• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.534-541
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• 2018

The number of stations existing in the same wireless channel is increasing due to the spread of the wireless LAN devices. CSMA/CA, a conventional wireless LAN protocol, uses a random backoff method. In the random backoff scheme, collision between stations is frequent in a dense region where the number of stations existing in the same channel is several tens or more, and the performance of the performance degradation of such a protocol, the IEEE 802.11ah standard proposed a Restricted Access Window(RAW) wireless access method. RAW improves performance by limiting the number of concurrent access stations by dividing the stations into several groups. In this paper, we propose a method to improve the performance of channel connection by using new group creation, group removal and group relocation algorithm according to traffic change by improving existing RAW method.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.520-534
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• 2003

In this paper, a performance evaluation model of the Fat-tree Network with the multiple-buffered crossbar switches is proposed and examined. Buffered switch technique is well known to solve the data collision problem of the switch network. The proposed evaluation model is developed by investigating the transfer patterns of data packets in a switch with output-buffers. Two important parameters of the network performance, throughput and delay, are then evaluated. The proposed model takes simple and primitive switch networks, i.e., no flow control and drop packet, to demonstrate analysis procedures clearly. It, however, can not only be applied to any other complicate modern switch networks that have intelligent flow control but also estimate the performance of any size networks with multiple-buffered switches. To validate the proposed analysis model, the simulation is carried out on the various sizes of Fat-tree networks that uses the multiple buffered crossbar switches. Less than 2% differences between analysis and simulation results are observed.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.303-310
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• 2008

To increase the lifetime of ad-hoc networks, a ratio of energy consumption for each node should be kept constant by equally distributing network traffic loads into all of the nodes. In this paper, we propose a modified AODV routing protocol to determine a possible route by considering a remaining battery capacity of a node and the degree of its usage. In addition, to reduce the amount of energy consumption during the path rediscovery process due to the huge amount of the AODV control messages the limited number of possible routes are stored into a routing table of a source node. When some links of a route fail, another possible path can be looked up in the table before the route discovery process should be initiated. We have tested our proposed method with a conventional AODV and a MMBCR method which is one of the power-efficient energy routing protocols based on the three performance metrics, i.e., the total remaining battery capacity, network lifetime and the ratio of data packets received by the destination node to compare their performance.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.181-188
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• 2002

There are recently a lot of inconvenience because every client should be set to the proxy server on the browser in order to control the access by means of the client authentication in the proxy server. The client authentication technology using the transparency cache in this paper will be transparently used for every user in the internet which option of the authentication function is simply set in the cache server. In addition, the administrator will get the benefit since he can control the traffic of each client and strengthen the security. And also, this system is expected to use in the eCRM deeply rotated to the tendency of the client in the field of the e-commerce like shopping mall in the internet since the administrator can monitor the pattern of the client using the internet. This technique can be applied to the company affiliated research center, the EC website, and the military where it is essential for the tight security even though there are no additional security devices.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.283-292
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• 2002

This paper develops a scheme of resource management for guaranteeing QoS of realtime traffic in wireless mobile internet environments Mobile terminal has significant impact on the QoS originating mobility provided to a real-time application. The currently proposed MRSVP is not clear the boundary of resource reservation tregion and also can give rise to signal overhead to maintain sessions. To solve above problem, we propose the new reservation protocol, mobile cluster based H-MRSVP to combine MRSVP with moving cluster concept. In this paper, we analytically design our model for guaranteeing the QoS of realtime traffic and compare the three schemes: guard channel allocation schemes, DCA and our model. The performance measures are the probabilities of new call blocking, handoff dropping, resource utilization and service completion versus the system offered Erlang load. Consequently, Simulation indicate our model is more flexible than DCA in a view pint of channel utilization and gains the advantage over guard channel scheme with respects to the mobility.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.501-511
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• 1996

