• Journal of Information Processing Systems
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• v.16 no.5
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• pp.1113-1128
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• 2020

Ad hoc networks play an important role in mobile communications, and the performance of nodes has a significant impact on the choice of communication links. To ensure efficient and secure data forwarding and delivery, an intelligent routing protocol (IAODV) based on learning method is constructed. Five attributes of node energy, rate, credit value, computing power and transmission distance are taken as the basis of segmentation. By learning the selected samples and calculating the information gain of each attribute, the decision tree of routing node is constructed, and the rules of routing node selection are determined. IAODV algorithm realizes the adaptive evaluation and classification of network nodes, so as to determine the optimal transmission path from the source node to the destination node. The simulation results verify the feasibility, effectiveness and security of IAODV.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2144-2165
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• 2016

In a vehicular ad hoc network, the communication links are unsteady due to the rapidly changing topology, high mobility and traffic density in the urban environment. Most of the existing geographical routing protocols rely on the continuous transmission of beacon messages to update the neighbors' presence, leading to network congestion. Source-based approaches have been proven to be inefficient in the inherently unstable network. To this end, we propose an opportunistic beaconless packet forwarding approach based on a modified handshake mechanism for the urban vehicular environment. The protocol acts differently between intersections and at the intersection to find the next forwarder node toward the destination. The modified handshake mechanism contains link quality, forward progress and directional greedy metrics to determine the best relay node in the network. After designing the protocol, we compared its performance with existing routing protocols. The simulation results show the superior performance of the proposed protocol in terms of packet delay and data delivery ratio in realistic wireless channel conditions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.2104-2117
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• 2014

The propagation of smart devices and the rapid expansion of wireless mobile networks have increased the need for ubiquitous device connectivity and contents access. DLNA is currently being used as the de facto standard for connectivity of consumer devices in the digital home. The guidelines provided by DLNA are intended to facilitate device and contents discovery, management, sharing and distribution. However, consumer experience with DLNA has been rather poor and usability not up to speed. Different problems and issues in limited compatibility have been reported due to manufacturer customizations. Such compatibility issues are often difficult to identify by average consumers who are not savvy in information communications and multimedia technology. In this paper, the design and implementation of a DLNA protocol inspection tool is presented for compatibility analysis among DLNA certified devices. The tool monitors the home network and performs analysis of the underlying protocols used by DLNA. The tool can be used for diagnostics and troubleshooting, enabling the user to identify compatibility issues between devices or problems in the network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2081-2100
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• 2013

In this paper, we propose a cooperative hybrid spectrum sharing protocol by jointly considering interweave (opportunistic) and underlay schemes. In the proposed protocol, secondary users can access the licensed spectrum along with the primary system. Our network scenario comprises a single primary transmitter-receiver (PTx-PRx) pair and a group of M secondary transmitter-receiver (STx-SRx) pairs within the transmission range of the primary system. Secondary transmitters are divided into two groups: active and inactive. A secondary transmitter that gets an opportunity to access the secondary spectrum is called "active". One of the idle or inactive secondary transmitters that achieves the primary request target rate $R_{PT}$ will be selected as a best decode-and-forward (DF) relay (Re) to forward the primary information when the data rate of the direct link between PTx and PRx falls below $R_{PT}$. We investigate the ergodic capacity and outage probability of the primary system with cooperative relaying and outage probability of the secondary system. Our theoretical and simulation results show that both the primary and secondary systems are able to achieve performance improvement in terms of outage probability. It is also shown that ergodic capacity and outage probability improve when the active secondary transmitter is located farther away from the PRx.

• Journal of Digital Convergence
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• v.14 no.2
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• pp.235-243
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• 2016

Legacy data centers are transforming toward cloud data centers according to the advance of mobile and Internet of Things technology, processing of big data, and development of cloud computing technology. The goal of cloud data centers is to efficiently manage energy and facility, and to rapidly provide service demands to users by operating virtualized ICT(Information and Communication Technology) resources. Accordingly, it requires to configure and operate networks for efficiently providing virtualized ICT resources. This paper analyzes networking technologies suitable for cloud data centers and presents ways to efficiently operate the data center.

• Journal of Applied Reliability
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• v.1 no.2
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• pp.121-138
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• 2001

Due to large demand for high speed and great capacity for data transfer, WDM, which uses the wavelength division multiplexing technique, is known as alternative way to satisfy those demand for its flexible network operation and management, easy network expansion with existing networks, and enhancement of efficient data transfer rate. For these reasons, a new high capacity WDM optical communication network plan was established. Therefore, the quality of currently deployed optical cables with 81.6 km in length should be assessed to ensure if high capacity WDM system could be implemented on existing optical cables. Two important characteristic parameters, Transfer Loss and PMD (Polarization Mode Dispersion), were measured to evaluate quality of existing optical cable. Transfer Loss was measured at 0.244 dB per kilometer, which is lower than the design standard value at 0.275 dB/km. The measured PMD value gave at 0.030ps/km, and it, therefore, satisfies the value recommended by ITU-T (International Telecommunication Union-T) of 0.5ps/km. In addition, the transfer characteristic for existing 2.5 Gbps and 10 Gbps system were measured and evaluated, and the results showed that error-free transfer is very much feasible. Computer simulation for DWDM system, which is likely be a future backbone network in Korea, to assess the transfer characteristic using the same condition employed for 2.5 Gbps and 10 Gbps was carried out as well. The simulation verified that a stable network operation and reliable service could be provided.

• Journal of Korea Spatial Information System Society
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• v.11 no.4
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• pp.65-73
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• 2009

With the rapid development of computer, information and communication technologies, the production and distribution of digital contents among various kinds of networks have become more common. In such environment, we need to store and to manage efficiently a large volume of geograpruc data because the amount of geographic data grows faster and faster. In this paper, as a key solution to manage efficiently such a huge amount of geograpruc data, we adopt the mechanism which compresses only the difference between original and updated data with high compression ratio. By transferring highly compressed updated part only instead of the entire of geographic data, we can reduce the network traffic during the download of contents and service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1047-1055
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• 2005

One of major characteristics in wireless LAN is terminal's frequent mobility, so it makes many overheads in the process of authentications repeatedly at each handoffs. So I propose IAPP(Inter Access Point Protocol) of IEEE 802.11f, modified context block and 4 way handshake of IEEE 802.11i, in order to implement secure and rapid handoff. The context block. I proposed, doesn't makes any communication with RADIUS server at handoff period. Therefore, it guarantee higher efficiency than existing handoff mechanisms. Also it can improve security vulnerability by padding authentication field in the context block for providing in advance against Replay and DoS(Denial of Service) attacks.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.267-274
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• 2015

Due to the difficulty of coordination in the cellular uplink, it is a practical challenge how to achieve the optimal throughput scaling with distributed scheduling. In this paper, we propose a distributed and opportunistic user scheduling (DOUS) that achieves the optimal throughput scaling in a single-input multiple-output interfering multiple-access channel, i.e., a multi-cell uplink network, with M antennas at each base station (BS) and N users in a cell. In a distributed fashion, each BS adopts M random receive beamforming vectors and then selects M users such that both sufficiently large desired signal power and sufficiently small generating interference are guaranteed. As a main result, it is proved that full multiuser diversity gain can be achieved in each cell when a sufficiently large number of users exist. Numerical evaluation confirms that in a practical setting of the multi-cell network, the proposed DOUS outperforms the existing distributed user scheduling algorithms in terms of sum-rate.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.