• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3572-3593
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• 2015

This article investigates the topology control problem in the space information network (SIN) using a hierarchical autonomous system (AS) approach. We propose an AS network topology control (AS-TC) algorithm to minimize the time delay in the SIN. Compared with most existing approaches for SIN where either the purely centralized or the purely distributed control method is adopted, the proposed algorithm is a hybrid control method. In order to reduce the cost of control, the control message exchange is constrained among neighboring sub-AS networks. We prove that the proposed algorithm achieve logical k-connectivity on the condition that the original physical topology is k-connectivity. Simulation results validate the theoretic analysis and effectiveness of the AS-TC algorithm.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.206-206
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• 2015

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.722-729
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• 2005

Ethernet passive optical networks (EPONs) are an emerging access network technology which has a point-to-multipoint topology. EPONs operate point-to-multipoint in the OLT-ONU direction, and point-to-point in the ONU-OLT direction. To support point-to-point emulation and shared LAM emulation, EPONs use multi-point control protocol (MPCP). The MPCP uses logical link identification (LLID) field for frame tagging and filtering between the OLT and ONUs. In this paper, I propose logical-group identification (LGID) for logical link-based multicasting or VLAN services in EPONs. Using LGID with new frame tagging and filtering rules, EPONs support differentiated multimedia broadcasting or multicasting services. Additionally, EPONs can support logical link-based VLAN services that divides ONUs into several subsets.

• ETRI Journal
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• v.27 no.4
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• pp.355-366
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• 2005

Automatic discovery of physical topology plays a crucial role in enhancing the manageability of modern metro Ethernet networks. Despite the importance of the problem, earlier research and commercial network management tools have typically concentrated on either discovering logical topology, or proprietary solutions targeting specific product families. Recent works have demonstrated that network topology can be determined using the standard simple network management protocol (SNMP) management information base (MIB), but these algorithms depend on address forwarding table (AFT) entries and can find only spanning tree paths in an Ethernet mesh network. A previous work by Breibart et al. requires that AFT entries be complete; however, that can be a risky assumption in a realistic Ethernet mesh network. In this paper, we have proposed a new physical topology discovery algorithm which works without complete knowledge of AFT entries. Our algorithm can discover a complete physical topology including inactive interfaces eliminated by the spanning tree protocol in metro Ethernet networks. The effectiveness of the algorithm is demonstrated by implementation.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.12-21
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• 2000

Arrangement graph has desirable properties for design requirements of a multihop lightwave network, such as node and edge symmetry, low diameter, simple routing, etc. In this paper, arrangement lightwave network based on arrangement graph model is proposed as new logical topology of multihop lightwave network. In the proposed scheme, multistar and grouping of network are used for improving reusability of wavelength and scalability. Also, this paper shows that the proposed scheme is an alternative logical topology for application requiring more nodes with limited wavelengths by evaluating performance with related works.

• Journal of KIISE:Information Networking
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• v.31 no.2
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• pp.224-232
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• 2004

To guarantee the reliability in multicast transmission, researches providing reliability through hierarchical control tree which is independent on data channel tree are known to provide high scalability. However, the logical control tree in transport layer constructed without topology information of the corresponding network layer tree may inefficiently use the network resources because the logical control tree is not closely related to the tree topology of the network layer. A router assisted control tree mechanism presented in this paper would improve the efficiency of the link as well as it would remove the replicated data. In addition, it requires to a router a small change which examines the message type of the control tree.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1452-1460
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• 2000

A series of papers in recent literature on logical topology design for wavelength routed optical networks have proposed mathematical models and solution methods unifying logical topology design wavelength assignment and traffic routing. The most recent one is by Krishnaswamy and Sivarajan which is more unifying and complete than the previous models. Especially the mathematical formulation is an integer linear program and hence regarded in readiness for an efficient solution method compared to the previous nonlinear programming models. The solution method in [7] is however elementary one relying on the rounding of linear program relaxation. When the rounding happens to be successful it tends to produce near-optimal solutions. In general there is no such guarantee so that the obtained solution may not satisfy the essential constraints such as logical -path hop-count and even wavelength number constraints. Also the computational efforts for linear program relaxation seems to be too excessive. In this paper we propose an improved and unifying solution method based on the same to be too excessive. In this paper we propose an improved and unifying solution method based on the same model. First its computation is considerably smaller. Second it guarantees the solution satisfies all the constraints. Finally applied the same instances the quality of solution is fairly competitive to the previous near optimal solution.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.86-88
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• 2022

LoRa has been evaluated as a promising technology for Internet of things networks. Theoretically, the technology is robust for long-range communication by using chirp spreading spectrum, provides several orthogonal logical channels in a physical channel, exploits spatial reusability by introducing a star-of-stars topology. A part of recent studies indicates the quasi-orthogonality, or the imperfect orthogonality, between logical channels. The channel elements, however, are both spreading factor and bandwidth. Nevertheless, Most of the researches only treat the spreading factor. This study presents the quasi-orthogonality between all of the logical channels built by variations of the both factors. Furthermore, it shows the performance varied by the logical channel interference.

• Management Science and Financial Engineering
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• v.6 no.2
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• pp.29-45
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• 2000

We consider the design of a two-level telecommunication network having logical full-mesh/star topology, with the implementation of conduit systems taken together. The design problem is then viewed as consisting of three subproblems: locating hub facilities, placing a conduit network, and installing cables therein to configure the logical full-mesh/star network. Without partitioning into subproblems as done in the conventional approach, the whole problem is directly dealt with in a single integrated framework, inspired by some recent successes with the approach. We successfully formulate the problem as a variant of the classical multicommodity flow model for the fixed charge network design problem, aided by network augmentation, judicious commodity definition, and some flow restrictions. With our optimal model, we solve some randomly generated sample problems by using CPLEX MIP program. From the computational experiments, it seems that our model can be applied to the practical problem effectively.

• Journal of Information Processing Systems
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• v.15 no.2
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• pp.440-448
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• 2019

The Internet of Things (IoT) is one of the main enablers for situation awareness needed in accomplishing smart cities. IoT devices, especially for monitoring purposes, have stringent timing requirements which may not be met by cloud computing. This deficiency of cloud computing can be overcome by fog computing for which fog nodes are placed close to IoT devices. Because of low capabilities of fog nodes compared to cloud data centers, fog nodes may not be deployed with all the services required by IoT devices. Thus, in this article, we focus on the issue of fog service placement and present the recent research trends in this issue. Most of the literature on fog service placement deals with determining an appropriate fog node satisfying the various requirements like delay from the perspective of one or more service requests. In this article, we aim to effectively place fog services in accordance with the pre-obtained service demands, which may have been collected during the prior time interval, instead of on-demand service placement for one or more service requests. The concept of the logical fog network is newly presented for the sake of the scalability of fog service placement in a large-scale smart city. The logical fog network is formed in a tree topology rooted at the cloud data center. Based on the logical fog network, a service placement approach is proposed so that services can be placed on fog nodes in a resource-effective way.