Typical integrated service digital network(ISDN) switching systems have several shortcomings including cumulated long call set-up delay and difficulty in higher speed packet communication. The problems come from the nature of X.25 packet swiching technique used in the systems. In this thesis, to solve the above problems, the use of frame relay service within the TDX-10 ISDN switching system is proposed and a frame handling susbsystem(FHS) is designed in order to support the high speed frame relay service in the TDX-10 switching systems. In the proposed TDX-10 architecture, the 64 Kbps packet communication can be executed more ef- ficiently and high speed packet communication is allowed. To measure theperformance characteristics of the proposed systemand to compare the performance with that of the proposed system is superior to that of the existion system and to compare the performance with that of the proposed system is superior to that of the existing system. The proposed switching system offers a seamless evolutionalry path from Narrowband-ISDNto Broadband-ISDNsince itallows anefficient channelutilization and speed packet communication.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.512-522
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• 1996

To provide broadband ISDN service for the users in scattered locations, the application of satellite communications network is seriously considered. To trans mit ATM cells efficiently in satellite communications, it is effective to use TDM A method. However, it is necessary to have a method to compensate the cell delayvari-ation caused by the difference between TDMA and ATM. This paper optimized the cell control time(Tc) when traffic inputs have poisson or markov modulated poisson process by applying cell delay variation characteristics of time stamp method, which has the most advantages among compensation methods or cell delay variation. This paper also intorduces a method of reducing the cell clumping phenomena by adapting discrete time stamp method, including the analysis and evalutation of the range of required quality of CDV distribution by ATM transmission.The result of the experiment shows that CDV distribution-range can be controlled to 1.2$\times$Tc which reduces overall cell delay variation by discrrete time stamp method.

• Journal of Korea Multimedia Society
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• v.3 no.2
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• pp.148-156
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• 2000

This paper proposed that an MPLS-based VPN using next-generation If switches and appropriate set of traffic engineering algorithms is the best way to implement QoS-capable IP VPNs. While ATM-based solution would not rely scalable the number of connections becomes too large, MPLS-based VPNs’ efficiency could be confirmed network delay time through performance evaluation. And we evaluated the performance about the If VPN based on proposed MPLS, at the result of evaluation. We figured out that delay increased more slowly in case of VPN based on MPLS comparing with the VPN based on ATM which has rapid delay increasement. Therefore we confirm that the VPN based on MPLS has high speed of packet processing and high degree of network efficiency through the performance evaluation.

• The Journal of the Korea Contents Association
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• v.3 no.2
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• pp.65-72
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• 2003

In this paper, the new scheme using a Combined Cache(CC) that combing the Paging and Routing Cache(PRC) and an alternative handoff method according to the type of data transmission for achieving the efficient realtime communication. The PRC and quasi-soft handoff method reduce the path duplication. But they increase the network traffic load because of the handoff state packet of Mobile Host(MH). Moreover the use the same handoff method without differentiating the type of transmission data. Those problems are solved by operating U with a semi-soft handoff method for realtime data transmission and with a hard handoff method for non-realtime data transmission. As a result or simulation a better performance is obtained because of the reduction of the number of control packet in case that the number of cells are below 20. And the packet arrival time and loss of packet decreased significantly for realtime data transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.331-337
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• 2014

Paradigm shift to cloud computing has increased the importance of security. Even though public cloud computing providers such as Amazon, already provides security related service like firewall and identity management services, it is not suitable to protect data in cloud environments. Because in public cloud computing environments do not allow to use client's own security solution nor equipments. In this environments, user are supposed to do something to enhance security by their hands, so the needs of visualized security management arises. To implement visualized security management, developing near realtime data handling & packet classification mechanisms are crucial. The key technical challenges in packet classification is how to classify packet in the manner of unsupervised way without human interactions. To achieve the goal, this paper presents automated packet classification mechanism based on naive-bayesian and packet Chunking techniques, which can identify signature and does machine learning by itself without human intervention.