• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2381-2388
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• 2015

It has been known that interference occurs between macrocell ans small-cell base stations in a heterogeneous network (HetNet) of LTE-A. For solving this problem, 3GPP suggested eICIC (Enhanced Inter Cell Interference Coordination) that includes ABS (Almost Blank Subframe) and power control. This paper proposes to use ABS with power control and derives an effective ABS ratio as a function of the number of users and HeNBs. Through simulation, we confirm that integration of ABS and power control can mitigate interference than using ABS only. Furthermore, we verify that an effective ABS ratio is different depending on the number of users and HeNBs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5458-5464
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• 2012

In LTE-Advanced that different networks coexist, it is considered that it is actually difficult to provide service continuity with a procedural and static control method applied to the existing voice service. This research suggests a resource management framework to support the service continuity effectively based on QoS support. In other words, as context information of mobile terminal and base station changes, set-up of related functions such as ISHO, cell selection, source allocation, load control, and QoS mapping is adapted; each function fits into the change, exchanges the process of reorganization, and interacts; these actions go toward to satisfy service continuity. For this aim, the sequence diagram between the function modules for supporting four kind of ISHO is described and then a scenario for ISHO is considered.

• Journal of the Society of Disaster Information
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• v.12 no.2
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• pp.167-175
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• 2016

Korea has faced with the problem of the whole national disaster safety due to the Sewol-ho and it reminded people and government of the importance of national safety. It is needed to establish the national unified network especially focused on the disaster site and also improved in the fields of law, system and organization related to the management of disaster. To do this, PS-LTE technology must to be adopted to the network and 700MHz is the most efficient bandwidth for the network. At the same time, we have to improve the management system for the response of disaster including standard procedure and the platform of disaster response system. In order to establish realistic and efficient emergency communications network, it is effective to build own network and use leased networks together. And the cost is estimated about 5.2 trillion won.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.57-66
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• 2012

LTE-Advanced network will form the high-speed IP backbone in collaboration with heterogeneous radio access networks for dynamic optimized resource utilization. In order to implement more innovative and attractive services such as U-Cloud streaming, LBS and mobile smart TV, a mobile terminal needs to support multiple sessions simultaneously. Efficient resource allocation schemes are necessary to maintain QoS of multiple sessions because service continuity may be defected by delay and information loss during handover. This paper proposes a resource allocation scheme to accommodate multiple sessions in a mobile terminal on handover period based on session priority mechanism. Simulation is focused on the forced termination probability of handover sessions. Simulation results show that our proposed method provides a better performance than the conventional method.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.10
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• pp.361-372
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• 2016

Identity Privacy issues such as exposures of IMSIs(International Mobile Subscriber Identities) in access network have been consistently raised throughout GSM, UMTS, LTE in 3GPP. The 3GPP specification uses temporary identities instead of IMSI to ensure anonymity of the user. Even if temporary identities are disclosed, Identity Privacy may be maintained at a safe level by security policies such as no linkability and periodic update. But in case of IMSI, it cannot be changed even though it is exposed. There still exist some situations that IMSI is used in clear text for the authentication. Therefore, a protective mechanism for the identity confidentiality is needed. In this paper we propose a protocol based on IBE(Identity-based Encryption) to protect permanent identities in access network. By simplifying the scheme, this protocol has minimized the system impact on current 3GPP environment. And this scheme can be applied to all kind of permanent identities and 3GPP AKA(Authentication and Key Agreement) protocols in access network.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.8
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• pp.729-734
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• 2016

The current domestic railway wireless communication networks transmit and receive data using several communication schemes such as VHF, TRS-ASTRO, and TRS-TETRA depending on the specific region. Recently, LTE scheme has been adopting in railway wireless communication systems to provide various services and increase reliability. It is critical to support the network interoperability between the existing communication schemes and new communication scheme for seamless data transmission. In this paper, we propose two interoperability schemes in railway communications networks, i.e., network oriented scheme and terminal oriented scheme. We consider the operation scenario for each scheme and compare two interoperability schemes. The practical implementation issues are also discussed based on suggested schemes.

