• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.75-84
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• 2017

It becomes more and more more important for the storage that supports high speed recording and stable access from network environment. As one field of basic science which produces massive astronomical data, VLBI(: Very Long Baseline Interferometer) is now demanding more data writing performance and which is directly related to astronomical observation with high resolution and sensitivity. But most of existing storage are cloud model based for the high throughput of general IT, finance, and administrative service, and therefore it not the best choice for recording of big stream data. Therefore, in this study, we design storage system optimized for high performance of I/O and concurrency. To solve this problem, we implement packet read and writing module through the use of libpcap and pf_ring API on the multi core CPU environment, and build a scalable storage based on software RAID(: Redundant Array of Inexpensive Disks) for the efficient process of incoming data from external network.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2004.11a
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• pp.265-271
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• 2004

The interaction network of protein -protein plays an important role to understand the various biological functions of cells. Currently, the high -throughput experimental techniques (two -dimensional gel electrophoresis, mass spectroscopy, yeast two -hybrid assay) provide us with the vast amount of data for protein-protein interaction at the proteome scale. In order to recognize the role of each protein in their network, the efficient bioinformatical and computational analysis methods are required. We propose a systematic and mathematical method which can analyze the protein -protein interaction network rigorously and enable us to capture the biological and physical essence of a topological character and stability of protein -protein network, and sensitivity of each protein along the biological pathway of their network. We set up a Laplacian matrix of spectral graph theory based on the protein-protein network of yeast proteome, and perform an eigenvalue analysis and apply a perturbation method on a Laplacian matrix, which result in recognizing the center of protein cluster, the identity of hub proteins around it and their relative sensitivities. Identifying the topology of protein -protein network via a Laplacian matrix, we can recognize the important relation between the biological pathway of yeast proteome and the formalism of master equation. The results of our systematic and mathematical analysis agree well with the experimental findings of yeast proteome. The biological function and meaning of each protein cluster can be explained easily. Our rigorous analysis method is robust for understanding various kinds of networks whether they are biological, social, economical...etc

• Molecules and Cells
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• v.27 no.3
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• pp.271-277
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• 2009

Proteins interact with each other within a cell, and those interactions give rise to the biological function and dynamical behavior of cellular systems. Generally, the protein interactions are temporal, spatial, or condition dependent in a specific cell, where only a small part of interactions usually take place under certain conditions. Recently, although a large amount of protein interaction data have been collected by high-throughput technologies, the interactions are recorded or summarized under various or different conditions and therefore cannot be directly used to identify signaling pathways or active networks, which are believed to work in specific cells under specific conditions. However, protein interactions activated under specific conditions may give hints to the biological process underlying corresponding phenotypes. In particular, responsive functional modules consist of protein interactions activated under specific conditions can provide insight into the mechanism underlying biological systems, e.g. protein interaction subnetworks found for certain diseases rather than normal conditions may help to discover potential biomarkers. From computational viewpoint, identifying responsive functional modules can be formulated as an optimization problem. Therefore, efficient computational methods for extracting responsive functional modules are strongly demanded due to the NP-hard nature of such a combinatorial problem. In this review, we first report recent advances in development of computational methods for extracting responsive functional modules or active pathways from protein interaction network and microarray data. Then from computational aspect, we discuss remaining obstacles and perspectives for this attractive and challenging topic in the area of systems biology.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4754-4773
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• 2018

In sensor medium access control (SMAC) protocol, sensor nodes can only access the channel in the scheduling and listening period. However, this fixed working method may generate data latency and high conflict. To solve those problems, scheduling duty in the original SMAC protocol is divided into multiple small scheduling duties (micro duty MD). By applying different micro-dispersed contention channel, sensor nodes can reduce the collision probability of the data and thereby save energy. Based on the given micro-duty, this paper presents an adaptive duty cycle (DC) and back-off algorithm, aiming at detecting the fixed duty cycle in SMAC protocol. According to the given buffer queue length, sensor nodes dynamically change the duty cycle. In the context of low duty cycle and low flow, fair binary exponential back-off (F-BEB) algorithm is applied to reduce data latency. In the context of high duty cycle and high flow, capture avoidance binary exponential back-off (CA-BEB) algorithm is used to further reduce the conflict probability for saving energy consumption. Based on the above two contexts, we propose an improved SMAC protocol, micro duty adaptive SMAC protocol (MDA-SMAC). Comparing the performance between MDA-SMAC protocol and SMAC protocol on the NS-2 simulation platform, the results show that, MDA-SMAC protocol performs better in terms of energy consumption, latency and effective throughput than SMAC protocol, especially in the condition of more crowded network traffic and more sensor nodes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.1-9
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• 2011

