• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4725-4747
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• 2020

Software defined networking (SDN) is considered to be one of the most promising paradigms in the future. To solve the scalability and performance problem that a single and centralized controller suffers from, the distributed multi-controller architecture is adopted, thus forms multi-domain SDN. In a multi-domain SDN network, it is of great importance to ensure a reliable control plane. In this paper, we focus on the reliability problem of multi-domain SDN against controller failure from perspectives of backup controller deployment and controller replication. We firstly propose a placement algorithm for backup controllers, which considers both the reliability and the cost factors. Then a controller replication mechanism based on shared data storage is proposed to solve the inconsistency between the active and standby controllers. We also propose a shared data storage layout method that considers both reliability and performance. Besides, a fault recovery and repair process is designed based on the controller backup and shared data storage mechanism. Simulations show that our approach can recover and repair controller failure. Evaluation results also show that the proposed backup controller placement approach is more effective than other methods.

• Smart Media Journal
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• v.12 no.2
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• pp.15-26
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• 2023

Due to the global COVID-19 pandemic, which has led to a shift towards remote work, the frequency of external access to important internal resources by companies has increased exponentially, exposing them to various security threats. In order to address these access security issues, ZTA (Zero Trust Architecture) has gained attention. ZTA operates on the principle of not trusting external or internal users, and manages access authentication and authorization strictly according to pre-established policies. This paper analyzes the definition of ZTA and key research trends, and summarizes different ZTA solutions for each company.

• Annual Conference on Human and Language Technology
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• 2019.10a
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• pp.339-342
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• 2019

본 논문에서는 소프트웨어 정의 네트워크를 이용한 한중일 한자-한국어 변환 키워드 도메인 이름 시스템을 제안하였다. 한자 체계를 주로 사용하는 한국, 중국, 일본에서 세 나라의 한자 수량이 너무 많기 때문에 우선 한국, 중국, 일본이 공용으로 사용하는 한자 체계인 CJK808을 가지고 연구하였다. 연구를 통해 CJK808 한자 체계에서 각 나라의 한자 특징도 많이 발견하였고, 그 중에서 표준자와 이체자의 다양성이 더욱 두드러졌다. SDN을 이용함으로써 관리 측면에서 다양한 이점을 얻을 수 있다. 제안하는 시스템을 통하여 사용자들은 한국, 중국, 일본 한자를 입력하면 SDN에서 관리하는 도메인 네임 서버를 통해 IP 주소를 얻을 수 있다.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.66-73
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• 2007

SDR technology is a fundamental wireless access technology that combines and accommodates multiple wireless communication standards in one transceiver system through just modifying software using modular communication platforms without any hardware modifications for RF and IF signal processing on the basis of high performance DSP devices. Various communication systems that are designed under diverse and complex network environments require the communication platforms on the basis of SDR supporting reorganization to guarantee simple and fast communication interfaces among the respective wireless networks. This paper introduces a main idea on the implementation of platform on the basis of SDR and a communication platform is designed for experiments that is composed of a DSP board with TMS320C6713 CPU, a FPGA board processing IF signals, and a module with RF transceiver processing wireless LAN frequency bandwidth. Various modulation schemes(BPSK, QPSK, and 16QAM) used in communication systems are applied and tested on the designed platform and the test results shows that it is possible to design a reconfigurable communication terminal platform.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.11
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• pp.635-642
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• 2004

The traditional communication protocols such as TCP/IP are not suitable for PC cluster systems because of their high software processing overhead. To eliminate this overhead, industry leaders have defined the Virtual Interface Architecture (VIA). VIA provides two different data transfer mechanisms, a traditional Send/Receive model and the Remote Direct Memory Access (RDMA) model. RDMA is extremely efficient way to reduce software overhead because it can bypass the OS and use the network interface controller (NIC) directly for communication, also bypass the CPU on the remote host. In this paper, we have implemented VIA-based RDMA mechanism in hardware. Compared to the traditional Send/Receive model, the RDMA mechanism improves latency and bandwidth. Our RDMA mechanism can also communicate without using remote CPU cycles. Our experimental results show a minimum latency of 12.5${\mu}\textrm{s}$ and a maximum bandwidth of 95.5MB/s. As a result, our RDMA mechanism allows PC cluster systems to have a high performance communication method.

