• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.27-30
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• 2004

본 논문에서는 무선 랜 환경에서 단말을 사용하는 사용자의 이동으로 인한 서비스영역의 변화에도 끊김 없는 서비스를 제공하기 위한 방식을 제안한다 제안방식은 이동하는 단말이 사용 가능한 채널탐색과정 중 MAC주소를 참조하여 단말의 이동을 알려주는 방식을 사용한다. 기존방식과 제안방식에 대해서 시뮬레이션을 통한 성능분석을 수행하였다. 단말의 이동을 채널탐색과정에서 인식함으로 단말에게 전송되어야 하는 데이터를 버퍼링 한 후 재결합과정이 발생하면 즉시, 전송하는 방식으로 구성되므로 핸드오프 기간 동안에 Throughput 감소가 적게 이루어짐을 확인하였다.

• 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.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.472-474
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• 2005

현재 높은 대역폭과 고속의 이동성을 가진 WiBro의 출현으로 기존에 존재하던 CDMA 및 WLAN와 같은 이기종망간의 연동 및 통합이 부각되었다. 서비스 커버리지가 넓은 CDMA나 초고속의 데이터 서비스를 제공하는 WLAN등과의 효율적인 연동을 통해 WiBro의 효용은 더욱 커질 수 있으며, 망 재사용측면이나 사용자의 편의면에서 매우 큰 성과를 얻을 수 있다. 이에 본 논문은 이기종망간의 효율적인 연동을 위한 방안을 제시하고 그에 따라 단말의 이기종망간 이동시 발생할 수 있는 핸드오프 문제를 해결하기 위해 이기종망간 고속 핸드오프 방안을 제시한다.

• Journal of Internet Computing and Services
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• v.5 no.3
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• pp.25-33
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• 2004

Mobile IP Low Latency Handoffs(l) allow greater support for real-time services on a Mobile IP network by minimizing the period of time when a mobile node is unable to send or receive IP packets due to the delay in the Mobile IP Registration process. However, on Mobile IP network with AAA servers that are capable of performing Authentication, Authorization, and Accounting(AAA) services, every Registration has to be traversed to the home network to achieve new session keys, that are distributed by home AAA server, for a new Mobile IP session. This communication delay is the time taken to re-authentication the mobile node and to traverse between foreign and home network even if the mobile node has been previously authorized to old foreign agent. In order to reduce these extra time overheads, we present a method that performs Low Latency Handoffs without requiring further involvement by home AAA server. The method re-uses the previously assigned session keys. To provide confidentiality and integrity of session keys in the phase of key exchange between agents, it uses a key sharing method by gateway foreign agent that performs a trusted thirty party. The proposed method allows the mobile node to perform Low Latency Handoffs with fast as well as secure operation.

• Journal of Internet Computing and Services
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• v.5 no.1
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• pp.25-32
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• 2004

Mobile computing environment makes it possible for computing activities to be maintained during movement even if a user changes its network point of attachment. Mobile IP is a standard protocol designed to be used in such mobile computing environment. However, Mobile IP has a drawback to incur a lot of handoff delays and waste network resources, since CoA(Care of Address) registration packets need to go through a HA(Home Agent) first whenever a mobile node moves. To solve this long-standing problem, this paper proposes a new scheme that, for infra-domain movement, efficiently performs local handoff without notifying the HA Specifically, based on the notion of load balance, the proposed scheme allows every FA(Foreign Agent) in a domain to become the root FA(also known as domain FA) dynamically, thus distributing the registration task into many other foreign agents. The dynamic root assignment through load balancing ultimately leads to fast network response due to less frequent transmission of registration packets.

• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.419-428
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• 2005

This paper divides domains into the intra, inter domain according to the mobile node's movement and .proposes the Fast RSVP algorithm on the HMIPv6. It is done to advance reservation using L2 beacon signal when MN is located to overlapped cell area. In case of intra-region handoff, the advance reservation is reserved at the nearest common router and In case of inter-region handoff, it is done to advance reservation through the other site MAP's QA(QoS Agent) to the AR and optimize CN's path. Because of using the bandwidth efficiently and switching the data path quickly, the proposal algorithm minimizes the service disruption by data routing.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.984-998
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• 1999

