• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권8호
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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%.

• 한국재난정보학회:학술대회논문집
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• 한국재난정보학회 2022년 정기학술대회 논문집
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• pp.47-48
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• 2022

기후변화 및 도심화로 인해 해마다 더 큰 규모의 다양하고 복잡한 재난들이 발생했고 발생하고 있다. 2022년을 기준으로 살펴보면, 3월 열흘동안 진행되었던 동해안 일대의 대규모 산불, 8월 초 수도권 집중호우, 9월 초 한반도를 통과한 초대형 태풍 제 11호 힌남노 등 다양한 종류의 대형 재난이 발생하였다. 본 논문은 재난이 발생하였을 때 재난정보를 전달하는 방식 중에서 이동통신망을 이용하는 긴급재난문자에 대한 것으로, 재난이 발생한 특정 지역에 정밀하게 효율적으로 재난정보를 제공하기 위한 지오펜싱(Geo-Fencing)을 적용하는 방식에 대해서 다룬다. 현재 긴급재난문자는 발령 최소 단위가 시군구로 제한되었기 때문에 예를 들어 심야시간에 발생한 특정 건물 화재등과 같은 재난에 대해서는 발령하는데 어려움이 있었다. 본 논문에서 제안하는 지오펜싱 기법을 적용하면, 읍면동보다 좁은 지역에도 긴급재난문자를 발령할 수 있게 되어 특정 지역에 국한된 재난에 대한 정보전달을 신속, 효율적으로 제공 가능하며 이를 통해 궁극적으로는 인명 피해 및 경제적 피해를 감소시킬 수 있게 될 것으로 예상된다.

• Journal of Communications and Networks
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• 제13권5호
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• pp.463-471
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• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제9권2호
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• pp.31-36
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• 2020

국방 통합 데이터센터(DIDC : Defense Integrated Data Center)의 설립으로 인력, 운영 비용 감소 및 효율적인 자원 관리가 가능해졌다. 그러나 4차 산업혁명과 더불어 미래의 전장에 추가될 드론, 로봇, IoT 등의 장비에서 나오는 수많은 전장의 데이터를 효과적으로 수집하고 관리하는 것이 현 체계를 통해서는 어려움이 있는 것이 사실이다. 따라서 이러한 점을 극복하기 위해 이동 통신 기술인 5G의 핵심 기술로 부상하고있는 네트워크 기술인 NFV와 SDN을 이용한 DIDC의 네트워크 체계에 대한 설계를 제안하고자 한다. 장비의 데이터 시트를 분석을 통해 장비마다 동일하게 존재하는 중복 기능을 하나의 VNF로 통합하여 트래픽을 처리한다면 에너지 효율성 증대 및 더욱더 효과적인 네트워크 관리가 가능할 것으로 판단한다.

• International Journal of Internet, Broadcasting and Communication
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• 제13권1호
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• pp.54-60
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• 2021

AR (Augmented Reality) is a technology that provides virtual content to the real world and provides additional information to objects in real-time through 3D content. In the past, a high-performance device was required to experience AR, but it was possible to implement AR more easily by improving mobile performance and mounting various sensors such as ToF (Time-of-Flight). Also, the importance of mobile augmented reality is growing with the commercialization of high-speed wireless Internet such as 5G. Thus, this paper proposes a system that can provide AR services via GNN (Graph Neural Network) using cameras and sensors on mobile devices. ToF of mobile devices is used to capture depth maps. A 3D point cloud was created using RGB images to distinguish specific colors of objects. Point clouds created with RGB images and Depth Map perform downsampling for smooth communication between mobile and server. Point clouds sent to the server are used for 3D object detection. The detection process determines the class of objects and uses one point in the 3D bounding box as an anchor point. AR contents are provided through app and web through class and anchor of the detected object.

