Dong-Hee Kwon

An efficient multicast routing protocol in wireless mobile networks

Providing multicast service to mobile hosts in wireless mobile networking environments is difficult due to frequent changes of mobile host location and group membership. If a conventional multicast routing protocol is used in wireless mobile networks, several problems may be experienced since existing multicast routing protocols assume static hosts when they construct the multicast delivery tree. To overcome the problems, several multicast routing protocols for mobile hosts have been proposed. Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, overheads resulting from frequent reconstruction of a multicast tree, etc. In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks. The proposed protocol introduces a multicast agent, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent may start multicast join process, which makes the multicast delivery route optimal. The proposed protocol reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams. We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals.

Access router information protocol with FMIPv6 for efficient handovers and their implementations

Mobile IPv6, which is a protocol being standardized by IETF for global IP mobility support, is expected to play a key role for future all-IP wireless networks. As the demands for delay sensitive real-time applications increase, the handover latency of mobile IPv6 becomes inadequate for these applications. There have been many proposals, such as fast handovers for mobile IPv6 (FMIPv6), to tackle this problem. However, FMIPv6 only concentrates on the protocol operation while it does not address other issues, such as radio access discovery and candidate access router discovery, that are critical to the handover performance of FMIPv6. Therefore, in this paper, we propose ARIP (access router information protocol), which performs a candidate access router discovery and a radio access network discovery in one protocol suite, to provide an efficient handover framework for MIPv6 and FMIPv6. ARIP is designed to cope with heterogeneous networks as well as homogeneous networks and to be closely coupled with FMIPv6 to provide an efficient handover operation. The performance evaluation of MIPv6, FMIPv6, and FMIPv6 with ARIP is performed in an actual network environment and the performance results show that FMIPv6 with ARIP gives the best performance in terms of handover latency

Performance comparison of mobile IPv6 and fast handovers for mobile IPv6 over wireless LANs

The increase of mobile devices is addressing a mobility support to facilitate handovers of mobile devices. Mobile IPv6 (MIPv6) has been proposed by IETF to solve this problem in the Internet. But, in MIPv6, there is a time interval that a mobile node (MN) cannot send or receive any packets during the handovers. The time interval is long enough for packets to be lost so that it is intolerable to be used for real-time traffics. Therefore, it is necessary to find out the method to reduce a handover latency. For this reason, Fast Handovers for Mobile IPv6 (FMIPv6) protocol has been proposed to reduce the MIPv6 handover latency. In FMIPv6, there are two operation modes due to the unpredictability of MNs mobility; the predictive mode and the reactive mode. In this paper, we discuss two modes of FMIPv6 and compare their performance with MIPv6 in a real test-bed network. The performance result shows that FMIPv6 has better handover performance than MIPv6 does. But, it also shows that FMIPv6 still suffers from the handover disruption time due to the IEEE 802.11 MAC layer handover. I. INTRODUCTION

Multicast routing protocol by multicast agent in mobile networks

Providing multicast service to mobile hosts is difficult due to frequent changes of mobile host location and group membership. To overcome the difficulty, several multicast protocols for mobile hosts have been proposed. Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, etc. In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast protocol using a multicast agent in wireless mobile networks, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent starts multicast join process, which makes the multicast delivery route optimal. The proposed protocol reduces data delivery path length and decreases not only the amount of duplicate copies of multicast datagrams but also multicast traffic load. We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals.

An Integrated Handover Scheme for Fast Mobile IPv6 Over IEEE 802.16e Systems

The IEEE 802.16e system supporting mobility on fixed wireless-MAN systems is supposed to be a mobile broadband wireless access (BWA) and evolve into 4G mobile communication systems. Although the system already defines its own mobility management algorithm, a network layer handover algorithm should be defined to support the mobility of mobile stations in the Internet. There are many active researches on how to apply the L3 handover protocol over the existing IEEE 802.16e L2 handover scheme, but most of the previous works have focused on the timing of L3 handover messages over the IEEE 802.16e L2 handover messages. In this paper, we propose a new handover scheme for fast mobile IPv6 over the IEEE 802.16e system. By integrating FMIPv6 with IEEE 802.16e system efficiently, the proposed scheme can minimize not only L3 handover latency but also packet losses.

Seamless handover support over heterogeneous networks using FMIPv6 with definitive L2 triggers

Various wireless communication systems have been developed and will be integrated into an IP-based network to offer end users the Internet access anytime and anywhere. In heterogeneous multi-access networks, one of main issues is to manage nodes’ mobility with session continuity and minimal handover latency. In order to support the mobility of mobile nodes, MIPv6 has been proposed by IETF. Even though MIPv6 provides a solution to handling nodes’ mobility in IPv6 networks, there is a significant problem due to its inability to support a seamless handover caused by long latency and high packet losses during a handover. FMIPv6 has been proposed to reduce MIPv6 handover latency by using an address pre- configuration method with the aid of L2 triggers. Current research defines a general L2 trigger model for seamless handover operation, but it does not address the exact timing and definitive criteria of L2 triggers which causes a significant effect on the handover performance of FMIPv6. This paper considers the available timing and accurate criteria of L2 triggers. With the definitive L2 triggers, we present a practical handover scenario to integrate L2 and L3 layers for low handover latency and low number of packet losses during a handover. We also study the impact of definitive L2 triggers on the handover performance of the FMIPv6 protocol in real testbeds and prove that the FMIPv6 protocol performs its handover operation prior to the L2 handover and obtains a seamless handover.