• Journal of Software Engineering Society
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• v.26 no.2
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• pp.45-52
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• 2013

A cloud computing service provider must assure Service Level Agreement (SLA) to provide reliable and consistent quality of service to a user. The SLA is a contract between the user and the service provider that connects to assure constant level such as availability to target provided service. The cloud computing is classified into IaaS, PaaS, and SaaS according to IT resources of the various cloud service. The existing SLA is difficult to reflect quality factors of service because it only considers factors about the physical Network environment. In this paper, we suggest the UDDI-based interchange process with the architecture and the specification language having a XML schema for the SLA specification. The quality requirements of SaaS are defined by a proposed specification language in the cloud environment. It is stored in the repository of a quality specification and exchanged on during the service binding time based on the exchange architecture.

• Journal of Advanced Navigation Technology
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• v.25 no.4
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• pp.299-304
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• 2021

Existing human activity recognition systems detect activities through devices such as wearable sensors and cameras. However, these methods require additional devices and costs, especially for cameras, which cause privacy issue. Using WiFi signals that are already installed can solve this problem. In this paper, we propose a CNN-based human activity recognition system using channel state information of WiFi signals, and present results of designing and implementing accelerated hardware structures. The system defined four possible behaviors during studying in indoor environments, and classified the channel state information of WiFi using convolutional neural network (CNN), showing and average accuracy of 91.86%. In addition, for acceleration, we present the results of an accelerated hardware structure design for fully connected layer with the highest computation volume on CNN classifiers. As a result of performance evaluation on FPGA device, it showed 4.28 times faster calculation time than software-based system.

• Journal of KIISE:Software and Applications
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• v.36 no.8
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• pp.633-641
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• 2009

In this paper, we proposed a new pattern classifier which can be incrementally learned, be added new class in learning time, and handle with analog data. Proposed pattern classifier has hierarchical structure and the classification rate is improved by using different metric for each levels. Proposed model is based on the Gaussian ARTMAP which is an artificial neural network model for the pattern classification. We hierarchically constructed the Gaussian ARTMAP and proposed the Principal Component Emphasis(P.C.E) method to be learned different features in each levels. And we defined new metric based on the P.C.E. P.C.E is a method that discards dimensions whose variation are small, that represents common attributes in the class. And remains dimensions whose variation are large. In the learning process, if input pattern is misclassified, P.C.E are performed and the modified pattern is learned in sub network. Experimental results indicate that Hierarchical Gaussian ARTMAP yield better classification result than the other pattern recognition algorithms on variable data set including real applicable problem.

• Smart Media Journal
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• v.4 no.2
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• pp.55-61
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• 2015

A bandwidth-enhanced ultra-wide band (UWB) CMOS balun-LNA is implemented as a part of a software defined radio (SDR) receiver which supports multi-band and multi-standard. The proposed balun-LNA is composed of a single-to-differential converter, a differential-to-single voltage summer with inductive shunt peaking, a negative feedback network, and a differential output buffer with composite common-drain (CD) and common-source (CS) amplifiers. By feeding the single-ended output of the voltage summer to the input of the LNA through a feedback network, a wideband balun-LNA exploiting negative feedback is implemented. By adopting a source follower-based inductive shunt peaking, the proposed balun-LNA achieves a wider gain bandwidth. Two LNA design examples are presented to demonstrate the usefulness of the proposed approach. The LNA I adopts the CS amplifier with a common gate common source (CGCS) balun load as the S-to-D converter for high gain and low noise figure (NF) and the LNA II uses the differential amplifier with the ac-grounded second input terminal as the S-to-D converter for high second-order input-referred intercept point (IIP2). The 3 dB gain bandwidth of the proposed balun-LNA (LNA I) is above 5 GHz and the NF is below 4 dB from 100 MHz to 5 GHz. An average power gain of 18 dB and an IIP3 of -8 ~ -2 dBm are obtained. In simulation, IIP2 of the LNA II is at least 5 dB higher than that of the LNA I with same power consumption.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.19-24
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• 2018

The IP Multimedia Subsystem(IMS) is an architectural framework for delivering IP multimedia services to mobile users. In order to guarantee the reliability and Quality of Service(QoS) of a variety of multimedia services, we need a new evolutionary approach that maintains the IMS based signaling platform which can perform the processing of flow through distributed controllers. Software Defined Network(SDN) is an architecture purporting to be distributed, dynamic, cost-effectives as well as adapting and seeking to be suitable for the high-bandwidth, dynamic nature of today's applications. It requires some methods for the control plane to communication with the data plane. One of such mechanisms is OpenFlow which is a prominent standard protocol and interface that is responsible for managing the network resources by using the remote SDN controller. In this paper, we propose a straightforward approach for integrating SDN technology together with the IMS architecture. Therefore we propose and construct a combined architecture model that performs flow processing using OpenFlow via the IMS based signaling platform, which maintains the existing telecom call service. Additionally, we describe some relevant experimentation results from the proposed architecture.