• Journal of KIISE:Information Networking
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• v.32 no.5
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• pp.641-649
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• 2005

Metro networks use the existing circuit-switching technology like SONET/SDH. Such circuit-switching based networks are inefficient in tarrying Internet traffic with bursty nature. Therefore, metro networks can become a bottleneck In order to resolve this problem, the IEEE 802.17 working group has proposed the RPR (Resilient Packet Ring) technology. In addition to this, the RPR fairness mechanism has been defined to provide fairness among the stations in the RPR network. However, the current RPR fairness mechanism has the problem of inefficient use of the available bandwidth after when the congestion at a node is resolved. In this paper, we propose an improved bandwidth allocation mechanism in which, after the congestion resolution at a node, the node estimates the number of nodes transmitting data and measures the remaining bandwidth and fairly allocates the available bandwidth to active nodes. To show the performance of our proposed mechanism, we have performed simulation and showed that the proposed mechanism offers higher bandwidth utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1254-1260
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• 2009

This paper proposes history-aware random early detection (HRED), a modified version of RED, to lessen bandwidth monopoly by a few of stations employing multiple parallel TCP flows. Stations running peer-to-peer file sharing applications such as BitTorrent use multiple TCP flows. If those stations share a link with other stations with only a small number of TCP flows, the stations occupy most of link bandwidth leading to undesirable bandwidth monopoly. HRED like RED determines whether to drop incoming packets according to probability which changes based on queue length. However it adjusts the drop probability based on bandwidth occupying ratio of stations, thus able to impose harder drop penalty on monopoly stations. The results of simulations assuming various scenarios show that HRED is at least 60% more effective than RED in supporting the bandwidth fairness among stations and at least 4% in utilization.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.52-66
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• 2010

Since large objects consume substantial resources, web proxy caching incurs a fundamental trade-off between performance (i.e., hit-ratio and latency) and overhead (i.e., resource usage), in terms of caching and relaying large objects to users. This paper investigates how and to what extent the current dedicated-server based web proxy caching scheme is affected by large file transfers in a high bandwidth campus network environment. We use a series of trace-based performance analyses and profiling of various resource components in our experimental squid proxy cache server. Large file transfers often overwhelm our cache server. This causes a bottleneck in a web network, by saturating the network bandwidth of the cache server. Due to the requests for large objects, response times required for delivery of concurrently requested small objects increase, by a factor as high as a few million, in the worst cases. We argue that this cache bandwidth bottleneck problem is due to the fundamental limitations of the current centralized web proxy caching model that scales poorly when there are a limited amount of dedicated resources. This is a serious threat to the viability of the current web proxy caching model, particularly in a high bandwidth access network, since it leads to sporadic disconnections of the downstream access network from the global web network. We propose a peer-to-peer cooperative web caching scheme to address the cache bandwidth bottleneck problem. We show that it performs the task of caching and delivery of large objects in an efficient and cost-effective manner, without generating significant overheads for participating peers.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.257-267
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• 2007

Bandwidth Trading(BT) represents a potential market with over 1 trillion USD across the world and high growth potential. BT is also likely to accelerate globalization of the telecommunications industry and massive restructuring driven by unbundling rush. However, systematic researches on BT remain at an infant stage. This study starts with structure analysis of the Internet industry, and discusses significance of Internet interconnection with respect to BT issues. We also describe the bandwidth commoditization trends and review technical requirements for effective Internet interconnection with BT capability. Taking a step further, this study explores the possibility of improving efficiency of network providers and increasing user convenience by developing an architectural prototype of Hub-&-Spoke interconnection model required to facilitate BT. The BT market provides an innovative base to ease rigidity of two-party contract and increase service efficiency. However, as fair, efficient operation by third party is required, this research finally proposes an exchanging hub named NIBX(New Internet Business eXchange).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1580-1584
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• 2010