Design and Implementation of an Efficient Multicast Support Scheme for FMIPv6

There have been many research efforts to solve the problem of providing IP multicast to mobile nodes (MNs). However, most of the existing mobile multicast routing protocols primarily have focused on constructing an efficient multicast tree for MNs while the issues of minimizing packet loss and multicast service disruption period during handovers are relatively given little concerns or even neglected. Although the protocols such as MMA and TBMoM address these issues, no performance measurement or analysis is provided. Meanwhile, Fast handovers for Mobile IPv6 (FMIPv6) is proposed to reduce the long handover latency of Mobile IPv6. However, FMIPv6 primarily focuses on reducing the handover latency by pre-configuring an address that will be used by a MN, while the issues related to multicast packet delivery are left unaddressed. In this paper we discuss the possible multicast subscription approaches in FMIPv6 to reduce the multicast service disruption period and packet loss during handovers. Then, we propose an efficient multicast support scheme for FMIPv6, which is derived from the consideration of the advantages and drawbacks of the discussed multicast subscription approaches in FMIPv6. Two versions of the proposed scheme, both of which operate in the context of FMIPv6 handovers, are introduced. The first version is designed to minimize the required modification to the existing FMIPv6 stack, while the second version is designed to eliminate inefficiencies that exist in the first version allowing some modifications to the existing protocol stacks. To evaluate the performance of the proposed scheme, we have implemented the proposed scheme on real systems and conducted an extensive set of experiments in a multicast enabled experimental network. The performance of the proposed scheme in terms of scalability is also examined by simulation study.

Multicast routing by mobility prediction for mobile hosts

In this paper, we propose an efficient multicast routing protocol based on mobile IP standard in wireless mobile networks. A mobile host that is located in a foreign network receives a tunneled multicast datagram from a multicast agent, which is located in a remote network or local network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent starts a multicast tree join operation if the mobile host is expected to remain the network relatively long period of time, while it does not start multicast tree join operation if the mobile host is expected to remain the network relatively short period of time. The proposed protocol tries to maximize the number of unnecessary multicast tree join operations. We examined performance of the proposed protocol by simulation under various environments and we got good performance results.

An efficient mobile multicast mechanism for fast handovers: A study from design and implementation in experimental networks

There have been many research efforts to solve the problem of providing IP multicast to mobile nodes (MNs). However, the issue of minimizing the packet losses and the multicast service disruption period during handovers are relatively given little concerns or even neglected. In this paper, we discuss the possible multicast subscription approaches in FMIPv6 to reduce the packet losses during handovers. Then, we propose an efficient multicast support mechanism for FMIPv6, which is derived from the consideration of the advantages and drawbacks of the discussed multicast subscription approaches. Two versions of the proposed protocol, both of which operate in the context of FMIPv6 handovers, are introduced. The first version is designed to minimize the required modification to the existing FMIPv6 stack, while the second version is designed to eliminate inefficiencies that exist in the first version allowing some modifications to the existing protocol stacks. To evaluate the performance of the proposed protocol, we have implemented the proposed protocol in real systems and conducted an extensive set of experiments in a multicast enabled experimental network. The performance of the proposed protocol in terms of scalability is also examined by simulation study. The experiment and simulation results show that the proposed protocol achieves good performance in terms of the number of packet losses, multicast service disruption period, traffic incurred by multicast packet delivery, and delivery path length.

A client-based vertical handoff approach for seamless mobility in next generation wireless networks

With the rapid growth of mobile Internet, offering seamless connectivity and high-speed multimedia services in different types of wireless networks are important features in next generation wireless networks (4G networks). Many researchers envision that the 4G networks will consist of many radio access technologies which integrate into all IP-based networks while providing seamless handoffs across the heterogeneous wireless networks. Mobile IP is a prominent solution to handle mobile nodespsila movement in IP-based networks. However, Mobile IP suffers from long handoff latency since it is designed to support the macromobility of a mobile node. Therefore, it is necessary to devise a scheme that offers seamless connectivity during Mobile IP handoffs across the heterogeneous wireless networks. In this paper, we propose a client-based handoff management system for multi-networks to provide end-users with seamless connectivity across heterogeneous wireless networks. Our proposed system is designed as a common network interface at a client side and provides transparent services to IP/MIP layers regardless of used wireless technologies. With this system, we also present vertical handoff performance over a loosely coupled cdma2000/WLAN experimental test-bed. The experimental results show that our system enables a mobile node to handoff seamlessly across different types of wireless networks without any modifications to the existing IP/MIP stack and core network.