• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.235-236
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• 2020

본 논문에서는 기존의 SDN(Software Defined Network)의 특징 및 활용 등에 대해 살펴보고 이를 활용한 네트워크의 고도화 및 보안 측면에서의 장단점 연구를 통해 향후 SDN이 보다 고도화 되어야 하는 방향을 제시한다. SDN은 소프트웨어 앱을 사용하여 네트워크를 지능화 하고 중앙에서 제어하거나 프로그래밍 할 수 있는 네트워크 아키텍처 접근법이다. 사업자는 기본 네트워크 기술에 상관없이 전체 네트워크를 일관적으로 전체적으로 관리할 수 있다. 물리적인 네트워크를 소프트웨어 기술을 이용하여 제어하는 네트워크 기술이다. SDN은 네트워크의 제어 플레인을 네트워크 트래픽을 전달하는 데이터 플레인과 분리한다는 개념이다. 이런 분리의 목적은 중앙에서 관리하고 프로그래밍이 가능한 네트워크를 만드는 것이다. 일부 SDN 구현 솔루션은 범용 네트워크 하드웨어를 통제하는 소프트웨어 기반 관리 플랫폼을 사용한다. 또 다른 접근법은 통합된 소프트웨어와 하드웨어를 사용하기도 한다. 하지만 이러한 SDN에도 많은 취약점이 존재하며 이를 보완할 수 있어야 하며 본 논문에서 이러한 방향을 제한하도록 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3701-3727
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• 2016

Recently Service Function Chaining (SFC) is promising to innovate the network service mode in modern networks. However, a feasible implementation of SFC is still difficult due to the need to achieve functional equivalence with traditional modes without sacrificing performance or increasing network complexity. In this paper, we present a configurable network service chaining (CNSC) mechanism to provide services for network traffics in a flexible and optimal way. Firstly, we formulate the problem of network service chaining and design an effective service chain construction framework based on integrating software-defined networking (SDN) with network functions virtualization (NFV). Then, we model the service path computation problem as an integer liner optimization problem and propose an algorithm named SPCM to cooperatively combine service function instances with a network utility maximum policy. In the procedure of SPCM, we achieve the service node mapping by defining a service capacity matrix for substrate nodes, and work out the optimal link mapping policies with segment routing. Finally, the simulation results indicate that the average request acceptance ratio and resources utilization ratio can reach above 85% and 75% by our SPCM algorithm, respectively. Upon the prototype system, it is demonstrated that CNSC outperforms other approaches and can provide flexible and scalable network services.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.579-586
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• 2019

The purpose of this study is to determine the rapid saving of life through the drones when natural disasters such as earthquake and fire occur. Drones are equipped with riders, temperature, hazardous gas sensors and wireless cameras are registered with the application server for monitoring the disaster site and real-time monitoring functions are performed to identify the situation on site before rescuing personnel are active. When monitoring finds a person to save, the application server provides real-time image information for effective life-saving.

• Journal of Internet Computing and Services
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• v.22 no.5
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• pp.27-33
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• 2021

With the broad adoption of the Internet of Things (IoT) in a variety of scenarios and application services, management and orchestration entities require upgrading the traditional architecture and develop intelligent models with ultra-reliable methods. In a heterogeneous network environment, mission-critical IoT applications are significant to consider. With erroneous priorities and high failure rates, catastrophic losses in terms of human lives, great business assets, and privacy leakage will occur in emergent scenarios. In this paper, an efficient resource slicing scheme for optimizing federated learning in software-defined IoT (SDIoT) is proposed. The decentralized support vector regression (SVR) based controllers predict the IoT slices via packet inspection data during peak hour central congestion to achieve a time-sensitive condition. In off-peak hour intervals, a centralized deep neural networks (DNN) model is used within computation-intensive aspects on fine-grained slicing and remodified decentralized controller outputs. With known slice and prioritization, federated learning communications iteratively process through the adjusted resources by virtual network functions forwarding graph (VNFFG) descriptor set up in software-defined networking (SDN) and network functions virtualization (NFV) enabled architecture. To demonstrate the theoretical approach, Mininet emulator was conducted to evaluate between reference and proposed schemes by capturing the key Quality of Service (QoS) performance metrics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4364-4384
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• 2021

The dynamic network state and the mobility of the terminals make the service function chain (SFC) orchestration mechanisms based on static and deterministic assumptions hard to be applied in SDN/NFV mobile edge computing networks. Designing dynamic and online SFC orchestration mechanism can greatly improve the execution efficiency of compute-intensive and resource-hungry applications in mobile edge computing networks. In order to increase the overall profit of service provider and reduce the resource cost, the system running time is divided into a sequence of time slots and a dynamic orchestration scheme based on an improved column generation algorithm is proposed in each slot. Firstly, the SFC dynamic orchestration problem is formulated as an integer linear programming (ILP) model based on layered graph. Then, in order to reduce the computation costs, a column generation model is used to simplify the ILP model. Finally, a two-stage heuristic algorithm based on greedy strategy is proposed. Four metrics are defined and the performance of the proposed algorithm is evaluated based on simulation. The results show that our proposal significantly provides more than 30% reduction of run time and about 12% improvement in service deployment success ratio compared to the Viterbi algorithm based mechanism.

