• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.506-511
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• 2011

In this paper, a rectenna for wireless power transmission at 900MHz is proposed. Rectenna is a device transforming RF power into DC power and it may consist of a antenna, rectifying and charging circuits. In this paper, we designed a slot antenna to receive 900MHz signal, a rectifying circuit of about 40% efficiency at 0dBm input, and a charging circuit to store a weak power signal and supply constant voltage to load. From the experiment using a RFID reader as a transmitter for 1W power, it was found that the proposed rectenna receiving about 0dBm power can supply 3.3V constant voltage to 50$k{\Omega}$ load during 280sec.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.572-575
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• 2007

In this paper, we proposed a internal antenna for Quad band for GSM/DCS/USPCS/WCDMA Handset. Antenna Structure is designed to PIFA type. Antenna planed two independence patterns to reduce the size for efficiency and used shoting pin and inverse seven_type slit. Also they miniaturized the antenna construction electronic length for duty. furthermore, they designed and producted the antena height for 5w and ground term for 40*80mm. It is because they have wondered the thickness of terminal. used of for reduce size efficiently. The radiation pattern characteristic of antenna is compared and analyzed E-plane and H-plane at 920MHz, 1800MHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9B
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• pp.1092-1097
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• 2011

An anti-collision protocol which tries to minimize the collision probability and identification time is the most important factor in all identification technologies. This paper focuses on methods to improve the efficiency of tag's process in identification systems. Our scheme, Binary Slotted Query Tree (BSQT) algorithm, is a memoryless protocol that identifies an object's ID more efficiently by removing the unnecessary prefixes of the traditional Query Tree (QT) algorithm. With enhanced QT algorithm, the reader will broadcast 1 bit and wait the response from the tags but the difference in this scheme is the reader will listen in 2 slots (slot 1 is for 0 bit Tags and slot 2 is for 1 bit Tags). Base on the responses the reader will decide next broadcasted bit. This will help for the reader to remove some unnecessary broadcasted bits which no tags will response. Numerical and simulation results show that the proposed scheme decreases the tag identification time by reducing the overall number of request.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.199-204
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• 2008

Sensor nodes have various energy and computational constraints because of their inexpensive nature and ad-hoc method of deployment. Considerable research has been focused at overcoming these deficiencies through faster media accessing, more energy efficient routing, localization algorithms and system design. Our research attempts to provide a method of improvement MAC performance in these issues. We show that traditional carrier-sense multiple access(CSMA) protocols like IEEE 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size, We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is a randomized CSMA protocol, but unlike previous legacy protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, it carefully decides a fixed-size contention window, non-uniform probability distribution of transmitting in each slot within the window. We show that it can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely used simulator ns-2. We, finally show that proposed MAC scheme comes close to meeting bounds on the best latency achievable by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to latency.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.4
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• pp.152-160
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• 1999

A high speed motor has been generating a lot of attention due to its performance-more light, thin, short, compact than ordinary motors. But they have low efficiency with high frequency power source because of the iron losses which may produce too much heat as well as the copper losses occurred in the rotor windings. The Halbach array can generate the strong magnetic field systems without additional magnetic materials, therefore the iron losses can be removed. In this paper, the Halbach array is applied to the field system for the high speed motor, and three dimensional FEM is used to analyze the field of the Halbach array considering with the leakage flux. The measured values of flux density are also compared with the FEM analysis. And the magnetic characteristics of the Halbach array field system are compared with those of the conventional field systems such as slot-iron type, PM-iron type. Consequently, it is confirmed that the Halbach array field system is more suitable to the high speed motor because it has high flux density, sinusoidal flux distribution than others.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1990-1992
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• 2001

In this paper, a NeuroFuzzy controller (NFC) with enhanced packet reservation multiple access (PRMA) protocol for QoS-guaranteed multimedia communication systems is proposed. The enhanced PRMA protocol adopts mini-slot technique for reducing contention cost, and these minislot are futher partitioned into multiple MAC regions for access requests coming from users with their respective QoS (quality-of-service) requirements. And NFC is designed to properly determine the MAC regions and access probability for enhancing the PRMA efficiency under QoS constraint. It mainly contains voice traffic estimator including the slot information estimator with recurrent neural networks (RNNs) using real-time recurrent learning (RTRL), and fuzzy logic controller with Mandani- and Sugeno-type of fuzzy rules. Simulation results show that the enhanced PRMA protocol with NFC can guarantee QoS requirements for all traffic loads and further achieves higher system utilization and less non real-time packet delay, compared to previously studied PRMA, IPRMA, SIR, HAR, and F2RAC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.5
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• pp.33-39
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• 2010

In this paper, we propose an improved anti-collision algorithm. We have designed an anti-collision unit using this algorithm for the 18000-6 Type C Class 1 Generation 2 standard (Gen2). The Gen2 standard uses a Q-algorithm for incremental method on the Dynamic Slot-Aloha algorithm. It has basically enhanced performance over the Slot-Aloha algorithm. Unfortunately, there are several non-clarified parts: initial value. If an incorrect value is selected, it causes degradation in performance. To increase throughput and system efficiency, and to decrease tag identification time, we propose an improved anti-collision algorithm. prorosed Q algorithm has an increment of 5% of system efficiency and a decrement of 9% of tag identification time.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.82-88
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• 2009

An adaptive cooperation system is considered with the cooperation decision strategy based on the differences between instantaneous signal-to-noise ratio (SNR) S-D and R-D channels. Specifically, if the quality of the direct link (S-D) is better than that of the link from the relay to the destination (R-D), the source will transmit to destination directly with all scheme's transmitted power. Otherwise, the source broadcasts the signal with a lower power in the first time slot. Then, in the second time slot, if the relay decodes its received signal correctly, it re-transmits the re-encoded signal to the destination else the source will transmit again with the remaining power. Firstly, the spectral efficiency is derived by calculating the probabilities of direct transmission and cooperation mode. Subsequently, the BER performance for the adaptive cooperation schemes is analyzed by considering the BER routine of each mode. Finally, the Monte-Carlo simulation results are presented to confirm the performance enhancement offered by the proposed schemes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.29-37
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• 2004

In RFID system one of the problems that we must solve is to devise a good anti-collision algorithm to improve the efficiency of tag identification which is usually low because of tag collision. Among the existing RFID anti-collision algorithms, Framed Slotted ALOHA algorithm though simple, has a disadvantage that the number of slots used to identify the tags increases exponentially as the number of tags does. In the paper, we propose a new anti-collision algorithm called Partial-Response Framed Slotted ALOHA(PRFSA) which restricts the number of responding tags by dividing the tags into a number of groups when there are large number of tags and changes the frame size when there are small tags. Since the proposed algorithm keeps the frame size and the number of responding tags in such a way that can increase slot utilization, the algorithm shows superior performance to the existing ones. The simulation results showed that the proposed algorithm improves the slot efficiency by 85～100% compared to the existing algorithm.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.782-783
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• 2008

This paper deals with optimum design criteria for premium efficiency of 250kW traction induction motor using response surface methodology (RSM) & finite element method (FEM). The RSM has been achieved to use the experimental design method in combination with Finite Element Method and well adapted to make analytical model for a complex problem considering a lot of interaction of design variables. The proposed procedure allows to define the rotor copper bar shape, stator slot and stator, rotor dimensions starting from an existing motor or a preliminary design.