• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.1881-1900
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• 2014

Since 802.11 wireless LANs are so widely used, it has become common for numerous access points (APs) to overlap in a region, where most of those APs are managed individually without any coordinated control. This pattern of wireless LAN usage is called the private OBSS (Overlapping Basic Service Set) environment in this paper. Due to frame collisions across BSSs, each BSS in the private OBSS environment suffers severe performance degradation. This study approaches the problem from the perspective of congestion control rather than noise or collision resolution. The retry limit, one of the 802.11 attributes, could be used for traffic control in conjunction with TCP. Reducing the retry limit causes early discard of a frame, and it has a similar effect of random early drops at a router, well known in the research area of congestion control. It makes the shared link less crowded with frames, and then the benefit of fewer collisions surpasses the penalty of less strict error recovery. As a result, the network-wide performance improves and so does the performance of each BSS eventually. Reducing the retry limit also has positive effects of merging TCP ACKs and reducing HOL-like blocking time at the AP. Extensive experiments have validated the idea that in the OBSS environment, reducing the retry limit provides better performance, which is contrary to the common wisdom. Since our strategy is basically to sacrifice error recovery for congestion control, it could yield side-effects in an environment where the cost of error recovery is high. Therefore, to be useful in general network and traffic environments, adaptability is required. To prove the feasibility of the adaptive scheme, a simple method to dynamically adjust the value of the retry limit has been proposed. Experiments have shown that this approach could provide comparable performance in unfriendly environments.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.87-96
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• 2012

This research overcomes limit of prevention of disasters connection manual that was stopping in existing administrative formality presentation, and allowed purpose in substantial prevention of disasters countermeasure presentation through powerful engineering access. Did operation plan manual Tuesday in contiguity crossing that can reduce confusion by vehicleses that detour by contiguity IC of disaster point to do unusualness ashes in freeway section for this and solve jam-up phenomenon that occur by processing way insufficiency for roundabout way vehicles when happen. Metropolitan areas to target type classification in the highway along the highway adjacent to the intersection at Main Line Blocking optimum operating point analysis and an analysis of countermeasures in case of disaster, the lower the road entering the highway depending on the type of operating at the intersection were different. Depending on the results of analysis, while each point of a disaster, according to the characteristics of geometric conditions, traffic conditions, identify and determine the operating room and the adjacent intersection of media, and building systems to promote the driver if the quick initial response from the impending disaster situations and the safety of drivers can be considered secure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1017-1027
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• 2006

Recently, Internet service providers are offering triple play service which combines voice and video services with the existing high speed Internet service under the common network infrastructure of IP protocol, so that they can create more benefit from operating a single network architecture. In line with this movement in the convergence of network and services, in this work we propose a bandwidth dimensioning method for the subscriber network of the IP network at flow level. To that purpose, let us propose a series of bandwidth dimensioning methods: bandwidth for best effort service only, bandwidth dimensioning for premium services, and bandwidth dimensioning schemes for the premium Internet services as well as the best effort service which comprise the TPS. Our link dimensioning method is based on the flow level that incorporates the flow blocking probability as a measure of grade of services(GoS), and investigates the characteristics of the proposed methods via extensive numerical experiments. After that, let us carry out a simulation experiment concerning the delay and loss performance of the packet scheduling for the premium services (QoS) using the bandwidth designed by our proposed method, via which the packet level quality of service (QoS) for the proposed link dimensioning method can be observed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.52-60
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• 2008

The deblocking filter in the H.264/AVC video coding standard helps to reduce the blocking artifacts produced in the decoding process. But it consumes one third of the computational complexity in H.624/AVC decoder, which advocates an efficient design of a hardware accelerator for filtering. This paper proposes an architecture of deblocking filter using two filters and some registers for data reuse. Our architecture improves the throughput and minimize the number of external memory access by increasing data reuse. After initialization, two filters are able to perform filtering operation simultaneously. It takes only 96 clocks to complete filtering for one macroblock. We design and synthesis our architecture using Dongbuanam $0.18{\mu}m$ standard cell library and the maximum clock frequency is 200MHz.