• Journal of Power Electronics
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• v.14 no.1
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• pp.61-73
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• 2014

Multiphase machines are characterized by high power density, enhanced fault-tolerant capacity, and low torque pulsation. For a voltage source inverter supplied multiphase machine, the probability of load imbalances becomes greater and unwanted low-order stator voltage harmonics occur. This paper deals with the PWM control of multiphase inverters under unbalanced load conditions and it proposes a novel near-five-vector SVPWM algorithm based on the five-phase six-leg inverter. The proposed algorithm can output symmetrical phase voltages under unbalanced load conditions, which is not possible for the conventional SVPWM algorithms based on the five-phase five-leg inverters. The cause of extra harmonics in the phase voltages is analyzed, and an xy coordinate system orthogonal to the ${\alpha}{\beta}z$ coordinate system is introduced to eliminate low-order harmonics in the output phase voltages. Moreover, the digital implementation of the near-five-vector SVPWM algorithm is discussed, and the optimal approach with reduced complexity and low execution time is elaborated. A comparison of the proposed algorithm and other existing PWM algorithms is provided, and the pros and cons of the proposed algorithm are concluded. Simulation and experimental results are also given. It is shown that the proposed algorithm works well under unbalanced load conditions. However, its maximum modulation index is reduced by 5.15% in the linear modulation region, and its algorithm complexity and memory requirement increase. The basic principle in this paper can be easily extended to other inverters with different phase numbers.

• Journal of Digital Contents Society
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• v.19 no.4
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• pp.801-808
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• 2018

The performance test methodology for switch, router or integrated networks that make up the wired network is not clearly defined. Due to smart phones and multimedia traffic, the speed of the network is rapidly increasing to 100Gbps. However, there is no formalized test method, and performance test related parts are still being tested based on old data. Telecommunication companies and companies are testing their requirements in their own BMT, and government or public institutions are requesting performance tests from external organizations. As the demand for the performance test of next generation network equipments and the integrated network increases, analysis of the performance test method should be done as soon as possible. Therefore, in this paper, we analyze the performance test method performed by the institute and propose guidelines that can be applied to all wired network equipment.

• 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 Society of Computer and Information
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• v.27 no.9
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• pp.101-112
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• 2022

In this paper, we analyze 5G network slicing and propose an efficient network slice configuration method in 5G mobile networks. Network slicing can be identified and performed based on the network slice instance information in 5G mobile networks. In case of discordance between the UE's network slice instance information and the network's one, the unnecessary signalling overhead occurs, when the UE's PDU Session Establishment request to the network fails. To solve this problem, this paper proposes two efficient network slice configuration methods, the UE-based ENSC(Efficient Network Slice Configuration) method and the Network-based ENSC method. The proposed schemes perform the prompt the configuration and provision of the updated network slice instance information between the UE and network and improve battery and resource efficiency and minimize unnecessary signalling overhead compared to existing methods in 5G mobile networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.7
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• pp.2257-2285
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• 2022

Cyber-physical systems (CPS) have been growing exponentially due to improved cloud-datacenter infrastructure-as-a-service (CDIaaS). Incremental expandability (scalability), Quality of Service (QoS) performance, and reliability are currently the automation focus on healthy Tier 4 CDIaaS. However, stable QoS is yet to be fully addressed in Cyber-physical data centers (CP-DCS). Also, balanced agility and flexibility for the application workloads need urgent attention. There is a need for a resilient and fault-tolerance scheme in terms of CPS routing service including Pod cluster reliability analytics that meets QoS requirements. Motivated by these concerns, our contributions are fourfold. First, a Distributed Non-Recursive Cloud Model (DNRCM) is proposed to support cyber-physical workloads for remote lab activities. Second, an efficient QoS stability model with Routh-Hurwitz criteria is established. Third, an evaluation of the CDIaaS DCN topology is validated for handling large-scale, traffic workloads. Network Function Virtualization (NFV) with Floodlight SDN controllers was adopted for the implementation of DNRCM with embedded rule-base in Open vSwitch engines. Fourth, QoS evaluation is carried out experimentally. Considering the non-recursive queuing delays with SDN isolation (logical), a lower queuing delay (19.65%) is observed. Without logical isolation, the average queuing delay is 80.34%. Without logical resource isolation, the fault tolerance yields 33.55%, while with logical isolation, it yields 66.44%. In terms of throughput, DNRCM, recursive BCube, and DCell offered 38.30%, 36.37%, and 25.53% respectively. Similarly, the DNRCM had an improved incremental scalability profile of 40.00%, while BCube and Recursive DCell had 33.33%, and 26.67% respectively. In terms of service availability, the DNRCM offered 52.10% compared with recursive BCube and DCell which yielded 34.72% and 13.18% respectively. The average delays obtained for DNRCM, recursive BCube, and DCell are 32.81%, 33.44%, and 33.75% respectively. Finally, workload utilization for DNRCM, recursive BCube, and DCell yielded 50.28%, 27.93%, and 21.79% respectively.