• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.701-712
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• 2012

The concept of $k$-shortest disjoint paths is considered important because the establishment of primary and backup forwarding paths exploiting shorter distance and faster propagation time is a dominant consideration for the design of a survivable backbone network. Therefore, we need to evaluate how well the concept of $k$-shortest disjoint paths is exploited for the design of a survivable ship backbone network considering the international standard related to ship backbone networks, the IEC61162-410 standard specifying how to manage redundant message transmissions among ship devices. Performance evaluations are conducted in terms of following objective goals: link capacity, hop and distance of primary and backup paths, even distribution of traffic flows, restoration time of backup forwarding paths, and physical network topology connectivity.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.227-234
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• 2008

The development of wireless network technology allows high data rate seamless communication irrespective of the place and time in various emerging mobile service environment. Unlike wired networks, however, wireless networks utilize expensive limited bandwidth. MBS(Multicast Broadcast Service), which is supported by mobile WiMAX system based on IEEE802.16e, overcomes this problem using a shared downlink channel for efficiently supporting a number of users. However. the coverage and throughput of the system are significantly affected by the channel condition. In this paper we propose on MBS system employing Mobile Multi-Hop Relay(MMR) and adaptive modulation and coding(AMC) scheme. The result of NS-2 computer simulation shows that the throughput and transmission time are substantially improved by the proposed approach compared to the existing MBS system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2078-2083
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• 2012

Tactical communication environment evolving for the purpose of providing services such as voice, video and text based on ALL-IP. Therefore, To be able to guarantee QoS level which meets the required level of subscriber for these services in the constrained tactical communication infrastructure, it is required to take the characteristics such as wireless transmission link, mobility of troops or personal into service quality scheme. In this paper, to support differentiated QoS for each individual or mission in the tactical communication environment, we presents a technique that can provide same QoS level which was served originally regardless of the situation to user's move through dynamically determining the QoS level to be provided at the time of the service request on VoIP-Switch.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.323-326
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• 2018

The purpose of this study is to suggest web accessibility improvement direction through web accessibility evaluation of 16 local government education and training institutions. For this purpose, we evaluated the websites of 14 education and training institutions excluding some websites. The evaluation was conducted through automatic evaluation by Open-WAX and manual evaluation by three experts. As a result of the analysis, although the web accessibility compliance rate improved, problems such as alternate text, skip link, and markup error prevention were found. This study suggests the future direction of research and adherence to web accessibility of local governments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2095-2100
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• 2012

In this paper, we propose the channel sounding scheme which is made for ideal communication between some application as well as the short distance of high speed data transmission in MIMO-OFDM system for Wireless PAN. This method is able to perceive the duration of the impulse response through the delaying of power delay profile, modeled a power delay profile which has an attenuate characteristic, and obtained the coefficient of channel response by ML (maximum likelihood). Through the amplitudes, phases and delays associated with each multipath component which were acquired from this channel sounding scheme, we can describe the wave propagation characteristics of channels between the transmitter and receiver so that the receiver could enhance not only the reliability but also the ability of communication link. Multi agent system models can be used to analyze the path of the system within any time frame. Further, parameter values can be perturbed to examine how the path of the system changes in response to exogenous shocks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1120-1127
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• 2007

In this paper, we propose a generalized processor sharing - dynamic resource allocation (GPS-DRA) scheme which allocates the required amount of resources to each hop dynamically in cellular-based multi-hop systems. In the hybrid-distributed system considered in this paper, a central controller such as a base station (BS) should allocate resources properly to each hop. However, due to changing channel condition with time, it is difficult to allocate as much amount of resources as each hop needs for transmission. GPS-DRA scheme allocates the required amount of resources dynamically to each hop based on the amount of resources used in previous frames by each hop. The amount of control overhead generated by GPS-DRA scheme can be very small because a central controller doesn't need to collect all link information for resource allocation. Our simulation results show that channel utilization increased about 16% and cell capacity increased about 65% compared to those of fixed resource allocation (FRA) scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.80-87
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• 2007

In this paper, link-level performance of a OFDMA technique, which has been considered as a standard for 802.16, 802.20, 3G-LTE, WiMax, and WiBro, is evaluated for next-generation wireless communication systems. While many researches have focused on uncoded forward-link performances, this paper provides a coded performance of a reverse-link OFDMA system. Performance degradation due to time offset among reverse-link users and frequency offset during FFT process is investigated. Transmitter and receiver antenna diversity techniques are used to overcome performance degradation. Performance of a OFDMA system is compared with a CDMA system in terms of FER and throughput to emphasize the advantage of OFDMA system for a reverse-link. Finally, under given specification, Eb/No required to achieve the maximum throughput of a reverse-link is proposed considering various coded rates and antenna permutations.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.11
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• pp.15-21
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• 1999

The scalability of optical cross-connect nodes is analyzed based on the limiting factor of transmission performance. The limiting factors considered are ASE noise accumulation and gain saturation in the optical amplifiers, and crosstalk in both wavelength multiplexers/demultiplexers and optical switches. When the wavelength multiplexer/demultiplexers crosstalk is lower than 25dB, Power Penalty is below 1dB for the cascaded transmission of 10 nodes with 4 input/output ports. When 10Gbps signals are transmitted through nodes with 4 and 16 input/output Ports, performance degradation due to switch crosstalk is dominant compared to that due to ASE noise accumulation if the switch crosstalk is larger than 30dB and 45dB, respectively. For the single stage transmission of 10Gbps signal with 21dB fiber link loss, the maximum loss of optical cross-connect nodes must be under 34dB to achieve the BER of $10^{-12}$.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.137-148
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• 2011

In the past, the domestic research on mobile forensics has been limited to cell phones. Increasing use of smart phones, studies on smart phone forensic will be conducted actively in the future. In particular, the study on Android forensic is very important because Android smart phone market share is increasing rapidly. In this paper, we describe an implementation of an Android smart phone forensic tool based on logical analysis. Compared with Oxygen Forensic Suite 2010, this tool saves time it takes to perform Android smart phone forensic because this tool provides search feature and resource links for extracted media information. So far, no smart phone forensic tool is introduced in Korea. Accordingly, this tool would contribute to the advancement of the technology on smart phone forensic.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.73-81
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• 2011

The WBAN(Wireless Body Area Network) technology is a short distance wireless network which provides each device's interactive communication by connecting devices inside and outside of body located within 3 meters. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. The The WBAN servides consists of both medical and non-medical applications. The medical application service uses the sensor that transfer the periodic traffic and have different data rates. It uses GTS method to guarantee QoS. In this paper, a new method is proposed, which are suitable design for MAC Protocol. Firstly, MAC frame structure and a primitive based on the WBAN are proposed. Secondly, we proposed the GTS algorithm improved the channel utilization based on the WFQ(Weighted Fair Queuing). The proposed scheduling method is improved channel utilization compared with i-Game(Round Robin scheduling method).