최근 개인 휴대 통신에 대한 관심도가 증가하면서 B-ISDN (Broadband Integrated Services Digital Network)과 같은 기존의 유선 망에서 제공하던 다양한 멀티미디어 응용 지원을 무선 망으로 확장시키기 위한 연구가 활발히 진행되고 있다. 그러나 기존의 유선 망에서는 멀티미디어 응용 지원을 위해 QoS (Quality of Service) Provisioning에 관한 많은 연구가 되어 있으나 무선 망에서는 이동성과 무선 전파의 열악한 전송으로 인해 새로운 QoS Provisioning 방법에 관한 연구가 필수적이다. 본 논문에서는 이러한 무선 망의 특수성으로 인해 발생할 수 있는 서비스의 질 저하와 강제 종료를 줄임으로써 지속적인 QoS를 보장해 주고 한정된 무선 자원을 효율적으로 사용하며 처리에 의한 오버헤드를 줄이기 위하여 다음과 같은 세 가지 방법을 제안하였다. 첫째, 핸드오프 강제 종료율을 줄이기 위하여 대역폭 예약 방법을 사용하되 특정 셀의 트래픽 특성에 맞게 또한 시간대에 따른 트래픽 특성에 따라 예약 대역폭의 양을 조절하는 적응적 대역폭 예약 방법이다. 둘째, 많은 경우 각 셀의 트랙픽 변화는 일정한 주기로 변화한다는 특성에 따라 과거의 트래픽 정보를 이용하는 예측 기반의 대역폭 예약 방법이다. 마지막으로 호의 종류, 트래픽 특성, 단말기의 이동 속도에 따라 다른 우선 순위에 의해 호 수락 제어를 수행하는 우선 순위 기반의 호 수락 제어를 제안하였다. 시뮬레이션을 통하여 기존에 제안된 방법과 성능 비교하여, 요구되는 수준의 QoS 보장과 효율적인 자원의 사용, 요구되는 처리비용의 최소화를 통해 전체 시스템의 성능 향상을 입증하였다.Abstract As interest in wireless hand-held terminals and in personal communications services increases recently, there have been broad studies on the ways to support multimedia applications provided in wired networks such as B-ISDN (Broadband Integrated Services Digital Network) in wireless networks. However, since many studies have focused on Quality of Service (QoS) Provisioning in wired networks to provide multimedia applications, new methods of QoS Provisioning are needed in wireless networks to resolve the problem of wireless channel fading and the difficulty of mobility occurred in wireless networks. This paper proposes three schemes of QoS Provisioning in wireless networks which will make continuous QoS guarantee and efficient use of limited wireless resources possible. The first scheme reserves bandwidth in proportion to the amount of real-time traffic in the neighbor cells to decrease the handoff dropping rate of delay sensitive real-time connections, adapting reserved bandwidth for efficient resource utilization. The second scheme is predictive bandwidth reservation scheme that utilizes the past handoff information. It can decrease overheads required to adapt bandwidth reservation. The last scheme is priority-based call admission control prioritizing traffic type (real-time traffic/ non-real-time traffic), connection type (new connection /handoff connection), and mobile terminal speed (fast mobile/slow mobile). Simulation results show that the proposed QoS Provisioning schemes improve the total system performance by achieving three goals - required QoS guarantee, higher bandwidth utilization and less overhead.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.5
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• pp.959-975
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• 2011

Wireless mesh networks enlarge the wireless coverage area by interconnecting relatively stationary wireless routers (mesh routers). As wireless mesh networks are envisioned to provide high-bandwidth broadband Internet service to a large community of users, the Internet gateway, which acts as a central point of Internet attachment for the mesh networks, is likely to suffer heavily from the scramble for shared wireless resources because of aggregated traffic toward the Internet. It causes performance decrement on end-to-end transmissions. We propose a scheme to balance the load in a mesh network based on link quality variation to different Internet gateways. Moreover, under the mesh coverage, mobile nodes can move around and connect to nearby mesh routers while still keeping the connections to the Internet through the best gateway in terms of link quality. In this structure, gateways perform the balancing procedure through wired links. Information about gateways and mobile node's location is distributed appropriately so that every mesh router can quickly recognize the best gateway as well as the positions of mobile nodes. This distributed information assists mobile nodes to perform fast handoff. Significant benefits are shown by the performance analysis.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.1
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• pp.35-46
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• 2012

The development of wireless communication systems has resulted in the availability of several access technologies at any geographic area, such as 3G networks, wireless local area networks (WLANs) and wireless broadband networks. The development of these technologies is provided for users who have experienced mobile network environments which are slow or fast-movement environment and change distance between the AP(Access Point). This paper describes network performance issues in various environmental changes. Also, Fuzzy logic is applied to evaluate the performance in vehicle networks around users' environmental factors to focusing on the minimizing of transfer time and costs. First, WLAN and 3G networks fixed distance between AP, Second, WLAN and 3G networks random distance between APs, finally above two environmental with vehicle Ad hoc networks is analyzed. These V2I and V2V environmental condition are assumed. Results which based on Fuzzy logic suggest an optimal performance in vehicle network environments according to vehicle speed and distance between APs. Proposed algorithm shows 21% and 13% improvement of networks performance in V2I and V2V environment.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.305-312
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• 2007

In this paper, we present a received signal strength (RSS) prediction model to timely Initiate link layer triggers for fast handoff in a wireless LAN system. Noting that the distance between a mobile terminal and an access point is not changed abruptly in a short time interval, an adaptive RSS predictor based on a stationary time series model is proposed. RSS data obtained from ns-2 simulations are used to identity the time series model and verify the predictability of the RSS data. The results suggest that an autoregressive process of order 1 (AR(1)) can be used to represent the measured RSSs in a short time interval and predict at least 1-step ahead RSS with a high confidence level.