• YAKHAK HOEJI
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• v.40 no.1
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• pp.102-111
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• 1996

LB10522 is a new parenteral broad spectrum cephalosporin with a catechol moiety at C-7 position of beta-lactam ring. This compound can utilize tonB-dependent iron transp ort system in addition to porin proteins to enter bacterial periplasmic space and access to penicillin-binding proteins (PBPs) which are the lethal targets of ${\beta}$-lactam antibiotics. The chelating activity of LB10522 to metal iron was measured by spectrophotometrically scanning the absorbance from 200 to 900nm. When $FeCl_3$ was added, optical density was increased between 450 and 800nm. LB10522 was more active against gram-negative strains in iron-depleted media than in iron-replete media. This is due to the increased expression of iron transport channels in iron-depleted condition. LB10522 showed a similar activity against E. coli DC2 (permeability mutant) and E. coli DCO (wild type strain) in both iron-depleted and iron-replete media, indicating a minimal permeaility barrier for LB10522 uptake. LB10522 had high affinities to PBP 3 and PBP 1A, 1B of E. coli. By blocking these proteins, LB10522 caused inhibition of cell division and the eventual death of cells. This result was correlated well with the morphological changes in E. coli exposed to LB10522. Although the in vitro MIC of LB10522 against P. aeruginosa 1912E mutant (tonB) was 8-times higher than that of the P. aeruginosa 1912E parent strain, LB10522 showed a similar in vivo protection efficacy against both strains in the mouse systemic infection model. This result suggested that tonB mutant, which requires a high level of iron for normal growth, might have a difficulty in surviving in their host with an iron-limited environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.759-761
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• 2016

Recent changes in the information security environment have led to persistent attacks on intelligent assets such as cyber security breaches, leakage of confidential information, and global security threats. Since existing information security systems are not adequate for Advanced Persistent Threat; APT attacks, bypassing attacks, and attacks on encryption packets, therefore, continuous monitoring is required to detect and protect against such attacks. Accordingly, this paper suggests an operation plan for managing an information security system to block the attack routes of advanced persistent threats. This is achieved with identifying the valuable assets for prevention control by establishing information control policies through analyzing the vulnerability and risks to remove potential hazard, as well as constructing detection control through controlling access to servers and conducting surveillance on encrypted communication, and enabling intelligent violation of response by having corrective control through packet tagging, platform security, system backups, and recovery.

• Convergence Security Journal
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• v.20 no.1
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• pp.85-92
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• 2020

None of the recent cases of military secret leakages have leaked internal information using networks. This is because the Internet and the Intranet are physically separated, and has a difficult process when transmitting and receiving data through the Internet. Therefore, most of the leaked paths are to copy and hand over secrets, shoot and send them with a smartphone, or disclose after remembering them. So, the technology of blocking and detecting military secret leakages through the network is not effective. The purpose of this research is to propose a method to prevent information leakage by focusing on the insider behaviors, the subject of leakage, rather than the military secret. The first is a preventive measure to prevent the leakage behavior of military secrets, the second is to block suspicious access to the military secret data, and the last is to detect the leakage behavior by insiders.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.394-400
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• 2010

Mobile Multi-hop Relaying (MMR) system can provide increased system capacity of wireless access network by coverage extension and enhanced transmission rate within the Base Station (BS) coverage area. The previous researches for the MMR system with a non-transparent mode Relay Station (RS) do not consider channel selection procedure of Mobile Station (MS), co-channel interference and Multi-hop Relay Base Station (MR-BS) coverage and RS coverage ratio in MMR system. In this paper, we investigate the performance of MMR uplink system in multicell environments with various topologies. The performance is presented in terms of call blocking probability, channel utilization, outage probability and system throughput by varying offered load. It is found that, for certain system parameters, the MMR uplink system achieve the maximum system throughput when MR-BS coverage to RS coverage ratio is 7.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.3
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• pp.499-505
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• 2014

According to the increasing use of smart devices such as smart phones and tablets, the service that targets mobile office, finance and e-government for convenience of usage and productivity has emerged significantly. As a result, important information is treated with the smart devices and also, the malicious activity that targets smart devices is increasing steadily. In particular, the damage case by harmful sites, malware distribution sites and phishing sites that targets smart devices has occurred steadily and it has emerged as a social issue. In the case of smart devices, the Android platform is occupied the 90% in Korea, 2013 therefore the method of device block level is required to resolve the social issues of smart devices. In this paper, we propose a method that can be effectively blocked when you try to access an illegal site to Web browser on the Android platform and develop the application and also analyze the wrong site block function.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.508-514
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• 2005

The research in internetworking between UMTS and WLAN, which is completed with merits and demerits, Is actively progressed to establish global roaming environments. This internetworking is classified into two groups: loosely-coupled and tightly-coupled. h tightly-coupled mechanism demands lots of investment and considerable amountof time to construct, which is directly connoted between UNTS and WLAN via IWU. On the other hand, a tersely-coupled mechanism is more scalable and easier to implement than a tightly-coupled one while it has critical drawbacks of packet loss and blocking of services due to handover delay. To alleviate these drawbacks. this work proposes a handover scheme between UMTS and WLAN, which is based on HMIPv6. The performance of the proposed scheme is evaluated by the simaulation. The proposed internetworking scheme based on HMIPv6 shows hotter performance than those based on MIPv6.