• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.1199-1202
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• 2017

IoT-Cloud 융합 가상 기계 시스템은 저성능의 사물인터넷 장비에서 고성능 클라우드 서버의 연산력을 제공받는 오프로딩 기법을 사용한다. 오프로딩 기법을 사용하는 경우 실행 대상 프로그램은 사물인터넷 장비와 클라우드 서버 사이에 일관성이 유지되어야하기 때문에 문맥 동기화가 필요하다. 기존 IoT-Cloud 융합 가상 기계의 문맥 동기화 방식은 전체 문맥 동기화를 시도하기 때문에 네트워크 오버헤드가 증가하여 비효율적이다. 네트워크 오버헤드는 오프로딩 실행 성능을 기존보다 감소시킬 수 있기 때문에 효율적인 오프로딩을 위해서는 오프로딩 실행에 필요한 문맥 정보만을 동기화하여 네트워크 오버헤드를 줄여야 한다. 본 논문에서는 효율적인 오프로딩 실행을 위해 정적 프로파일링을 통해 추출된 문맥 정보를 기반으로 오프로딩 실행에 필요한 문맥 정보만을 동기화하는 문맥 동기화기를 설계 및 구현하였다. 오프로딩 실행에 필요한 문맥 정보만 동기화가 이뤄지면 문맥 동기화 시 발생하는 네트워크 오버헤드의 크기가 줄어들기 때문에 효율적인 오프로딩 실행이 가능하다.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.1203-1206
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• 2017

IoT-Cloud 융합 가상 기계 시스템은 오프로딩 기법을 사용하여 저성능 사물인터넷 장비에서 고성능 클라우드 서버의 연산력을 제공받는다. 이 경우 오프로딩 실행 대상 프로그램은 사물인터넷 장비와 클라우드 서버의 실행환경에서 일관성이 유지되어야하기 때문에 문맥 동기화가 필요하다. 현재 문맥 동기화 방식은 전체 문맥 동기화를 시도하기 때문에 네트워크 오버헤드가 증가하여 비효율적이다. 본 논문은 오프로딩 실행에 필요한 문맥 정보만을 동기화하는 효율적인 문맥 동기화를 위해서 정적 프로파일링을 통해 오프로딩 실행 대상 작업에 동기화가 필요한 문맥 정보들을 사전에 추출하였다. 추출된 문맥 정보를 기반으로 문맥 동기화가 이뤄지면 오프로딩 실행에 필요한 문맥 정보만을 동기화하기 때문에 네트워크 통신 오버헤드 감소를 기대할 수 있다.

• Journal of Internet Computing and Services
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• v.14 no.2
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• pp.73-85
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• 2013

As a way of augmenting constrained resources of mobile devices such as CPU and memory, many works on mobile cloud computing (MCC), where mobile devices utilize remote resources of cloud services or PCs, /have been proposed. A typical approach to resolving resource problems of mobile nodes in MCC is to offload functional components to other resource-rich nodes. However, most of the current woks do not consider a characteristic of dynamically changed MCC environment and propose offloading mechanisms in a conceptual level. In this paper, in order to ensure performance of highly complex mobile applications, we propose four different types of offloading mechanisms which can be applied to diverse situations of MCC. And, the proposed offloading mechanisms are practically designed so that they can be implemented with current technologies. Moreover, we define cost models to derive the most sutilable situation of applying each offloading mechanism and prove the performance enhancement through offloadings in a quantitative manner.

