Author: Zhang, Liang
Title: Design of high performance mobile communication protocols
Degree: M.Phil.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations
Mobile communication systems -- Design and construction
Telecommunication systems
Computer network protocols
Department: Department of Computing
Pages: xii, 129 p. : ill. ; 30 cm
Language: English
Abstract: The notion of mobility takes various forms in networking and distributed systems. On one hand, the development of mobile and wireless communication networks allows users to change their access points of connecting to the network while maintaining their current sessions. On the other hand, mobile code and mobile agents provide high flexibility for the configuration of distrusted systems. In this thesis, a Mobile Object (MO) denotes a mobile entity which can be a mobile phone, a mobile node or a mobile agent. In recent years, researchers have proposed a wide range of schemes for the location management and the message delivery in mobile communication. However, each scheme has it own assumptions, design goals and methodology, making it difficult to adapt to different application requirements. In this thesis, we aim at discovering new approaches in designing adaptive mobile communication protocols that are more reliable in a fault-prone environment, more asynchronous with less constrains on MO's mobility, more efficient in terms of communication costs and more scalable to future system expansion. We propose a novel mailbox based scheme, which associates each MO with a mailbox while allowing them to be decoupled when needed. Message passing between the sender and the receiver is now divided into two steps: 1) from the sender to the receiver's mailbox, and 2) from the mailbox to the receiver. During each migration, a MO can decide whether to bring its mailbox to the new location or to leave the mailbox at its current location. This flexible approach allows us to design a variety of protocols that can be made adaptive to specific application requirements by properly evaluating tradeoffs among various design considerations. To explore the benefits of the mailbox based scheme, we apply it to two different contexts: mobile agent and Mobile IP. In the mobile agent context, we propose an Adaptive and Reliable Protocol (ARP), which is proved to possess many desirable characteristics such as location transparency, asynchrony, scalability and adaptability. By properly determining the mailbox's migration pattern, the ARP can outperform both the home-server based scheme and the distributed-registration based scheme. To further enhance efficiency and reliability, we extend the ARP with a path pruning algorithm and a two-layer fault-tolerant architecture. In the path pruning algorithm, the location management cost is greatly reduced as the algorithm can effectively identify and remove the redundant hosts on the mailbox's migration path so that fewer messages are required for the location management. In the two-layer fault-tolerant architecture, the low layer abstracts away network failures and provides reliable point-to-point message passing between two Mobile Agent Platforms (MAP); the high layer overcomes message loss caused by host failures and accomplishes reliable end-to-end message delivery between two mobile agents. In the Mobile IP context, by introducing the mailbox, we can achieve adaptive location management that enables dynamic tradeoff between the packet delivery cost and the location management cost so as to minimize the total communication cost. Since the mailbox is located somewhere in the network close to the receiver, the packet retransmission cost could also be reduced.
Rights: All rights reserved
Access: open access

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