• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.160-167
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• 1987

This paper proposes a CS/MLBP(carrier sence/message and location based priority) reservation sheme in integrated data/voice local area networks. In this sceme reservation can be done with only 2 reservation bits regardless of the total number of stations in the network. Thus the reservation time is shorter than that of DSMA scheme(6) where reservation time is proportional to the logarithm of the total number of stations. Simulation results show that, as compared to DSMA scheme, this control scheme improves th delay-throughput characteristics of both the data and the voice traffic, reduces the lossrate of voice packet at heavy load. Results also show that the performance of the propoxed scheme is independant of the total number of the stations allowed.

• Journal of Digital Contents Society
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• v.12 no.3
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• pp.299-307
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• 2011

The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF. The DCF controls the transmission based on CSMA/CA The BEB backoff algorithm of DCF shows relatively excellent performance in situation that the number of competing station is less, but has a problem that performance of throughput and delay is degraded in situation that the number of competing station is increased. This paper mathematically analyzes an MIMD backoff algorithm considering retry limit that increases the CW to doubled after collision and decreases smoothly the CW to halves after successful transmission in order to reduce the collision probability. To prove efficiency of the MIMD backoff algorithm, lots of simulations are conducted and analyzed.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.157-164
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• 2008

In this paper we suggest a scheduling algorithm that transmits periodic traffics efficiently in tree-structured wireless sensor networks (WSNs). The related research[l] showed the problems such as increasing the energy consumption and decreasing the data throughput as the depth of tree increases. To solve these problems. we use idle time slots and avoid the redundancy at data transmission. Also we suggest the algorithm that transmits the control packet when it is similar to a previously measured data. And if emergency data is occurred, our proposed algorithm transits that data in EDP(Emergency Data Period) for reducing the wait time. The proposed algorithm shows more data throughput and less energy consumption than that of the related research.

• Journal of Communications and Networks
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• v.17 no.2
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• pp.172-183
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• 2015

To provide an efficient link maintenance approach, we propose a cross layer medium access control (LM-MAC) protocol for multichannel cognitive radio ad hoc networks. Link establishment and reliable transmission are two key problems for a perfect link maintenance mechanism. Since the cognitive user (CU) pairs have to reestablish their links each frame, in the proposed MAC protocol, three different access modes are designed to guarantee transmission efficiency in continuous frames. To enhance the transmission reliability, each CU will create a father spectrum list (FSL) after joining in the network. FSL is divided into three groups of sub-channels with different functions to compensate the packet loss caused by the primary users' appearance and the deep fading. Meanwhile, since the transmitter and the receiver will share the same FSL, periodical cooperative sensing is adopted to further optimize the former problem. Finally, compared with the existing opportunistic multichannel (OMC)-MAC protocol, the proposed LM-MAC protocol achieves better system performance in terms of saturation throughput, continuity and access delay.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.453-462
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• 2007

NGN is a packet-based converged network to support session and non-session based services in QoS-enabled broadband transport technologies. Resource and admission control functions(RACF) of NGN have been considering COPS and SNMP as resource management protocols to collect network topology and resource status information of transport network. This paper defines requirements of resource management in NGN transport network, and proposes protocol independent information model to keep consistency of data models of each resource management protocol. Based on this information model described with UML class diagram, we designed and implemented NGN resource management system on Web Services.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.561-562
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• 2017

Software defined networking technology allows centralized and powerful network control by separating packet processing and network control. However, powerfulness of software-defined networking technology threats the network itself. Most security researches of software-defined networking focus on discovering and defending network vulnerabilities. But, there is not much security for this technology itself. In this paper, the security vulnerabilities that can occur in this networking technology are analyzed and the security requirements of it are proposed. The biggest threats are the threats to the controller, the reliability problem between the controller and the switch must be solved, and a technique to detect attacks that malfunction by manipulating configuration information are needed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.344-358
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• 2011

Wireless tactical network (WTN) is the most important present-day technology enabling modern network centric warfare. It inherits many features from WMNs, since the WTN is based on existing wireless mesh networks (WMNs). However, it also has distinctive characteristics, such as hierarchical structures and tight QoS (Quality-of-Service) requirements. Little research has been conducted on hierarchical protocols to support various QoS in WMN. We require new protocols specifically optimized for WTNs. Control packets are generally required to find paths and reserve resources for QoS requirements, so data throughput is not degraded due to overhead. The fundamental solution is to adopt topology aggregation, in which a low tier node aggregates and simplifies the topology information and delivers it to a high tier node. The overhead from control packet exchange can be reduced greatly due to decreased information size. Although topology aggregation is effective for low overhead, it also causes the inaccuracy of topology information; thus, incurring low QoS support capability. Therefore, we need a new topology aggregation algorithm to achieve high accuracy. In this paper, we propose a new aggregation algorithm based on star topology. Noting the hierarchical characteristics in military and hierarchical networks, star topology aggregation can be used effectively. Our algorithm uses a limited number of bypasses to increase the exactness of the star topology aggregation. It adjusts topology parameters whenever it adds a bypass. Consequently, the result is highly accurate and has low computational complexity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.1
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• pp.241-269
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• 2012

Wireless networks composed of multimedia-enabled resource-constrained sensor nodes have enriched a large set of monitoring sensing applications. In such communication scenario, however, new challenges in data transmission and energy-efficiency have arisen due to the stringent requirements of those sensor networks. Generally, congested nodes may deplete the energy of the active congested paths toward the sink and incur in undesired communication delay and packet dropping, while bit errors during transmission may negatively impact the end-to-end quality of the received data. Many approaches have been proposed to face congestion and provide reliable communications in wireless sensor networks, usually employing some transport protocol that address one or both of these issues. Nevertheless, due to the unique characteristics of multimedia-based wireless sensor networks, notably minimum bandwidth demand, bounded delay and reduced energy consumption requirement, communication protocols from traditional scalar wireless sensor networks are not suitable for multimedia sensor networks. In the last decade, such requirements have fostered research in adapting existing protocols or proposing new protocols from scratch. We survey the state of the art of transport protocols for wireless multimedia sensor networks, addressing the recent developments and proposed strategies for congestion control and loss recovery. Future research directions are also discussed, outlining the remaining challenges and promising investigation areas.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.4
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• pp.87-94
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• 2016

This paper proposes an energy transmission method to maximize energy efficiency of a based station. This method makes use of classification of service type to solve an inefficient use of transmission power, which is from exponential relationship between the legacy data throughput and transmission power. The proposed one is a way to find the most energy-efficiency points with the transmitted optimal amount of data on users in a base station of wireless network environment. For this, we propose EETA (Energy-Efficient Transmission Algorithm) which can control the amount of data and the holding time at the base station. As a result, the proposed method can improve the energy efficiency of about 10% compared to the legacy base station.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.261-266
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• 2009

We analyze the performances of the DCF, which is the medium access control protocol of IEEE 802.11 WLAN, assuming normal traffic condition. There have been much less research efforts under the normal condition than those under the saturated one. This paper proposes an analytical method of approximating the transmission attempt rate under normal condition as proportional to that under saturated condition. In result, we show that we can obtain the transmission attempt rate and the packet collision probability which quickly converge using iterative computations of relatively simple equations, and using these results we derive the network throughput and medium access delay. Numerical results show that our method is much less complex than those based on the Markov Chain while it can predict the performances quite accurately.