• Journal of KIISE
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• v.44 no.2
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• pp.213-222
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• 2017

The Internet of Things (IoT) technology is rapidly developing in recent years, and is applicable to various fields. A smart factory is one wherein all the components are organically connected to each other via a WSN, using an intelligent operating system and the IoT. A smart factory technology is used for flexible process automation and custom manufacturing, and hence needs adaptive network management for frequent network fluctuations. Moreover, ensuring the timeliness of the data collected through sensor nodes is crucial. In order to ensure network timeliness, the power consumption for information exchange increases. In this paper, we propose an IEEE 802.15.4e DSME-based distributed scheduling algorithm for mobility support, and we evaluate various performance metrics. The proposed algorithm adaptively assigns communication slots by analyzing the network traffic of each node, and improves the network reliability and timeliness. The experimental results indicate that the throughput of the DSME MAC protocol is better than the IEEE 802.15.4e TSCH and the legacy slotted CSMA/CA in large networks with more than 30 nodes. Also, the proposed algorithm improves the throughput by 15%, higher than other MACs including the original DSME. Experimentally, we confirm that the algorithm reduces power consumption by improving the availability of communication slots. The proposed algorithm improves the power consumption by 40%, higher than other MACs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4B
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• pp.323-332
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• 2006

In this paper, we consider a WDM based metro ring connecting broadband access networks by using FT-TR (Fixed Transmitter-Tunable Receiver) type access nodes and a new MAC protocol for fair transmission is proposed. The basic channel access scheme is CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) and the transferred optical slot is changed to be empty slot by SS(Source-Stripping) which drops a packet from ring-rotated slot. This empty slot can be either used to send head-of-line packet in buffer or transmitted to next access node. In former cases, there is the improvement of network throughput, but latter case leads unfairness problem of transmission. Thus the proposed MAC protocol exploits the advantages form tow cases. It gives downstream access nodes chance to use empty slots and limits the unconditional usage of empty slots at upstream access nodes with probability as called p-Persistent MAC protocol. We use a numerical analysis to evaluate bandwidth efficiency and maximum node throughput and compares simulation results in terms of node throughput, fairness factor, transfer delay depending on probability. Under two different FT-TR type architectures for metro ring network the proposed MAC protocol is evaluated and compared.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.561-571
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• 2006

RFID technology, as one contact-less identification technology with using electronic tag, is the field where its multiple researches have been studied. Especially, in the field of supply chain management, when it is necessary to identify a lot of objects by real-time, performance of anti-collision algorithm for multiple tag identification has an effect on performance of entire system. GEN2 is global, open, interoperability protocol for UHF RFID system, the active researches and developments are processed about it. In this paper, we introduce an anti-collision algorithm based on Slotted-ALOHA for GEN2 protocol, focus on estimating number of tags and setting number of slots and review the previous works. We propose new scheme that can estimate number of tags efficiently, and define system efficiency newly when it's used in setting number of slots. We also present result of compare and analysis with previous scheme through simulation. The proposed scheme of estimating number of tags is easy to implement, number of tags which is less than 4 times of number of slots can estimate tags efficiently, we also proved that identification efficiency based on weighted-slot distinguished with definition of previous slot efficiency can improve system efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4889-4902
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• 2018

It is a challenging issue to improve the energy efficiency of neighbor discovery in WSNs. This paper proposes an optimal discovery model (ODM) for the first time. Based on the model, we investigate the influence of the relative size of two unequal active slots on the energy efficiency. ODM provides the energy optimal value of the length of the larger active slot at a given duty cycle. Other than existing methods, the worst-case latency bound of ODM is only one period. This is a subversive conclusion, because almost all other related methods are based on a wake-up schedule that contains several periods. We theoretically deduce that ODM can reduce worst-case discovery latency by 43.89% compared to Searchlight-Trim when their duty cycles are the same. The simulations verify the advantage of ODM.

