• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.133-134
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• 2014

이동통신망 내에서 셀룰러 주파수를 공유하여 사용하는 D2D(Device-to-Device) 단말들이 밀집한 지역에서는 D2D 단말이 대부분의 자원을 점유하므로 셀룰러 단말이 통신을 할 수 없는 문제점이 있다. 본 논문에서는 이러한 환경에서 셀룰러 통신을 보장하기 위해 셀룰러 단말과 인접한 범위에 있는 일부 D2D 단말에 대한 모드 선택기법을 제안한다. 제안기법은 밀집된 D2D 단말들로 인해 가용자원이 없는 셀룰러 단말의 주변에 있는 D2D 단말을 셀룰러 모드로 전환한다. 이를 통해 셀룰러 단말은 D2D 단말이 밀집한 지역에서 셀룰러 통신에 사용할 자원을 확보하여 셀룰러 통신을 할 수 있다. 시뮬레이션을 통해 이동통신망에서 D2D 밀집지역에 있는 셀룰러 통신의 성능이 향상되었음을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2258-2276
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• 2019

Resource sharing is one of the main goals achieved by network virtualization technology to enhance network resource utilization and enable resource customization. Though resource sharing can improve network efficiency by accommodating various users in a network, limited infrastructure capacity is still a challenge to ultra-low latency service operators. In this paper, we propose an inter-slice resource borrowing schema based on the device-to-device (D2D) potentiality especially for ultra-low latency transmission in cellular networks. An extended and modified Kuhn-Munkres bipartite matching algorithm is developed to optimally achieve inter-slice resource borrowing. Simulation results show that, proper D2D user matching can be achieved, satisfying ultra-low latency (ULL) users' quality of service (QoS) requirements and resource utilization in various scenarios.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.386-386
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• 2012

We studied a bilateral switching device for spin transfer torque (STT-MRAM) based on 3D device simulation. Metal/P/N+or Metal/N/P+ junction device with $30{\times}30nm2$ area which is composed of one side schottky junction at Metal/P/N+ and Metal/N/P+ provides sufficient bidirectional current flow to write data by a drain induced barrier lowering (DIBL). In this work, Junction device confirmed that write current is more than 30 uA at 2 V, It is also has high on-off ratio over 105 under read operation. Junction device has good process feasibility because metal material of junction device could have been replaced by bottom layer of MTJ. Therefore, additional process to fabricate two outer terminals is not need. so, it provides simple fabrication procedures. it is expected that Metal/P/N+ or Metal/N/P+ structure with one side schottky junction will be a promising switch device for beyond 30 nm STT-MRAM.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.594-596
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• 2012

D2D 통신은 이동통신 단말 간 직접통신을 지원함으로써 단말 간 통신 성능과 무선자원의 사용효율을 향상시킬 수 있는 기술이다. 본 논문에서는 D2D 단말이 기존 이동통신망의 무선자원을 재사용하는 경우 발생할 수 있는 간섭의 영향과 그로 인한 이동통신망의 통신성능을 분석한다. 시뮬레이션을 통해 D2D 단말의 위치, 송신전력, 페어 간 거리에 따른 이동통신 및 D2D 통신의 성능변화를 확인하였으며, 해당 결과는 향후 D2D 간섭완화 관련 연구를 위한 참고자료로 활용할 수 있을 것으로 기대된다.

• Current Optics and Photonics
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• v.1 no.5
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• pp.514-524
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• 2017

We proposed an integrated wavelength-selective photodetector based on a grating-assisted contradirectional coupler and a graphene absorption layer for a coarse wavelength division multiplexing (CWDM) communication system. The center wavelength of the absorption spectrum of the proposed device can be tuned simply by changing the period of the grating, and the proposed device structure is suitable to forming a cascaded structure. Therefore, an array of the proposed device of different grating periods can be used for simultaneous wavelength demultiplexing and signal detection in a CWDM communication system. Our theoretical study showed that the designed device with a grating length of $500{\mu}m$ could have an absorption of 95.1%, an insertion loss of 0.2 dB, and a 3 dB bandwidth of 7.5 nm, resulting in a -14 dB crosstalk to adjacent CWDM channels. We believe that the proposed device array can provide a compact and economic solution to receiver implementation in the CWDM system by combining functions of wavelength demultiplexing and signal detection.

