• Journal of the Economic Geographical Society of Korea
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• v.12 no.4
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• pp.477-493
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• 2009

This research aims to examine Korean regional innovation governance, find structural problems, and explore alternative strategies of regional innovation governance. Especially the alternative governance was searched through the case study of Daegu-Kyungbuk mobile cluster, of which formulation Samsung is the anchor institution. Regional innovation governance in this research is defined as a policy system to link knowledge generation & diffusion subsystem and knowledge application & exploitation subsystem, and institutional conditions to steer the system. "Social Capital Assessment Tool (SOCAT)" of the World Bank was utilized for the appreciation of cluster governance. The regional innovation governance of Daegu-Kyungbuk mobile cluster is characterized as production networks dominated by one-to-one relationship between Samsung and hardware/software developers, decentralized R&D networks and policy networks with multiple hubs. Major policy agents have not developed networks with local companies, and rare are interactions between the policy agents. Local companies, especially software developers, responded they have had experiences to cooperate for local problem solving and shared their community goal, however, the degree of trust in major local project leaders is not high. Local hardware/software developers with core technologies need to be cooperative to develop similar technologies or products in Daegu-Kyungbuk mobile cluster. Regional administrative actors, such as the City of Daegu and Kyungsangbuk-do, and diverse innovation-related institutes should build cooperative environment where diverse project-based cooperation units are incessantly created, taken apart, and recreated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.661-667
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• 2018

Tactical communication radio systems that employ software defined radios(SDRs) have been developed for achieving high-speed data transmissions and voice communications. Such systems possess multiband and multichannel features, and can potentially replace several existing radio systems. This paper proposes a design for wideband antennas by incorporating a diplexer matching network for tactical vehicles. The proposed antenna design includes two radiators(upper and lower) and a diplexer matching network connected to the end of the feed line such that the LC matching networks are interleaved in the lower radiator and spring mount. By employing the diplexer matching network, the designed antenna can perform wideband impedance matching for the fifty ohm feed line. The designed LC networks aid in varying the effective electrical length of the antenna according to the operation frequency. The primary objective behind adjusting the electrical length is to vary the current distribution above and below the LC networks. The proposed antenna was fabricated and tested in an open site. The obtained evaluation results show that the designed antenna can achieve a relative bandwidth of 190% with a VSWR value of 3.5:1, and can attain good antenna gains over VHF and UHF bands.

• Journal of Information Processing Systems
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• v.13 no.3
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• pp.546-558
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• 2017

The amount of multimedia traffic over the Internet has been increasing because of the development of networks and mobile devices. Accordingly, studies on multicast, which is used to provide efficient multimedia and video services, have been conducted. In particular, studies on centralized multicast tree construction have attracted attention with the advent of software-defined networking. Among the centralized multicast tree construction algorithms, the group Takahashi and Matsuyama (GTM) algorithm is the most commonly used in multiple multicast tree construction. However, the GTM algorithm considers only the network-cost overhead when constructing multicast trees; it does not consider the temporary service disruption that arises from a link change for users receiving an existing service. Therefore, in this study, we propose a multiple multicast tree construction algorithm that can reduce network cost while avoiding considerable degradation of service quality to users. This is accomplished by considering both network-cost and link-change overhead of users. Experimental results reveal that, compared to the GTM algorithm, the proposed algorithm significantly improves the user-experienced quality of service by substantially reducing the number of linkchanged users while only slightly adding to the network-cost overhead.

• Information and Communications Magazine
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• v.13 no.3
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• pp.61-70
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• 1996

In this paper, the architecture of the LAN Emulation service defined by the ATM Forum is introduced. In order to use the vast base of the existing LAN application software in ATM network. LAN Emulation provides a MAC layer service emulating connectionless services of legacy LANs on ATM networks. LAN Emulation forms a logical overlay network, called and emulated LAN, on top of an ATM network. LAN Emulation service comprises a set of LAN Emulation Clients(LECs) residing in end stations of an emulated LAN and three logical service entities : LAN Emulation Configuration Server (LECS), LAN Emulation Server(LES). and Broadcast and Unknown Server(BUS). LEC utilizes the services provided by these three servers to provide seamless interworking between legacy LANs and ATM networks, and to support transparent communications between LAN applications over ATM.

