• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2666-2687
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• 2022

As a new alternative communication scheme in 5G, unmanned aerial vehicle (UAV) is used as a relay in the remote base station (BS) for assistant communication. In order to ameliorate the quality of the backhaul link, a UAV backhaul transmission scheme based on improved Nash equilibrium (NE) strategy is proposed. First, the capacity of air-to-ground (A2G) channel by the link preprocess is maximized. Then, the maximum utility function of each UAV is used as the basis of obtaining NE point according to the backhaul channel and the backhaul congestion. Finally, the improved NE strategy is applied in multiple iterations until maximum utility functions of all the UAVs are reached, and the UAVs which are rejected by air-to-air (A2A) link during the process would participate in the source recovery process to construct a multi-hop backhaul network. Simulation results show that average effective backhaul rate, minimum effective backhaul rate increases by 10%, 28.5% respectively in ideal A2G channel, and 11.8%, 42.3% respectively in fading channel, comparing to pure NE strategy. And the average number of iterations is decreased by 5%.

• The Journal of Korean Institute of Information Technology
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• v.17 no.2
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• pp.71-77
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• 2019

With 5G standards proceeding in earnest and increasing demand for services of indoor localization, research on indoor location recognition is being studied in various industrial fields, and research based on fingerprint recognition technology using Wireless Local Area Network (WLAN) is representative. In this paper, we propose an indoor positioning system based on fingerprinting technique that uses Cloud Radio Access Network (C-RAN) architecture and Channel State Information (CSI). In order to improve the performance in indoor positioning, we combined existing fingerprinting method and K nearest neighbor (KNN) technology which is one of the machine running technique. The performance improvements of the proposed indoor positioning system was verified by comparative experiments with the existing localization technique in a indoor localizztion testbed.

• KNOM Review
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• v.23 no.2
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• pp.1-10
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• 2020

Network Function Virtualization (NFV) is a key technology of 5G networks that has the advantage of enabling building and operating networks flexibly. However, NFV can complicate network management because it creates numerous virtual resources that should be managed. In NFV environments, service function chaining (SFC) composed of virtual network functions (VNFs) is widely used to apply a series of network functions to traffic. Therefore, it is required to dynamically allocate the right amount of computing resources or instances to SFC for meeting service requirements. In this paper, we propose Deep Q-Networks (DQN)-based auto-scaling to operate the appropriate number of VNF instances in SFC. The proposed approach not only resizes the number of VNF instances in SFC composed of multi-tier architecture but also selects a tier to be scaled in response to dynamic traffic forwarding through SFC.

• Electronics and Telecommunications Trends
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• v.36 no.4
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• pp.34-47
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• 2021

To realize remote surgery from hundreds of kilometers away, a new communication environment with ultra-low latency and high-precision features is required. Thus, ultra-high precision networking technology that guarantees the maximum latency and jitter of end-to-end traffic on an Internet-scale wide area network is in development as part of 6G network research. This paper describes the current status of various networking technologies in ITU-T, ETSI, IEEE, and IETF to ensure ultra-low latency and high precision in wired networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.473-493
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• 2019

5G vehicular communication is one of key enablers in next generation intelligent transportation system (ITS), that require ultra-reliable and low latency communication (URLLC). To meet this requirement, a new hybrid vehicular network structure which supports both centralized network structure and distributed structure is proposed in this paper. Based on the proposed network structure, a new vehicular network utility model considering the latency and reliability in vehicular networks is developed based on Euclidean norm theory. Building on the Pareto improvement theory in economics, a vehicular network uplink optimization algorithm is proposed to optimize the uplink utility of vehicles on the roads. Simulation results show that the proposed scheme can significantly improve the uplink vehicular network utility in vehicular networks to meet the URLLC requirements.

• Journal of the Korean Professional Engineers Association
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• v.34 no.5
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• pp.69-72
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• 2001

The national 2G-3G roaming is emerging as one of essential and important issues In Korea in connection with the recent granting of 3G licenses. Accustomed to the current seamless coverage and superb quality of 2G networks, many subscribers have very high expectations of an equal or better service provisioning by 3G networks. However, it is very unlikely for 3G operators to successfully build their networks as comprehensive as the current 2G networks in the beginning of network implementation and commercial launch. Therefore,3G operators are seriously considering the national 2G-3G roaming in Korea. In this paper. 1 would like to discuss and present a technical implementation scheme and problems that need to be solved fer successfully realizing the national 2G-3G roaming.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.179-186
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• 2000

Optical coupling coefficients and misalignment tolerance of 155 Mbps optical transmitter module of passive alignment technology, to be usable in ATM system, B-NT (Broadband Network Termination) system, and 10 G transmission system for information super-highway networks, were calculated, compaired with it's engineer samples, and discussed. These engineer samples of -4.5 dBm maximum output power were packaged in the method of butt coupling of flat-fiber and tested reliability evaluation. Hence the cheap packaging method of optical transmitter module was researched. rched.

• Electronics and Telecommunications Trends
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• v.32 no.6
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• pp.66-72
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• 2017

The frequency range of a radio wave is from 3kHz to 300GHz, and radio technologies use this range to improve the quality of human lives. Radio technologies have entered a new phase of communication. The core infrastructure used as the basis for technologies leading the fourth industrial evolution, such as artificial intelligence, the Internet of Things, autonomous cars/drones, augmented reality, robots, and remote medical diagnoses, is the 5G network. The 5G network enables transmitting and receiving large amounts of data at very high speed. In particular, application technologies with artificial intelligence have been studied, including radar, wireless charging, electromagnetic devices and their effects on humans, EMI/EMC, and microwave imaging. In this study, we present a future radio technology that is needed to prepare for the upcoming industrial revolution and digital transformation.

• Electronics and Telecommunications Trends
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• v.30 no.1
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• pp.133-143
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• 2015

최근 기술발전으로 컴퓨터 수준의 스마트 디바이스를 이용한 무선 인터넷 서비스 이용이 확대되고 있어 이에 따른 트래픽 증가를 효율적으로 수용하기 위한 새로운 이동통신시스템과 네트워크 구조 연구가 활발하게 진행되고 있다. 이러한 과정에 유선 IT 분야에서 선행적으로 진행된 SDN(Software Defined Network) 및 cloud & virtualization 기술들을 이동통신의 액세스 또는 서비스 플랫폼 환경에 적용하는 선도적인 연구개발이 진행되고 있어 SDN 및 cloud & virtualization 분야에 대한 최근 동향을 파악하고 이러한 기술들이 이동통신분야에 적용되는 다양한 사례들을 분석하여 새로운 형태의 네트워크 및 시스템 구조와 방식에 대한 연구개발 방향을 제시한다.

• Computers and Concrete
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• v.24 no.5
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• pp.469-488
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• 2019

In this research study, the artificial neural networks approach is used to estimate the ultimate shear capacity of reinforced concrete beams with transverse reinforcement. More specifically, surrogate approaches, such as artificial neural network models, have been examined for predicting the shear capacity of concrete beams, based on experimental test results available in the pertinent literature. The comparison of the predicted values with the corresponding experimental ones, as well as with available formulas from previous research studies or code provisions highlight the ability of artificial neural networks to evaluate the shear capacity of reinforced concrete beams in a trustworthy and effective manner. Furthermore, for the first time, the (quantitative) values of weights for the proposed neural network model, are provided, so that the proposed model can be readily implemented in a spreadsheet and accessible to everyone interested in the procedure of simulation.