Gugrajah_Yuvaan_ Ramesh_2003.pdf

Introduction Chapter J
The problems that face the development of ad hoc networks include limited power
from portable power sources and the need for suitable power control algorithms, low
bandwidth and high error rates from wireless channels, medium access control
strategies, scheduling policies, security algorithms and routing protocols that can
cope with the mobility and changes in topology. This dissertation focuses on routing
in ad hoc networks.
1.2. Routing in Ad Hoc Networks
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The Mobile Ad Hoc Networking (MANET) [Man02] working group was created
within the Internet Engineering Task Force (IETF) in the mid 1990s when mobile
computing became popular and viable communications equipment based on radio
frequency and infrared were developed. The key focus of the working group is to
develop and evolve ad hoc network routing specifications for standardization. Due to
the constantly changing topology and lack of central controller the routing protocol
implemented needs to be distributed and dynamic, efficiently utilizing available
resources and achieving fast route convergence.
In current cellular networks, user mobility is handled by forwarding calls via the
user's home network to the visited network. This forwarding principle also applies to
Mobile IP [Perkins98]. A roaming user that enters a foreign network is associated
with a visiting address provided by a foreign agent. The home agent establishes an
Internet Protocol (IP) tunnel to the foreign agent using the provided visiting address.
Any packet sent to the roaming user's home address is first sent to the home agent
which redirects it to the foreign agent via the visiting address. This forwarding
approach is only useful where only the nodes at the edges of fixed networks are
mobile.
In ad hoc networks this is not the case. Nodes at the centre of the network can also
move, with the whole network being based on the idea that mobile devices behave
both as routers and as hosts. Therefore, in an ad hoc network, mobility is handled by
the routing algorithm, which needs to take care of changes in topology.
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