• Journal of The Korean Association of Information Education
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• v.4 no.2
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• pp.140-146
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• 2001

Scheduling strategy in the Education-on-Demand system should be designed to service the isochronous requests from several learners with single disk retrieval to improve the performance of the system. In this paper, the scheduling strategy which reduces the disk I/O and buffer consumption by utilizing the resources of the learner's system has been proposed. All the requests from the learner are not serviced from the server but forwarded to the learner's system which preserves the requested information. Therefore, the server can increase the throughput and reduces the initial latency time of the user. The proposed strategy has been compared to the conventional method by simulations and proved to be more efficient.

• ETRI Journal
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• v.37 no.1
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• pp.66-76
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• 2015

In this work, we propose an efficient selective retransmission method for multiple-input and multiple-output (MIMO) wireless systems under orthogonal frequency-division multiplexing (OFDM) signaling. A typical received OFDM frame may have some symbols in error, which results in a retransmission of the entire frame. Such a retransmission is often unnecessary, and to avoid this, we propose a method to selectively retransmit symbols that correspond to poor-quality subcarriers. We use the condition numbers of the subcarrier channel matrices of the MIMO-OFDM system as a quality measure. The proposed scheme is embedded in the modulation layer and is independent of conventional hybrid automatic repeat request (HARQ) methods. The receiver integrates the original OFDM and the punctured retransmitted OFDM signals for more reliable detection. The targeted retransmission results in fewer negative acknowledgements from conventional HARQ algorithms, which results in increasing bandwidth and power efficiency. We investigate the efficacy of the proposed method for optimal and suboptimal receivers. The simulation results demonstrate the efficacy of the proposed method on throughput for MIMO-OFDM systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4307-4325
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• 2016

With the aim of solving the problems of long processing times, high memory consumption and low event throughput in the current processing approaches in out-of-order RFID event streams, an efficient complex event processing method based on INFA-HTS (Improved Nondeterministic Finite Automaton-Hash Table Structure) is presented in this paper. The contribution of this paper lies in the fact that we use INFA and HTS to successfully realize the detection of complex events for out-of-order RFID event streams. Specifically, in our scheme, to detect the disorder of out-of-order event streams, we expand the traditional NFA model into a new INFA model to capture the related RFID primitive events from the out-of-order event stream. To high-efficiently manage the large intermediate capturing results, we use the HTS to store and process them. As a result, these problems in the existing methods can be effectively solved by our scheme. The simulation results of our experiments show that our proposed method in this paper outperforms some of the current general processing approaches used to process out-of-order RFID event streams.

• Plant Biotechnology Reports
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• v.4 no.2
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• pp.129-138
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• 2010

An efficient transformation system for high-throughput functional genomic studies of kiwifruit has been developed to overcome the problem of necrosis in Actinidia arguta explants. The system uses Agrobacterium tumefaciens strain EHA105 harbouring the binary vector pART27-10 to inoculate leaf strips. The vector contains neomycin phosphotransferase (nptII) and ${\beta}$-glucuronidase (GUS) (uidA) genes. A range of light intensities and different strengths of Murashige and Skoog (MS) basal salt media was used to overcome the problem of browning and/or necrosis of explants and calli. Callus browning was significantly reduced, resulting in regenerated adventitious shoots when the MS basal salt concentration in the culture medium was reduced to half-strength at low light intensity ($3.4\;{\mu}mol\;m^{-2}\;s^{-1}$) conditions. Inoculated leaf strips produced putative transformed shoots of Actinidia arguta on half-MS basal salt medium supplemented with 3.0 $mg\;l^{-1}$ zeatin, 0.5 $mg\;l^{-1}$ 6-benzyladenine, 0.05 $mg\;l^{-1}$ naphthalene acetic acid, 150 $mg\;l^{-1}$ kanamycin and 300 $mg\;l^{-1}$ $Timentin^{(R)}$. All regenerated plantlets were deemed putativ transgenic by histochemical GUS assay and polymerase chain-reaction analysis.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1097-1106
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• 2004

