• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.279-281
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• 2016

이동 멀티미디어 서비스의 서비스 지속성은 패킷 손실과 전송 지연에 영향 받기 때문에 효율적인 핸드오버 제어가 필수적이다. 본 연구에서는 LTE-A 이동통신시스템에서 멀티미디어 서비스의 QoS를 보장하기 위한 핸드오버 수락 제어 방법을 제안한다. 이동 단말기 및 기지국의 상태 정보 변화에 따라 핸드오버 수락 여부를 동적으로 제어할 목적으로 네 가지 종류의 시스템 간 핸드오버를 지원하고자 하는 모듈간의 연계 순서도를 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.9
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• pp.1220-1226
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• 2021

In this paper, we propose a probabilistic handover scheme for enhancing spectral efficiency in drone-based wireless communication systems. When a moving drone base station (DBS) provides the drone-based wireless communication service to a user equipment (UE) located on the ground, our proposed handover scheme considers the distance between DBS and UE and small scale fading. In addition, our proposed handover scheme considers a handover probability to mitigate the signalling overhead that may occur when performing frequent handovers. Through simulations for drone-based wireless communication systems, we evaluate the spectral efficiency and the handover probability of our proposed handover scheme and the conventional handover scheme. The simulation results show that our proposed handover scheme can achieve higher average spectral efficiency than the conventional handover scheme which considers only the distance between DBS and UE.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.3
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• pp.174-183
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• 2007

4G 네트워크로 불라는 차세대 네트워크는 All IP 기반으로 구성되며 여기서는 다양한 특성을 갖는 네트워크 간의 통합이 이루어질 것으로 예측된다. 이러한 4G 네트워크에서의 동종 혹은 이종 망간의 이동 단말의 끊김없는 이동성 제공이 중요한 요소 기술 중 하나로 간주된다. 이동성 제공을 위해 IETF 워킹 그룹에서는 Mobile IP (MIP) 기술을 제안하였고, 차세대 네트워크에서 중요한 역할을 수행할 것으로 판단된다. 그러나 MIP 기술은 이동 단말의 매크로 이동성 (macro mobility)을 지원하기 위해 제안되었기 때문에 긴 핸드오버 지연 시간에 따른 패킷 손실 및 성능 저하를 초래하는 문제점이 존재한다. 따라서 차세대 네트워크에서 이동 단말의 이종 망 핸드오버를 지원하기 위해서는 기존 구축된 네트워크와의 호환성을 제공해 주는 것과 동시에 끊김없는 연결성을 제공해 주는 기법이 필요하다. 그러므로 본 논문에서는 이종 망간의 이동 단말의 움직임에도 끊김없는 연결성을 제공해 줄 수 있는 핸드오버 시스템을 제안한다. 제안하는 시스템은 공통 네트워크 인터페이스로 설계되어 사용되는 무선 기술에 상관없이 투명한 서비스를 IP/MIP 레이어에 제공한다. 본 논문에서는 제안한 시스템을 바탕으로 약결합 네트워크 기반의 cdma2000/무선랜 설험 네트워크를 구축하여 이동 단말의 버티컬 핸드오버 성능을 측정한다. 측정한 핸드오버 성능을 바탕으로 제안한 시스템이 기존 코어 네트워크 및 IP/MIP 레이어 수정없이 여러 이종 망간의 핸드오버 시에 끊김없는 서비스를 이동 단말에게 제공해 준다는 것을 보여준다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.6
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• pp.43-53
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• 2014

Supporting handover functionality in V2I communication environments is important to provide higher quality service to users on the road. Wireless Access in Vehicular Environments(WAVE) standards define some features that devices can communicate with each other more efficiently in vehicular environments but they do not include handover function for providing effective V2I services. In this paper, we introduce a handover scheme in WAVE system and show the performance result of proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.342-351
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• 2008

In this paper, a new handover procedure for OFDM-based multi-hop relay systems is proposed to reduce the handover overhead by distinguishing inter-cell handover event from intra-cell handover event at the level of physical layer using a hierarchical design concept of preamble. A Subcell ID concept for identifying RS in a cell is proposed in the design of hierarchical manner, in addition to the existing Cell ID for identifying BS. The decision on either inter-cell handover or intra-cell handover is made by the signal quality measure of CBINR(Carrier of BS to Interference and Noise Ratio) and CRINR(Carrier of RS to Interference and Noise Ratio), provided by the hierarchical preamble. The proposed handover procedure can simplify scanning procedure and skip/simplify network re-entry procedure (capability negotiation, authorization, registration), resulting in a significant reduction of handover overhead.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.865-873
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• 2010

