You-Ze Cho

Load balanced routing protocols for ad hoc mobile wireless networks

Mobile ad hoc networks are collections of mobile nodes that can dynamically form temporary networks without the need for pre-existing network infrastructure or centralized administration. These nodes can be arbitrarily located and can move freely at any given time. Hence, the network topology can change rapidly and unpredictably. Because wireless link capacities are usually limited, congestion is possible in MANETs. Hence, balancing the load in a MANET is important since nodes with high loads will deplete their batteries quickly, thereby increasing the probability of disconnecting or partitioning the network. This article discusses the various load metrics and summarizes the principles behind several existing load balanced ad hoc routing protocols. Finally, a qualitative comparison of the various load metrics and load balanced routing protocols is presented.

Reduction of Handover Latency Using MIH Services in MIPv6

In this paper, we propose an enhanced handover mechanism with new additional primitives and parameters to the media independent handover (MIH) services defined in the IEEE 802.21. The proposed scheme can reduce handover latency for mobile IPv6 (MIPv6) by removing the router discovery time. Moreover, when the proposed mechanism is applied to the FMIPv6, we can increase the probability that the FMIPv6 can be performed in predictive mode by reducing the handover initiation time, thereby we can reduce the expected handover latency in the FMIPv6. In addition, with the proposed scheme, we can design the network cost-effectively by reducing coverage overlap between adjacent cells because the handover initiation time in the FMIPv6 is decreased

Performance Evaluation of AODV and DYMO Routing Protocols in MANET

Routing protocols for mobile ad hoc networks (MANETs) have been explored extensively in recent years. Among these routing protocols, Ad Hoc On-demand Distance Vector (AODV) and Dynamic Manet On-demand (DYMO) routing protocols have been standardized by the IETF MANET WG and are the most popular reactive routing protocols for MANETs. Therefore, in this paper, we present the results of the comparison of two reactive routing protocols, namely AODV and DYMO, based on packet-level simulations using an ns-2 simulator. Simulations are run to estimate the total throughput, routing overhead, and average packet size of the routing control packets.

An efficient rate-based algorithm for point-to-multipoint ABR service

A new efficient consolidation algorithm at a branch-point switch for point-to-multipoint available bit rate (ABR) service is proposed. In the scheme, among the received backward resource management (RM) cells with the same sequence number, each branch point passes only one of them, so that the source gets exactly one backward RM cell corresponding to every forward RM cell it generates. Simulation results show that the proposed scheme can achieve a faster response to congestion status and a lower consolidation noise compared with the existing algorithms, particularly in network environments with a large number of branch points on a path.

Performance of optical burst switching techniques in multi-hop networks

We investigate the performance of reservation mechanisms for optical burst switching (OBS) in multiple hop network environments. We first review current research on wavelength reservation schemes for OBS, and investigate the path length priority effect of existing just-enough-time (JET) scheme. Then, we propose a novel hop-by-hop priority increasing (HPI) scheme. The simulation results showed that the proposed scheme could avoid the path length priority effect and enhance the end-to-end throughput in multiple hop network environments.

Seamless Handover Scheme for Proxy Mobile IPv6

In a network-based approach such as proxy mobile IPv6 (PMIPv6), the serving network controls mobility management on behalf of the mobile node (MN). Thus, the MN is not required to participate in any mobility-related signaling. PMIPv6 is being standardized in the IETF NetLMM WG. However, the PMIPv6 still suffers from a lengthy handover latency and packet loss during a handover. In this paper, we propose a seamless handover scheme for PMIPv6. The proposed handover scheme uses the Neighbor Discovery message of IPv6 to reduce the handover latency and packet buffering at the Mobile Access Gateway (MAG) to avoid the on-the-fly packet loss during a handover. In addition, it uses an additional packet buffering at the Local Mobility Anchor (LMA) to solve the packet ordering problem. Simulation results demonstrate that the proposed scheme could avoid the on-the-fly packet loss and ensure the packet sequence.

An efficient on-demand routing approach with directional flooding for wireless mesh networks

Current on-demand ad-hoc routing protocols are not appropriate for wireless mesh networks (WMNs), because flooding-based route discovery is both redundant and expensive in terms of control message overhead. In this paper, we propose an efficient on-demand routing approach with directional flooding (DF), which is suitable for the WMNs with limited mobility. In the route discovery process to reach a gateway, our DF scheme can reduce the number of route request (RREQ) packets broadcast by using a restricted directional flooding technique. Simulation results show that ad hoc on-demand distance vector (AODV) with DF (AODV-DF) can significantly reduce routing overhead by RREQ packets and enhance overall performance compared with the original AODV.

Performance of burst-level bandwidth reservation in ATM LANs

The authors investigate burst-level bandwidth reservation schemes in ATM LANs and compare the performance of REQ/ACK and on-the-fly reservation schemes for a client-server model with a single ATM switch. To compare performance, they derive an analytical model for the mean burst transfer delay, blocking probability and throughput. They discuss the dependence of these performance parameters on the propagation delay-to-burst duration ratio and peak rate-to-link speed ratio. They show that, for moderate propagation delay-to-burst duration ratio, the on-the-fly scheme is more desirable since the REQ/ACK scheme has limited achievable throughput for fast reservation traffic due to unused bandwidth during the REQ-ACK cycle. Also, for a given burst length (in bits), the delay performance of REQ/ACK scheme is more sensitive to increase in the peak rate than the on-the-fly scheme.<<ETX>>

Directional AODV Routing Protocol for Wireless Mesh Networks

In most application scenarios, Wireless Mesh Networks (WMNs) are stationary or quasi-stationary with support of minimal mobility, in which most of their traffic is destined to the Internet through a gateway. Ad hoc On-demand Distance Vector (AODV) is not appropriate for such WMNs, because flooding-based route discovery is both redundant and very expensive in terms of control message overhead. In this paper, we propose a directional AODV (D-AODV) routing protocol based on hop count to a gateway. In the route discovery to a gateway, D-AODV can reduce the number of broadcasting route request (RREQ) packets by using a restricted directional flooding technique. Simulation results showed that D-AODV could significantly reduce routing overhead by RREQ packets and enhance overall throughput performance.

An Efficient Hybrid Routing Approach for Hybrid Wireless Mesh Networks

A hybrid mesh network is the most generic type of Wireless Mesh Networks (WMN) and is a combination of static mesh routers and mobile mesh clients. Static mesh routers are typically much less resource-constrained than mobile mesh clients, and are also often equipped with multiple radio interfaces. Furthermore, most of the traffic is directed to/from a gateway, as the mesh clients generally access services on the Internet or other networks. Thus, routing protocols need to distinguish the types of mesh node and take account of the traffic pattern in hybrid mesh networks. This paper proposes a Hybrid Distance Vector (HDV) routing protocol for hybrid mesh networks, which combines the tree-based routing strategy with the reactive routing strategy. Simulation results demonstrate that the proposed HDV routing protocol can outperform AODV and AODV-ST routing protocols in terms of the routing overhead, network throughput, and end-to-end delay in a hybrid mesh network.