The typical web cluster architecture consists of replicated real servers and a virtual server that routes client requests among the real servers. In this paper, we proposed an efficient dynamic load distribution method with load prediction for the web cluster systems. The virtual server transmit status request message to real servers in other to get load states. However the load states dose not accurate during load distribution, thus the virtual server predict the load status of real servers and assign a request of the client to the minimum loaded real server. The proposed distribution methods works not related to partial breakdown of real servers, thus the system works with high availability. We also show that the proposed distribution method preserve scalable property and improve the throughput through a set of simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.888-894
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• 2015

This paper describes an efficient hardware design of Lightweight Encryption Algorithm (LEA) developed by National Security Research Institute(NSRI). The LEA crypto-processor supports for master key of 128-bit. To achieve small-area and low-power implementation, an efficient hardware sharing is employed, which shares hardware resources for encryption and decryption in round transformation block and key scheduler. The designed LEA crypto-processor was verified by FPGA implementation. The LEA core synthesized with Xilinx ISE has 1,498 slice elements, and the estimated throughput is 216.24 Mbps with 135.15 MHz.

• Journal of Communications and Networks
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• v.11 no.6
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• pp.615-625
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• 2009

Worldwide inter-operability for microwave access (WiMAX) is a promising technology that provides high data throughput with low delays for various user types and modes of operation. While much research had been conducted on physical and MAC layers, little attention has been paid to a comprehensive and efficient security solution for WiMAX. We propose a hybrid security solution combining identity-based cryptography (IBC) and certificate based approaches. We provide detailed message exchange steps in order to achieve a complete security that addresses the various kind of threats identified in previous research. While attaining this goal, efficient fusion of both techniques resulted in a 53% bandwidth improvement compared to the standard's approach, PKMv2. Also, in this hybrid approach, we have clarified the key revocation procedures and key lifetimes. Consequently, to the best of knowledge our approach is the first work that unites the advantages of both techniques for improved security while maintaining the low overhead forWiMAX.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.72-79
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• 2014

This paper presents a method for constructing a pipeline-aware quasi-cyclic irregular repeat accumulate low-density parity-check (PA-QC-IRA-LDPC) codes and efficient rate-1/2 (2016, 1008) PA-QC-IRA-LDPC decoder architecture. A novel pipeline scheduling method is proposed. The proposed methods efficiently reduce the critical path using pipeline without any bit error rate (BER) degradation. The proposed pipeline-aware LDPC decoder provides a significant improvement in terms of throughput, hardware efficiency, and energy efficiency. Synthesis and layout of the proposed architecture is performed using 90-nm CMOS standard cell technology. The proposed architecture shows more than 53% improvement of area efficiency and much better energy efficiency compared to the previously reported architectures.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4367-4386
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• 2015

The concept of Internet of Things (IoT) has shed new light on WSN technologies. MAC protocol issues improving the network performance are important in WSNs because of the increase in demand for various applications to secure spectrum resources. Cognitive radio (CR) technology is regarded as a solution to the problems in this future wireless network. In recent years, energy efficiency has become an issue in CR networks. However, few relevant studies have been conducted. In this paper, an energy-efficient non-overlapping channel MAC (ENC-MAC) for CR-enabled sensor networks (CRSNs) is proposed. Applying the dedicated control channel approach, ENC-MAC allows the SUs to utilize channels in a non-overlapping manner, and thus spectrum efficiency is improved. Moreover, the cooperative spectrum sensing that allows an SU to use only two minislots in the sensing phase is addressed to en-hance energy efficiency. In addition, an analytical model for evaluating the performance, such as saturation throughput, average packet delay, and network lifetime, is developed. It is shown in our results that ENC-MAC remarkably outperforms existing MAC protocols.

• 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.