In this paper, a novel schedulability criteria is developed to provide handover calls with Quality of Service (QoS) guarantees in terms of both minimum available bandwidth, maximum tolerated packet delay, and other additive QoS constraints as required by the real-time mobile traffic. This requires prediction of the handover time using mobility trends on the mobile station, which is used as input to this work. After the handover time and the QoS are negotiated, the destination base station makes attempts to give priority to handover calls over new calls, and pre-reserves resources that will have more chance of being available during the actual handover.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1067-1072
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• 2014

As the service continuity of mobile multimedia service is affected by packet loss and delay, the efficient handover control is essentially required. This paper proposes a handover admission control scheme to satisfy service continuity of mobile multimedia services in LTE-Advanced System. In this method, based on context information of mobile terminal and base station changes, the sequence diagrams between the function modules for controlling new sessions and ISHO sessions are proposed. Simulation is done for performance analysis with the measure of transmission delay and packet loss rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.377-386
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• 2008

In this paper, a new handover management scheme has been proposed to reduce handover latency and to support fast handover without packet losses, so that it may be applicable to the wireless mobile Internet system such as IPv6-based WiBro system. To minimize the handover latency in processing of movement detection, we propose the handover management scheme which simplifies the handover message exchanging procedure between mobile subscriber station (MSS) and network by integrating layer 2 and layer 3 handovers efficiently based on the layer2 information. To reduce the processing delay from new care-of-address (NCoA) configuration during handover, we propose that NCoA is created, distributed and managed by new access control router (NACR). In addition, in order to minimize the packet transmission delay and eliminate the packet losses, the proposed scheme employs a crossover router (CR) which is upper network located over PACR and NACR and employs the packet buffering for MSS. The simulation study shows that the proposed scheme achieves loss-free packet delivery and low latency in the environment of narrow overlapped cell area or high velocity of the MSS, comparing the performance with the conventional schemes.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.64-66
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• 2023

Low Earth Orbit(LEO) Non-Terrestrial-Network(NTN) 은 위성을 사용하여 통신 서비스를 제공하지 못하는 도시 이외의 산간, 바다, 항공기 또는 외진 지역에 통신 서비스를 제공하는 모델이다. Terrestrial Network(TN) 핸드오버에서 사용되는 Measurement-Based Triggering(MHT)의 경우 User Equipment(UE)에서 측정된 값을 기반으로 Measurement Report를 전달한다. 그러나 NTN 환경에서의 HO triggering은 TN 과는 달리 장거리 통신을 요구하고 위성이 빠른 속도로 이동함에 따라 MHT에 사용되는 지표들을 대체할 방법이 필요하다. 이 논문에서는 측정 유효성을 대체할 수 있는 지표로 UE와 셀 중심 간의 거리 및 고도 각을 활용하여 HO triggering을 예측하는 시스템을 제안한다. 제안한 예측 시스템은 핸드오버 triggering 예측에 대해 우수한 성능을 보였으며 좋은 측정 결과를 얻을 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.240-249
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• 2011

In this paper, we consider a cell management and handover method in an IEEES02.16e based femto-cell systems. In a femto-cell system, Mobile Stations (MS) and Base Stations (BS) are temporarily overloaded during the process of MOB_NBR-ADV message because it includes huge information of macro-cell and a large number of femto-cells. Also, MS can be handover into another cell frequently, i.e. ping-pong phenomenon, if it is located in a overlapped cell area. In a femtocell system, so-called ping-pong phenomenon will burden the network opreation. In this paper, we propose construction of MOB_NBR-ADV message and it provides fast scanning and efficent handover by means of preselecting the candidate target femto-cells. Also, an adaptive method of hysteresis margin for handover is proposed. The simulation results show that the proposed schemes improve the MS's handover-related performance in terms of scanning power and scanning time compared with the conventional managements scheme of femto-cell systems.