• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.883-892
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• 2002

Mobile IP has been designed only to maintain communications as they move from place to place, so it doesn't guarantee Quality of Service (QoS). QoS in mobile IP is important to provide multimedia and real-time applications services in mobile environment, and it is closely related to handoff delay. Therefore, handoff delay problem is actively studied to guarantee QoS as a main issue in mobile IP research area. In this paper, we suggest SNMP Information-based routing that adds keyword management method to Information-based routing in active network in order to resolve such a problem, and then suggest QoS controlled handoff based on SNMP Information-based routing. After modeling of suggested method and existing handoff method, simulations are carried out with NS -2 for performance evaluation. The results of simulations show the some improvement on handoff delay, and therefore on QoS improvement.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.1069-1072
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• 2003

초고속 인터넷의 보급이 일반화되고, PDA 및 노트북 등의 휴대 이동 컴퓨팅 기기의 사용이 증가하면서, 점차 이동 인터넷 서비스를 요구하는 사용자의 수요가 증가하고 있다. 현재 무선 인터넷 제공을 위한 주요 인프라는 이동 통신망이나 무선랜 망이다. 그러나 무선랜 망 기술의 경우 2 계층에서 이동성을 지원하기 때문에 하부 기술에 대한 의존성으로 인하여 도메인 내에서의 이동서에 대해서만 지원하므로 다른 도메인영역으로의 이동을 지원하는데는 어려움이 있다. 그래서 본 연구에서는 이동 인터넷 사용자들에게 끊김 없는 서비스 제공 및 핸드오프 지연을 줄이기 위하여 IEEE 무선랜 기반 2 계층 핸드오프 기술과 3 계층에서의 이동성을 제공함으로써 하부기술에 독립적인 글로벌 로밍을 지원하는 Mobile IPv6 기술을 제안하고 또한 3 계층에서의 핸드오프 지연 감소 및 핸드오프시에 실시간 서비스 제공을 위한 Mobile IPv6 Fast 핸드오버에 대한 기술의 장, 단점을 연구분석하고 2 계층 및 3 계층 핸드오프 기술의 연동을 통하여 실시간 서비스를 위한 보다 향상된 핸드오프를 수행할 수 있는 방안을 제시한다.

• 한국IT서비스학회:학술대회논문집
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• 2003.05a
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• pp.550-559
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• 2003

mobile IP는 단순히 이동성을 지원하는 것만을 목표로 제안되었기 때문에, 새로운 네트워크로의 연결만을 보장할 뿐, 핸드오프 후의 QoS는 보장하지 못한다. mobile IT에서 QoS는 이동 환경에서 멀티미디어 서비스나 실시간 서비스 제공 시 매우 중요시 되는 문제로, 핸드오프에 의한 지연과 밀접히 연관되어있다. 이에 따라 이동 환경에서 QoS를 보장하기 위해, 핸드오프 지연 문제는 주요 이슈로서 활발히 연구되고 있다. 본 논문에서는 이러한 문제를 해결하기 위해, 선행 연구로 액티브 네트워크에서의 정보기반 라우팅에 키워드 관리 방법을 추가한 SNMP 정보 기반 라우팅을 제시하고, 이를 이용하여 핸드오프 지연을 최소화하는 QoS 향상 기법을 제시한다. 또한 라우팅 컨버전스 시간을 설정하여 기존 핸드오프 방법과 함께 제시한 기법에서 필요한 요소를 모델링한 후 NS-2를 사용하여 시뮬레이션 하였다. 시뮬레이션 결과는 제시한 기법이 핸드오프 지연을 최소화함으로써, 결과적으로 QoS가 향상되었음을 입증한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.909-917
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• 2004

Mobility support is one of the most important functions to provide seamless data transfer for real-time multimedia services in wireless networks. In this paper, we analyze and compare the handoff delay performances for several architectures such as MIP-RO, SIP, MIP-RO/CIP and SIP/CIP, which are expected to be a promising solution to support IP mobility management. For the analysis, we make the detailed message flows of those architectures in handoffs, and then make an analytical model to compute the handoff delay for each scheme. Numerical results showed that the SIP/CIP approach outperformed other schemes in the viewpoints of the handoff delay.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.77-80
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• 2003