• 정보통신설비학회논문지
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• 제5권1호
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• pp.43-59
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• 2006

A compact and broadband $4\times1$ array antenna was developed for 3G smart antenna system testbed. The $4\times1$ uniform linear away antenna was designed to operate at 1.885 to 2.2GHz with a total bandwidth of 315MHz. The array elements were based on the novel broadband L-probe fed inverted hybrid E-H (LIEH) shaped microstrip patch, which offers 22% size reduction to the conventional rectangular microstrip patch antenna. For steering the antenna beam, a commercial variable attenuator (KAT1D04SA002), a variable phase shifter (KPH350SC00) with four units each, and the corporate 4-ways Wilkinson power divider which was fabricated in-house were integrated to form the beamforming feed network. The developed antenna has an impedance bandwidth of 17.32% $(VSWR\leq1.5)$, 21.78% $(VSWR\leq2)$ with respect to center frequency 2.02GHz and with an achievable gain of 11.9dBi. The design antenna offer a broadband, compact and mobile solution for a 3G smart antenna testbed to fully characterized the IMT-2000 radio specifications and system performances.

• ETRI Journal
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• 제44권6호
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• pp.945-954
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• 2022

The 5G mobile network is promising to handle the dynamic traffic demands of user equipment (UE). Unmanned aerial vehicles (UAVs) equipped with wireless transceivers can act as flying base stations in heterogeneous networks to ensure the quality of service of UE. However, it is challenging to efficiently allocate limited bandwidth to UE due to dynamic traffic demands and low network coverage. In this study, a blockchain-enabled bandwidth allocation framework is proposed for secure bandwidth trading. Furthermore, the proposed framework is based on the Cournot oligopoly game theoretical model to provide the optimal solution; that is, bandwidth is allocated to different UE based on the available bandwidth at UAV-assisted-based stations (UBSs) with optimal profit. The Cournot oligopoly game is performed between UBSs and cellular base stations (CBSs). Utility functions for both UBSs and CBSs are introduced on the basis of the available bandwidth, total demand of CSBs, and cost of providing cellular services. The proposed framework prevents security attacks and maximizes the utility functions of UBSs and CBSs.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.357-359
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• 2021

대량 운송 수단인 철도 시스템은 고속화 및 자동화 시대를 넘어 이를 통합한 스마트 철도 시스템으로 진화하고 있다. 이와 같은 스마트 철도 시스템을 구축 및 운용하기 위해서는 5G-R과 같은 모바일 통신 기술과 빅데이터, 딥러닝, 인공지능 및 블록체인과 같은 융복합 정보기술 등이 포괄되는 통신 네트워크 기술이 활용되어야 한다. 본 논문에서는 이와 같은 스마트 철도 시스템을 위한 통신 네트워크 구조를 제안한다. 본 논문에서 제안하는 스마트 철도 통신 네트워크 구조는 고속철도의 안전 운행, 철도 관리, 고객 서비스를 포괄하는 평면단위의 계층구조로 구성되며 필요에 따라 이를 평면간 혼합한 기능을 가질 수도 있다. 본 연구의 결과는 스마트 철도 통신 네트워크의 구축, 운영 및 유지 관리와 철도통신 시스템 표준화 연구 등에 활용될 수 있다.

• ETRI Journal
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• 제42권5호
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• pp.686-699
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• 2020

In this paper, we propose a supervised-learning-based spatial performance prediction (SLPP) framework for next-generation heterogeneous communication networks (HCNs). Adaptive asset placement, dynamic resource allocation, and load balancing are critical network functions in an HCN to ensure seamless network management and enhance service quality. Although many existing systems use measurement data to react to network performance changes, it is highly beneficial to perform accurate performance prediction for different systems to support various network functions. Recent advancements in complex statistical algorithms and computational efficiency have made machine-learning ubiquitous for accurate data-based prediction. A robust network performance prediction framework for optimizing performance and resource utilization through a linear discriminant analysis-based prediction approach has been proposed in this paper. Comparison results with different machine-learning techniques on real-world data demonstrate that SLPP provides superior accuracy and computational efficiency for both stationary and mobile user conditions.

• 전자통신동향분석
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• 제35권5호
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• pp.30-42
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• 2020

Unlike in previous generations of mobile technology, machine learning (ML)-based self-healing research trend are currently attracting attention to provide high-quality, effective, and low-cost 5G services that need to operate in the HetNets scenario where various wireless transmission technologies are added. Self-healing plays a vital role in detecting and mitigating the faults, and confirming that there is still room for improvement. We analyzed the research trend in self-healing framework and ML-based fault detection, fault diagnosis, and fault compensation. We propose that to ensure that self-healing is a proactive instead of being reactive, we have to design an ML-based self-healing framework and select a suitable ML algorithm for fault detection, diagnosis, and outage compensation.