Eun Kyoung Paik

An Adaptive Network Mobility Support Protocol in Hierarchical Mobile IPv6 Networks

The network mobility (NEMO) basic support protocol provides collective mobility for a group of nodes in vehicular area networks. Since the NEMO basic support protocol always performs the same operations, regardless of a mobile networks characteristics, it cannot achieve optimal performance. We propose an adaptive NEMO support protocol based on hierarchical mobile IPv6. The proposed protocol jointly optimizes binding update (BU) traffic and tunneling overhead by employing the adaptive BU strategy, depending on the session-to-mobility ratio (SMR). Specifically, both the mobile router (MR) and the visiting mobile nodes (VMNs) configure two care-of-addresses: 1) on-link care-of-address (LCoA) and 2) regional care-of-address (RCoA). If the SMR is lower than a predefined threshold, the MR and VMNs perform RCoA and LCoA BU procedures to their home agents (HAs), respectively. Otherwise, LCoA and RCoA BU procedures are conducted by the MR and VMNs, respectively. Via analytical models, we evaluate the performance of the adaptive NEMO support protocol against other NEMO support protocols and derive the optimal SMR threshold. Numerical results demonstrate that the adaptive NEMO support protocol is a valuable solution for promising NEMO applications.

Load sharing and session preservation with multiple mobile routers for large scale network mobility

By means of network mobility (NEMO) support, users can organize their various communication devices into a network, called a mobile network. In a mobile network, the mobile router provides the connectivity to the Internet and mobility management transparency for the rest of the mobile nodes in the mobile network. So, it is important for the mobile router to assure reliable communications and a high data rate for the group of nodes behind it. In support of broadband wireless communications, the use of multiple mobile routers would allow the transfer of large volumes of data to a group of mobile nodes. This paper addresses the protocol issues arising from the use of multiple mobile routers, and analyzes the influence of mobility on load sharing and session preservation when there are multiple mobile routers. Simulation results with different configurations show that session preservation and load sharing schemes are influenced by application mobility behavior and wireless access technologies.

Prediction-based fast handoff for mobile WLANs

As the demand for pervasive mobile wireless Internet grows, wireless local area network (WLAN) is receiving a lot of attention because of its high data rate and low cost. However, WLAN uses a small cell size, which leads to cell discontinuity and frequent handoff, rendering fast mobility problematic. This paper proposes the prediction-based fast handoff scheme that supports broadband wireless access in fast moving vehicles. The scheme uses network mobility and the mobility characteristics of public vehicles to predict handoff. Thus, the WLAN itself moves as a moving unit using a handoff prediction and decision scheme. The proposed prediction-based scheme supports seamless handoff across continuous cells, and reduces packet loss across discontinuous cells. The scheme is applicable to mobile users who send and receive large volumes of wireless data on fast moving public vehicles, such as trains, buses and aircraft.

RBU+: Recursive Binding Update for end-to-end route optimization in nested mobile networks

In this paper, we propose an end-to-end route optimization scheme for nested mobile networks, which we refer to as Recursive Binding Update plus (RBU+). A nested mobile network is a hierarchical form of mobile networks. Nested mobile networks suffer from a pinball routing problem with hierarchical mobile routers. This problem becomes more serious in the case of macro mobility, as the routing distance becomes longer. To solve the pinball routing problem of nested mobile networks, in this paper we propose the Recursive Binding Update (RBU) and three distinct solutions for the end-to-end routing in mobile networks using the method of obtaining the route from the Top Level Mobile Router (TLMR) to the destination Mobile Network Node (MNN). The solutions for end-to-end routing include source routing, Table Driven Forwarding (TDF), and Route Request Broadcast (RRB). From the results of the simulations, it was shown that RBU+RRB presents the best performances among the different solutions. When combined with an end-to-end routing capability, RBU+ provides optimal routing in nested mobile networks. RBU+ reduces the pinball routing cost, and this reduction becomes more significant as the degree of nesting becomes higher and the distance between the home agents of the mobile router and its parent/child mobile routers becomes longer. When combined with an appropriate reverse route optimization scheme, the routing costs are independent of the degree of nesting and the distance between the Home Agents (HAs).

Seamless mobility support for mobile networks on vehicles across heterogeneous wireless access networks

This paper proposes an architecture designed for mobile networks, i.e. a network that moves as a single unit. The proposed architecture organizes routers and hosts located inside a vehicle into a mobile network. It enables passengers to access the Internet while the vehicle moves. To support IPv6 addressing, mobility management and consistent Internet connectivity, it comprises mobile DHCPv6 agents, a handoff management center (HMC) and multiple mobile routers. The mobile DHCPv6 agent moves with the mobile network and allocates IPv6 addresses to the nodes within the mobile network, thus enabling packets to be correctly routed to their destinations. The HMC implements location management and forward loss recovery (FLR) based on mobility anticipation. Multiple mobile routers access heterogeneous wireless access networks so as to maintain Internet connectivity, even though one single wireless access network does not cover all of the areas through which the mobile network navigates. With the proposed architecture, passengers and fixed devices inside vehicles can access the Internet with seamless mobility across heterogeneous networks.