• The KIPS Transactions:PartC
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• v.14C no.4
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• pp.383-388
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• 2007

In this paper, we propose a new signal frame structure based on Alamouti code that can maintain the same performance as Alamouti code and increase spectral efficiency. The proposed signal frame structure can increase spectrum efficiency to approach 1(bit/s/Hz) since it can process n bit data during (n+1) time slot. In order to verify two performances, we derive closed form BER via mathematical approach, and compare with the simulation result in Rayleigh fading plus AWGN channel. Then we find that the two performances are exactly same.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.194-196
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• 2001

Light dimming is based on adjusting the voltage which gets to the lamp. Light dimming has been possible for many decades by using adjustable power resistors and adjustable transformers. The power electronics have proceeded quietly since 1960. Between 1960-1970 thyristors and triacs came to market. Using those components it was quite easy to make small and inexpensive light dimmers which have goof efficiency. This type of electronic light dimmers became available after 1970 and are nowadays used in very many locations like homes, restaurants, conference rooms and in stage lighting. But the problem of thyristor dimmer have been that it has poor efficiency and voltage drop. Recently IGBT(Insulated Gate Bipolar Transistor) control is a new way to do light dimming for improving this problems. IGBT dimmer has many other advantages over traditional thyristor dimmer there are no huge current spikes and EMI caused by turn on Using IGBT it is possible to make the turn-off rate relatively slot to achieve quite operations in terms of EMI and acoustical or incandescent lamp filament noise. For the development of IGBT dimmer. This paper shows the effects of IGBT dimmer compared with thyristor dimmer through a simulation using EMTDC.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.665-671
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• 2007

The purpose of this study is to find out a flow characteristics required by the design of a computer case and to provide information about the preliminary data of cooling efficiency of CPU and a flow inside of a case. We examined a flow characteristic-suction a tracing particle occurred from a surge tand installed at an inlet into a computer case and moving it to a exit duct-experimentally by using PIV. The experimental device was consists of a fan inflowing and discharging the air into the computer case and a slot installed with a CPU cooling ran add-on, and analyzed the data of Re-stress distribution, velocity distribution, and kinetic energy distribution. This research will make a great contribution to improvement of the efficiency and performance of notebook, workstation, server, and all the design of electronic devices using large scale integrated(LSI) as well as usual computers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.8
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• pp.119-124
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• 2004

In this paper, we are designed and fabricated circular polarization microstrip patch antenna of 5［GH］z bandwidth for the wireless LAN and the ISM. We are proposed new structure that removed the section which intersected at a right angle and were composed to four separated slots. The antenna of proposed structure could solve parasitic elements from intersected in a right angle and weak coupling efficiency from asymmetry between feed line and a slot. The proposed cross slots antenna is easily impedance matching and increased impedance bandwidth. Also this is increased efficiency and a bandwidth of antenna and reduce back lobe of radiation pattern. We designed 2${\times}$2 array antenna of 5［GHz］ band. It took impedance bandwidth 280［MHz］(VSWR < 1.5) and gam 12.5［dBi］

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.705-706
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• 2008

There has been, in recent years, effort to make cast copper rotors for industrial use of induction motors. Because the incorporation of copper for the conductor bars and end rings of the induction motor in place of aluminum would result in attractive improvements in motor energy efficiency. The purpose of this method is a reducing the copper loss as using higher conductivity of copper. In this paper as the single phase induction motor is studied, the stator slots and coil turn number is designed for adjusting the slot fill factor and improving its efficiency. At this time design is basis on calculation of reducing loss. And finally this paper shows that the before and after result is compared and analyzed.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.153-160
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• 2015

Hybrid Electric Vehicles(HEVs) have seriously come into prevalence recently as car manufacturers and consumers have become more aware of the environmental and economic problems of conventional vehicles. For the alternative power-train and battery cooling systems in HEVs, an effective thermal management system is required, and many automakers are interested in using Brushless DC(BLDC) motors for cooling fans for the overall traction unit's performance and energy saving capability. This paper presents the development status of BLDC motors as major parts of the power-train, i.e. the engine cooling and battery cooling fans of HEVs. A design that uses BLDC motors for the power-train and each battery cooling fan, is successfully implemented through using electro-magnetic analysis, and prototype BLDC motors are examined. As experimental results, the BLDC motors achieved an efficiency of 85% as engine cooling fans and 72% as a battery thermal management fan motor. The electric cogging noise is significantly reduced by changing the skew of the slot pitch angle and optimizing the magnetic shape.