of assumed model are identified. Pole/zero-placement PID controller is designed for the identified model. The desired pole/zeros are determined so that the closed-loop has overshoot free step response. The developed auto-tuning PID controller was successfully applied to the temperature control of RTP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.367-370
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• 2017

This paper proposes a method for selecting efficient relay nodes in stochastic DTN model. Delay Tolerant Network (DTN) uses the Carry and Forward method, which creates a bundle layer for efficient communication, selects relay nodes between different networks and heterogeneous networks, and forwards messages. DTN is basically composed of mobile nodes so DTN has no fixed routing route and it has long latency due to intermittent connection. Therefore, the nodes constituting the DTN necessarily have the characteristics to store the messages, and the capacity of the stored messages and nodes affects the performance of the network. Stochastic DTN model proposed a Markov model that changes randomly over time to analyze the performance of DTN. In this paper, we use stochastic message distribution and node contact probabilities using contact time analyzed through message generation and extinction in order to select efficient relay nodes in stochastic DTN model.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.227-236
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• 1992

In this paper, a simulation program of relaying system including the CT and CPD ( capacitive potential device ) is developed to study the effect of its operation under various system conditions. To deal with the dynamic characteristics of relaying system, state space technique is applied, and then the state equations of CT, CPD and mho distance relay are constructed. Also the dynamic response characteristics of overall relaying system is verified by digital simulation. Since the proposed model is capable of taking arbitrary input waveforms from EMTP in analyzing its dynamic responses, the effects of CT-saturation and CPD-subsidence transient characteristics on the operating points of who distance relay can be accurately prodicted. It gives more effective results, compared with the model without considering those characteristics by checking the exprimental data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.473-479
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• 2015

Thermal relays are sometimes used instead of long time overcurrent relays for motor protection. But, it is difficult for any relay design engineer to adequately approximate motor heating curves which represent the average of a difficult-to-define thermal zone. Thermal relays frequently may not provide sufficient protection on heavy overloads. Digital multifunction relays are microprocessor-based devices. These relays offer highly reliable and advanced protection of motors. If a situation can be mathematically described, the microprocessor in a digital relay can be programmed to tackle that problem. Today's motor protection is accomplished with digital protective relays. Digital relays offer additional, highly important features to complement protection. The best way to prevent short in motor is to not overheat and degrade the insulation.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2636-2638
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• 2000

In this paper, we show the simple methods of designing the Smith predictor for the long dead time processes. We are using the relay feedback to model the processes in the second-order plus dead time structure. The model is able to represent a various class of processes dynamics including low- or high-order, and monotonic or oscillatory process. A PID type controller is proposed for the main controller in the Smith controller, which insure the stability of overall system. Simulation Examples are also provided to illustrate the effectiveness and applicability of the proposed controller.

• ETRI Journal
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• v.37 no.4
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• pp.717-726
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• 2015

In this paper, we study an asymmetric two-way relaying network where two source nodes intend to exchange information with the help of multiple relay nodes. A hybrid time-division broadcast relaying scheme with joint relay selection (RS) and power allocation (PA) is proposed to realize energy-efficient transmission. Our scheme is based on the asymmetric level of the two source nodes' target signal-to-noise ratio indexes to minimize the total power consumed by the relay nodes. An optimization model with joint RS and PA is studied here to guarantee hybrid relaying transmissions. Next, with the aid of our proposed intelligent optimization algorithm, which combines a genetic algorithm and a simulated annealing algorithm, the formulated optimization model can be effectively solved. Theoretical analyses and numerical results verify that our proposed hybrid relaying scheme can substantially reduce the total power consumption of relays under a traffic asymmetric scenario; meanwhile, the proposed intelligent optimization algorithm can eventually converge to a better solution.