IEEE 802.11 무선랜에서 보안 문제는 무선 구간의 암호화와 인증 문제를 들 수 있다. 본 연구에서는 무선랜에서 핸드오프 인증으로 인해 발생하는 지연을 줄이기 위한 방안으로 WEP 키를 저장한 수 있는 캐시를 AP에 적용하는 방안에 대하여 연구하였다. 본 연구 결과에 의해 핸드오프가 빈번하게 일어나는 무선 인터넷 환경에서 각 AP에 캐시를 사용하여 초기 인증시 생성된 WEP 키를 저장하여 재사용함으로써 핸드오프 처리 지연에 대한 개선 효과가 있음을 확인할 수 있었다. 이와 같은 결과를 최근 활성화 되고 있는 무선 인터넷에 활용하면 향 후 폭발적으로 늘어날 무선 단말기의 핸드오프시 지연에 효율적으로 대응할 수 있을 것이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2401-2409
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• 2015

This paper proposes the improved handoff mechanism for IEEE 802.11 wireless LANs. When a wireless mobile node moves out of the coverage of its currently associated AP(Access Point) and needs to be re-associated with a new AP, a handoff procedure is initiated. Channel scanning process during a handoff procedure occupies over 90% of total handoff latency. Long latency leads to many packet losses and service discontinuity, which degrades wireless network performance. This paper describes about the new mechanism to improve handoff performance by skipping channel scanning during a handoff procedure. In oerder for that, acquires neighboring AP information such as its address, location, channel number in use, the number of associated nodes before handoff, and delivers the information to its associated mobile nodes. The mobile nodes can reduce handoff latency and perform more exact handoff using the delivered AP information. We have conducted simulations to analyze our proposal's performance and confirmed that handoff latency and the number of handoff occurrences are decreased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.1-6
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• 2011

We have considered fast handoff algorithms to support seamless streaming in wireless LANs. It is impossible to provide seamless streaming service while moving within wireless LANs, In this paper, we proposed a new handoff algorithm where the critical value for handoff can be adjusted according to peripheral wireless circumstances. This algorithm can prevent an unnecessary scanning job and save handoff delay time through the active scanning procedure to the specific channel groups. Also, we evaluated the handoff performance of our proposed algorithm, and compared it with the performance of the existing wireless LAN. We can see that the performance with our proposal is better than that of the general wireless LAN.

• Journal of the Korea Society of Computer and Information
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• v.19 no.2
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• pp.67-75
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• 2014

In this paper, we proposed offloading delay method which determines effectively offloading timing by measuring of handoff delay and offloading time at mobile node side in mobile environment. The propose method measures each of handoff delay and offloading time and making decision of proper offloading timing on mobile node side. Therefore, it is possible to support cloud computing without changing previous implemented cloud computing structure for fixed node in a mobile environment. We compare the energy consumption of server and node to analyze efficiency of proposed method by using existing method of energy consumption measurement. Simulation results shows the reducing energy consumption more than previous method and operation time similar to previous method.

• Journal of KIISE:Information Networking
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• v.31 no.2
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• pp.131-145
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• 2004

Mobile IP has been designed only to maintain communications as mobile devices move from a place to a place, so it does not guarantee Quality of Service (QoS). Hierarchical MIPv6 improved QoS somewhat using Mobility Anchor Point(MAP), but QoS guarantee problem still remains. QoS in mobile IP is important to provide multimedia and real-timeapplications services in a mobile environment, and QoS is closely related to handoff delay. Therefore, handoff delay problem is actively studied as a main issue in mobile IP research area to guarantee QoS. In this paper, we suggest SNMP Information-based routing that adds keyword management method to Information-based routing in an active network in order to resolve such a problem, Suggested QoS controlled method and existing handoff method, simulations are carried out with NS-2 for performance evaluation. The results of simulations show an improvement on handoff delay, and consequently the QoS improvement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.4
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• pp.329-333
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• 2003

In this paper we analyze the performance of the low latency pre-registration handoff method of mobile IP by computer simulation. Packet losses and delays are evaluated in terms of system utilization. Foreign agents that participate in the handoff process can be modeled as queues representing input and output ports. Therefore, we propose an analytical model of pre-registration handoff by using open queueing network model. Simulation results are shown for validating analytical estimates.