• Journal of Information Processing Systems
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• v.14 no.1
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• pp.228-238
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• 2018

With the rapid advancement of Internet services, there has been a dramatic increase in services that dynamically provide Internet resources on demand, such as cloud computing. In a cloud computing service, because the number of users in the cloud is changing dynamically, it is more efficient to utilize a flexible network technology such as software-defined networking (SDN). However, to efficiently support the SDN-based cloud computing service with limited resources, it is important to effectively manage the flow table at the SDN switch. Therefore, in this paper, a new flow management scheme is proposed that is able to, through efficient management, speed up the flow-entry search speed and simultaneously maximize the number of flow entries. The proposed scheme maximizes the capacity of the flow table by efficiently storing flow entry information while quickly executing the operation of flow-entry search by employing a hash index. In this paper, the proposed scheme is implemented by modifying the actual software SDN switch and then, its performance is analyzed. The results of the analysis show that the proposed scheme, by managing the flow tables efficiently, can support more flow entries.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.9-22
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• 2006

When the legacy multicast routing protocols are adopted in If-based mobile core networks, there are some problems such as traffic injection from unnecessary sources, traffic overhead by group management and router performance degradation by large amount of multicast session information. In this paper, we propose a stateless multicast mechanism which has no need to maintain multicast information for session status and reduces redundant network overhead for maintaining multicast tree. In addition interworking with IGMPv3 gets rid of traffic from unnecessary sources which have no registration from receivers. The operations of essential components including a gateway node for interworking with the legacy Internet multicast network, a gateway node for transparency to radio access network and a intermediate node in mobile core networks, are definitely defined and the proposed communication architecture is completed. Finally we evaluate and approve the performance of the proposed architecture by means of well-designed network simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.709-730
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• 2017

To address the challenge of unprecedented growth in mobile data traffic, ultra-dense network deployment is a cost efficient solution to offload the traffic over some small cells. The overlapped coverage areas of small cells create more than one candidate access points for one mobile user. Signal strength based user association in IEEE 802.11 results in a significantly unbalanced load distribution among access points. However, the effective bandwidth demand of each user actually differs vastly due to their different preferences for mobile applications. In this paper, we formulate a set of non-linear integer programming models for joint user association control and user demand guarantee problem. In this model, we are trying to maximize the system capacity and guarantee the effective bandwidth demand for each user by soft-association control with a software defined network controller. With the fact of NP-hard complexity of non-linear integer programming solver, we propose a Kernighan Lin Algorithm based graph-partitioning method for a large-scale network. Finally, we evaluated the performance of the proposed algorithm for the edge users with heterogeneous bandwidth demands and mobility scenarios. Simulation results show that the proposed adaptive soft-association control can achieve a better performance than the other two and improves the individual quality of user experience with a little price on system throughput.

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.153-158
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• 2008

The technology of Software Defined Radio (SDR) is a possible solution to interwork flexibly between various wireless transport protocols. Ubiquitous network, like u-health service network, includes sensor devices or nodes which do not facilitate all the same transport protocols to access network. As such this may be in such unreachable situations as poverty of all required AP (Access Point)’s, faults or contention in a path of particular protocol communication, etc. This paper presents research results of modeling and simulation to analyze transport performance of multi-protocol ubiquitous network which includes SDR-based interwork nodes and congestion-controlled AP’s. Focusing mainly on dynamics of overall transport performance rather than protocol execution procedures, this paper employs the Zeigler’s DEVS (Discrete Event Systems Specification) methodology and DEVSim++simulation environment to experiment.

• Journal of Digital Contents Society
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• v.19 no.7
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• pp.1271-1279
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• 2018

The telecommunication industry, which has traditionally formed its own market area, has also been affected by the after shock of the digitalization triggered by computer communications. In the telecommunications industry, digitalization or digital services refers to network functional virtualization supported by software defined networks. The digitalization of the telecom industry is changing rapidly, and the participants are not limited to the traditional equipment suppliers and service providers in established market, but includes virtually all social entities. To understand this new change, focusing on whether the traditional equipment suppliers that have traditionally played a pivotal role in the center of change will continue its role in this new era of digitalization or not, and how they are progressing toward end-to-end digital services, the goal of digitalization, will lead us to the good understanding of ongoing digitalization.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.6
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• pp.1069-1080
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• 2022

Zero trust, which means never trust anything before verifying it, is emerging as a hot issue in security field. After authenticating users, zero trust establishes network boundaries so that only networks in the trusted range can be accessed. This concept is also consistent with the concept of SDP, which performs pre-verification and creates a network boundary with a dynamic firewall so that clients can access only as many as they have permission to connect. Therefore, we recommend the SDP model as an example of how zero trust can be achieved in a zero trust architecture. In this paper, we point out the areas where SDP needs to be modified for zero trust and suggest ways to overcome them. In addition, we propose an onboarding method, which is one of the processes for becoming an SDP entity, and present performance measurement results.