• Journal of IKEEE
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• v.11 no.4
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• pp.331-339
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• 2007

The problem of architecting a reliable transport system across an overlay network using split TCP connections as the transport primitive is mainly considered. The considered overlay network uses the application-level switch in each intermediate host. We first argue that natural designs based on store-and-forward principles that are maintained by split TCP connections of hop-by-hop approaches. These approaches in overlay networks do not concern end-to-end TCP semantics. Then, a new transport protocol-Overlay Transport Protocol (OTP)-that manages the end-to-end connection and is responsible for the congestion/flow control between source host and destination host is proposed. The proposed network model for the congestion and flow control mechanisms uses a new window size-Ownd-and a new timer in the source host and destination host. We validate our analytical findings and evaluate the performance of our OTP using a prototype implementation via simulation.

• Journal of the Korea Society for Simulation
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• v.14 no.4
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• pp.55-68
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• 2005

The advancement in semiconductor technology is leading toward smaller critical dimension designs and larger wafer manufactures. Due to such phenomena, semiconductor industry is in need of an accurate control of the process. Photolithography is one of the key processes where the pattern of each layer is formed. In this process, precise superposition of the current layer to the previous layer is critical. Therefore overlay parameters of the semiconductor photolithography process is targeted for this research. The complex relationship among the input parameters and the output metrologies is difficult to understand and harder yet to model. Because of the superiority in modeling multi-nonlinear relationships, neural networks is used for the simulator modeling. For training the neural networks, conjugate gradient method is employed. An experiment is performed to evaluate the performance among the proposed neural network simulator, stepwise regression model, and the currently practiced prediction model from the test site.

• Smart Media Journal
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• v.2 no.1
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• pp.8-16
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• 2013

The significant enhancement of the edge portion of computer networks including user-side machines and last mile network links encourages the research of the overlay network based data dissemination systems. Varieties of overlay network based data dissemination systems has distinct purposes, and each of them has a proper structure of an overlay network and a efficient communication protocol. In this paper, overlay network based data dissemination systems for Flash Dissemination, whose target is the distribution of relatively small size data to very large number of recipients within very short time, are explored. Mainly two systems, RECREW and FaReCAST, are introduced and analyzed in the aspects of design considerations for overlay networks and communication protocols. According to evaluations for flash dissemination scenarios, it is observed that the proposed overlay network based flash dissemination systems outperforms the previous overlay network based multicasting systems, in terms of the reliability and the dissemination delay. Moreover, the theoretical analysis of the reliability of data dissemination is provided by analysing FaReCAST.

• Journal of KIISE:Information Networking
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• v.34 no.4
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• pp.239-245
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• 2007

New multimedia services over the cellular/WLAN overlay networks require different Quality of Service (QoS). In the cellular/WLAN overlay structure, the main issue of load balancing is to balance the available bandwidth among different networks. In this paper, we propose a new online network management scheme. Our proposed scheme is designed to improve bandwidth utilization by balancing the traffic load between the cellular network and WLANs. Simulation results indicate the superior performance of our proposed framework to strike the appropriate performance balance between contradictory QoS requirements under widely varying diverse traffic loads.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.81-86
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• 2007

New multimedia services over the cellular/WLAN overlay networks require different Quality of Service (QoS). Therefore, efficient network management system is necessary in order to provide QoS sensitive multimedia services while enhancing network performance. In this paper, we propose a new online network management scheme that implements bandwidth reservation, congestion and transmission control strategies. Our online approach to network management exhibits dynamic adaptability, flexibility, and responsiveness to the current traffic conditions in multimedia overlay networks. Simulation results indicate the superior performance of our proposed scheme to strike the appropriate performance balance between contradictory QoS requirements under widely varying diverse traffic loads.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.6
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• pp.90-97
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• 2012

In this paper, the new user mobility model which can be utilized to register user's location for interworking with heterogeneous overlay convergent networks under the time-varying radio propagation environment has been proposed. Thus the user mobility model is considered in order to evaluate the behaviors of users in the overlay convergent networks. This Mobile IP user mobility model will be very useful to model the user mobility behaviors and can be used to estimate the signaling traffic and frequency spectrum demands for massive data transfer for the heterogeneous overlay convergent networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.7
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• pp.1638-1656
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• 2013

The demand for multimedia streaming services is increasing rapidly. To meet this demand, there has been much research and many practical developments for providing multimedia services. A push-to-talk (PTT) service is one of the multimedia streaming services that have been deployed not only over IP multimedia subsystem (IMS) but also in peer-to-peer (P2P) overlay networks. The benefit of PTT has been demonstrated in the literature. However, the need for using PTT service in communication can be arbitrary among users, regardless what kind of PTT services they use. This demand does not support current PTT systems, so an expansion of PTT services still be limited. Moreover, the combination of PTT services in IMS and P2P networks will help operators to provide more scalable PTT services. Therefore, in this paper, we proposed a model to support PTT service interworking between IMS and P2P overlay networks. We also introduced our system design and some interworking service scenarios. We confirmed our architecture through implementation and testing.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.190-192
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• 2012

In this paper, we present theoretical queuing analysis for hybrid overlay/underlay Cognitive Radio (CR) system by applying M/M/1 queuing model where the rate of arrival and the service capacity are subject to Poisson alterations. Numerical results are used to prove a high degree of accuracy for the derived expressions. The result can be used as a benchmark to evaluate the performance of a hybrid overlay/underlay CR system.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.446-459
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• 2016

In this paper, we propose virtual direction multicast (VDM) for video multicast applications on peer-to-peer overlay networks. It locates the end hosts relative to each other based on a virtualized orientation scheme using real-time measurements. It builds multicast tree by connecting the nodes, which are estimated to be in the same virtual direction. By using the concept of directionality, we target to use minimal resources in the underlying network while satisfying users' quality expectations. We compare VDM against host multicast tree protocol.We simulated the protocol in a network simulator and implemented in PlanetLab. Results both from simulation and PlanetLab implementation show that our proposed technique exhibits good performance in terms of defined metrics.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.82-85
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• 2019

An adaptive power control scheme is proposed for the cognitive relay networks with joint overlay and underlay spectrum sharing model. The transmit power of the secondary user is adjusted adaptively according to the spectrum sensing results and the interference channel condition. The outage probability of the secondary user is compared by Monte - Carlo simulations between the fixed power control scheme and pure overlay or underlay spectrum sharing schemes. The results show that, by employing the adaptive power control strategy, the interference probability of the secondary user to the primary user is decreased by 70 % ~ 80 % under the same outage probability. Also, the outage probability of the secondary user is reduced by 1 ~ 2 orders of magnitude under the same interference probability. Thus, the performance of the spectrum sharing is improved effectively.