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Abstract

This thesis analyses Internet connectivity for Mobile Ad-hoc JVETworks (MANETs). A MANET consists of a number of mobile nodes, interconnected wirelessly, that together form a network without explicit routers and centralised instances. Ad-hoc routing protocols are utilised for discovering routes between nodes of the MANET whereas a route may consist of multiple relay nodes that forward data from a source to a destination node (multihop route).

In order to connect nodes of a MANET to the Internet an interface node is introduced. This interface node is called an Internet gateway that must initially be discovered by the MANET nodes to gain Internet connectivity. Therefore extended ad-hoc routing protocols are used.

In general, there exist two well-established approaches for discovering an Internet gateway. The first well-established approach is called the proactive approach, where Internet gateways flood the MANET periodically whereas in the second well-established approach nodes of the MANET solicit for Internet gateways reactively. Both approaches use MANET flooding for discovering an Internet gateway and MANET flooding is known to increase the protocol overhead in MANETS.

The main objective of the research presented in this thesis is to develop an Internet gateway discovery algorithm that avoids MANET flooding and to investigate the new algorithm in terms of the control message overhead and the provided throughput to the mobile nodes of the MANET by simulations. Additionally in the thesis a protocol efficiency index is derived from simulation results to allow a fast comparison between simulation results with different parameters.

This thesis presents the new HELLO message based algorithm for Internet gateway discovery. HELLO messages are a typical element of MANET routing protocols used for neighbourhood management and are now enhanced for Internet gateway discovery. By avoiding MANET flooding the control message overhead is minimised. The HELLO message based algorithm for Internet gateway discovery is examined and investigated by simulations and it shows a decrease of the control message overhead of up to 2.6 times compared to the well-established approaches in the simulated scenario setups.

Furthermore the thesis presents two extensions to the well-established and the HELLO message based Internet gateway discovery algorithms. The first extension utilises additional control messages in order to optimise a multihop route from the Internet gateway to an ad-hoc mobile node. This first extension applies only for proactive algorithms for Internet gateway discovery and it provides a benefit in terms of data throughput to mobile nodes by 10% in the scenario setup simulated in this thesis.

The second extension allows mobile nodes of a MANET to choose between multiple discovered Internet gateways. The selection to which Internet gateway a MANET node connects to is based upon a certain newly presented metric. This new metric is based on the length of a MANET route and the amount of traffic an Internet gateway is already forwarding. Simulations show a benefit of up to 438% in terms of throughput depending on the actual scenario setup.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QA Mathematics > QA75 Electronic computers. Computer science T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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