In this paper, we made an analysis of the effective optical pulse stream generation. This is different from conventional approaches, which use fiber or waveguide delay line circuits. The optical pulse multiplication phenomenon occurs when the optical pulse's spectral width is greater than the transfer bandwidth of the coupler used. Therefore, the effective optical pulse stream generation can be controlled by using fiber couplers with different equivalent transfer bandwidths. The pulse separation spacing is controlled by number of cascaded coupler in optical loop mirror coupler scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.39-48
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• 2008

Recently, many multimedia services have emerged in Internet such as real-time and non- real time services. However, in this Internet environment, we have some limitations to satisfy each service feature. To guarantee the service features in Measurement-Based Admission Control(MBAC) based system on the flow-aware network, there is the method applying Dynamic Priority Scheduling(DPS) algorithm that gives a higher priority to an earlier incoming flow in all of the link bandwidth. This paper classifies all flows under several groups according to flow characteristics on per-flow MBAC algorithm based system. In each flow group, DPS algorithm is applied. This paper proposes two methods that are a DPS based bandwidth borrowing method and a bandwidth dynamic allocation method. The former is that if low priority class has available bandwidths, the flow of high priority class borrows the bandwidth of low priority class when high priority flow has insufficient bandwidth to connect a flow call. The later is that the each group has a minimum bandwidth and is allocated the bandwidth dynamically according to the excess rate for available bandwidth. We compare and analyze the characteristics of the two proposed methods through the simulation experiments. As the results of the experiment, the proposed methods are more effective than existing DPS based method on the packet loss and delay characteristics. Consequently the proposed two methods are very useful in various multimedia network environments.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.12
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• pp.39-48
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• 2001

We have studied the design of the photonic bandgap (PBG) structure on the microstrip line that can effectively control the fractional bandwidth of the passband formed in the stopband by adding the stub in the cell of the microstrip PBG structure. As the length of the stub increases, the cutoff frequency and the center frequency of the stopband are decreased, while the bandwidth of the stopband is increased. We have also found that the fractional bandwidth of the passband formed in stopband by the introduction of defect decreases as the stub length is increased. These results mean that adding the stub in the normal PBG structure is an effective way to control the fractional bandwidth. As an application example, we have implemented a microwave duplexer using the proposed structure.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.291-298
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• 2007

This paper presents a signal processing algorithm to control the dynamic bandwidth of a single-degree-of-freedom (SDF) dynamic sensor system. An accelerometer is a representative SDF sensor system. In this paper, a moire-fringe-based fiber optic accelerometer is newly used for the test of the algorithm. The accelerometer is composed of one mass, one damper and one spring as a SDF dynamic system. In order to increase the dynamic bandwidth of the accelerometer, it is needed to increase the spring constant or decrease the mass. However, there are mechanical difficulties of this adjustment. Therefore, the presented signal processing algorithm is very effective to overcome the difficulties because it is just adjustment in the signal processing software. In this paper, the novel fiber optic accelerometer is introduced shortly, and the algorithm is applied to the fiber optic accelerometer to control its natural frequency and damping ratio. Several simulations and experiments are carried out to prove the performance of the algorithm. As a result, it is shown that the presented signal processing algorithm is a good way to broaden the dynamic bandwidth of the fiber optic accelerometer.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.143-150
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• 2019

Cloud computing has recently become an attractive solution for massively multiplayer online games(MMOGs), as it lifts operators from the burden of buying and maintaining hardware. Peer-to-peer(P2P) -based solutions present several advantages, including the inherent scalability, self-repairing, and natural load distribution capabilities. We propose a hybrid architecture for MMOGs that combines technological advantages of two different paradigms, P2P and cloud computing. An efficient and effective provisioning of resources and mapping of load are mandatory to realize an architecture that scales in economical cost and quality of service to large communities of users. As the number of simultaneous players keeps growing, the hybrid architecture relieves a lot of computational power and network traffic, the load on the servers in the cloud by exploiting the capacity of the peers. For MMOGs, besides server time, bandwidth costs represent a major expense when renting on-demand resources. Simulation results show that by controlling the amount of cloud and user-provided resource, the proposed hybrid architecture can reduce the bandwidth at the server while utilizing enough bandwidth of players.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.375-376
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• 2009