• 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.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.19-24
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• 2016

In Long Term Evolution-Advanced (LTE-A), small cell enhancement(SCE) has been developed as a cost-effective way of supporting exponentially increasing demand of wireless data services and satisfying the user quality of service(QoS). However, due to the dense and irregular distribution of a large number of small cells, the offloading scheme should be applied in the small cell network. In this paper, we propose an user offloading scheme for SCE in LTE-Advanced system. We divide the small cells into different clusters according to the reference signal received power(RSRP) from user equipment(UE). Within a cluster, We apply the user offloading scheme with the consideration of the number of users and interference conditions. Simulation results show that proposed scheme can improve the throughput, and spectral efficiency of small cell users. Eventually, proposed scheme can improve overall cell performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.39-44
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• 2013

Long Term Evolution (LTE) - Advanced has developed Heterogeneous Network (HetNet) that consists of a mix of macrocells and low-power nodes such as picocells to improve the system performance. Also, to encourage data offloading in HetNet, Cell Range Expansion (CRE) have been introduced. In this paper, we propose a cell selection scheme based on Signal to Interference plus Noise Ratio (SINR) for optimal offloading effect. And we manage the interference for user located in cell range expanded region using Almost Blank Subframe (ABS) with flexible ABS ratio to improve the spectrum efficiency in time domain. Simulation results show that proposed scheme can improve spectrum efficiency of macrocell and picocell user. Eventually, proposed scheme can imporve overall user performance.

• Electronics and Telecommunications Trends
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• v.28 no.2
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• pp.58-69
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• 2013

LTE 기반의 펨토셀 활용과 개발에 대한 요구는 LTE로의 이동통신 서비스가 본격화되면서, 최근 몇 년간 중요한 이슈로 자리매김하고 있다. 기지국 장비의 재설치와 주파수의 효율적인 활용 측면에서 펨토셀 기지국은 이동통신 서비스 사업자와 가입자에게 동시에 중요한 역할을 수행할 것으로 보인다. 이러한 펨토셀 기지국의 필요성을 충족시켜 주기 위해서는 펨토셀 기지국의 형상과 기능에서 그 본래의 요구를 만족시켜 주는 것이 중요하다. 무엇보다도, LTE 기반의 펨토셀 기지국은 기기의 간편한 설치와 매크로셀 기지국의 오프로딩이라는 역할을 충실히 수행할 수 있는지가 핵심적 평가 요소가 될 것이다. 이를 위해서는 펨토셀 기지국의 핵심 부품인 베이스밴드 SoC(System on a Chip) 성능 및 기능이 펨토셀 기지국 전체의 경쟁력을 판단하는 데 중요한 척도 중에 하나가 될 것이다. 본고에서는 이러한 관점에서 ETRI가 개발한 LTE 펨토셀 기지국의 베이스밴드 SoC를 중심으로 그 형상과 개발 과정을 기술하고 해외 업체들의 베이스밴드 칩셋의 형상과 개발상황에 대해서 자세히 기술하기로 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.229-239
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• 2013

Recently, device-to-device (D2D) communications have been highlighted to improve the spectral efficiency and offer various user experiences in cellular networks. In this paper, we survey standards and literatures related to the D2D technology and address various advantages of D2D technology, and the problems to be resolved before practically implemented. Especially, by considering an important interference issue between cellular and D2D links, five resource allocation and interference management scenarios are provided and their performances are evaluated through the system level simulations. The simulation results show that the use of D2D significantly improve the cell capacity and the D2D user rate due to the effects of frequency reuse and data off-loading. Notably, it is also shown that an optimal D2D communication range exists to maximize the system performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.654-663
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• 2014

Heterogeneous network (HetNet) with the various types of cells, e.g., with the different cell size and transmit power, has been introduced to improve the cell coverage and areal capacity in cellular mobile communication system. In this paper, we consider a practical situation in which all cells share the same wireless resource while some of them have a limited backhaul capacity. More specifically, we formularize a cell association problem that utilizes the minimum wireless resource while satisfying the quality of service (QoS) of all users in terms of their transmission time constraint, and propose a distributed algorithm to find the optimal solution. In the event of bottleneck at the backhaul link in some small cells, the proposed algorithm off-loads some users to the adjacent cell with the less congested backhaul capacity. Finally, we verify that the proposed algorithm supports the more numbers of users to satisfy the specified level of QoS than the conventional user association scheme under the limited access and backhaul capacities.