• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.35-48
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL and CRRM. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate and the system service cost.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.271-280
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate, the system service cost and handover attempt number.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.268-274
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• 2008

With the advances in wireless communication technologies, mobile users require to get seamless services anywhere and anytime. To relize these demands, network interworking and vertical handover are necessary between heterogeneous wireless access technologies with multi-interface mobile station. A lot of organizations are doing research on the network integration schemes based on loosely and tightly integrated architectures, and research on vertical handover schemes mainly based on Mobile IP in loosely integrated environments. But actually, the tightly integrated scheme can support more faster vertical handover because heterogeneous access networks are combined tightly. However, vertical handover schemes in tightly integrated environments are conceptually proposed without any detail signaling procedures. Therefore, this paper defines a tightly integrated architecture between UMTS and WLAN, and proposes a soft vertical handover signaling procedure. The proposed soft vertical handover scheme is evaluated by the OPNET simulator, and we confirm the proposed scheme can support seamless services.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.123-132
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• 2005

By complementary integration of WLAN and UMTS, a Beyond third Generation(B3G) mobile network can be constructed to establish the fastest global roaming environments, There are 2 types of B3G networks: loosely-coupled and tightly-coupled, A tightly-coupled network demands lots of investment and considerable amount of time to construct. On the other hand a loosely-coupled network is more scalable and easier to implement than a tightly-coupled one, But it has critical drawbacks of packet loss and blocking of services due to handover delay, To alleviate these drawbacks this thesis proposes a vertical handover procedure between WLAN and UMTS, which is based on MAP of HMIPv6, Performance of the proposal is evaluated in terms of blocking probabilities, The proposed procedure based on HMIPv6 shows better performance than those based on MIP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.492-501
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• 2007

UMTS-WLAN interworking approach can make the best use of the advantages of both networks by eliminating the stand-alone defects of the two services. For the interworking mechanisms of WLANs and UMTS networks, two major solutions have been proposed, namely loose coupling and tight coupling. The loose coupling approach provides separate data paths for WLAN and UMTS. On the other hand, the tight coupling provides a full integration of the WLAN network and the UMTS core network. The loose coupling has been preferred due to the simplicity and less reconfiguration requirement. However, loose coupling is worse in seamless mobility, QoS provision, and network security. In order to lessen the problems involved in the UMTS-WLAN interworking approaches, we propose a new interworking network architecture and a fast vertical handover scheme by employing Mobility Anchor(MA) for interworking between the two different networks. MA can enable authentication and session initialization before L2 handover of the mobile terminal, so that the seamless and fast vertical handover become possible. Thru analysis and numerical experiments, we proved that the proposed scheme has been validated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10B
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• pp.638-643
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• 2007

Interconnecting wireless local area networks (WLANs) with third generation (3G) cellular networks has become an issue of great interest. However, a Vertical Handover (VHO) causes an abrupt change in link bandwidth. Due to such a change, TCP triggers unnecessary fast retransmission during a Downward VHO (DVHO) from a cellular network to a WLAN, causing throughput degradation. Thus, we propose a new reordering mechanism for DVHO that suppresses unnecessary retransmission due to the spurious duplicate acknowledgments. We analytically investigate the throughput of TCP in the literature and our proposed scheme. Through the numerical and simulation results, it is shown that our proposed TCP achieves better performance in terms of throughput, compared with Nodupack with SACK.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.52-54
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• 2004

B3G(Beyond 3 Generation) 망의 구조는 글로벌 로ald환경 구축을 위해서 3세대망인 UMTS와 WLAN의 각각의 장단점을 보완하여 통합한 것이다. 현재 B3G 망의 구조는 크게 loosely-coupled와 장기적 접근을 요구하는 tightly -coupled 방식으로 나눌 수 있다. Loosely-coupled 방식은 tightly-coupled 방식에 비해 독립적 확장이 가능하고 비교적 구현이 쉬우나 핸드오버의 지연으로 인한 패킷 손실과 서비스 끊김 등의 단점이 있다. 본 논문에서는 이를 개선하기 위하여 HMIPv6의 MAP를 사용하여 UMTS와 WLAN의 인터네트워킹에 대한 수직적 핸드오버 프로시저를 제안한다. 각 단계별 총 지연시간을 통하여 블로킹 확률을 측정해 본 결과 제안된 HMIPv6를 사용한 방식이 기존의 MIPv6를 사용한 방식보다 성능이 우수함을 확인하였다.

• Journal of KIISE:Information Networking
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• v.34 no.4
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• pp.239-245
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• 2007

New multimedia services over the cellular/WLAN overlay networks require different Quality of Service (QoS). In the cellular/WLAN overlay structure, the main issue of load balancing is to balance the available bandwidth among different networks. In this paper, we propose a new online network management scheme. Our proposed scheme is designed to improve bandwidth utilization by balancing the traffic load between the cellular network and WLANs. Simulation results indicate the superior performance of our proposed framework to strike the appropriate performance balance between contradictory QoS requirements under widely varying diverse traffic loads.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4492-4497
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• 2013

An important features of next-generation wireless networks will be heterogeneous environment in which a mobile terminal will be able to connect to multiple radio access networks and network selection mechanisms play an important role in ensuring QoS for users in this environment. In this paper, our study is concerned with an extension of the well known AHP to the group decision making methods. The users requested specific QoS divide into a group and the access networks with similar characteristics split into a group. Between each group, the one group is selected and within that group, the best access networks will be assigned according to priority order by network selection algorithm. The experimental results of MATLAB simulation show that the every user in each services can select the same network with decision value as large as 0.9. Consequently, the proposed network selection mechanism is more effective than conventional one in integrated UMTS and WLAN networks.