Gugrajah_Yuvaan_ Ramesh_2003.pdf

Routing Protocolsfor Ad Hoc Networks Chapter 2
[Royer99], Neighbor Supporting Ad Hoc Multicast Routing Protocol [LeeOO], and
Multicast Core Extraction Distributed Ad Hoc Routing (MCEDAR) [Sinha99].
Geocasting is a variation of multicasting and is the problem of sending a message to
all nodes located within a particular region. The multicast group is implicitly defined
as the set of nodes within a specified area. Geocast routing protocols which use
flooding and adaptations of the GPS based unicast routing protocols are described in
[Navas97], [Ko99] and [Basagni99].
Multicasting in ad hoc networks is difficult because after sufficient information about
the topology of the network is obtained and a tree or mesh is computed, there may be
very little time before the calculated mesh or tree becomes inadequate.
2.4. Summary
One of the areas of active research in ad hoc networks is in the design of routing
protocols. The mobility of the nodes in the network results in dynamic and
unpredictable topologies. The routing protocols for ad hoc networks need to
determine viable routes from the source node to the destination node without
compromising the data, but at the same time need to be able to adjust to changes in
the topology.
The unicast protocols can be divided into proactive routing protocols and reactive
routing protocols. The proactive protocols are modifications of the routing protocols
used for wired networks and maintain updated routing tables. The reactive protocols
search for a route only when one is needed by a source, and usually implement some
type of flooding mechanism in order to find a current route to the destination.
Comparative simulations of the routing protocols have shown that the reactive
protocols are better equipped to contend with the constantly changing ad hoc
network environment. The proactive routing protocols have been found to add to the
congestion of the network due to the constant updates of the routing tables.
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