• Journal of the Korea Society of Computer and Information
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• v.27 no.10
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• pp.95-103
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• 2022

As 5G mobile communication services gradually expand in P2P (peer-to-peer) or D2D (device-to-device) applications, traffic-oriented stream control such as YouTube streaming is emerging as an important technology. In D2D communication, the type of data stream most frequently transmitted by users is a video stream, which has the characteristics of a large-capacity transport stream. In a D2D communication environment, this type of stream not only provides a cause of traffic congestion, but also degrades the quality of service between D2D User Equipments (DUEs). In this paper, we propose a Traffic-Oriented Stream Scheduling (TOSS) scheme to minimize the interruption of dynamic media streams such as video streams and to optimize streaming service quality. The proposed scheme schedules the media stream by analyzing the characteristics of the media stream and the traffic type in the bandwidth of 3.5 GHz and 28 GHz under the 5G gNB environment. We examine the performance of the proposed scheme through simulation, and the simulation results show that the proposed scheme has better performance than other comparative methods.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.1
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• pp.5-10
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• 2015

D2D (Device-to-Device) communication underlaying LTE-advanced networks is a promising technology to improve the system capacity and spectral efficiency. By sharing the same radio resources with cellular user equipments, D2D communications can significantly enhance the overall spectral efficiency. However, it may cause interference between D2D link and cellular link. Careful resource allocation and interference coordination between cellular and D2D communications are very important and need to be properly handled. This paper proposes a radio resource allocation scheme based on FFFR (Flexible Fractional Frequency Reuse) for D2D communication underlaying cellular networks. The base station selects randomly resource blocks assigned to cellular users, and reuses them for a D2D pair. Through simulations, we have confirmed that the proposed scheme improves the system throughput, reduces the computational complexity, and mitigates the interference of D2D link and cellular link.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.750-757
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• 2017

Recently, mobile internet traffic has rapidly increased as the huge increase of the smart phone and mobile devices. D2D get attention, because D2D is known that it reduce the traffic load of the base station and also improves the reliability of the network performance. However, D2D has a problem that the efficiency decreases as interference is increased. In this paper, we propose a resource allocation scheme to use the resources efficiently when the D2D link share the cellular resources in the cellular network based the uplink. D2D communication utilizes the location information for allocating resources when the eNB know the location of all devices. The proposed scheme select some cellular user using location informations in order to ensure performance of the D2D communication. and D2D link choose cellular user that performs resource allocation using only selected cellular user. Simulation results show optimal value of resource selection in order to ensure most performance of the D2D communication.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.9
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• pp.263-272
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• 2023

Industrial Internet of Things (IIoT) is an important factor in increasing production efficiency in industrial sectors, along with data collection, exchange and analysis through large-scale connectivity. However, as traffic increases explosively due to the recent spread of IIoT, an allocation method that can efficiently process traffic is required. In this thesis, I propose a two-stage task offloading decision method to increase successful task throughput in an IIoT environment. In addition, I consider a hybrid offloading system that can offload compute-intensive tasks to a mobile edge computing server via a cellular link or to a nearby IIoT device via a Device to Device (D2D) link. The first stage is to design an incentive mechanism to prevent devices participating in task offloading from acting selfishly and giving difficulties in improving task throughput. Among the mechanism design, McAfee's mechanism is used to control the selfish behavior of the devices that process the task and to increase the overall system throughput. After that, in stage 2, I propose a multi-armed bandit (MAB)-based task offloading decision method in a non-stationary environment by considering the irregular movement of the IIoT device. Experimental results show that the proposed method can obtain better performance in terms of overall system throughput, communication failure rate and regret compared to other existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.277-288
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• 2013

3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.