An ad-hoc network is a collection of mobile nodes (wireless communication devices) that
transmit data over systems that do not require any centralized control, such as that found in
cellular networks. This makes ad-hoc networks suitable for military type applications, since
there is no need for an established backbone infrastructure and hence no single-point-of-failure.
However, other uses of ad-hoc systems include search and rescue missions, law enforcement
operations, commercial and educational communication of laptop (and other handheld device)
data, as well as in the transmission of environmental sensor information.
The mobile ad-hoc concept brings many design challenges. The dynamic freedom of movement
from mobile nodes causes random, sometimes rapidly time changing topologies, which are
inappropriate for use through traditional wired protocols. In addition, wireless networks
generally contain greater bandwidth, processing and power constraints than their wired
counterparts, since they are implemented on embedded mobile, handheld devices. Thus, a
different approach is needed in the wireless network domain. This has resulted in wireless
routing protocols employing adaptive, multi-hop, distributed methodologies in which each node
additionally acts as a router for each of its neighbouring nodes, in order to achieve a large
degree of network connectivity.
However, due to the broadcast nature of wireless transmissions, ad-hoc systems contain a point-to-
multipoint communication architecture, making it well suited to multi-path traffic. One such
application is in multicasting, which sends data from one source to two (or more) destinations.
But, due to the shared characteristics of the communication channel, such traffic may cause
multiple contentions and collisions to occur, which will degrade the efficiency and performance
of a protocol.
This dissertation examines these different design tradeoffs through the use of a freely available
simulation package, known as NS-2 (Network Simulator - version 2). In addition, a novel
routing protocol, known as LAMP (Location Aided Multicasting Protocol), is developed to
handle time-bounded audio information, which is employed in a network that consists of sixteen
commercial handheld devices.
LAMP utilizes a destination-sequenced, next-hop routing table to forward multicast data. Since
mobility causes neighbouring nodes to continually change, next-hop links need to be
periodically updated. But, between each update period, a next-hop link may become broken.
Thus, if a packet is required to be routed, for which its' next-hop link is unknown, LAMP
reverts to a localized location aided flood to find a path to that destination. However, since
flooding causes network congestion, it is only employed when its' table forwarding scheme
fails.
Results have shown that LAMP improves packet delivery ratios by up to 5% over exisiting
flood-limiting schemes: Furthermore, LAMP has been shown to be comparable to leading
schemes, even when employed to route data to a single source-destination pair. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9016 |
| Date | January 2003 |
| Creators | Dearham, Nicholas Joseph. |
| Contributors | McDonald, Stephen A. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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