• Journal of KIISE
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• v.42 no.6
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• pp.723-733
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• 2015

The OTT service that provides multimedia video has spread over the Internet for terminals with a variety of resolutions. The terminals are in communication via a networks such as 3G, LTE, VDSL, ADSL. The service of the network has been increased for a variety of terminals giving rise to the need for a new way of encoding multimedia is increasing. SVC is an encoding technique optimized for OTT services. We proposed an efficient multimedia management system for the SVC encoded multimedia data. The I/O trace was generated using a zipf distribution, and were comparatively evaluated for performance with the existing system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.2
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• pp.38-44
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• 2013

In this paper, we designed and implemented a mobile video transmission device with 1080i resolution and 30fps frame rate using wireless multi-access technologies. The video acquisition delay time of 16us and jitter of 21ms for this equipment were obtained, respectively. The device is designed to access various communication networks. In order to evaluate the performance of its video transmission capability, a server and monitoring viewer are implemented. In the performance test using LTE network, 211ms delay time was obtained at 3Mbps transmission. Rendering of 1fps frame rate at the 265kbps transmission was confirmed for the transmission test using Inmarsat network.

• Information and Communications Magazine
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• v.33 no.6
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• pp.9-17
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• 2016

본고에서는 5G 망에서의 서비스 요구사항을 만족하기 위한 구조로서 Network Slicing 구조를 제안하고 세부 적용방안을 기술한다. 이를 위해 5G 서비스를 우선 정의하고 그에 따른 서비스 요구사항을 도출한 후, 이러한 요구사항과 관련해 현재 망의 문제점에 대해 기술하고 망 개선을 위한 기술 요구사항을 정립한다. 특히, 5G에서의 중요성이 높아질 것으로 전망되고 있는 'Network Slicing'의 필요성 및 개념에 대해 서술한다. Network Slicing에 대한 제조사들의 솔루션 동향, 3GPP 등 단체의 표준화 동향, APN 방식의 P-LTE/DECOR/RAN Slicing 등 관련 기술의 발전 동향을 포함한 5G Network Slicing 주요 기술 동향에 대해서 알아본다. 또한, Slice의 관리 및 BSS/OSS등과의 연계를 위한 통신사업자 입장에서의 플랫폼 요구사항을 정리한다. 5G Network Slicing을 충족하기 위한 주요 기술로 C/U plane 분리구조, 범용 서버를 활용한 NFV/SDN, Edge 기반의 분산된 수평적 네트워크, 데이터 오프로딩 및 지연시간 절감을 위한 Edge Computing 등을 들 수 있고 효율적인 자원 관리를 위한 Orchestration 등에 대해서도 알아본다. 이를 기반으로 하여 사업자 입장에서 5G Core Network 기술을 선도함은 물론이고 향후, 조기 상용화를 위한 진화 방향을 제시하고자 한다.

• Electronics and Telecommunications Trends
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• v.30 no.4
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• pp.140-150
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• 2015

모바일 트래픽 증대는 향후 급격히 증가할 것으로 예측되며 LTE에서 AII-IP기반의 고속 대용량 데이터처리는 망의 부하증가를 의미한다. 비디오 컨퍼런싱, 온라인 음악, 게임, 영화 스트리밍, 네트워크 브라우징, 블로깅 등 현재 온라인 상에서 급격하게 사용되고 있는 새로운 애플리케이션들은 높은 대역폭(Bandwidth)과 고속용량이 필요하고 망 운용자들은 대역폭과 네트워크 용량 한계점을 줄이기 위한 해결책에 관심을 갖게 되었다. 이를 위해 3GPP에서는 데이터 오프로딩(Data Offloading) 기술을 정의하였으며 이는 펨토셀과 non-3GPF액서스 망 등과 정합하는 기술을 제공하였다. 본고에서는 망의 부하를 줄이기 위한 이들 오프로딩 기술에 대한 요구사항, 구조 및 구현 시 고려해야 하는 주요 이슈들에 대해서 살펴본다.