In this paper, we propose an efficient method to create clusters of geographically distributed base stations which cooperatively transmit signals in cellular mobile communication systems. The proposed method utilizes a sequential selection approach to choose candidate base stations which can provide maximum weighted sum-rate gain when they participate in the cooperative transmission with the existing cluster. In particular, the proposed method limits the maximum number of base stations in a cluster by considering the system operational and implementation complexities. Moreover, the combinations of clusters dynamically change along with variations of channel environments. Through computer simulations, performance of the proposed method is verified by comparing with the non-cooperative transmission method and the static clustering method. Numerical result shows that the proposed sequential selection based clustering method is especially advantageous for the performance improvement of lower percentile users in terms of average throughput, and thus the proposed method can effectively improve the fairness among users.

• Journal of the Korea Society for Simulation
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• v.16 no.2
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• pp.17-26
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• 2007

In this paper, we propose a basic virtual grid-based routing algorithm in order to devise an efficient routing method in ad hoc networks using the location information of nodes, energy level, etc. A packet is forwarded to the X-axis direction at first based on the location information of a destination node, and then it is forwarded to the Y-axis direction as its location becomes close to the destination from the viewpoint of the X-axis. Due to the selection of next hop nodes to deliver a packet from a certain node to a destination node, we can regard the whole network as a virtual grid network. The proposed routing algorithm determines routing paths using the local information such as the location information of a destination and its neighbor nodes. Thus, the routing path setup is achieved locally, by which we can expect reduction in network traffics and routing delays to a destination. To evaluate the performance of the proposed routing algorithm, we used the network simulator ns2 and compared its network throughput with that of an existing routing algorithm.

• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.65-74
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• 2014

IEEE 802.11n standard has introduced the new schemes in MAC and PHY layers to improve network throughput. Frame aggregation and Block ACK are mainly defined to increase the efficiency of the MAC layer. There exists still problem in IEEE 802.11n. When block ACK request and/or response frames are missing or received in error, the sender does not know the status (success/failure) of each frame in the aggregated large frame and retransmits all the frames. This can cause a lower network performance. To solve this problem, we propose a new effective scheme, called reduced retransmission of MPDUs (RRM) scheme. In the proposed scheme, when a sender does not receive a block ACK response frame, it just transmits a next data frame and requests a block ACK. Therefore, it can retransmits the erroneous frames. Performance of the proposed scheme is investigated by simulation. Our results show that the proposed scheme is very effective and improves the performance under a wide range of channel error conditions.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1083-1092
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• 2016

In this paper, the performance of the optical code-division multiple access (OCDMA) technology on a plastic optical fiber (POF) access network, which had received much attention due to its low weight, large core diameter, flexibility, easy installation, and especially its high bandwidth, is analyzed. Recently, POF was a very attractive candidate for transmission media in an access network based on OCDMA technology. But the conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels which are restricted by BER, and so, in this paper, to resolve this problem a novel multi-priority reservation protocol is also proposed. By using this reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict could be avoided. And this protocol can efficiently support the transmission of multimedia messages that require the different time-delay. The network throughput and average delay using various system parameters have been investigated by numerical analysis and simulation experiments. These results shows that the multi-priority reservation protocol in this POF access network based on OCDMA technology is valid and efficient.

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.44-51
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• 2013

Routers should perform fast IP address lookup for Internet to provide high-speed service. In this paper, we present a hybrid parallel IP address lookup structure composed of four-stage pipeline. It achieves parallelism at low cost by using multiple SRAMs in stage 2 and partitioned TCAMs in stage 3, and improves the performance through pipelining. The smart distributor in stage 1 does not transfer any IP address identical to previous one toward the next stage, but only uses the result of the previous lookup. So it improves throughput of lookup by caching effects, and decreases the access conflict to TCAM bank in stage 3 as well. In the last stage, the reorder buffer rearranges the completed IP addresses according to the input order. We evaluate the performance of our parallel pipelined IP lookup structure comparing with previous hybrid structure, using the real routing table and traffic distributions generated by Zipf's law.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1082-1088
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• 2005

Generating fast round key in AES Rijndael algorithm using three key sizes, such as 128, 192, and 256-bit keys is a critical factor to develop high throughput AES processors. In this paper, we propose on-the-fly round key generator which is applicable to the pipelined and non-pipelined AES processor in which cipher and decipher nodes must be implemented on a chip. The proposed round key generator has modular and area-and-time efficient structure implemented with simple connection of two key expander modules, such as key_exp_m and key_exp_s module. The round key generator for non-pipelined AES processor with support of three key lengths and cipher/decipher modes has about 7.8-ns delay time under 0.25um 2.5V CMOS standard cell library and consists of about 17,700 gates.