R-BU: recursive binding update for route optimization in nested mobile networks

This paper proposes recursive binding update (R-BU) that optimizes routing for nested mobile networks. Nested mobile network is a hierarchical form of mobile networks, e.g. a wireless personal area network (PAN) in a vehicular network. A mobile network moves as a single unit with one or more mobile routers that connect it to the global Internet. Nested mobile networks have pinball routing problem with hierarchical mobile routers. This problem becomes more serious in the case of macro mobility as the routing distance becomes longer. To solve the pinball routing problem of nested mobile networks, we propose routing optimization scheme called R-BU based on recursive binding update. R-BU maintains optimal route to the destination by updating its binding recursively. R-BU requires no changes in existing mobile IP except binding update operation. By using R-BU, correspondent nodes can maintain optimal route to their destinations after some convergent time. R-BU reduces pinball routing cost and the reduction is more useful as the degree of nesting becomes deeper and the distance between the home agents of a mobile router and its parent/child mobile routers becomes longer.

Load sharing and session preservation with multiple mobile routers for large scale mobile networks

By means of NEtwork MObility (NEMO) support, users can organise their various communication devices into a subnet called mobile network. The Mobile Router (MR) provides the connectivity to the internet and mobility management transparency for the rest of the mobile nodes in the mobile network. So, the MR must assure reliable communications and a high data rate for the group of nodes behind it. In support of broadband wireless communications, the use of multiple MRs would allow the transfer of large volumes of data to a group of mobile nodes. This paper addresses the protocol issues arising from the use of multiple MRs, and analyses the influence of mobility patterns on load sharing and session preservation. Then, two mobility-aware selection schemes are proposed, which select a MR. Firstly, the best-connected MR selection scheme is designed for regular mobility and is based on the fact that the most recently updated binding remains effective for the longest period of time. It preserves the connection from the mobile network to the internet whether the accessible area is continuous or not, and this even in a fast handoff environment. Secondly, the most-beneficial MR selection scheme is designed for random mobility. The simulation results show that the performance varies depending on the hardware configuration. Based on these results, it was found that application-awareness is critical to achieve good performance.

Mobility-Aware Mobile Router Selection and Address Management for IPv6 Network Mobility

Network mobility (NEMO) extends IP mobility to moving networks, which are groups of nodes that often constitute a subnet of a mobile router (MR). To realize this collective mobility, there are a number of important issues such as addressing and multihoming. With the proliferation of mobile nodes connected to the Internet, the efficient allocation/deallocation of addresses is becoming a vital requirement. We propose a collaborative address management scheme for network mobility, where the home DHCPv6 agent of a mobile network performs prefix delegation, while the mobile DHCPv6 agent (in the mobile network) allocates the IPv6 address to each mobile node. Also, network mobility with multiple MRs is taken into consideration. To provide a mobile network that has multiple MRs with robust Internet connectivity, we propose mobility-aware mobile router selection schemes. The concept of “mobility awareness” refers to the capability of a moving network in a vehicle (e.g., a train) to pinpoint the most stable Internet connectivity, by choosing the mobile router based on the vehicle’s movement pattern. The simulation shows that the proposed scheme outperforms a round-robin mobile router selection scheme in terms of the amount of carried traffic.

Service Differentiation Using Mobile Femtocell Virtualization

This paper proposes a service differentiation architecture using virtualization of mobile femtocell. Network-prefix division multiple access (NDMA) is proposed to enable mobile devices inside a moving space to access the Internet with different service demands. With the NDMA scheme, our architecture provides multiple virtual mobile networks for diverse services which are optimized under different network conditions. We experimented on the operation of the proposed architecture with testbed implementation. The result shows the ability of multiple degrees of QoS over each virtual mobile network with additional benefits of personalization, mobility management aggregation, and so on.

Design of SIP transformation server for efficient media negotiation

Voice over IP (VoIP) is one of the advanced services supported by the next generation mobile communication. VoIP should support various media formats and terminals existing together. This heterogeneous environment may prevent diverse users from establishing VoIP sessions among them. To solve the problem an efficient media negotiation mechanism is required. In this paper, we propose the efficient media negotiation architecture using the transformation server and the Intelligent Location Server (ILS). The transformation server is an extended Session Initiation Protocol (SIP) proxy server. It can modify an unacceptable session INVITE message into an acceptable one using the ILS. The ILS is a directory server based on the Lightweight Directory Access Protocol (LDAP) that keeps user¡*s location information and available media information. The proposed architecture can eliminate an unnecessary response and re-INVITE messages of the standard SIP architecture. It takes only 1.5 round trip times to negotiate two different media types while the standard media negotiation mechanism takes 2.5 round trip times. The extra processing time in message handling is negligible in comparison to the reduced round trip time. The experimental results show that the session setup time in the proposed architecture is less than the setup time in the standard SIP. These results verify that the proposed media negotiation mechanism is more efficient in solving diversity problems.